JP5200152B2 - Spatial information detection device - Google Patents

Description

The present invention relates to the detection device of the spatial information.

  In general, in a light detection element that generates a charge by light irradiation and extracts a light reception output corresponding to the amount of received light, the light reception output also changes according to the amount of light received. However, the maximum value of the light reception output is limited by the size of the part from which the generated charge is extracted as the light reception output.

  In order to expand the dynamic range of the path for taking out the generated charge as a light receiving output, in the path for transferring the charge using the CCD, a certain amount of charge is weighed to be an unnecessary charge, and the remaining charges excluding the unnecessary charge It is considered that charges are transferred and used for light reception output (see, for example, Patent Document 1 and Patent Document 2).

In this configuration, a certain amount of unnecessary charges unrelated to the input signal can be removed from the charges to be transferred, and as a result, the amount of charges to be transferred can be reduced, thereby reducing the size of the path for transferring charges. It becomes possible.
Japanese Patent Laid-Open No. 7-22436 Japanese Patent Laid-Open No. 7-22437

  However, in the configurations described in Patent Document 1 and Patent Document 2, since the charge is weighed in the charge transfer process, the charge amount generated by light irradiation exceeds the limit of the charge amount that can be generated. In this case, the information on the amount of received light is already lost from the charge given in the transfer process. That is, if the techniques described in Patent Document 1 and Patent Document 2 are adopted, the size of the site for generating electrons by light irradiation can be reduced even though the size of the path for transferring charges can be reduced. There is a problem that you can not.

The present invention has been made in view of the above-described reasons, and the object thereof is to reduce the possibility of saturation in the photoelectric conversion unit, to enable downsizing of the photoelectric conversion unit, and to further reduce the turn-off period and the lighting period. It is possible to collect a lot of signal light information obtained during the lighting period and to increase the amount of spatial information that can be collected per unit time. in subjecting Hisage detection equipment spatial information had use a light detecting element which is.

Detection device of the spatial information according to the present invention includes an optical detecting element, a light emitting source for projecting light as signal light to a target space the modulated light intensity by the modulation signal, the modulation signal of the received light quantity of the light detection element synchronously A signal processing unit that detects spatial information of the target space using a received light output that reflects a fluctuation component of signal light obtained by separating a certain amount of bias component from an amount of charge corresponding to the amount of received light detected at the timing A photoelectric conversion unit that generates charge by light irradiation, and the charge generated by the photoelectric conversion unit is used to increase / decrease a certain amount of bias component and received light amount. A charge separation unit that separates a specified amount of unnecessary charge corresponding to a bias component, which is regarded as a sum of fluctuation components that fluctuate following, and an unnecessary charge separated from the charge generated by the photoelectric conversion unit The signal processing unit is an operation in which charges are generated by the photoelectric conversion unit, and a signal extraction unit that extracts the effective charge stored in the charge storage unit as a light receiving output. And the operation of separating the unnecessary charge from the charge generated in the photoelectric conversion unit and accumulating the effective charge in the charge accumulation unit is repeated a plurality of times, and the charge accumulated in the charge accumulation unit is The light detection element is controlled so as to be extracted as a light receiving output from the charge extraction unit, and the light emission source is operated to provide a lighting period in which light is emitted from the light emission source and a light extinction period in which light is not emitted. The amount of unnecessary charge that is separated from the amount of charge corresponding to the amount of light received during the lighting period while leaving the amount of charge corresponding to the fluctuation component of the signal light is determined based on the amount of received light obtained during the extinguishing period. The photodetecting element is controlled to perform a weighing operation for equally dividing a predetermined amount of unnecessary charge into a plurality of prescribed times, and the amount of unnecessary charge separated in one weighing operation is continued during the extinguishing period. It is characterized in that it is specified to increase as the time increases .

  According to this configuration, unnecessary charges are separated from the charges generated by the light received by the light detection element, so that the influence of ambient light is reduced and the light emitted from the light source contributes to the light reception output. The ratio can be increased. Therefore, when detecting spatial information based on the relationship between the light projected from the light source and the light received by the light detection element, it becomes easier to detect the degree of change in the light projected from the light source, and detection of spatial information. Accuracy can be increased.

In addition, according to this configuration, the amount of unnecessary charge that is separated in one weighing operation is specified to increase as the duration of the extinguishing period increases, and unnecessary charges are separated multiple times. Compared with the case where unnecessary charges are separated at a time, the duration of the extinguishing period can be shortened. Since the time required for the weighing operation is about two to three digits shorter than the extinguishing period, by shortening the extinguishing period, the total processing time of the extinguishing period and the lighting period can be shortened. As a result, a large amount of signal light information obtained during the lighting period can be collected, and the amount of spatial information that can be collected per unit time can be increased.
In this spatial information detection device, the photodetection element is a potential well formed in a semiconductor in which the charge separation unit and the charge storage unit flow into the charge separation unit. In this case, the charge flowing into the charge storage section over the potential barrier formed between the charge separation section and the charge storage section is the effective charge, and the charge remaining in the charge separation section is the unnecessary charge. The main surface of the semiconductor is provided with a barrier control electrode at a portion corresponding to the potential barrier, and the amount of unnecessary charge is adjusted by changing the height of the potential barrier according to the voltage applied to the barrier control electrode. Is preferred.
According to this configuration, since it is only necessary to dispose electrodes on the main surface of the semiconductor, it can be easily realized by using a semiconductor manufacturing technique. Further, since the amount of unnecessary charges is adjusted by changing the height of the potential barrier, the amount of unnecessary charges can be easily adjusted only by adjusting the voltage applied to the barrier control electrode.
In this spatial information detection device, the photodetection element is a potential well formed in a semiconductor in which the charge separation unit and the charge storage unit flow into the charge separation unit. In this case, the charge flowing into the charge storage section over the potential barrier formed between the charge separation section and the charge storage section is the effective charge, and the charge remaining in the charge separation section is the unnecessary charge. The main surface of the semiconductor is provided with a separation electrode at a portion corresponding to the charge separation portion, and the unnecessary charge separated by changing the depth of the potential well serving as the charge separation portion according to the voltage applied to the separation electrode. It is preferred that the amount be adjusted.
According to this configuration, since it is only necessary to dispose electrodes on the main surface of the semiconductor, it can be easily realized by using a semiconductor manufacturing technique. In addition, since the amount of unnecessary charge is adjusted by changing the depth of the potential well serving as the charge separation portion, the amount of unnecessary charge can be easily adjusted only by adjusting the voltage applied to the separation electrode.
In the spatial information detection device, the light detection element includes an element formation layer made of a first conductivity type semiconductor, a second conductivity type well formed on a main surface of the element formation layer, and the charge separation unit. It is provided with a light receiving period in which a charge is discarded and a control electrode arranged on the main surface of the well, and a charge is generated by light irradiation to the well, and a weighing period in which a certain amount of unnecessary charge is separated Correspondingly, the voltage applied to the control electrode is controlled, a plurality of control electrodes are arranged side by side on the main surface of the well, and in the weighing period, a potential barrier is formed in a region corresponding to any control electrode in the well, In addition, it is preferable that a potential well serving as the charge separation portion and a potential well serving as the charge storage portion are formed in a region corresponding to another control electrode with a potential barrier interposed therebetween.
According to this configuration, it is possible to easily realize a configuration in which unnecessary charges are separated in the weighing period from charges generated in the light receiving period by using a semiconductor, and the light receiving period and the weighing period are controlled by controlling the timing of applying the voltage. Can be realized easily. In addition, since a potential well serving as a charge separation unit and a charge storage unit is formed using a plurality of control electrodes, and a potential barrier is formed using the control electrodes, a simple configuration in which a plurality of control electrodes are simply arranged. It becomes a composition. Furthermore, since a waste part for discarding the charge of the charge separation unit is provided, the charge separation unit discards the charge before the unnecessary charge is weighed by the charge separation unit. Increases accuracy.

  In this spatial information detection apparatus, a plurality of the photoelectric conversion units are arranged, the charge separation unit is provided for each photoelectric conversion unit, and the signal processing unit is an amount of unnecessary charges to be separated in one weighing operation. It is preferable that the number of weighing operations is set to the same number in all the charge separation units by setting for each charge separation unit.

  According to this configuration, although the light detection element has a plurality of photoelectric conversion units, the number of times of the weighing operation is the same so that the timing of the weighing operation can be collectively controlled by the entire light detection element. Operation timing control is facilitated.

  In this spatial information detection device, the signal processing unit is configured to make a remainder smaller than a predetermined amount when divided by the amount of unnecessary charge separated in one weighing operation over the entire photoelectric conversion unit. It is preferable to reduce the amount of unnecessary charges separated by one weighing operation and to increase the number of weighing operations by shortening the extinguishing period.

  According to this configuration, when separating unnecessary charges by multiple weighing operations, the number of weighing operations is increased by shortening the extinguishing period. While the same number of weighing operations are performed in the photoelectric conversion units, the remaining amount of undesired charges generated in each photoelectric conversion unit remains unseparated, and components other than signal light in the charge extracted as the light receiving output The amount of contamination can be reduced.

  In this spatial information detection apparatus, the signal processing unit controls the light detection element so that a discard period for separating unnecessary charges calculated based on the amount of received light obtained in the extinguishing period is provided a plurality of times in the lighting period. In addition, the weighing operation is performed a plurality of times in one disposal period, and the number of weighing operations is increased every prescribed number of disposal periods. The prescribed number of times is the amount of charge due to noise components generated in one lighting period. It is preferable to define the amount of unnecessary charges discarded by one weighing operation.

  According to this configuration, it is possible to reduce the ratio of unnecessary charges caused by noise components in the light reception output, and it is possible to widen the dynamic range of components corresponding to signal light in the light reception output.

  In this spatial information detection device, the signal processing unit increases the amount of unnecessary charge to be separated in the next lighting period when the light reception output reaches a predetermined saturation level during the lighting period which is a fixed time each time. Is preferred.

  According to this configuration, even if the light reception output reaches the saturation level, saturation is less likely to occur in the next lighting period, and the possibility that spatial information can be detected increases.

  In this spatial information detection device, it is preferable that the signal processing unit increases the amount of unnecessary charges separated in the lighting period by increasing the number of operations for discarding unnecessary charges in the lighting period.

  According to this configuration, since the number of operations for discarding unnecessary charges is only managed when controlling the amount of unnecessary charges to be discarded, the control is easy.

  In this spatial information detection device, the signal processing unit controls the light detection element to perform an operation of discarding unnecessary charges a plurality of times during the lighting period, and provides a time interval for each operation, It is preferable to shorten the time interval as the light receiving output is larger.

  According to this configuration, the operation of discarding unnecessary charges is performed a plurality of times during the lighting period, and a time interval is provided between the operations of discarding unnecessary charges, thereby accumulating in the photoelectric conversion unit during the lighting period. If unnecessary charges are increased, unnecessary charges are discarded, and the rate of increase of charges accumulated in the photoelectric conversion unit decreases, and saturation of received light output is suppressed even in environments where the intensity of ambient light is high. Can do. That is, unnecessary charges are not discarded together at the end of the lighting period, but unnecessary charges are discarded little by little during the lighting period, so that the amount of charges accumulated in the photoelectric conversion unit hardly reaches a saturation level. . Moreover, since the time interval of the weighing operation is shortened in an environment where there is a lot of ambient light, saturation due to ambient light can be suppressed by reducing the rate of increase of the charge accumulated in the photoelectric conversion unit.

  The operation of discarding unnecessary charges may be either a single weighing operation or an operation of continuously performing a plurality of weighing operations. The period during which a plurality of weighing operations are continuously performed corresponds to a discard period in an embodiment described later.

  In this spatial information detection apparatus, it is preferable that the signal processing unit selects a time during which the lighting period is continued from a plurality of types.

  According to this configuration, the dynamic range for the signal light can be expanded by selecting the duration of the lighting period according to the received light intensity of the signal light.

  In this spatial information detection apparatus, it is preferable that the signal processing unit selects a time during which the lighting period continues from a plurality of types, and increases or decreases the number of weighing operations according to the time during which the lighting period continues.

  According to this configuration, the dynamic range for the signal light can be expanded by selecting the duration of the lighting period according to the received light intensity of the signal light, and the weighing is performed with respect to the change of the duration of the lighting period. Since the amount of unnecessary charge to be discarded is adjusted by increasing or decreasing the number of operations, even if the duration of the lighting period is increased or decreased, the duration of the extinguishing period is kept constant, and the extinguishing period and the lighting period are totaled The increase / decrease of the time spent can be made relatively small. In other words, if the duration of the extinguishing period is kept relatively short, the total increase / decrease of the extinguishing period and the lighting period is only the increase / decrease of the duration of the lighting period. The maximum value of the total time is smaller than when the time during which the extinguishing period continues is increased or decreased.

  Note that a charge holding portion may be provided as described in the following embodiments. That is, the photodetecting element includes a charge holding unit that holds charges generated by irradiating the photoelectric conversion unit with light at a predetermined timing, and performs charge separation according to the amount of charge held in the charge holding unit. It is preferable that the amount of charges separated as unnecessary charges in the portion is adjusted.

  According to this configuration, if the charge generated by receiving light at a predetermined timing in the photoelectric conversion unit is held in the charge holding unit, the charge amount separated as unnecessary charge is associated with the received light amount received at the predetermined timing. Can do. For example, if it is used in combination with a light emitting source and a lighting period in which light is emitted from the light emitting source and a light extinguishing period in which light is not emitted are provided, only ambient light is received during the light extinguishing period to determine the amount of unnecessary charges, If unnecessary charges are separated from the generated charges, an amount of unnecessary charges corresponding to the components of the ambient light can be separated.

Further, in this photodetecting element, the charge separation portion is disposed on the main surface side of the semiconductor with the holding well disposed in the holding well via an insulating layer, and one of the barrier control electrode and the separation electrode is electrically And a voltage corresponding to the amount of charge held in the charge holding portion. According to this configuration, a voltage corresponding to the amount of charge accumulated in the holding well is generated in the holding electrode. Since one of the barrier control electrode and the separation electrode is electrically connected, if a suitable amount of charge is accumulated in the holding well, the potential of the part corresponding to the barrier control electrode or the separation electrode is determined and separated. It is possible to automatically determine the amount of unwanted charge to be made.

  Alternatively, in this photodetector, a holding well as a charge holding portion is provided on the main surface side of the semiconductor, and one of the barrier control electrode and the separation electrode is electrically connected to the holding well, and the charge holding portion is It is preferable to apply a voltage corresponding to the held charge amount to one of the electrodes.

  According to this configuration, since a voltage corresponding to the amount of charge accumulated in the holding well is applied to one of the barrier control electrode and the separation electrode, if an appropriate amount of charge is accumulated in the holding well, the barrier control electrode or the separation The amount of unnecessary charges to be separated can be automatically determined by determining the potential of the part corresponding to the electrode. Moreover, since the barrier control electrode or separation electrode and the holding well are electrically connected, if the charge of the holding well is discarded, the charge remaining on the barrier control electrode or the separation electrode can be discarded at the same time. The amount of charge accumulated in the holding well is accurately reflected in the amount of unnecessary charges, and the weighing accuracy can be improved.

  The photodetector includes a gate electrode that is provided on the main surface of the semiconductor at a portion between the photoelectric conversion unit and the charge holding unit and controls the timing of transferring the charge generated by the photoelectric conversion unit to the charge holding unit. Is preferred.

  According to this configuration, since the transfer timing of the charge from the photoelectric conversion unit to the charge holding unit is controlled by the gate electrode, the charge at a desired timing can be transferred to the charge holding unit.

  In this photodetecting element, it is preferable that a plurality of charge separation sections and charge storage sections are provided, and the charge holding section is shared by two adjacent barrier control electrodes.

  This configuration is suitable for detecting the amount of received light at two kinds of timings such that the amount of ambient light received does not substantially change, and holds a charge equivalent to the amount of ambient light received If the charge holding part is held in the unit, the charge holding part is shared with respect to the received light amount obtained at two kinds of timings, so that the element area can be reduced as compared with the case where the charge holding part is provided independently.

  In this photodetecting element, an element forming layer made of a semiconductor of the first conductivity type, a discarding part in which charges in the charge separation part are discarded, a second conductivity type well formed on the main surface of the element forming layer, A plurality of sensitivity control electrodes arranged in a straight line on the main surface of the well, and the charge separation unit, the charge storage unit, and the charge holding unit are sensitive in a direction orthogonal to the direction in which the sensitivity control electrodes are arranged. It is preferable that the control electrodes are arranged in parallel.

  According to this configuration, since the charge separation unit, the charge storage unit, and the charge holding unit are arranged on the side of the sensitivity control electrode, the sensitivity control electrode can be arranged at equal intervals, and along the sensitivity control electrode. This makes it easier to control the transfer of charges. Furthermore, since a waste part for discarding the charge of the charge separation unit is provided, the charge separation unit discards the charge before the unnecessary charge is weighed by the charge separation unit. Increases accuracy.

  In this photodetecting element, an element forming layer made of a semiconductor of the first conductivity type, a second conductivity type well formed on the main surface of the element forming layer, a waste part for discarding the charge of the charge separation part, A plurality of sensitivity control electrodes arranged in a straight line on the main surface of the well, and the charge separation unit and the charge holding unit are arranged in a direction perpendicular to the direction in which the sensitivity control electrodes are arranged. It is preferable that they are arranged side by side.

  According to this configuration, since the charge separation unit and the charge storage unit are arranged on a straight line on which the sensitivity control electrodes are arranged, unnecessary charges can be separated in the same direction as the direction in which charges are transferred along the sensitivity control electrode. Therefore, the procedure required for separating unnecessary charges can be reduced. In addition, the charge holding unit is disposed on the side of the charge separation unit and the charge storage unit. However, since the charge separation unit and the charge storage unit are disposed between the sensitivity control electrodes, the charge control unit is different from the direction in which the sensitivity control electrodes are arranged. There are few operations for transferring charges in the direction, and the control wiring is simplified and the operation is simplified. Furthermore, since a waste part for discarding the charge of the charge separation unit is provided, the charge separation unit discards the charge before the unnecessary charge is weighed by the charge separation unit. Increases accuracy.

  In the case of using a photodetecting element having a charge holding unit, the photodetecting element is controlled by controlling the voltage applied to the gate electrode after generating the charge in the photoelectric converting unit to transfer the charge from the photoelectric converting unit to the charge holding unit. It is preferable to separate unnecessary charges determined according to the charge amount of the charge holding unit from the charges generated by the photoelectric conversion unit after transferring and transferring the charge to the charge holding unit.

  According to this method, since the timing of transferring the charge generated by the photoelectric conversion unit to the charge holding unit is controlled by the voltage applied to the gate electrode, the charge corresponding to the amount of light received during a desired period is transferred to the charge holding unit. Then, it is possible to separate unnecessary charges according to the charge amount of the charge transferred to the charge holding unit from the charge corresponding to the amount of received light in the period after transfer. That is, effective charges reflecting the difference between the amount of received light during the period in which the charge transferred to the charge holding unit is generated and the amount of received light during an appropriate period thereafter can be extracted as the received light output.

  In the case of using a light detection element including a charge holding unit, a spatial information detection device includes a light detection element, a light emission source that projects light whose intensity is modulated by a modulation signal as signal light, and a light detection element. Using the received light output that reflects the fluctuation component of the signal light obtained by separating a certain amount of bias component from the charge corresponding to the received light amount detected at the timing synchronized with the modulation signal among the received light amount, A signal processing unit that detects spatial information, and includes a lighting period in which light is emitted from a light source and a light-out period in which light is not emitted, and charges generated by irradiating light to the photoelectric conversion unit in the light-off period are charged. It is preferable that the amount of charges separated as unnecessary charges in the charge separation unit is adjusted in accordance with the amount of charges held in the holding unit and held in the charge holding unit during the lighting period.

  According to this configuration, since the amount of unnecessary charge to be separated in the lighting period is determined by the amount of light received during the extinguishing period of the light emitting source, the charge generated by receiving light during the extinguishing period by the photoelectric conversion unit is held in the charge holding unit. For example, the amount of charge separated as unnecessary charge can be associated with the amount of received light received during the extinguishing period. In other words, if the amount of unnecessary charge is determined by receiving only ambient light during the extinguishing period, and the unnecessary charge is separated from the charge generated during the lighting period, an amount of unnecessary charge corresponding to the component of the ambient light can be separated. Become.

  In this spatial information detection device, the light detection element includes a charge holding unit that holds charges generated by the photoelectric conversion unit in one of the two sections having different phases of the modulation signal, and the signal processing unit holds the charge. By applying a voltage corresponding to the amount of charge held in the unit to the barrier control electrode, it corresponds to the amount of charge generated in the photoelectric conversion unit in the one section from the charge generated in the photoelectric conversion unit in the other section It is preferable to separate unnecessary charges.

  According to this configuration, the amount of unnecessary charge is automatically determined by the amount of received light in one of the two sections having different phases of the modulation signal, and the effective charge becomes a charge amount corresponding to the difference between the two sections. That is, it is possible to obtain a light reception output corresponding to the difference in the amount of light received between the two sections.

According to the configuration of the present invention, it is possible to shorten the processing time obtained by adding the turn-off period and the turn-on period. As a result, a large amount of signal light information obtained during the lighting period can be collected, and the amount of spatial information that can be collected per unit time can be increased.

1 is a cross-sectional view showing a first embodiment. It is operation | movement explanatory drawing which shows the relationship of the potential same as the above. It is operation | movement explanatory drawing which shows the relationship of a voltage same as the above. It is a block diagram which shows the structural example of the detection apparatus using the same as the above. It is operation | movement explanatory drawing which shows the operation example same as the above. It is operation | movement explanatory drawing which shows the other operation example same as the above. It is operation | movement explanatory drawing which shows the other operation example same as the above. It is operation | movement explanatory drawing which shows another operation example same as the above. (A) (b) is sectional drawing which shows two types of structural examples of Embodiment 2. FIG. It is operation | movement explanatory drawing which shows the relationship of the potential same as the above. It is operation | movement explanatory drawing which shows the relationship of a voltage same as the above. Embodiment 3 is shown, (a) is a plan view, (b) is a sectional view taken along line XX of FIG. (A), and (c) is a sectional view taken along line YY of FIG. (A). FIG. 6 is a plan view showing a fourth embodiment. It is operation | movement explanatory drawing same as the above. FIG. 10 is a plan view showing a fifth embodiment. FIG. 10 is a cross-sectional view showing a sixth embodiment. It is operation | movement explanatory drawing which shows the relationship of the potential same as the above. FIG. 10 is a cross-sectional view showing a seventh embodiment. It is operation | movement explanatory drawing which shows the relationship of the potential same as the above. FIG. 10 is a cross-sectional view showing an eighth embodiment. FIG. 10 is a cross-sectional view showing a ninth embodiment. It is operation | movement explanatory drawing which shows the relationship of the potential same as the above. It is operation | movement explanatory drawing which shows the relationship of a voltage same as the above.

(Embodiment 1)
The present embodiment is a cell having a minimum configuration, and an image sensor can be configured by arranging a large number of such cells.

  As shown in FIG. 1, one cell 1 is formed on the main surface side of an element forming layer 11 made of a first conductivity type (p-type in the illustrated example) semiconductor (assuming silicon in the illustrated example). A well 12 made of a semiconductor of a second conductivity type (n-type in the illustrated example) is formed, and an isolation electrode 14a and a storage electrode 14b are formed on the main surface of the well 12 via an insulating layer (for example, silicon oxide or silicon nitride) 13. The barrier control electrode 14c is arranged. The element forming layer 11 is formed on the second conductivity type substrate 10. The separation electrode 14a, the storage electrode 14b, and the barrier control electrode 14c are assumed to have translucency. In this embodiment, an example in which electrons are used among the charges generated by light irradiation will be described. However, when holes are used, the conductivity type of the semiconductor may be changed, and the polarity of the voltage described later may be changed. .

  Among the separation electrode 14a, the storage electrode 14b, and the barrier control electrode 14c, the storage electrode 14b is formed with the widest width. In the illustrated example, the widths of the separation electrode 14a, the storage electrode 14b, and the barrier control electrode 14c are different. However, a plurality of electrodes having the same width are arranged and the same voltage is applied to a plurality of adjacent electrodes. By doing so, you may make it handle equivalent to a wide electrode. For example, if two adjacent electrodes are used for the separation electrode 14a, three adjacent electrodes are used for the storage electrode 14b, and one electrode is used for the barrier control electrode 14c, the same width can be obtained. By using six electrodes, the functions of the separation electrode 14a, the storage electrode 14b, and the barrier control electrode 14c can be realized.

  Since the well 12 is n-type and surrounded by the p-type element formation layer 11, the voltage (separation electrode 14a, storage electrode 14b, barrier control) is applied to any of the separation electrode 14a, storage electrode 14b, and barrier control electrode 14c. In the state where the voltages to be applied to the electrodes 14 c are not applied (Va, Vb, Vc), the potential for electrons is lower in the well 12 than in the element formation layer 11. That is, the region where the well 12 is formed forms a potential well for electrons. In the figure, hatched portions represent electrons. The potential inside the well 12 can be controlled by the voltages Va, Vb, and Vc applied to the separation electrode 14a, the storage electrode 14b, and the barrier control electrode 14c.

  Now, it is assumed that light is irradiated with the charge in the well 12 being emptied. In order to empty the electrons in the well 12, the electrons are discarded through the drain 23 (see FIG. 15) serving as a discarding portion provided adjacent to the well 12, or the electrons in the well 12 are not shown. To the outside as a light receiving output through the unit. The charge extraction unit can adopt the same configuration as the vertical transfer unit or horizontal transfer unit of the CCD image sensor.

  When light is applied to the separation electrode 14a, the storage electrode 14b, and the barrier control electrode 14c without applying the voltages Va, Vb, and Vc as in the period Ta in FIG. 3, electrons are generated in the element formation layer 11 including the well 12. And holes are generated, and the generated electrons are accumulated in the well 12 as shown in FIG. That is, the well 12 functions as the photoelectric conversion unit D1. If a voltage (that is, a positive voltage) that is higher than the reference potential that is the potential of the element formation layer 11 is applied to any of the separation electrode 14a, the storage electrode 14b, and the barrier control electrode 14c. The potential well can be set deeper, and the electron accumulation efficiency can be increased.

  After electrons by light irradiation are accumulated in the photoelectric conversion unit D1, a negative voltage Vc is applied to the barrier control electrode 14c during the period Tb in FIG. 12 forms a potential barrier B1. The potential barrier B1 converts the potential well inside the well 12 into two potential wells, that is, a charge separation portion D2 that is a region corresponding to the separation electrode 14a and a charge storage portion D3 that is a region corresponding to the storage electrode 14b. To divide.

  In a state where the potential barrier B1 is formed and the charge separation unit D2 and the charge storage unit D3 are partitioned (period Tc in FIG. 3), the charge is passed through the drain 23 (see FIG. 15) as a discard unit provided close to the well 12. If the electrons in the separation part D2 are discarded, the electrons remain only in the charge storage part D3 as shown in FIG. The amount of electrons remaining in the charge storage portion D3 reflects the amount of received light during the period Ta in FIG.

  Next, as in the period Td in FIG. 3, the positive voltage Va is applied to the separation electrode 14a, and the voltage Vc applied to the barrier control electrode 14c is removed. At this time, as shown in FIG. 2D, the charge separation part D2 becomes a potential well deeper than the charge accumulation part D3, and the potential barrier B1 between the charge separation part D2 and the charge accumulation part D3 is removed. All the electrons accumulated in the charge storage unit D3 flow into the charge separation unit D2. That is, all the electrons accumulated in the charge storage unit D3 are transferred to the charge separation unit D2.

  When all the electrons in the well 12 move to the charge separation portion D2, a predetermined negative voltage Vc having a negative polarity is applied to the barrier control electrode 14c as in the period Te in FIG. 3, and then applied to the separation electrode 14a. Remove the voltage Va. That is, as shown in FIG. 2E, the potential barrier B1 is formed in the well 12, the charge separation part D2 and the charge storage part D3 are divided again, and the potential well as the charge separation part D2 is further shallowed. . Here, the capacity (volume) of the charge separation unit D2 is determined using the height of the potential barrier B1 as a variable. That is, the capacitance of the charge separation unit D2 is determined according to the voltage Vc applied to the barrier control electrode 14c. The voltage Vc applied to the barrier control electrode 14c is set so that the potential of the potential barrier B1 does not exceed the potential of the element formation layer 11.

  When the amount of electrons flowing into the charge separation unit D2 in the state of FIG. 2D exceeds the capacity of the charge separation unit D2 in the state of FIG. 2E, the potential barrier B1 is exceeded from the charge separation unit D2. As a result, electrons flow into the charge storage portion D3. The amount of electrons flowing into the charge separation unit D2 in the state of FIG. 2D corresponds to the amount of electrons generated by light irradiation (actually, the amount of electrons in FIG. 2C). The amount of electrons flowing into the charge storage unit D3 in the state of FIG. 2 (e) excludes electrons corresponding to the capacity of the charge separation unit D2 set in the state of FIG. 2 (e) from the electrons generated by light irradiation. Amount.

  Hereinafter, the electrons separated by the charge separation unit D2 are referred to as unnecessary charges, and the electrons that have flowed into the charge storage unit D3 are referred to as effective charges. Normally, unnecessary charges are discarded and effective charges are taken out as a light receiving output. This regards electrons generated by light irradiation in the photoelectric conversion unit D1 as the sum of a certain amount of bias component due to ambient light or the like and a fluctuation component that includes information of interest and fluctuates in accordance with increase / decrease in the amount of received light. This is because the bias component does not contain information of interest, and is discarded as an unnecessary charge. Since the effective charge obtained in this way simply discards a certain amount of electrons from the amount of electrons corresponding to the amount of received light, the amount of change in the amount of received light itself is preserved. There is no change in the information amount.

  2A to 2E, light is irradiated while electrons are moved in the well 12, and electrons are continuously accumulated in the well 12, so that FIG. The amount of electrons generated by light irradiation in the period from FIG. 2B to FIG. 2E can be ignored with respect to the amount of electrons generated by the photoelectric conversion unit D1 as in FIG. There is a need to reduce it. The period of FIG. 2A is on the order of ms, for example, and the period from FIG. 2B to FIG. 2E can be on the order of μs, so that the error can be ignored.

  As described above, in the present embodiment, a predetermined amount of electrons generated by light irradiation in the photoelectric conversion unit D1 is weighed by the charge separation unit D2, and the remaining electrons after weighing are measured by the charge storage unit D3. To be used as an effective charge. Therefore, the amount of effective charges stored in the charge storage unit D3 is smaller than the amount of electrons corresponding to the received light amount (= time integration of the received light beam), but reflects the received light amount by light irradiation. Become. In this way, even when the amount of received light is large, a certain amount of the generated charges is removed as unnecessary charges by the charge separation unit D2, so that saturation is less likely to occur.

  Further, in this embodiment, the photoelectric conversion unit D1 is formed in the well 12, but electrons generated by the photoelectric conversion unit provided separately from the well 12 are transferred to the well 12, and then the electrons are obtained by the procedure described above. Parts may be weighed. In this case, since the well 12 can be shielded from light, errors caused by light irradiation in the period from FIG. 2A to FIG. 2E can be reduced.

  Furthermore, in the above example, the potential of the electron storage unit D3 is not changed during the period of FIG. 2D, and the potential of the charge separation unit D2 and the potential of the potential barrier B1 are lowered, but the charge separation unit D2 Without lowering the potential of the potential barrier B1, the potential of the potential barrier B1 is lowered (becomes higher than the potential barrier B1 of FIG. 2E) and the potential of the charge storage portion D3 is raised (made higher than the potential barrier B1). Electrons may be allowed to flow from the charge storage unit D3 into the charge separation unit D2.

  By the way, in the state of FIG. 2 (e), in order to weigh a certain amount of electrons as unnecessary charges in the charge separation unit D2, all electrons flowing into the charge storage unit D3 through the potential barrier B1 flow into the charge storage unit D3. It is necessary to let If the amount of electrons flowing into the charge storage unit D3 exceeds the capacity of the charge storage unit D3, there is a problem that the electron separation unit D2 cannot measure a certain amount of unnecessary charges. In order to solve this problem, if the capacitance is set to be large without changing the depth of the charge storage portion D3, the area occupied by the well 12 with respect to the element formation layer 11 increases, leading to an increase in the size of the photodetecting element. Therefore, in order to solve the above-described problem, a technique for adjusting the depth of the charge storage portion D3 is employed.

  The depth of the charge storage portion D3 is related to the height of the potential barrier B1, and the charge amount of unnecessary charges is determined by the relative height of the potential barrier B1 with respect to the potential at the bottom of the charge separation portion D2. By adjusting the bottom potential of the charge separation unit D2 without changing the relative height of the potential barrier B1 with respect to the bottom potential, even if the amount of received light increases or decreases, a certain amount of unnecessary charges are generated in the electron separation unit D2. It becomes possible to weigh.

  In order to properly set the bottom potential of the charge separation unit D2, the amount of received light must be evaluated. For the evaluation of the amount of received light, a technique can be used in which electrons accumulated in the photoelectric conversion unit D1 are taken out of the light detection element and evaluated by an external circuit of the light detection element. In this case, the evaluation result in the external circuit is reflected in the voltage applied to the separation electrode 14a. Depending on the evaluation result of the amount of received light, there may be a case where it is not necessary to weigh electrons in the charge separation unit D2. In that case, the electrons remaining in the charge storage portion D3 in the state of FIG.

  That is, the separation electrode 14a, the storage electrode 14b, and the barrier control electrode so that the light detection element performs two operations, that is, an operation of extracting a received light output for evaluating the amount of received light and an operation of extracting the received light output after weighing. The voltage applied to 14c is controlled by an external circuit. In the period for obtaining the light reception output for evaluating the amount of received light, the charge is not weighed, the charge accumulated in the photoelectric conversion unit D1 is taken out as it is as the light reception output, and by this light reception output, the separation electrode 14a and the storage electrode 14b And the voltage applied to the barrier control electrode 14c are determined, and one of the height of the potential barrier B1 and the depth of the charge storage portion D3 is determined. Next, with respect to the charge corresponding to the amount of received light, unnecessary charges are weighed in the above-described procedure, and the remaining electrons are taken out as a received light output.

  By the way, the light receiving output after weighing must store information on the amount of received light. Therefore, when configuring a passive sensor that does not use a light emitting source, the amount of fluctuation in the amount of received light is reflected in the received light output after weighing by keeping the amount of unnecessary charge weighed after evaluating the amount of received light constant. Adopt the configuration. In the case of configuring an active sensor using a light source, a period during which the light source is turned on (hereinafter referred to as “lighting period”) and a period during which the light source is turned off (hereinafter referred to as “light-out period”) are provided. The amount of received light during the extinguishing period is evaluated, and unnecessary charges are removed from the electric charge obtained during the lighting period. With this operation, the amount of unnecessary charges corresponding to ambient light such as natural light and illumination light can be removed from the charge obtained during the lighting period, and the dynamic range for the light emitted from the light source is substantially expanded. Will be.

  In the above-described operation, it is assumed that the unnecessary charge weighing operation is performed only once, and the amount of unnecessary charge is determined only by the height of the potential barrier B1, but the amount of unnecessary charge is measured by the charge separation unit D2. It can also be adjusted by changing the number of times to do. That is, the capacitance of the charge separation unit D2 is kept constant, and after weighing in the charge separation unit D2 in the state of FIG. 2 (e), the electrons of the charge separation unit D2 are discarded, and further, the state of FIG. 2 (d) The amount of unnecessary charge is adjusted by repeating the operation of returning the electrons of the charge storage unit D3 to the charge separation unit D2 and weighing the electrons in the charge separation unit D2 in the state of FIG. Is possible.

  In the operation shown in FIG. 2, when the unnecessary charge is weighed by the charge separation unit D2, the voltage applied to the barrier control electrode 14c or the voltage to be applied to the separation electrode 14a is applied after flowing the charge into the charge separation unit D2. Although it is adjusted, after the capacitance of the charge separation part D2 is determined by adjusting the voltage applied to the barrier control electrode 14c or the voltage applied to the separation electrode 14a, the charge may flow into the charge separation part D2. .

In the following, as an example of configuring an active sensor, as shown in FIG. 4, a configuration in which light is emitted from a light source 2 into a target space, and light from the target space is received by a light detection element 1 as signal light. Is taken as an example, and the case where ambient light such as natural light or illumination light is mixed in the light received by the light detection element 1 is assumed to obtain a light reception output by reducing the components of the environmental light. Therefore, the amount of electrons weighed as unnecessary charges is set so as to reflect the amount of ambient light received. The light reception output of the light detection element 1 is given to the light reception processing circuit 3, and desired information is extracted from the light reception output. The operations of the light detecting element 1, the light emitting source 2, and the light receiving processing circuit 3 are controlled by a timing signal output from the timing control circuit 4. That is, the timing control circuit 4 alternately repeats the lighting period for turning on the light source 2 and the extinguishing period for turning it off so that the light detection element 1 and the light receiving processing circuit 3 perform the following operations in the lighting period and the extinguishing period. Is given a timing signal. That is, in the configuration shown in the figure, the light receiving processing circuit 3 and the timing control circuit 4 constitute a signal processing unit. The signal processing unit may be configured by a microcomputer that executes an appropriate program.

  In the following, the operation of weighing a desired amount of unnecessary charges without weighing them once will be described. In this operation, when the amount of unnecessary charge to be discarded is Qg, Qg is not discarded at a time but is discarded at k times by Qg / k (k is a positive integer). The discarding of unnecessary charges includes an operation that repeats a plurality of times without leaving time and an operation that repeats a plurality of times with a time interval, and the following description exemplifies a case where both are mixed.

  In other words, a period in which one weighing operation for weighing and discarding unnecessary charges is repeated m times is a disposal period, and the disposal period is repeated n times in the lighting period (m is a positive integer of 2 or more, n is 1) More positive integers). This relationship is shown in FIG. In FIG. 5, the extinguishing period Pd and the lighting period Pb are shown once, but the extinguishing period Pd and the lighting period Pb are alternately repeated. In the operation shown in FIG. 5A, the lighting period Pb is provided with n (2 times in the illustrated example) discard periods Pt, and each discard period Pt is m times (in the illustrated example 5 times). Unnecessary charge weighing operation W (the operation of separating and discarding unnecessary charges is called the weighing operation W hereinafter) is performed. That is, the weighing operation W is performed n × m times during the lighting period Pb. In each discard period Pt, unnecessary charges are discarded so that only an amount of electrons corresponding to the amount of received signal light remains. Therefore, the amount of unnecessary charges discarded by one weighing operation W is an amount obtained by dividing the amount of unnecessary charges discarded in the disposal period Pt into m equal parts. Further, the amount of unnecessary charges discarded in one weighing operation W is set according to the amount of received light in the extinguishing period Pd. That is, k = m in the operation described below.

  First, an advantage of weighing the unnecessary charge by dividing it into a plurality of times instead of weighing the unnecessary charge once will be described. In general, the charge amount (electron amount) Q stored in correspondence with the amount of light received by the light detection element is proportional to the area S of the photoelectric conversion unit D1 (charge storage unit D3) and the light reception time t. If the amount of charge accumulated per unit time in a unit area is q, then Q = q × S × t. Since the configuration in which the height of the potential barrier B1 is determined by the amount of charge accumulated in the extinguishing period Pb is adopted, the height ΔV of the potential barrier B1 is a function of the amount of charge Q accumulated in the extinguishing period Pb. , ΔV (Q) = α × q × S × t. Here, α is a coefficient for converting the charge amount Q into the height ΔV (Q) of the potential barrier B1. The amount of unwanted charges weighed at a time can be adjusted by changing the height ΔV (Q) of the potential barrier B1.

  It can be seen that any of the four variables can be changed to change the height ΔV (Q) of the potential barrier B1. Here, the time t is in the order of ms as described in the first embodiment, and the time required for weighing is in the order of μs. Therefore, if the time t for determining the amount of unnecessary charges can be shortened, the extinction period Pd can be shortened and the percentage of time available for collecting spatial information can be increased. However, if the time t is shortened, the amount of charge Q that can be weighed at one time is reduced. Therefore, a desired amount of unnecessary charges is discarded by increasing the number of times of weighing.

  Note that it is conceivable to increase at least one element of the coefficient α, the charge amount q, and the area S in order to reduce the charge amount Q that can be weighed at one time while shortening the time t. Increasing the coefficient α increases noise components such as shot noise, leading to an increase in error, and the charge amount q is difficult to adjust because it is determined by the specifications of the light detection element and the intensity of received light. If the area S is increased, the problem of an increase in size arises. Therefore, the coefficient α, the charge amount q, and the area S are not changed.

  The amount of unnecessary charge discarded in one weighing operation W is determined by the amount of charge accumulated in the extinguishing period Pd as described above, and this amount of charge depends on the received light intensity of the ambient light and the length of the extinguishing period Pd (time t ) Function. That is, the amount of unnecessary charge discarded in one weighing operation W is defined to increase as the extinguishing period Pd becomes longer (actually, it is defined by a linear function or a cubic function). Therefore, as described above, if the amount of unnecessary charges to be discarded in the disposal period Pt is Qg, and the amount of unnecessary charges discarded in one weighing operation W is Qg / m, the amount of charges Qg is reduced in one time. The length of the extinguishing period Pd is 1 / m with respect to the length of the extinguishing period required for weighing. That is, by adopting a configuration in which the weighing operation W is performed m times, the length of the turn-off period Pd when weighing a desired amount of unnecessary charges is reduced to 1 / m.

  According to the above-described operation, the turn-off period Pd is shortened, while the time required for the weighing operation W is increased by the number of times of the weighing operation W, but the turn-off period is on the order of ms, and the time of the weighing operation W is Since it is on the order of μs, the total time of the turn-off period Pd and the turn-on period Pb can be shortened as compared with the case of weighing once. For example, assuming that the extinguishing period of 7 ms is required when the unnecessary charge is weighed once, the extinguishing period can be shortened to 1 ms when the unnecessary charge is weighed 7 times. That is, even if it takes 100 μs for one weighing operation W, the total of the turn-off period Pd and the turn-on period Pb is less than 2 ms.

  As described above, the time until the light receiving output is taken out can be reduced by shortening the extinguishing period Pd compared with the case where the unnecessary charges are weighed once, and weighing the desired amount of unnecessary charges by a plurality of weighing operations W. It can be shortened. In addition, even when the intensity of the ambient light received during the extinguishing period Pd is relatively large, the amount of electrons generated by the photoelectric conversion unit D1 is reduced by shortening the extinguishing period Pd, and as a result, the photodetecting element 1 Is prevented from being saturated.

  In the above-described operation, the weighing operation W is performed m times during the disposal period Pt, and the disposal period Pt is provided n times during the lighting period Pb. Here, the lighting period Pb is set to a fixed time every time. By performing the weighing operation W a plurality of times for each disposal period Pt, the effect of shortening the extinguishing period Pd is enhanced, but the number of weighing operations W in the lighting period Pb may be set appropriately. For example, it is possible to provide the disposal period Pt only once in the lighting period Pb and perform the weighing operation W a plurality of times during the disposal period Pt. Moreover, it is also possible to set it as the operation | movement which performs the weighing operation W once for each disposal period Pt.

  However, from the viewpoint of the received light intensity of the ambient light, it is desirable to provide the discard period Pt a plurality of times in the lighting period Pb. In particular, when the amount of light received during the extinguishing period Pd is large (that is, when the received light intensity of the ambient light is large), it is desirable to increase the number of discard periods Pt during the lighting period Pb. The reason for this will be described with reference to FIG.

  Now, assuming that the disposal period Pt is provided four times in the lighting period Pb, a certain amount of unnecessary charge is discarded in each disposal period Pt in the lighting period Pb from time t0 to time t2, as shown in FIG. Therefore, the electrons accumulated in the charge accumulation unit D3 increase as a whole by accumulating electrons while repeatedly decreasing every discard period Pt.

  In such an operation, if the amount of unnecessary charges discarded in one discard period Pt and the number of discard periods Pt are appropriate, the amount of electrons accumulated in the charge accumulation unit D3 is saturated with the photodetecting element 1. Although the level L1 is not exceeded, but there is more ambient light than expected, a phenomenon occurs in which the amount of electrons in the charge storage unit D3 exceeds the saturation level L1 before the lighting period Pb ends at time t2. (In FIG. 6A, the saturation level L1 is exceeded at time t3). When the saturation level L1 is exceeded, the information of the signal light is lost from the light receiving output extracted from the light detecting element 1.

  Therefore, it is necessary to detect whether the saturation level L1 has been reached during the lighting period Pb. In order to detect that the saturation level L1 has been reached, for example, the discard period Pt may be set so that the lighting period Pb ends after a fixed time has elapsed since the last discard period Pt in the lighting period Pb. The time from the last discard period Pt to the end of the lighting period Pb is set to the time between adjacent discard periods Pt.

  Assuming that four discard periods Pt are set in the lighting period Pb as in the above example, when saturation occurs between the third discard period Pt and the fourth discard period Pt, Since unnecessary charges are discarded in the fourth discard period Pt, if the received light output is taken out at the end of the discard period Pt, the received light output becomes smaller than the saturation level L1, and saturation cannot be detected. On the other hand, as described above, if the lighting period Pb ends after a certain time has elapsed from the end of the discard period Pt, and the light reception output is taken out at that time, the light reception output reaches the saturation level L1. From this, it is possible to detect that saturation has been reached in the lighting period Pb.

  Even when the amount of electrons in the charge storage unit D3 exceeds the saturation level L1 by time t2, when the number of discard periods Pt is increased, it can be adjusted so as not to exceed the saturation level L1 without changing the lighting time Pb There is. For example, as shown in FIG. 6A, when the weighing period Pt is provided four times in the lighting period Pb from time t1 to time t2, the amount of electrons accumulated in the charge accumulation unit D3 is the fourth weighing. Even when the saturation level L1 is exceeded immediately before reaching the period Pt, if the weighing period Pt in the lighting period Pb is increased to five times as shown in FIG. 6B, the amount of electrons accumulated in the charge accumulation unit D3 is timed. It may be possible not to exceed the saturation level L1 by t3. In other words, by setting the time interval of the discard period Pt to be relatively short, if unnecessary charges are discarded before the light detecting element 1 is saturated, the light reception of electrons corresponding to the signal light is performed even in an environment with a lot of ambient light. As a result, it is possible to increase the ratio of the output to the output, and as a result, it is possible to extract the received light output having the information of the signal light even when the received light intensity of the ambient light is high.

  The number of weighing periods Pt in the light reception period Pb is determined using at least the light reception output of the light reception amount and the light reception output in the extinguishing period Pd obtained from the light detection element 1. A procedure for determining the number of weighing periods Pt will be described. In addition, since a plurality of weighing operations W are collectively performed in the weighing period Pt, the operation in one weighing period Pt is also an operation for discarding unnecessary charges, and the weighing period Pt is performed a plurality of times in the lighting period. The provision of the time interval in the weighing period Pt corresponds to the operation of discarding unnecessary charges being performed a plurality of times with a time interval.

  The amount of received light during the extinguishing period Pd reflects the intensity of light received from the ambient light. Therefore, if the amount of received light during the extinguishing period Pd is determined, the amount of unnecessary charge accumulated during the light receiving period Pb can be estimated. Further, the amount of charge discarded in one weighing period Pt is determined by the amount of light received during the extinguishing period Pb. Therefore, when the amount of light received during the extinguishing period Pb is obtained, the tendency of the amount of electrons accumulated in the light receiving period Pb over time can be known. At this time, the amount of electrons corresponding to the signal light is unknown, but it can be considered that the amount of electrons corresponding to the signal light increases almost uniformly in the light receiving period Pb, and is discarded in consideration of the saturation level L1. The amount of unnecessary charges to be estimated can be estimated, and a candidate value can be obtained for the number of weighing periods Pt.

  If the candidate value is determined, whether or not the number of weighing periods Pt is properly set is evaluated by monitoring the magnitude of the light reception output when the operation is performed with the candidate value in the light reception processing circuit 3. In this evaluation, an upper limit value and a lower limit value to be compared with the light reception output are set, and the number of weighing periods Pt is adjusted by comparing the light reception output with the upper limit value and the lower limit value.

  For example, if the light receiving output exceeds the upper limit value, the number of weighing periods Pt is increased by one with respect to the candidate value to be a new candidate value, and if it is below the lower limit value, the number of weighing periods Pt is set to the candidate value. Decrease once and use for new candidate values. By repeating this process, the received light output amount can be maintained at an appropriate value between the upper limit value and the lower limit value. When the received light output is not between the upper limit value and the lower limit value, the received light output is not adopted, and the received light output of the period is interpolated or substituted with the received light output of another period.

  Note that, instead of determining the candidate value for the number of times of the weighing period Pt by the amount of light received during the extinguishing period Pd, a predetermined default value may be used as the candidate value. In this case, the amount of received light during the extinguishing period Pd is used only for determining the amount of unnecessary charges to be discarded in one weighing operation W. Note that the number of weighing operations W in one weighing period Pt is not changed.

  In order to determine the number of weighing periods Pt in the light receiving period Pb, the light receiving processing circuit 3 performs the above-described processing based on the received light amount and the light receiving output in the extinguishing period Pd, and the weighing period Pt determined in the light receiving processing circuit 3. The timing control circuit 4 controls the operation of the photodetecting element 1 according to the number of times. Note that the process of adjusting the number of weighing periods Pt so that the light reception output falls between the upper limit value and the lower limit value does not need to be performed for each light reception period Pb, and an appropriate number of light reception periods Pb depending on the use environment. You should do it every time. That is, a standard frequency may be set as a default value, and the adjustment frequency may be increased in a place where the change in the ambient light is large, and the adjustment frequency may be reduced in a place where the change in the ambient light is small.

  When the light reception output reaches the saturation level during the lighting period Pb, the light reception output obtained during the lighting period Pb cannot be used for detecting spatial information. Therefore, this light reception output is discarded, and an appropriate light reception output is obtained in the next and subsequent lighting periods Pb by changing the amount of unnecessary charges separated in the next lighting period Pb. Here, as an example of a technique for changing the amount of unnecessary charges, the above example shows an example in which the number of weighing periods Pt is changed. However, if the extinguishing period Pd is lengthened, the charges discarded in one weighing period Pt. The amount increases. In addition, when sensitivity control electrodes 17a to 17h (see FIG. 12) described later are provided, the sensitivity control electrode 17a that applies a voltage for forming a potential well that accumulates charges as the photoelectric conversion unit D1 in the extinction period Pd. If the number of ~ 17h is changed, the light receiving area is substantially changed. Therefore, by increasing the light receiving area in the extinguishing period Pd, the amount of charge discarded in the weighing period Pt can be increased. .

  As is apparent from the above-described principle, for the purpose of performing the weighing operation W so as not to exceed the saturation level L1, the weighing operation W is performed one by one, rather than performing a plurality of weighing operations W together in the weighing period Pt. It is more desirable to carry out the operation over the entire lighting period Pb. That is, as shown in FIG. 5B, it is desirable to provide a time interval between the weighing operations W every time during the lighting period Pb. Further, it is desirable that the time interval is set to be shorter as the light reception output in the extinguishing period Pd is larger. If this technique is employed, the rate of increase in the amount of charge accumulated in the charge accumulation unit D3 is reduced, and the amount of accumulated charge is less likely to reach the saturation level L. That is, the effect of suppressing the saturation of the charge storage portion D3 is enhanced.

  Incidentally, the amount of unnecessary charges to be discarded in one discard period Pt is calculated so as to leave all of the amount of electrons generated by the signal light, but a plurality of weighing operations W are performed in one discard period Pt. Since the amount of unnecessary charges discarded in one weighing operation W is determined by the amount of received light in the extinguishing period Pb, it is difficult to leave the entire amount of electrons corresponding to the signal light and only that amount of electrons. It is. Therefore, an amount of electrons slightly larger than the total amount of electrons corresponding to the signal light is left as a margin. However, in order to increase the dynamic range with respect to the signal light, it is necessary to reduce the amount of electrons as much as possible.

  The amount of unnecessary charge discarded in one weighing operation W is determined by the amount of received light in the extinguishing period Pd, and this amount of received light is a function of the length (duration) of the extinguishing period Pd. If the total amount of unnecessary charges to be discarded in the period Pt is calculated, the amount of unnecessary charges to be discarded in one weighing operation W can be determined so as to reduce the margin by changing the length of the extinguishing period Pd. Is possible.

  If the extinguishing period Pd is shortened, the amount of unnecessary charges discarded in one weighing operation W is small, so that the margin is reduced, and the extinguishing period Pd is performed so that one weighing operation W is performed in one discarding period Pt. It is also possible to reduce the margin by increasing the length. However, when the former operation is adopted, the number of weighing operations W increases, so that the proportion of the weighing operation W in the lighting period Pb increases. When the latter operation is adopted, the extinguishing period Pb becomes long. Regardless of which configuration is employed, the amount of information obtained from signal light per unit time is reduced.

  On the other hand, an upper limit and a lower limit are set for the number of weighing operations W in one disposal period Pt, and an upper limit and a lower limit are set for the extinguishing period Pb. Therefore, the extinction period Pd can be made relatively short by determining the amount of unnecessary charges to be discarded in one weighing operation W and the number of weighing operations W in one disposal period Pt so that the margin is minimized. However, it is possible to set conditions in the discard period Pt so that the number of weighing operations W does not become extremely large.

  By the way, the amount of unnecessary charges discarded in the disposal period Pt is calculated as the product of the number of weighing operations W in the disposal period Pt and the amount of unnecessary charges discarded in one weighing operation W. The amount of unnecessary charge discarded by W is determined by the amount of received light in the extinguishing period Pd. The amount of light received during the extinguishing period Pd is determined by the received light intensity of the ambient light and the length (duration) of the extinguishing period Pd.

  In order to set the conditions for the discard period Pt, a default value is set for the length of the extinguishing period Pd, and first, the received light intensity of the ambient light is estimated using the received light quantity during the extinguishing period Pd of the default value time. The total amount of unnecessary charges to be discarded is determined for each disposal period Pt. Further, the amount of unnecessary charges to be discarded in one weighing operation W is determined using the amount of received light in the extinguishing period Pd having a default length.

  Next, the quotient and the remainder are obtained by dividing the total amount of unnecessary charges to be discarded for each discard period Pt by the amount of unnecessary charges to be discarded in one weighing operation W. If the quotient is between the upper limit and the lower limit of the number of times of the weighing operation W in the disposal period Pt, the amount of unnecessary charges to be discarded in one weighing operation W is determined so as to reduce the remainder, and according to this amount The length of the turn-off period Pd is calculated backward. If the length of the turn-off period Pd obtained from the reverse calculation result is within the range between the upper limit and the lower limit, the turn-off period Pd is set to the length of the reverse calculation result.

  When the number of weighing operations W or the length of the extinguishing period Pd deviates from the range between the upper limit and the lower limit, the frequency or the length is adjusted so as to be within the range between the upper limit and the lower limit. To do.

  In addition, an image sensor is configured by providing a plurality of photoelectric conversion units D1, and if the above-described control is performed on all the photoelectric conversion units D1, the processing load increases. Therefore, unnecessary charges separated in one weighing operation W in advance. However, it is effective to shorten the extinguishing period Pd and increase the number of times of the weighing operation W so as to be smaller than the specified value over all the photoelectric conversion units D1. If the amount of unnecessary charge to be weighed by one weighing operation W is reduced, the number of times of the weighing operation W is increased, but the time required for one weighing operation W is very small. There is little increase in the total time from receiving light to discarding unnecessary charges and obtaining light reception output. Rather, since the turn-off period Pd is shortened, the time for detecting the spatial information in the turn-on period Pb is relatively increased.

  In an image sensor including a plurality of photoelectric conversion units D1, the number of weighing operations W may be set equal in each photoelectric conversion unit D1 in order to simplify the control of the operation timing by the output of the timing control circuit 4. desirable. Therefore, as described above, in order to reduce the amount of unnecessary charges separated by one weighing operation W, it is desirable to set the number of times of the weighing operation W in the disposal period Pt as much as possible.

  By the way, when unnecessary charges are weighed and discarded as described above, most of the received light output becomes a component corresponding to the signal light. However, if the received light intensity of the signal light is large, the light detection element 1 is saturated, and conversely, If the received light intensity is low, the S / N ratio decreases due to the influence of internal noise such as shot noise. In the above-described operation example, the amount of unnecessary charge to be discarded is adjusted while keeping the length of the lighting period Pb constant. However, if the received light amount of the signal light is adjusted on the light receiving side, the length of the lighting period Pb is set. It is necessary to adjust.

  Accordingly, as shown in FIG. 7A, the lengths of the lighting periods Pb1, Pb2, and Pb3 can be selected from a plurality of types, and the lengths of the lighting periods Pb1, Pb2, and Pb3 are set so as to obtain an appropriate light reception output. It is conceivable to expand the dynamic range for the signal light by selecting. That is, the lengths of the lighting periods Pb1, Pb2, and Pb3 are determined so that a light receiving output as large as possible can be obtained within a range in which the light detecting element 1 is not saturated. When this technique is adopted, the length of the lighting periods Pb1, Pb2, and Pb3 changes, so that the amount of unnecessary charges to be discarded also changes.

  If the lengths of the lighting periods Pb1, Pb2, and Pb3 are changed under an environment where the ambient light and the signal light have the same conditions, the lighting periods Pb1, Pb2, and Pb3 are long when unnecessary charges are not discarded. The amount of electric charge corresponding to ambient light and signal light also increases. Therefore, similarly to the other operation examples described above, it is necessary to discard unnecessary charges so that saturation does not occur before the unnecessary charges are discarded.

  Since the amount of unnecessary charges in one weighing operation W increases or decreases according to the amount of ambient light received in the extinguishing periods Pd1, Pd2, and Pd3, the extinguishing period depends on the length of the lighting periods Pb1, Pb2, and Pb3. If the lengths of Pd1, Pd2 and Pd3 are changed, the amount of unnecessary charges weighed at a time can be adjusted according to the lighting periods Pb1, Pb2 and Pb3.

  In other words, the amount of unnecessary charge accumulated in the lighting periods Pb1, Pb2, and Pb3 is proportional to the length of the lighting periods Pb1, Pb2, and Pb3, and the amount of unnecessary charge that is discarded in one weighing operation W is the light-out period Pd1. , Pd2, and Pd3 are proportional to the amount of received light, so that the same number of discard periods Pt are provided in the lighting periods Pb1, Pb2, and Pb3 regardless of the length of the lighting periods Pb1, Pb2, and Pb3. , Pb2, Pb3 and the length of the extinguishing periods Pd1, Pd2, Pd3 are set in a proportional relationship, the amount of unnecessary charges to be discarded can be adjusted appropriately. However, even if the lighting periods Pb1, Pb2, and Pb3 are different, the number of the discard periods Pt in the lighting periods Pb1, Pb2, and Pb3 needs to be equal. Therefore, the time interval of the discard periods Pt is set to be equal to that of the lighting periods Pb1, Pb2, and Pb3. Adjust according to the length.

  In the above-described operation, the lengths of the extinguishing periods Pd1, Pd2, and Pd3 are changed according to the lengths of the lighting periods Pb1, Pb2, and Pb3. However, as shown in FIG. 7B, the lighting periods Pb1, Pb2, and Pb2, respectively. Regardless of the length of Pb3, the length of the extinguishing period Pd may be kept constant, and the number of weighing operations W in one weighing period Pt may be changed according to the length of the lighting periods Pb1, Pb2, and Pb3. Since the amount of unnecessary charges discarded during the weighing operation W is determined by the amount of received light in the extinguishing period Pd, it does not change even if the lighting periods Pb1, Pb2, and Pb3 are different. Therefore, the number of times of the weighing operation W in the discarding period Pt is changed every lighting period Pb1, Pb2, Pb3.

  In this operation, the amount of unnecessary charges discarded in one discarding period Pt is adjusted according to the length of the lighting periods Pb1, Pb2, and Pb3. Therefore, the length of the extinguishing periods Pd1, Pd2, and Pd3 is substantially reduced. Functions in the same manner as adjusting the. However, since the amount of unnecessary charges to be discarded in the discard period Pt is an integral multiple of the amount of unnecessary charges to be discarded in one weighing operation W, the extinguishing period Pd1 depends on the length of the lighting periods Pb1, Pb2, Pb3. , Pd2, and Pd3, the amount of components other than the signal light may slightly increase in the received light output.

  In the operation in which the weighing operation W is performed a plurality of times in the lighting period Pb, the amount of unnecessary charges discarded in one weighing operation W is reduced as compared with the operation in which the weighing operation W is performed only once in the lighting period Pb. As a result, the turn-off period Pd is shortened, so that the total time of the turn-off period Pb and the turn-on period Pb can be shortened. In addition, by providing a plurality of discard periods Pt in the lighting period Pb, it is possible to accumulate electrons corresponding to the signal light while maintaining a state that does not exceed the saturation level L1 even when there is a lot of ambient light.

  On the other hand, in the case where a plurality of discard periods Pt are provided in the lighting period Pb, the amount of unnecessary charges discarded in one discard period Pt is not discarded as a component corresponding to signal light as unnecessary charges. Therefore, residual unnecessary charges may be accumulated while repeating the discard period Pt a plurality of times. That is, the amount of unnecessary charges discarded in one discarding period Pt is ideally defined so that only an amount of electrons corresponding to the signal light remains, but in practice, an amount corresponding to the signal light Since residual electrons other than electrons are generated, the residual electrons generated for each discard period Pt are accumulated while the discard period Pt is repeated, and the light reception output includes a component of residual electrons in addition to the component corresponding to the signal light. .

  That is, as shown in FIG. 8, the amount of electrons V1 accumulated up to each discarding period Pt in the lighting period Pb is the sum of the amount of unnecessary charges V2 to be discarded and the amount of electrons V3 corresponding to the signal light. In addition to the electrons corresponding to the signal light, the remaining electrons (charge amount V4) are included in the electrons after the unnecessary charges are discarded. Residual electrons are mostly generated by internal noise such as shot noise, and cannot be estimated from the amount of received light in the extinguishing period Pd. However, although the amount of residual electrons for each discard period Pt due to shot noise or the like varies with the passage of time, it becomes an almost constant amount on average.

  Residual electrons as described above are generated every discard period Pt and accumulated during the lighting period Pb. Therefore, when the discard period Pt is repeated in the lighting period Pb, it is considered that the amount of residual electrons eventually reaches the amount of unnecessary charges discarded in one weighing operation W. Since the average value of the amount of residual electrons can be estimated as described above, the number of disposal periods Pt until the amount of residual electrons reaches the amount of unnecessary charges discarded in one weighing operation W is estimated. Can do.

  Thus, by increasing the number of weighing operations W by one each time the number of discard periods Pt reaches the estimated number, residual electrons can be significantly reduced. In addition, this operation can suppress a decrease in dynamic range with respect to signal light due to the influence of residual electrons.

  In the operation of performing the weighing operation W a plurality of times in the lighting period Pb, the amount of unnecessary charges to be discarded is estimated using the received light quantity in the extinguishing period Pd. 1 is optimally adopted in the configuration of this embodiment. Even in each of the embodiments described below, electrons corresponding to the amount of received light in the extinguishing period Pd are light. If a configuration for taking out the detection element 1 is added, it can be adopted.

  Further, the light extinction period Pd for estimating the amount of unnecessary charge does not have to be provided alternately with the lighting period Pb, and the amount of unnecessary charge estimated in one light extinction period Pd is applied in a plurality of lighting periods Pb. Also good. In this case, since the time interval between the adjacent lighting periods Pb can be shorter than the extinguishing period Pb, the ratio of the period for receiving the signal light to the unit time is increased, and as a result, the space of the target space is increased. The period for detecting information can be increased. The relationship between the turn-off period Pd and the turn-on period Pb can be set similarly in the embodiments described below.

(Embodiment 2)
In the first embodiment, the technique for adjusting the amount of electrons weighed as unnecessary charges according to the amount of received light has been described. However, in the technique described in the first embodiment, the amount of received light must be evaluated by an external circuit of the light detection element. Therefore, a circuit for controlling the potential barrier B1 in the external circuit is required. That is, the scale of the external circuit is increased. This embodiment eliminates the need for an external circuit for controlling the potential barrier B1 by providing a function of automatically changing the amount of electrons to be weighed as unnecessary charges in accordance with the amount of received light. is there.

As a configuration for the photodetecting element 1 to automatically change the amount of unnecessary charges, in this embodiment, as shown in FIG. 9A, a well is formed on the main surface of the element forming layer 11 separately from the well 12. 12 is provided with a holding well 15 having the same conductivity type and a high impurity concentration (that is, the holding well 15 has a conductivity type of n ⁺ ), and a holding electrode 14d is interposed in the holding well 15 via the insulating layer 13. Are facing each other. In the element formation layer 11, the gate electrode 14 e is opposed to the region between the well 12 and the holding well 15 through the insulating layer 13. The holding electrode 14d is electrically connected to the barrier control electrode 14c, and regions corresponding to the holding electrode 14d and the gate electrode 14e in the element formation layer 11 are shielded from light by the light shielding film 16.

By the way, since the n ^{+ -type} holding well 15 is surrounded by the p-type element formation layer 11, a potential well for electrons is formed in the holding well 15 similarly to the well 12. However, since the holding well 15 has an impurity concentration higher than that of the well 12, the holding well 15 is not applied to any of the separation electrode 14a, the storage electrode 14b, the barrier control electrode 14c, and the holding electrode 14d. A potential well deeper than the well 12 is formed in 15. The potential well formed in the holding well 15 functions as a charge holding unit D4 that holds electrons.

  As the amount of electrons held in the holding well 15 increases, the potential of the holding electrode 14d decreases, and the potential of the barrier control electrode 14c connected to the holding electrode 14d also decreases. If the potential of the barrier control electrode 14c decreases, the potential barrier B1 increases and the capacitance of the charge separation unit D2 increases. That is, if the amount of electrons held in the holding well 15 is increased as the ambient light increases, the amount of electrons that can be separated as unnecessary charges can be increased according to the ambient light. Regardless, the dynamic range for the signal light can be kept substantially constant.

  In order to increase or decrease the amount of electrons held in the holding well 15 in accordance with the increase or decrease in the ambient light, the photoelectric conversion unit D1 transfers and holds the electrons generated when the ambient light is irradiated to the holding well 15 Is required. That is, a period for transferring the charges generated in the photoelectric conversion unit to the holding well 15 is provided. Since the holding well 15 is shielded from light by the light shielding film 16, the amount of electrons held in the holding well 15 does not change even when the element forming layer 11 or the well 12 is irradiated with light.

  By the way, in this embodiment, since the barrier control electrode 14c is connected to the holding electrode 14d, the height of the potential barrier B1 corresponding to the barrier control electrode 14c cannot be arbitrarily controlled. The length is determined by the amount of electrons held in the holding well 15. As described above, since the height of the potential barrier B1 corresponding to the barrier control electrode 14c cannot be arbitrarily controlled, the height of the potential barrier B1 as shown in FIGS. 2A to 2D described in the first embodiment. I can't adjust it. Therefore, in the present embodiment, a technique for adjusting the potentials of the charge separation unit D2 and the charge storage unit D3 is adopted, and electrons are moved in the same procedure as in the first embodiment.

  This will be described in more detail. As in the first embodiment, a potential well formed in the well 12 in a state where no voltage is applied to the separation electrode 14a and the storage electrode 14b is used as the photoelectric conversion unit D1. Further, a drain 23 (see FIG. 15) is provided adjacent to the holding well 15, and the electrons accumulated in the holding well 15 can be discarded. First, electrons remaining in the well 12 and the holding well 15 are discarded. In this state, no voltage is applied to any of the separation electrode 14a, the storage electrode 14b, the barrier control electrode 14c, the holding electrode 14d, and the gate electrode 14e, and the well 12 has a potential well similar to that shown in FIG. The potential well is formed and functions as the photoelectric conversion unit D1. At this time, the light source is not turned on, and only ambient light is incident on the photoelectric conversion unit D1. Therefore, the electrons generated in the photoelectric conversion unit D1 during this period correspond to the amount of ambient light received.

  When electrons in a period from when the electrons in the well 12 and the holding well 15 are discarded until a predetermined time elapses are accumulated in the photoelectric conversion unit D1 as an amount of electrons corresponding to the amount of received ambient light, The electrons are transferred to the holding well 15. That is, the holding well 15 holds an amount of electrons corresponding to the ambient light during the extinguishing period when no light is emitted from the light source. When electrons are transferred from the photoelectric conversion unit D1 to the holding well 15, a positive voltage is applied to the gate electrode 14e to lower the potential barrier B2 between the photoelectric conversion unit D1 and the holding well 15. Further, a positive voltage is applied to the separation electrode 14 a and the storage electrode 14 b to raise the potential of the photoelectric conversion unit D 1 higher than the potential of the holding well 15. By this operation, electrons can be moved from the well 12 to the holding well 15.

  Note that the amount of electrons transferred to the holding well 15 only needs to correspond to the amount of light received during the extinguishing period of the light emitting source, so that all the electrons generated by the photoelectric conversion unit D1 need to flow into the holding well 15. Rather, the amount of electrons moved from the well 12 to the holding well 15 only needs to correspond to the amount of light received by the photoelectric conversion unit D1 during the light-emitting source extinguishing period. When the charge corresponding to the light-emitting source extinction period is held in the holding well 15, the height of the potential barrier B1 formed corresponding to the barrier control electrode 14c is determined as shown in FIG. That is, the capacity of the charge separation unit D2 is determined. If the amount of electrons flowing into the holding well 15 increases, the surface potential of the holding well 15 decreases, so that the potential of the holding electrode 14d also decreases following the decrease in the surface potential. As a result, the barrier control electrode 14c As a result, the voltage applied to the voltage decreases and the potential barrier B1 increases. Since no voltage is applied to the separation electrode 14a, the storage electrode 14b, and the gate electrode 14e during the period Ta in FIG. 11, the potentials of the barrier control electrode 14c and the holding electrode 14d are held in the charge holding unit D4. It depends on the amount of electrons that are being used.

  Since electrons remaining in the photoelectric conversion unit D1 after moving electrons from the photoelectric conversion unit D1 to the charge holding unit D4 are unnecessary, photoelectric conversion is performed using the drain 23 (see FIG. 15) provided adjacent to the well 12. The electrons remaining in the part D1 are discarded.

  Next, when the light source is turned on, light obtained by adding the ambient light and the signal light enters the photoelectric conversion unit D1. Here, since the potential barrier B1 corresponding to the amount of electrons held in the charge holding unit D4 is formed in the photoelectric conversion unit D1, an amount of electrons not exceeding the height of the potential barrier B1 is accumulated. That is, both the region corresponding to the separation electrode 14a and the region corresponding to the storage electrode 14b in the well 12 function as the photoelectric conversion unit D1, but in the same manner as the operation illustrated in FIG. 2B of the first embodiment. The well 12 is divided into two regions across the potential barrier B1.

  Of the two regions, the electrons accumulated in the charge separation unit D2 corresponding to the separation electrode 14a are not used and discarded, and the electrons accumulated in the charge accumulation unit D3 corresponding to the storage electrode 14b are used. Therefore, in the present embodiment, during the lighting period in which light is emitted from the light emitting source, the region corresponding to the storage electrode 14b in the well 12 substantially functions as the photoelectric conversion unit D1, and the charge storage unit D3 is photoelectrically operated. This is also used as the conversion unit D1.

  The voltage applied to the separation electrode 14a is not changed from the period Ta as in the period Tb in FIG. 11, but the electrons in the charge separation unit D2 are discarded as shown in FIG. 10B using the drain 23 (see FIG. 15). To do. Thereafter, a positive voltage is applied to the separation electrode 14a as in the period Tc of FIG. 11 and a negative voltage is applied to the storage electrode 14b, so that the potential of the charge separation portion D2 is increased as shown in FIG. Pull down. At this time, if the potential of the charge separation unit D2 is greatly lowered, the potential barrier B1 is also lowered, and electrons can flow into the charge separation unit D2 from the charge storage unit D3 (photoelectric conversion unit D1).

  Instead of lowering the potential of the charge separation unit D2, the potential of the charge storage unit D3 may be raised. However, in order for all the electrons in the charge storage unit D3 to flow into the charge separation unit D2, it is necessary to set the potential of the charge storage unit D3 to be equal to or higher than the potential of the potential barrier B1. Further, the potential of the charge separation unit D2 may be lowered and the potential of the charge storage unit D3 may be raised at the same time.

  After all the electrons in the charge storage portion D3 flow into the charge separation portion D2, the voltage applied to the separation electrode 14a and the storage electrode 14b is removed as in the period Td in FIG. At this time, the capacity of the charge separation unit D2 is determined, and as shown in FIG. 10D, among the electrons accumulated in the charge separation unit D2, the electrons exceeding the capacity of the charge separation unit D2 cross the potential barrier B1 and become charged. It flows into the accumulation part D3. That is, among the electrons generated in the photoelectric conversion unit D1, the capacitance of the charge separation unit D2 determined according to the amount of electrons held in the charge holding unit D4 (that is, the amount of electrons corresponding to the light-emitting source extinguishing period). A certain amount of electrons corresponding to is separated as unnecessary charges, and the electrons returned to the charge storage portion D3 are used as effective charges.

  As described above, in the present embodiment, the height of the potential barrier B1 is automatically adjusted inside the light detection element without using an external circuit, and the amount of unnecessary charges is determined according to the amount of received ambient light. Therefore, the dynamic range of the received light output with respect to the signal light can be kept substantially constant regardless of the amount of ambient light received.

  In the case of configuring an image pickup device in which a large number of photoelectric conversion units D1 are arranged, if the potential for determining the amount of unnecessary charges is controlled by an external circuit for each pixel, the configuration of the external circuit becomes very complicated. If a technique for automatically adjusting the amount of unnecessary charges according to the amount of ambient light received is employed, an external circuit for determining the amount of unnecessary charges is substantially unnecessary. In addition, when integrating an external circuit together with an image sensor on a semiconductor substrate, the relative area of the photoelectric conversion unit D1 occupying the semiconductor substrate decreases and S / N deteriorates. However, in this embodiment, an external circuit is substantially unnecessary. Therefore, high S / N can be obtained. Other configurations and operations are the same as those of the first embodiment.

  In this embodiment, the gate electrode 14e is used to control the timing of transferring electrons from the potential well as the photoelectric conversion unit D1 formed in the well 12 to the potential well as the charge holding unit D4 formed in the holding well 15. Although used, the gate electrode 14e may be omitted, and electrons may be transferred from the photoelectric conversion unit D1 to the charge holding unit D4 by controlling the voltage applied to the separation electrode 14a and the storage electrode 14b.

  For example, when a positive voltage is applied to the separation electrode 14a and the storage electrode 14b to form a potential well and electrons are accumulated in the photoelectric conversion unit D1, a negative voltage is applied to the separation electrode 14a and the storage electrode 14b. The electrons accumulated in the well 12 move toward the holding well 15. Note that by applying a negative voltage to the storage electrode 14b, the potential barrier between the well 12 and the holding well 15 is broken, and the movement of electrons from the well 12 to the holding well 15 is facilitated. Further, since a negative voltage is applied to the separation electrode 14a, the electrons accumulated in the well 12 are prevented from moving to the left in FIG. 9A.

  After electrons move from the well 12 to the holding well 15, a positive voltage is applied to the separation electrode 14 a and the storage electrode 14 b to form a potential well in the well 12. By such an operation, electrons can be transferred from the photoelectric conversion unit D1 to the charge holding unit D4 without using the gate electrode 14e.

  Further, instead of the configuration of FIG. 9A, as shown in FIG. 9B, the barrier control electrode 14c is directly electrically connected to the holding well 15 formed in the well 12 as the charge holding portion D4. Is more desirable. As shown in FIG. 9A, when the holding electrode 14d is provided in the holding well 15 via the insulating layer 13, both the barrier control electrode 14c and the holding electrode 14d are electrically separated from the other components. As time elapses, charges accumulate in the barrier control electrode 14c and the holding electrode 14d and the wiring connecting them. If such charges exist, the voltage applied to the barrier control electrode 14 c may not accurately reflect the charge amount of the holding well 15. In order to remove this type of charge, a configuration in which a reset switch for removing the charge between the barrier control electrode 14c and the holding electrode 14d can be considered. However, if the reset switch is provided, the apparatus is enlarged and manufactured. There is a risk of increasing costs.

  Therefore, in the configuration shown in FIG. 9B, a configuration in which the barrier control electrode 14c is directly electrically connected to the holding well 15 is employed. The wiring that directly connects the holding well 15 and the barrier control electrode 14c can be formed by a diffusion wiring. Further, when adopting a configuration in which the holding electrode 14d is connected to the holding well 15 without using the insulating layer 13, the metal wiring may be used.

  The well 12 is provided with a reset drain 100 adjacent to the holding well 15, and a reset electrode 14 r is provided on the main surface of the well 12 between the holding well 15 and the reset drain 100. A constant voltage for extracting electrons through the connection line 110 is applied to the reset drain 100. When a voltage is applied to the reset electrode 14r to form a channel between the holding well 15 and the reset drain 100, the holding well 15 The electrons accumulated in the drain are discarded through the reset drain 100.

  As described above, if a configuration in which the barrier control electrode 14c is directly electrically connected to the holding well 15 is adopted, when an appropriate voltage is applied to the reset electrode 14r to discard the electrons in the holding well 15, Since the charges on the barrier control electrode 14c and the wiring are also discarded at the same time, it is possible to remove the influence of the charges accumulated in the barrier control electrode 14c and the wiring, and as a result, it is possible to increase the weighing accuracy of unnecessary charges. In addition, this structure is employable also in Embodiment 3-5 demonstrated below. In the above-described configuration, the voltage applied to the barrier control electrode 14c is controlled by the charge holding unit D4. However, a configuration in which the voltage applied to the separation electrode 14a is controlled by the charge holding unit D4 can be adopted. .

(Embodiment 3)
In the present embodiment, similarly to the configuration of the second embodiment, by providing the charge holding unit D4, the capacity of the charge separation unit D2 is automatically set according to the amount of received ambient light. However, the intensity of light emitted from the light source during the lighting period of the light source is modulated with a modulation signal having a constant frequency, and the received light output corresponding to the received light amount at the timing synchronized with two sections having different phases in the modulation signal is extracted. A photodetecting element that can be used will be described. In the present embodiment, the waveform of the modulation signal is a sine wave, and the received light quantity in a section in which the phase is synchronized with 0 to 180 degrees (hereinafter referred to as section P0) and the section in which the phase is synchronized with 180 to 360 degrees (hereinafter, referred to as section P0). It is assumed that the received light output corresponding to the received light amount in the section P2) is taken out. The waveform of the modulation signal may be a rectangular wave, a triangular wave, or a sawtooth wave, and the interval for detecting the amount of received light may of course be outside the above range.

  Further, the present embodiment constitutes an image sensor in which a large number of cells 1 are arranged so that the light reception output of the above-described two sections can be extracted simultaneously every time one frame of light reception output is extracted from the image sensor. It is configured. In order to extract the light reception output of two sections in one frame, a configuration for detecting the amount of received light for each section and a structure for storing the light reception output for each section are required for one cell 1. Therefore, the photoelectric conversion unit D1 is provided separately from the charge separation unit D2 and the charge storage unit D3.

  This will be described in more detail. The photoelectric conversion unit D1 has a configuration in which a plurality (eight in the illustrated example) of sensitivity control electrodes 17a to 17h are arranged on a well (not shown) formed on the main surface of the element forming layer 11 via an insulating layer 13. Have. The well has a conductivity type different from that of the element formation layer 11, and is formed separately from the well 12 functioning as the charge separation portion D2 and the charge storage portion D3, and charges are transferred to the well 12 through the gate. Although desirable, the charge may be transferred by being formed continuously with the well 12 and controlling the potential. Of the eight sensitivity control electrodes 17a to 17h, the four sensitivity control electrodes 17a to 17d form a group corresponding to one section, and the remaining four sensitivity control electrodes 17e to 17h correspond to the other section. become. A control line 21a is connected to each of the sensitivity control electrodes 17a to 17h, and a voltage can be individually applied to each of the sensitivity control electrodes 17a to 17h. In addition, the site | part to which the connection line 21a and each sensitivity control electrode 17a-17h are connected is shown by x.

  The vertical direction in FIG. 12A corresponds to the vertical direction in the image sensor, and in the figure, only one cell 1 is shown in the vertical direction. That is, one cell 1 in the vertical direction includes eight sensitivity control electrodes 17a to 17h. In the figure, a part of the cell 1 adjacent to the one cell 1 in the horizontal direction is also shown. The sensitivity control electrodes 17a to 17h are continuous across the two cells 1 in the horizontal direction. A cell separation unit 20 is provided between the cells 1 adjacent in the horizontal direction to prevent crosstalk between the cells 1 in the horizontal direction. The cell isolation portion 20 is formed on the main surface side of the element formation layer 11 using a semiconductor having a conductivity type different from that of the element formation layer 11. In the illustrated example, four control lines 21a are arranged with the cell separation unit 20 interposed therebetween. Therefore, the area of the control line 21a occupying the photoelectric conversion unit D1 in the two cells 1 adjacent in the horizontal direction can be made equal, and the sensitivity of the photoelectric conversion unit D1 in the two adjacent cells 1 can be made equal. it can. In the vertical direction, the sensitivity control electrodes 17a to 17h at the same position in each cell 1 are connected to the same control line 21a.

  In the present embodiment, as described above, the photoelectric conversion unit D1 including the sensitivity control electrodes 17a to 17h is provided separately from the charge separation unit D2 and the charge storage unit D3, and the charge separation unit D2 and the charge storage unit D3. And the charge holding portion D4 are arranged side by side in the horizontal direction with respect to the sensitivity control electrodes 17a to 17h. Although not shown in FIG. 12, in the cell 1 on the right side of the two adjacent cells 1 in the horizontal direction, the charge separation unit D2, the charge storage unit D3, and the charge holding unit D4 are on the right side of the photoelectric conversion unit D1. Placed in the left cell 1. Further, the charge separation unit D2 and the charge storage unit D3 are provided for each group of sensitivity control electrodes 17a to 17h, and the charge holding unit D4 is shared by both groups constituting one cell 1. This is because the charge holding unit D4 holds an amount of electrons corresponding to the ambient light, and it can be considered that the ambient light does not change in both groups. With this configuration, the voltage applied to the barrier control electrode 14c is also equal in both groups, and the height of the potential barrier B1 is the same in both groups.

  In each group, the storage electrode 14b is provided adjacent to the sensitivity control electrodes 17c and 17f, and the electrons generated by the photoelectric conversion unit D1 can be transferred from the portion corresponding to the sensitivity control electrodes 17c and 17f to the charge storage unit D3. It is like that. Here, by adjusting the potential relationship between the photoelectric conversion unit D1 and the charge storage unit D3, electrons can be moved from the charge storage unit D3 to the photoelectric conversion unit D1. In addition, a gate electrode (not shown) may be disposed at a site between the photoelectric conversion unit D1 and the charge storage unit D3 to control the flow of charges between the photoelectric conversion unit D1 and the charge storage unit D3. .

  In each group, the separation electrode 14a is provided adjacent to the sensitivity control electrodes 17a and 17h. Further, the holding electrode 14d shared by both groups is disposed at a portion straddling the sensitivity control electrodes 17d and 17e. The separation electrode 14a, the storage electrode 14b, and the gate electrode 14e are each connected to the control line 21b, and the barrier control electrode 14c and the holding electrode 14d are connected through the connection line 22. That is, the separation electrodes 14a, the storage electrodes 14b, and the gate electrodes 14e provided in each group are connected to the control line 21b, and the charge separation unit D2, the charge storage unit D3, and the charge are connected using the three control lines 21b. The movement of electrons with respect to the holding part D4 is controlled. For the control line 21b and the connection line 22, the connection parts of the separation electrode 14a, the storage electrode 14b, the barrier control electrode 14c, the holding electrode 14d, and the gate electrode 14e are indicated by x.

  The voltage applied to the sensitivity control electrodes 17a to 17h is controlled to synchronize with a modulation signal that modulates the intensity of light projected from the light source. For example, a positive voltage is applied to the sensitivity control electrodes 17a to 17d and the sensitivity control electrode 17f in the section P0, and a positive voltage is applied to the sensitivity control electrode 17c and the sensitivity control electrodes 17e to 17h in the section P2. To do. When a positive voltage is applied to each of the sensitivity control electrodes 17a to 17h, a potential well for accumulating electrons is formed at a portion corresponding to each of the sensitivity control electrodes 17a to 17h in the cell.

  Therefore, when the voltage applied to the sensitivity control electrodes 17a to 17h is controlled as described above, in the section P0, electrons by light irradiation are accumulated in the portion corresponding to the sensitivity control electrodes 17a to 17d in the well. Further, in the section P2, electrons by light irradiation are accumulated at portions of the well corresponding to the sensitivity control electrodes 17e to 17h. That is, by controlling the voltage pattern applied to the sensitivity control electrodes 17a to 17h, the area in which electrons are generated by light irradiation is changed, and the sensitivity of the light detection element is substantially controlled. Is equivalent to

  In the section P0, the potential well is also formed in the part corresponding to the sensitivity control electrode 17f. Therefore, the electrons accumulated in the section P2 are held in the potential well, and in the section P2, the part corresponding to the sensitivity control electrode 17c is held. The formed potential well holds electrons accumulated in the section P0.

  Therefore, electrons by light irradiation can be accumulated for each section over a plurality of periods of the modulation signal (for example, if the modulation signal is 10 MHz and the period for generating electrons in the photoelectric conversion unit D1 is 15 ms). Even during the period in which electrons are held in the parts corresponding to the sensitivity control electrodes 17c and 17f, electrons are generated in the parts corresponding to the sensitivity control electrodes 17c and 17f, but the period in which the electrons are accumulated and the period in which the electrons are held. Since the area ratio for collecting electrons is 4: 1, the amount of held electrons reflects the amount of received light in each section of the modulation signal. In short, the amount of electrons corresponding to the section P0 and the section P2 can be held in the sensitivity control electrodes 17c and 17f, respectively.

  The electrons held in the parts corresponding to the sensitivity control electrodes 17c and 17f are transferred to the charge storage unit D3. In the transfer, a positive voltage is applied to the storage electrode 14b, and a negative voltage is applied to the sensitivity control electrodes 17a to 17h. While electrons are moved among the charge separation unit D2, the charge storage unit D3, and the charge holding unit D4, a negative voltage is applied to the sensitivity control electrodes 17a to 17h, whereby the photoelectric conversion unit D1 is applied. The movement of electrons can be prevented. Since the sensitivity control electrode 17c holds electrons in the section P2 and the sensitivity control electrode 17f holds electrons in the section P0, the timing at which the charge storage unit D3 of each group receives electrons from the photoelectric conversion unit D1 is different.

  Electrons generated in the photoelectric conversion unit D1 during the light-off period of the light emitting source are transferred from the charge storage unit D3 to the charge holding unit D4 through a portion corresponding to the gate electrode 14e. Here, although a modulation signal is not required during the light-emitting source extinguishing period, the voltage applied to the sensitivity control electrodes 17a to 17h is controlled at the same timing as the light-emitting source lighting period, and the photoelectric conversion unit D1 receives ambient light. An amount of electrons corresponding to the amount of light is generated. Therefore, electrons corresponding to ambient light are transferred to the charge storage portion D3 in both groups in one cell 1. The electrons may be transferred from either one of the charge storage units D3 to the charge holding unit D4, but the electrons may be transferred from both. When an amount of electrons corresponding to the amount of ambient light is transferred to the charge holding unit D4, a voltage is applied to the barrier control electrode 14c connected to the holding electrode 14d via the connection line 22, and the ambient light is applied to the well 12. A potential barrier B1 corresponding to the amount of light is formed.

  Thereafter, in the lighting period of the light emitting source, the photoelectric conversion unit D1 accumulates electrons for each group, thereby holding the electrons in the sections P0 and P2 in the areas corresponding to the sensitivity control electrodes 17c and 17f, respectively. Next, electrons are moved from the photoelectric conversion unit D1 to the charge storage unit D3. Thereafter, the operation is the same as that of the second embodiment. Electrons are moved from the charge accumulation unit D3 to the charge separation unit D2, and unnecessary charges corresponding to the capacity of the charge separation unit D2 are weighed and discarded, and effective charges are accumulated. Return to part D3. By this operation, the charge accumulation unit D3 retains an effective charge obtained by separating unnecessary charges of an amount defined by the amount of received light during the light-off period of the light-emitting source among the electrons accumulated in the photoelectric conversion unit D1 during the light-emitting source lighting period. .

  This embodiment employs a configuration in which effective charges remaining in the charge storage unit D3 are transferred back to the photoelectric conversion unit D1. That is, by applying a negative voltage to the storage electrode 14b and applying a positive voltage to the sensitivity control electrodes 17c and 17f, electrons as effective charges are transferred from the charge storage unit D3 to the photoelectric conversion unit D1. The electrons transferred to the photoelectric conversion unit D1 are transferred in the vertical direction by using the sensitivity control electrodes 17a to 17h as vertical transfer electrodes, and are taken out as light reception outputs to the outside of the light detection element in the same manner as the CCD image sensor. It is.

  In the configuration of the present embodiment, since the parts other than the photoelectric conversion unit D1 operate even if light is shielded, a process of separating unnecessary charges by shielding the charge separation unit D2, the charge storage unit D3, and the charge holding unit D4. During this period, it is possible to prevent electrons generated by light irradiation from entering the effective charge as an error. However, since the weighing period for separating the unnecessary charges and extracting the effective charges is sufficiently short compared to the light receiving period in which the charges due to light irradiation are accumulated in the photoelectric conversion unit D1 as in the above-described embodiments, the charge separation unit D2 and the charge storage portion D3 may not be shielded from light. Even in this case, the charge holding portion D4 needs to be shielded from light.

  In the present embodiment, in the period during which the operation of weighing unnecessary charges is performed, the photoelectric conversion unit D1 does not accumulate electrons by light irradiation, and thus the charge storage unit D3 is also used as the photoelectric conversion unit D1. The error can be reduced compared to the above. Other configurations and operations are the same as those of the second embodiment.

  By the way, Embodiments 2 and 3 show a spatial information detection device using a light detection element provided with a charge holding portion D4 in combination with a light emission source. The case where the charge holding unit D4 holds the amount of electrons corresponding to the amount of received light has been described. In this apparatus, by using the relationship between the light reception output of the light detection element and the light projected from the light emission source, it is possible to obtain information on the target space where light is projected from the light emission source. Spatial information related to the target space includes the presence / absence of the object, the reflectance of the object, the distance to the object, and the like. ) Can be configured in various ways.

  When calculating the presence / absence or reflectance of an object in the target space, it is not necessary to modulate the light intensity during the lighting period of the light source, but to determine the distance to the object existing in the target space, The intensity of the light to be projected is modulated with a modulation signal having a predetermined frequency, and the light detection element detects the amount of received light at a plurality of timings synchronized with the modulation signal. This is a technique for detecting the time of flight until the light projected from the light source enters the light detection element as the phase difference of the modulated light, and the phase of the modulation signal is different for the calculation of the phase difference. The difference between the received light amounts of the two sections is used.

  In the configuration example of the third embodiment, effective charges are obtained for each of the two sections P0 and P2, and therefore, it is possible to use for calculating the distance by obtaining the difference between the effective charges. In the configuration example of the second embodiment, if electrons obtained in one of the two sections P0 and P2 are held in the charge holding unit D4, an amount of electrons corresponding to the amount of light received in this section is unnecessary. Since it becomes electric charge and is subtracted from the electrons obtained in the other section, the amount of effective charge obtained corresponds to the difference between the received light amounts of the two sections P0 and P2. That is, when the distance is calculated by an external circuit, the amount of calculation for the light reception output of the light detection element can be reduced.

  In the configuration in which the effective charge is an amount corresponding to the difference between the received light amounts of the two sections P0 and P2, if the electrons in the two sections P0 and P2 are alternately held in the charge holding unit D4, which one is held. Accordingly, errors occur alternately in different directions. Therefore, if the two light reception outputs are averaged, an error caused by separation of unnecessary charges can be canceled out, and information on the target space obtained based on the light reception output can be obtained with high accuracy.

(Embodiment 4)
In the present embodiment, similarly to the third embodiment, the intensity of light projected from the light source is modulated by a modulation signal having a constant frequency, and the received light amount corresponds to the received light amount at the timing synchronized with two sections having different phases in the modulation signal. 1 shows a light detection element that can take out outputs. However, in the third embodiment, the charge separation unit is associated with each of the received light amount in the section P0 in which the phase of the modulation signal is synchronized with 0 to 180 degrees and the received light quantity in the section P2 in which the phase is synchronized with 180 to 360 degrees. Although the configuration in which D2 and the charge storage unit D3 are provided is adopted, the present embodiment shows a configuration in which the charge separation unit D2 and the charge storage unit D3 are shared with respect to the amount of light received in the sections P0 and P2.

  As shown in FIG. 13, the photoelectric conversion unit D1 is similar to the third embodiment in that eight sensitivity control electrodes 17a to 17h are provided for one cell 1, but the charge separation unit D2 and the charge accumulation unit The part D3 and the charge holding part D4 are asymmetric in the vertical direction in the configuration of the third embodiment, but are asymmetric in the present embodiment. A region E3 for forming the charge separation unit D2 and the charge storage unit D3 is provided on the side of the region E1 where the sensitivity control electrodes 17a to 17d are arranged in the photoelectric conversion unit D1, and the photoelectric conversion unit D1 has a charge as described later. It is also shared as the storage unit D3. The region E4 where the charge holding portion D4 is formed is provided on the side of the region E2 where the sensitivity control electrodes 17e to 17h are disposed.

  A receiving electrode 14f adjacent to the sensitivity control electrode 17a in the photoelectric conversion unit D1 is provided in the region E3 where the charge separation unit D2 and the charge storage unit D3 are formed, and sensitivity control is performed on the potential well formed below the receiving electrode 14f. By making it relatively deep with respect to the potential well formed under the electrode 17a, the electric charge accumulated in the potential well formed under the sensitivity control electrode 17a can be received from the photoelectric conversion unit D1. It is.

  Further, in the region E3, the separation electrode 14a, the barrier control electrode 14c, and the storage electrode 14b are arranged on the sides of the sensitivity control electrodes 17b, 17c, and 17d, respectively. In the illustrated example, only the barrier control electrode 14c is reduced in size, but the dimensional relationship as in this configuration is not essential.

  On the other hand, in the region E4 in which the charge holding portion D4 is formed, the gate electrode 14e is provided in a portion straddling the sensitivity control electrodes 17e to 17g in the photoelectric conversion portion D1, and sensitivity control is performed on the potential well formed below the gate electrode 14e. The charge accumulated in the potential well formed under the sensitivity control electrode 17f can be received from the photoelectric conversion unit D1 by being deeper than the potential well formed under the electrode 17f. is there.

  In the region E4, the holding electrode 14d is disposed on the opposite side of the photoelectric conversion unit D1 with respect to the gate electrode 14e. Therefore, if a potential well is formed under the holding electrode 14d in the same manner as in the second and third embodiments, the potential well under the sensitivity control electrode 17f is adjusted by appropriately adjusting the potential under the gate electrode 14e. The charge accumulated in the potential can flow into the potential well below the holding electrode 14d.

  After the charge is transferred to the charge holding portion D4, which is a potential well below the holding electrode 14d, the potential of the barrier control electrode 14c is determined by the amount of charge held in the charge holding portion D4. The height of the potential barrier formed below is determined.

  A drain (overflow drain) 23 is formed adjacent to the well 12 (see FIG. 1) in the element formation layer 11 (see FIG. 1).

  The operation of this embodiment will be described below with reference to FIG. In the same manner as in the third embodiment, the light emission source is provided with a light extinction period, and in order to use the light detection element of the present embodiment, first, in the light extinction period (S1), the sensitivity control electrodes 17e to 17h in the photoelectric conversion unit D1 A positive voltage is applied, and the sensitivity control electrodes 17a to 17d are set to a reference potential (a negative voltage may be applied. Similarly, a state where the reference potential is applied is a state where a negative voltage is applied. Can be replaced). In addition, the separation electrode 14a, the storage electrode 14b, the holding electrode 14d, the gate electrode 14e, and the receiving electrode 14f provided in the regions E3 and E4 are also set to the reference potential.

  Through the above-described operation, electrons corresponding to the received light amount of the ambient light are accumulated in the region E2 corresponding to the sensitivity control electrodes 17e to 17h in the photoelectric conversion unit D1 (S2). After electrons corresponding to the amount of ambient light received are accumulated in the region E2, a positive voltage is applied only to the sensitivity control electrode 17f, and the other sensitivity control electrodes 17a to 17e, 17g, and 17h are set as reference potentials. . By this operation, electrons corresponding to the received light amount of the ambient light are accumulated in the potential well corresponding to the sensitivity control electrode 17f.

  Next, by applying a positive voltage to the gate electrode 14e, a channel is formed under the gate electrode 14e, and electrons are transferred from the potential well under the sensitivity control electrode 17f to the holding portion D4 under the holding electrode 14d. Transfer (S3). When electrons are transferred to the holding unit D4, the potential of the holding electrode 14d becomes a potential corresponding to the amount of received ambient light, and the potential of the barrier control electrode 14c also becomes the same potential. That is, the height of the potential barrier formed under the barrier control electrode 14c is determined.

  Next, it shifts to the lighting period in which light is emitted from the light emitting source (S4). In the lighting period, since the signal light whose intensity is modulated by the modulation signal is projected, the following operation is performed in order to individually extract the received light output corresponding to the received light amount in the section P0 and the section P2. Here, it is assumed that electrons corresponding to the amount of received light in the section P0 are accumulated in the region E1, and electrons corresponding to the amount of received light in the section P2 are accumulated in the region E2.

  First, a positive voltage is applied to the sensitivity control electrodes 17a to 17d in the region E1 and the sensitivity control electrode 17f in the region E2, and the remaining sensitivity control electrodes 17e, 17g, and 17h in the region E2 are used as reference potentials. S5) An operation in which a positive voltage is applied to the sensitivity control electrode 17b in the region E1 and the sensitivity control electrodes 17e to 17h in the region E2, and the remaining sensitivity control electrodes 17a, 17c, and 17d in the region E1 are set as reference potentials. (S6) is performed once (or a plurality of times) at a period synchronized with the modulation signal. By this operation, electrons corresponding to the received light quantity in the section P0 are accumulated in the potential well corresponding to the sensitivity control electrode 17b, and electrons corresponding to the received light quantity in the section P2 are accumulated in the potential well corresponding to the sensitivity control electrode 17f. Is done.

  Next, a process of separating unnecessary charges from electrons corresponding to the received light amounts in the sections P0 and P2 and extracting effective charges is performed. Since electrons corresponding to the amount of light received in the section P0 are accumulated in the potential well corresponding to the sensitivity control electrode 17b, a positive voltage is applied to the sensitivity control electrode 17a and sensitivity control is performed using the sensitivity control electrode 17b as a reference potential. Electrons are transferred to the potential well corresponding to the electrode 17a. Further, a positive voltage is applied to the receiving electrode 14f, and the sensitivity control electrode 17a is used as a reference potential to transfer electrons to the potential well below the receiving electrode 14f. That is, the electrons corresponding to the received light amount of the section P0 accumulated in the area E1 are transferred to the area E3.

  The electrons transferred to the region E3 flow from the potential well corresponding to the receiving electrode 14f to the charge separation portion D2 formed corresponding to the separation electrode 14a. Here, since the height of the potential barrier between the charge separation unit D2 and the charge storage unit D3 is determined, a certain amount of unnecessary charges remain in the charge separation unit D2, and other effective charges remain in the charge storage unit D3. Flow into. Unnecessary charges in the charge separation unit D2 are discarded through the drain 23. In this way, unnecessary charges are weighed from the electrons corresponding to the received light quantity in the section P0, and effective charges are extracted (S8).

  The effective charge obtained as described above is transferred to a potential well formed under the sensitivity control electrode 17d provided adjacent to the storage electrode 14b. That is, effective charges obtained by separating unnecessary charges corresponding to the received light amount of the ambient light from the received light amount of the section P0 are transferred from the region E3 to the region E1 (S9).

  By the way, it is necessary to separate unnecessary charges for the electrons accumulated in the region E2. In the region E2, electrons corresponding to the amount of light received in the section P2 are accumulated in the potential well corresponding to the sensitivity control electrode 17f. Therefore, in order to transfer the electrons to the region E3, the potential well corresponding to the sensitivity control electrode 17f It is necessary to transfer electrons to the potential well formed corresponding to the sensitivity control electrode 17a. At this time, the charge transferred to the region E1 in step S9 also needs to be transferred in the vertical direction so as not to be mixed with the effective charge obtained from the received light quantity in the section P0. Therefore, electrons (effective charges in the section P0) are transferred from the potential well below the sensitivity control electrode 17d to the potential well below the sensitivity control electrode 17g of the adjacent cell 1, and from the potential well below the sensitivity control electrode 17f. Transfers electrons (electrons in the section P2) to the potential well below the sensitivity control electrode 17a (S10).

  After electrons corresponding to the amount of received light in the section P2 are transferred to the potential well below the sensitivity control electrode 17a, the electrons are transferred from the region E1 to the region E3, and unnecessary charges are separated from the electrons to charge effective charges. The data is taken out to the storage unit D3 (S11 to S13). That is, the effective charge in the section P2 can be taken out by performing the same process as in steps S7 to S9. This effective charge is transferred to the potential well below the sensitivity control electrode 17d, and the effective charge is returned from the region E3 to the region E1 (S14).

  When effective charges in the sections P0 and P2 are obtained by the above-described operation, the effective charges are transferred in the vertical direction and temporarily returned to the positions of the sensitivity control electrodes 17b and 17f (S15). Such an operation is repeated a predetermined number of times during the lighting period (S16), and finally the electrons remaining in the potential well corresponding to the sensitivity control electrodes 17b and 17f are taken out as a light receiving output (S17).

  Disposal electrodes 14g and 14h are provided between the separation electrode 14a and the drain 23 and between the holding electrode 14d and the drain 23, respectively, and are discarded every time the charge is transferred from the region E1 to the region E3. The unnecessary charge is discarded by controlling the voltage applied to the electrode 14g, and the ambient light held in the holding unit D4 by controlling the voltage applied to the discarding electrode 14h every time the charge is transferred from the region E2 to the region E4. Corresponding electrons are discarded. Other configurations and operations are the same as those of the first embodiment.

(Embodiment 5)
In the configuration of the fourth embodiment, the configuration is shown in which the region E3 having a function of separating unnecessary charges is arranged on the side of the region E1 where the sensitivity control electrodes 17a to 17h are arranged (different portions in the horizontal direction). In this embodiment, as shown in FIG. 15, a configuration example is described in which regions E3 having a function of separating unnecessary charges are arranged in the vertical direction with respect to the regions E1 and E2 where the photoelectric conversion units D1 are provided. To do.

  In the present embodiment, six sensitivity control electrodes 17a to 17f are provided for one cell 1, and each of the three sensitivity control electrodes 17a to 17c and 17d to 17f has a received light amount in the sections P0 and P2, respectively. Regions E1 and E2 for accumulating corresponding charges are formed. In addition, a region E3 for separating unnecessary charges is provided between cells 1 adjacent in the vertical direction, and charges corresponding to the received light amount of ambient light are held on the side of the region E3 (parts separated in the horizontal direction). An area E4 is provided.

  That is, the region receiving electrode 14f is disposed adjacent to the sensitivity control electrode 17f of one cell in the vertical direction, and the separation electrode 14a and the barrier control electrode 14c are opposite to the sensitivity control electrode 17f with respect to the receiving electrode 14f. And the storage electrode 14b are arranged in order. The sensitivity control electrode 17a of another cell 1 is arranged on the opposite side of the barrier control electrode 14c with respect to the storage electrode 14b.

  Further, with respect to the region E3 where the receiving electrode 14f, the separation electrode 14a, the barrier control electrode 14c, and the storage electrode 14b are arranged, the gate electrode 14e is sandwiched between the receiving electrode 14f, the separation electrode 14a, and the barrier control electrode 14c. The holding electrode 14d is disposed. Here, the barrier control electrode 14 c is connected to the holding electrode 14 d via the connection line 22. The area E1, E2, E3, E4 is surrounded by the drain 23, and a waste electrode 14g is disposed between the holding portion D4 and the drain 23 formed corresponding to the holding electrode 14d. Each electrode described above is disposed on the surface of an n-type well 12 formed in the p-type element formation layer 11.

  The operation of the present embodiment is basically the same as the operation of the fourth embodiment, and a positive voltage is applied to the sensitivity control electrodes 17d to 17f corresponding to the region E2 in the photoelectric conversion unit D1 during the extinction period. The sensitivity control electrodes 17a to 17c in the region E1 are set to a reference potential. Further, the separation electrode 14a, the storage electrode 14b, the barrier control electrode 14c, the holding electrode 14d, the gate electrode 14e, and the receiving electrode 14f are also set to the reference potential. Therefore, electrons corresponding to the amount of ambient light received are accumulated in the region E2 of the photoelectric conversion unit D1. After electrons corresponding to the amount of ambient light received are accumulated in the region E2, a positive voltage is applied only to the sensitivity control electrode 17f of the sensitivity control electrodes 17a to 17f in the regions E1 and E2, and the integration is performed. The collected electrons are accumulated in the potential well corresponding to the sensitivity control electrode 17f.

  Electrons accumulated in the potential well corresponding to the sensitivity control electrode 17f are transferred to the holding portion D4 below the holding electrode 14d through the receiving electrode 14f and the gate electrode 14e. At this stage, the height of the potential barrier formed under the barrier control electrode 14c is set so as to correspond to the ambient light.

  Next, when shifting to a lighting period in which light is emitted from the light emitting source, a positive voltage is applied to the sensitivity control electrodes 17a to 17c and 17e and sensitivity control is performed in association with the sections P0 and P2 synchronized with the modulation signal. A period in which the operation of using the electrodes 17d and 17f as a reference potential and the operation of applying a positive voltage to the sensitivity control electrodes 17b and 17d to 17f and using the sensitivity control electrodes 17a and 17b as a reference potential are synchronized with the modulation signal. At least once. By this operation, electrons corresponding to the amount of received light in the section P0 are accumulated on the sensitivity control electrode 17b, and electrons corresponding to the amount of received light in the section P2 are accumulated on the sensitivity control electrode 17e.

  Here, if the electrons accumulated in the sensitivity control electrode 17e are transferred in the vertical direction and transferred to the charge separation portion D1, which is a potential well below the separation electrode 14a, the height of the potential barrier below the barrier control electrode 14c. Accordingly, unnecessary charges are separated, and only effective charges are accumulated in the charge accumulation section D2 below the accumulation electrode 14b. That is, effective charges corresponding to the section P2 are accumulated in the charge accumulation unit D2. Here, unnecessary charges in the charge separation unit D1 are discarded through the drain 23 through a path (not shown).

  In the illustrated example, the drain 23 is described to be continuous on the upstream side (assuming a case where electrons are transferred from the upper side to the lower side in the drawing) and the downstream side of the separation electrode 14a. It is desirable to separate the drain 23 from the side. When this configuration is adopted, unnecessary charges to be discarded are transferred under any one of the sensitivity control electrodes 17a to 17f (for example, the sensitivity control electrode 17e) adjacent to the upstream drain 23, and electrons are transferred to the drain 23. A voltage to be drawn (for example, + 15V) is applied, and a voltage (for example, −5V) for pushing out electrons is applied to the sensitivity control electrode 17e at the site where unnecessary charges have been transferred. In addition, a voltage for pushing out electrons is also applied to the sensitivity control electrodes 17c, 17d, 17f, and 17g adjacent to the sensitivity control electrode 17e at the site where unnecessary charges have been transferred. By this operation, unnecessary charges flow to the drain 23 and are discarded without flowing toward the sensitivity control electrodes 17c, 17d, 17f, and 17g.

  Next, electrons corresponding to the received light amount in the section P0 accumulated in the potential well formed under the sensitivity control electrode 17b are transferred in the vertical direction, and the charge separation portion D1 which is the potential well under the separation electrode 14a. Forward to. At this time, the effective charge in the section P2 stored in the charge storage portion D2 below the storage electrode 14b is also transferred in the vertical direction, and is formed in the potential well formed below the sensitivity control electrode 17b of the cell 1 adjacent in the vertical direction. Retreat to.

  If electrons corresponding to the amount of light received in the section P0 are transferred to the charge separation section D1 as described above, unnecessary charges are separated, and effective charges in the section P0 are stored in the charge storage section D2.

  The effective charge of the section P0 stored in the charge storage unit D2 and the effective charge of the section P2 stored in the potential well below the sensitivity control electrode 14b are transferred upward in FIG. 15 in the vertical direction. By controlling the voltage applied to the storage electrode 14b, the effective charge stored in the charge storage portion D2 can get over the potential barrier below the barrier control electrode 14c. Thus, by transferring the effective charges in the reverse direction, the effective charges in the sections P0 and P2 can be accumulated in the potential well below the sensitivity control electrodes 14b and 14e.

  After the above-described operation is repeated a specified number of times during the lighting period, the effective charge is taken out as a light receiving output. In the operation of the present embodiment, the number of procedures is reduced compared to the operation of the fourth embodiment, and the operation is facilitated. Other configurations and operations are the same as those of the first embodiment.

(Embodiment 6)
In the embodiment described above, the separation electrode 14a, the storage electrode 14b, the barrier control electrode 14c, the holding electrode 14d, and the gate electrode 14e have different width dimensions. However, in the present embodiment, an electrode having the same width is used. By arranging a plurality of electrodes and appropriately combining the electrodes, an operation similar to that of a configuration using electrodes having substantially different widths is performed. Further, in the present embodiment, as in the third embodiment, it is assumed that the intensity of light projected from the light source is modulated by a sinusoidal modulation signal, and the charges accumulated in the sections P0 and P2 are taken out as light reception outputs. To do. However, the photoelectric conversion unit D1 is also used as the charge separation unit D2 and the charge storage unit D3, and the charge holding unit D4 is not provided.

  As shown in FIG. 16, in one cell 1 in this embodiment, control electrodes 18a to 18l having the same width are arranged at equal intervals in a well 12 provided on the main surface of an element formation layer 11 with an insulating layer 13 interposed therebetween. It is. In the present embodiment, one cell 1 is constituted by twelve control electrodes 18a to 18l. In one cell 1, wiring is performed so that the voltages applied to the control electrodes 18a to 18l can be individually controlled.

  The operation as the photoelectric conversion unit D1 is substantially the same as the operation using the sensitivity control electrodes 17a to 17h of the third embodiment. However, in the present embodiment, in the light receiving period, the electrons corresponding to the received light amount in the section P0 are integrated using the control electrodes 18a to 18i, and the electrons corresponding to the received light quantity in the section P2 are integrated using the control electrodes 18d to 18l. To do. This operation will be described with reference to FIG. In FIG. 17, the symbols (a) to (l) arranged side by side correspond to the control electrodes 18a to 18l.

  First, during the light receiving period, during the operation as the photoelectric conversion unit D1, a positive voltage is applied to the control electrodes 18a to 18i in the section P0 as shown in FIG. Electrons are accumulated in a region corresponding to ˜18i. Further, in the section P2, as shown in FIG. 17B, a positive voltage is applied to the control electrodes 18d to 18l, and electrons are accumulated in a region corresponding to the nine control electrodes 18d to 18l. The electrons accumulated by light irradiation in each of the sections P0 and P2 are held in a region other than the region where the electrons are accumulated. That is, in the section P0 in which electrons are accumulated in the region corresponding to the control electrodes 18a to 18i, the electrons in the section P2 are held in the region corresponding to the control electrode 18k, and the electrons corresponding to the control electrodes 18d to 18l are accumulated. In the section P2, the electrons in the section P0 are held in a region corresponding to the control electrode 18b. By repeating the operations in the sections P0 and P2 many times, an amount of electrons corresponding to the amount of received light is held in the region corresponding to the control electrode 18b in the well 12.

  The light receiving period ends and an amount of electrons corresponding to the amount of received light in the section P0 is accumulated in the region corresponding to the control electrode 18b, or an amount of electrons corresponding to the amount of received light in the section P2 corresponds to the control electrode 18k. Then, the operation moves to a weighing period, and an operation of separating unnecessary charges and leaving effective charges is started.

  For example, in order to separate unnecessary charges from the electrons held in the region corresponding to the control electrode 18b, the electrons accumulated in the section P0 are held in the potential well formed in the region corresponding to the control electrode 18b. A negative voltage is applied to the control electrode 18a to form a potential barrier. Further, in order to use the region corresponding to the control electrodes 18d and 18e as the charge storage unit, the electrons accumulated in the section P2 are transferred. That is, as shown in FIGS. 17C and 17D, potential barriers corresponding to the control electrodes 18c to 18h are sequentially formed, and the electrons accumulated in the section P2 are transferred.

  Next, as shown in FIG. 17E, a positive voltage is applied to the control electrodes 18d and 18e to form a potential well serving as the charge storage portion D3, and the voltage applied to the control electrode 18c is controlled. A potential barrier B3 having a predetermined height is formed. By this operation, unnecessary charges remain in the potential well corresponding to the control electrode 18b, and electrons that have flowed into the potential well corresponding to the control electrodes 18d and 18e beyond the potential barrier B3 are used as effective charges.

  Next, as shown in FIG. 17F, the potential corresponding to the control electrode 18c is increased to prevent leakage of effective charges corresponding to the period P0, and at the same time, the electrons accumulated in the period P2 correspond to the control electrode 18k. Accumulate in potential wells. In this state, a potential well serving as the charge storage portion D3 is formed in a region corresponding to the control electrodes 18g to 18i, and a potential barrier corresponding to the control electrode 18j is formed.

  In order to separate unnecessary charges from electrons held in the potential well corresponding to the control electrode 18k, the potential barrier B4 is lowered by controlling the voltage applied to the control electrode 18j, as shown in FIG. The amount of unnecessary charge among the electrons accumulated in the section P2 is determined by the height of the potential barrier B4 at this time. That is, the region corresponding to the control electrode 18k functions as the charge separation unit D2.

  After the unnecessary charges are separated, as shown in FIG. 17H, the potential barrier corresponding to the control electrode 18j is increased, and the effective charge leakage in the section P2 accumulated in the potential wells corresponding to the control electrodes 18g to 18i. To prevent. Note that unnecessary charges remaining on the control electrodes 18b and 18k are discarded.

  By the above-described operation, unnecessary charges can be separated from electrons generated by light irradiation in the sections P0 and P2, and effective charges can be extracted. In the present embodiment, since the control electrodes 18a to 18l are arranged in a line, if a voltage is applied to the control electrodes 18a to 18l at an appropriate timing in the same manner as the vertical transfer register of the CCD image sensor, electrons that are effective charges are used. Can be transferred in the arrangement direction of the control electrodes 18a to 18l. A light receiving output is obtained by taking out the electrons to the outside of the light detection element. That is, in the configuration of the present embodiment, the photoelectric conversion unit D1 is also used as the charge separation unit D2 and the charge storage unit D3, and is also used as the charge extraction unit. Moreover, since the process which isolate | separates an unnecessary charge can be performed simultaneously about the electron produced | generated corresponding to two area P0, P2, the processing time which isolate | separates an unnecessary charge can be shortened.

  In the configuration example described above, an example in which the same operation as that of the first embodiment is shown, but the voltage applied to the control electrodes 18b and 18k is controlled by the amount of electrons held in the charge separation unit D4 provided separately. For example, as in the second embodiment or the third embodiment, the amount of unnecessary charges can be automatically adjusted. Other configurations and operations are the same as those of the above-described embodiments.

(Embodiment 7)
As in the sixth embodiment, the present embodiment has a configuration in which a plurality of control electrodes 19a to 19i having the same width are arranged. However, in the sixth embodiment, one cell 1 is composed of twelve control electrodes 18a to 18l. In the present embodiment, as shown in FIG. An example in which the control electrodes 19a to 19i are configured is shown ((a) to (i) side by side in FIG. 19 correspond to the control electrodes 19a to 19i, respectively). As described in the sixth embodiment, since six control electrodes are used to integrate electrons corresponding to one section of the phase of the modulation signal and to separate unnecessary charges, the nine control electrodes 19a to 19i Therefore, the accumulation of electrons and the separation of unnecessary charges corresponding to the two sections of the phase of the modulation signal cannot be performed in independent regions. That is, some areas are used overlapping in both sections. In the sixth embodiment, the operation of separating unnecessary charges from the electrons accumulated in both sections can be performed at the same time. However, in the configuration of the present embodiment, a partial area is used in an overlapping manner. The operation of separating the unnecessary charges from the accumulated electrons is performed at different times.

  Specifically, the operation shown in FIG. 19 is performed, and as shown in FIGS. 19A and 19B, during the period of functioning as the photoelectric conversion unit D1 so as to integrate electrons generated by light irradiation. In addition, a period in which a negative voltage is applied to the control electrodes 19g and 19i and a period in which a negative voltage is applied to the control electrodes 19a and 19c are alternately provided. Both periods are set in synchronization with the modulation signal. For example, the state of FIG. 19A corresponds to the section P0, and the state of FIG. 19B corresponds to the section P2. In this case, in the state of FIG. 19A, the region corresponding to the control electrodes 19a to 19f functions as the photoelectric conversion unit D1 with respect to the section P0, and in the state of FIG. 19B, the control voltage 19d with respect to the section P2. A region corresponding to ˜19i functions as the photoelectric conversion unit D1. The electrons accumulated in the section P0 are held in a region corresponding to the control electrode 19b, and the electrons accumulated in the section P2 are held in a region corresponding to the control electrode 19h.

  After performing the operation of alternately repeating the states of FIGS. 19 (a) and 19 (b) for a sufficiently long time, unnecessary charges are separated from the electrons held in the regions corresponding to the control electrodes 19b and 19h, and the control electrodes 19b, An operation of leaving an effective charge in a region corresponding to 19h is performed. Since the region corresponding to the control electrodes 19b and 19h is a region where the effective charge remains, it functions as the charge storage portion D3.

  In the illustrated example, after unnecessary charges are separated from the electrons accumulated in the section P2 shown in FIG. 19B, unnecessary charges are separated from the electrons accumulated in the section P0 shown in FIG. While separating the unnecessary charge from the electrons accumulated in the section P2, the electrons accumulated in the section P0 are held in the region corresponding to the control electrode 19b, and the effective charge obtained by separating the unnecessary charges from the electrons accumulated in the section P2 is controlled. The region corresponding to the electrodes 19d to 19f is held.

  This will be described more specifically. First, after the electrons by light irradiation are accumulated in the photoelectric conversion unit D1, as shown in FIG. 19C, the electrons accumulated in the section P0 are held in the potential well formed in the region corresponding to the control electrode 19b. Further, a negative voltage is applied to the control electrode 19g to form a potential barrier. This state continues until unnecessary charges are separated from the electrons accumulated in the section P2. In the state of FIG. 19C, the electrons accumulated in the section P2 are held in the potential well formed in the region corresponding to the control electrodes 19d to 19f. That is, the electrons accumulated in the section P2 and accumulated in the area corresponding to the control electrodes 19d to 19i are collected in the area corresponding to the control electrodes 19d to 19f.

  This operation is a pre-operation for forming an empty potential well without electrons in a region corresponding to the control electrode 19h, as shown in FIG. That is, at the stage where the accumulation of electrons by light irradiation is completed, the electrons accumulated in the section P2 exist in the region corresponding to the control electrode 19h, so that the control electrodes 19g to 19i are applied to the control electrodes 19g to 19i as shown in FIG. By applying a negative voltage, when a potential well is formed in a region corresponding to the control electrode 19h as shown in FIG. 19D, a potential well without electrons can be formed.

  Next, as shown in FIGS. 19E and 19F, the electrons held in the region corresponding to the control electrodes 19d to 19f are moved to the region corresponding to the control electrode 19h. At this time, first, a potential well is formed in a region corresponding to the control electrodes 19f to 19h, a potential barrier is formed in a region corresponding to the control electrodes 19c to 19e, and further, a region corresponding to the control electrode 19f and the control electrode 19g are formed. A potential barrier is sequentially formed in the corresponding region, and electrons are accumulated in the region corresponding to the control electrode 19h. At this stage, empty potential wells are formed in regions corresponding to the control electrodes 19d to 19f. That is, a plurality of states exist between the state of FIG. 19E and the state of FIG. 19F, but are omitted in the figure. Further, regarding the potential, the state of FIG. 19F and the state of FIG. 19D are the same, but in the state of FIG. 19D, electrons exist only in regions corresponding to the control electrodes 19d to 19f. On the other hand, the state of FIG. 19 (f) is different in that electrons exist only in the region corresponding to the control electrode 19h. In the figure, the intermediate process from the state of FIG. 19 (e) to the state of FIG. 19 (f) is omitted.

  In the process so far, the electrons accumulated in the section P2 are accumulated in the region corresponding to the control electrode 19h. Next, as shown in FIG. 19G, the potential barrier B5 corresponding to the control electrode 19g is lowered. The potential barrier B5 has a function similar to that of the potential barrier B1 described in the first embodiment. The region corresponding to the control electrode 19h serves as a charge separation portion D2 and has an amount of electrons determined by the height of the potential barrier B5. Is weighed. Electrons that exceed the capacity of the charge separation portion D2 flow over the potential barrier B5 and flow into the charge storage portion D3 that is a region corresponding to the control electrodes 19d to 19f.

  After electrons flow into the charge storage unit D3, as shown in FIG. 19 (h), if the voltage applied to the control electrode 19g is negative and the potential barrier B5 is increased, unnecessary charges and the charge storage unit of the charge separation unit D2 are increased. The effective charge of D3 can be completely separated, and if unnecessary charges in the potential well corresponding to the control electrode 19h serving as the charge separation part D2 are discarded as shown in FIG. Effective charges can remain in the corresponding regions. This effective charge is an amount corresponding to the amount of light received in the section P2.

  On the other hand, the amount of electrons held in the region corresponding to the control electrode 19b corresponds to the amount of light received in the section P0. Unnecessary charges are separated from the electrons by the procedure shown in FIGS. 19 (j) to 19 (o). During this period, the state in which the effective charge of the section P2 is held in the region corresponding to the control electrodes 19d to 19f is maintained. The feature of this embodiment is that the region corresponding to the control electrode 19h not only functions as the charge separation unit D2 for the electrons in the section P2, but also serves as the charge separation unit D2 for the electrons in the section P0. .

  That is, after discarding unnecessary charges, first, as shown in FIGS. 19J and 19K, the electrons in the section P0 held in the region corresponding to the control electrode 19b are moved to the region corresponding to the control electrode 19h. At this time, the potentials of the regions corresponding to the control electrodes 19a and 19i are lowered to equalize the potentials of the regions corresponding to the control electrodes 19a, 19b, 19h and 19i, and then electrons are brought to the region corresponding to the control electrode 19h. Although the state between FIGS. 19 (j) and 19 (k) is omitted in the figure, the potential in the region corresponding to the order of the control electrodes 19b, 19a, 19i is increased, and electrons are only present in the region corresponding to the control electrode 19h. In the integrated state, the potential of the region corresponding to the control electrodes 19a and 19b is lowered.

  With the above-described operation, the electrons in the section P0 are held in the region corresponding to the control electrode 19h, and the region corresponding to the control electrode 19h functions as the charge separation unit D2. That is, as shown in FIG. 19 (l), a potential barrier B6 is formed by the potential of the region corresponding to the control electrode 19i, and the electrons over the potential barrier B6 enter the regions corresponding to the control electrodes 19a and 19b as effective charges. Inflow. That is, the region corresponding to the control electrodes 19a and 19b functions as the charge storage unit D3.

  Thereafter, as shown in FIG. 19N, the potential barrier B6 corresponding to the control electrode 19i is increased as shown in FIG. 19M, and the electrons in the charge separation portion D2 and the charge storage portion D3 are separated, as shown in FIG. If electrons that are unnecessary charges accumulated in the potential well corresponding to the control electrode 19h serving as the charge separation portion D2 are discarded, the electrons corresponding to the received light amount in the section P2 are held in the regions corresponding to the control electrodes 19d to 19f. Thus, electrons corresponding to the amount of received light in the section P0 are held in regions corresponding to the control electrodes 19a and 19b. In addition, after taking out these electrons, it returns to the operation | movement of Fig.19 (a) (b), and the electron by light irradiation is integrated | stacked.

  If the configuration of this embodiment is adopted, the number of control electrodes is reduced as compared with the configuration of Embodiment 6, and the area occupied by one cell 1 can be reduced accordingly. When an image sensor is configured by arranging a plurality of cells 1 and one cell 1 as one pixel, the area occupied by one pixel is reduced, resulting in an improvement in resolution. Other configurations and operations are the same as those of the above-described embodiments.

(Embodiment 8)
In each of the above-described embodiments, a configuration in which a certain amount of unnecessary charges defined using a potential well is weighed is shown. However, in this embodiment, a certain amount of unnecessary charges defined among electrons generated by light irradiation are measured. As a weighing method, a technique for discarding a specified amount of unnecessary charges will be described.

  In the present embodiment, as shown in FIG. 20, a disposal well 25 is formed on the main surface side of the element formation layer 11 separately from the well 12 that becomes the photoelectric conversion portion D <b> 1 formed on the main surface side of the element formation layer 11. In addition, a waste gate electrode 26 is provided on the main surface of the element formation layer 11 via the insulating layer 13 at a portion between the well 12 and the waste well 25. Further, a waste electrode 27 is ohmically joined to the waste well 25. The waste well 25 has the same conductivity type as that of the well 12 and has an impurity concentration higher than that of the well 12.

  A constant positive voltage is always applied to the waste electrode 27 so that electrons accumulated in the waste well 25 are discarded through the waste electrode 27. In addition, when a positive voltage is applied to the waste gate electrode 26, a channel is formed between the well 12 and the waste well 25 to allow electrons to move. Electrons in the well 12 travel through this channel toward the waste well 25. Here, if the voltage applied to the waste gate electrode 26 and the waste electrode 27 is kept constant, the mobility of electrons from the well 12 toward the waste well 25 becomes substantially constant.

  Therefore, after electrons are accumulated by light irradiation in the photoelectric conversion unit D1 provided in the well 12, a specified constant voltage is applied to the disposal gate electrode 26 for a specified period of time, and electrons are transferred from the well 12 to the disposal well 25. Move. As described above, since the mobility of the moving electrons is constant, an amount of electrons approximately proportional to the time during which the voltage is applied to the waste gate electrode 26 can be moved to the waste well 25. That is, among the electrons generated in the well 12, if the electrons moved to the waste well 25 are used as unnecessary charges and the electrons remaining in the well 12 are used as effective charges, a specified amount of unnecessary charges are separated. become. The effective charge remaining in the well 12 is taken out as a light receiving output.

  In the configuration of the present embodiment, the amount of unnecessary charges is determined by the voltage applied to the waste gate electrode 26 and the waste electrode 27 and the time during which the voltage is applied to the waste gate electrode 26. As described above, the waste gate electrode 26 Since the voltage applied to the waste electrode 27 is kept constant, the amount of unnecessary charges is a function of the time during which the voltage is applied to the waste gate electrode 26. In the configuration of this embodiment, not only the well 12 functions as the photoelectric conversion unit D1, but also the effective charge remains in the well 12, so that the well 12 also functions as the charge storage unit D3. Further, the disposal well 25, the disposal gate electrode 26, and the disposal electrode 27 function as the charge separation unit D2. Other configurations and operations are the same as those of the above-described embodiment. However, since the amount of charge to be discarded is a function of time and not voltage, a configuration for automatically determining the amount of charge to be discarded according to the amount of received ambient light as in the second and third embodiments is used. Cannot be adopted.

(Embodiment 9)
In each of the above-described embodiments, the configuration in which unnecessary charges are separated by controlling the voltage applied to the plurality of electrodes arranged on the main surface of the element formation layer 11 is employed. The charge separation unit D2 that performs weighing is not provided with an electrode that controls the movement of electrons, and the voltage applied to the transfer control electrode 31 provided in the charge transfer unit for taking out the received light output is controlled to control the charge transfer unit. An example in which the charge storage unit D3 is used will be described. That is, in each of the above-described embodiments, the same electrode arrangement as that of the frame transfer type electrode configuration in the CCD image sensor is employed. However, in this embodiment, the interline transfer (IT) type electrode configuration in the CCD image sensor is employed. The example which employ | adopted the same electrode arrangement | positioning is shown.

As shown in FIG. 21, the p-type element formation layer 11 is formed on an n-type substrate 10, and an n ^{+ -type} well 12 and an n-type well 12 are formed on the main surface side of the element formation layer 11. A transfer well 32 is arranged via a p ^{+ -type} barrier well 33. The transfer well 32 has a configuration similar to that of an IT type CCD image sensor, and a transfer control electrode 31 is disposed on the main surface of the transfer well 32 via an insulating layer 34. The transfer well 32 is covered with a light shielding film 35. A number of transfer control electrodes 31 are arranged in a direction orthogonal to the plane of FIG. 21, and when transferring electrons, the order in which voltages are applied to the transfer control electrodes 31 is controlled as is well known in the art. In addition to the transfer control electrode 31, the drain electrode 36 ohmically connected to the substrate 10 is used together for weighing the unnecessary charges. The well 12 is also used as the photoelectric conversion unit D1 and the charge separation unit D2.

  In this embodiment, no electrode is provided in the well 12, and the element formation layer 11 and the well 12 are of different conductivity types, so that a potential well is formed in the well 12 as shown in FIG. Is done. The barrier well 33 forms a potential barrier B 7 between the well 12 and the transfer well 32. In this state, all the electrons in the transfer well 32 are discharged. In addition, no voltage is applied to the transfer control electrode 31, and a positive voltage (for example, 5 volts) is applied to the drain electrode.

  After electrons by light irradiation are generated in the photoelectric conversion unit D1, a relatively large positive voltage (for example, 10 volts) is applied to the transfer control electrode 31. The potential barrier B7 formed in the barrier well 33 lowers the potential as the voltage applied to the transfer control electrode 31 is higher. If an appropriate voltage higher than the voltage at the time of transferring electrons is applied to the transfer control electrode 31, a part of the electrons accumulated in the well 12 by light irradiation exceeds the potential barrier B7 as shown in FIG. Into the transfer well 32. Since the height of the potential barrier B 7 is determined by the voltage applied to the transfer control electrode 31, a predetermined amount of electrons remain in the well 12. That is, the well 12 functions as the charge separation unit D2, and the transfer well 32 functions as the charge storage unit D3.

  When unnecessary charges remain in the well 12 and effective charges flow into the transfer well 32, the voltage application to the transfer control electrode 31 is stopped, and the drain electrode 36 has a relatively high positive voltage (for example, 15 volts). ) Is applied. In this state, as shown in FIG. 22E, the potential barrier B7 becomes high, and the potential well formed in the transfer well 32 becomes shallow. That is, the effective charge that has flowed into the transfer well 32 is held in the charge storage portion D3. Unnecessary charges remaining in the well 12 are discarded through the drain electrode 36.

  With the above-described operation, a predetermined amount of electrons generated by light irradiation can be separated as unnecessary charges, and the remaining effective charges can be left in the transfer well 32. The effective charge can be transferred in a direction orthogonal to the plane of the figure by controlling the voltage applied to the transfer control electrode 31 and performing the same operation as the vertical transfer register of the CCD image sensor. Other configurations and operations are the same as those of the other embodiments described above.

  By the way, in the case of detecting information on the target space by combining the light detection element having the configuration of the present embodiment shown in FIG. 21 and a light source that emits light whose intensity is modulated by a modulation signal, modulation is performed. It is necessary to extract the amount of received light corresponding to a predetermined section of the signal phase. In such a case, for example, as shown in FIG. 23A, a relatively high positive voltage (for example, 15 volts) is applied to the transfer control electrode 31 in the light receiving period T1 to the transfer well 32. By forming a deep potential well, electrons generated in the photoelectric conversion unit D1 (well 12) by light irradiation flow into the transfer well 32, and as shown in FIG. The voltage applied to is changed in two steps (for example, 15 volts and 5 volts) in synchronization with the modulation signal, so that electrons are discarded and the electrons flow into the potential well formed in the transfer well 32. The state to be made is created alternately. If the voltage applied to the waste electrode 36 is set to a low voltage at the timing of extracting the charge used for the light receiving output from the charge generated by the photoelectric conversion unit D1, the charge can be caused to flow into the transfer well 32. Changes in the potential well in the light receiving period T1 are shown in FIGS.

  After changing the voltage applied to the waste electrode 36 many times during the light receiving period in which the above-described operation is performed, the process proceeds to the weighing period T2. In the weighing period T2, first, a negative voltage (for example, -5 volts) is applied to the transfer control electrode 31 so as to shallow the potential well in the transfer well 32, and the electron is discarded from the well 12 so as not to be discarded. The voltage applied to the electrode 36 is relatively low (for example, 5 volts). With this relationship, electrons can be returned from the transfer well 32 to the well 12. The operation of weighing after returning the electrons to the well 12 is as described above.

DESCRIPTION OF SYMBOLS 11 Element formation layer 12 Well 14a Separation electrode 14b Storage electrode 14c Barrier control electrode 14d Holding electrode 14e Gate electrode 17a-17h Sensitivity control electrode 18a-18l Control electrode 19a-19i Control electrode B1-B7 Potential barrier D1 Photoelectric conversion part D2 Charge separation Part D3 Charge storage part D4 Charge holding part

Claims (12)

The amount corresponding to the amount of received light detected at the timing synchronized with the modulation signal among the received light amount of the light detection element, the light source that projects the light whose intensity is modulated by the modulation signal into the target space as signal light A spatial information detection apparatus comprising: a signal processing unit that detects spatial information of a target space using a light receiving output that reflects a fluctuation component of signal light obtained by separating a certain amount of bias component from the charge of The photodetecting element includes a photoelectric conversion unit that generates charges by light irradiation , and a total of a charge component generated by the photoelectric conversion unit and a fluctuation component that varies in accordance with increase / decrease in the amount of received light. A charge separation unit that separates a predetermined amount of unnecessary charge corresponding to the deemed bias component, and a charge storage unit that accumulates the remaining charge separated from the charge generated by the photoelectric conversion unit as an effective charge. Comprising a part, and a charge take-out portion for taking out the stored effective charge in the charge storage unit as the light reception output, signal processing unit, generated by the operation and the photoelectric conversion unit charge is generated in the photoelectric conversion portion After the unnecessary charge is separated from the charge and the operation of accumulating the effective charge in the charge accumulation unit is repeated a plurality of times, the charge accumulated in the charge accumulation unit is extracted from the charge extraction unit as a light receiving output. The amount of light corresponding to the amount of light received during a specified fixed lighting period is controlled so that the light-emitting element is operated to operate the light-emitting source so as to provide a lighting period in which light is emitted from the light-emitting source and a light-out period in which light is not emitted. The amount of unnecessary charge that is separated from the remaining charge by leaving the amount of charge corresponding to the fluctuation component of the signal light is determined by the amount of received light obtained during the extinguishing period, and a plurality of amounts that define the determined amount of unnecessary charge The photo-detecting element is controlled so as to perform a weighing operation that is divided into equal parts, and the amount of unnecessary charge that is separated in one weighing operation is specified so as to increase as the duration of the extinguishing period continues. An apparatus for detecting spatial information , characterized in that: In the photodetecting element, the charge separation unit and the charge storage unit are potential wells formed in a semiconductor, and when the charge generated by the photoelectric conversion unit flows into the charge separation unit, the charge separation unit The charge flowing into the charge storage section across the potential barrier formed between the charge storage section and the charge storage section is the effective charge, and the charge remaining in the charge separation section is the unnecessary charge. The barrier charge electrode is provided at a portion corresponding to the barrier, and the amount of unnecessary charges is adjusted by changing the height of the potential barrier according to the voltage applied to the barrier control electrode. Spatial information detection device. In the photodetecting element, the charge separation unit and the charge storage unit are potential wells formed in a semiconductor, and when the charge generated by the photoelectric conversion unit flows into the charge separation unit, the charge separation unit The charge flowing into the charge storage section across the potential barrier formed between the charge storage section and the charge storage section is referred to as the effective charge, and the charge remaining in the charge separation section is used as the unnecessary charge. A separation electrode is provided at a portion corresponding to the separation portion, and the amount of unnecessary charges to be separated is adjusted by changing the depth of the potential well serving as the charge separation portion according to the voltage applied to the separation electrode. The spatial information detection device according to claim 1 . The photodetecting element includes an element forming layer made of a first conductivity type semiconductor, a second conductivity type well formed on a main surface of the element forming layer, and a discarding unit in which charges of the charge separation unit are discarded. And a control electrode arranged on the main surface of the well, and applied to the control electrode in association with a light receiving period for generating charges by irradiating light to the well and a weighing period for separating a certain amount of unnecessary charges A plurality of control electrodes are arranged side by side on the main surface of the well, and a potential barrier is formed in a region corresponding to one of the control electrodes in the well during the weighing period and corresponds to another control electrode. 2. The spatial information detection device according to claim 1, wherein a potential well serving as the charge separation unit and a potential well serving as the charge storage unit are formed in a region with a potential barrier interposed therebetween . A plurality of the photoelectric conversion units are arranged and the charge separation unit is provided for each photoelectric conversion unit, and the signal processing unit sets the amount of unnecessary charges to be separated in one weighing operation for each charge separation unit. The spatial information detection device according to claim 1, wherein the number of weighing operations is set to the same number in all the charge separation units. The signal processing unit shortens the turn-off period so that the remainder when dividing by the amount of unnecessary charge separated in one weighing operation is smaller than a prescribed amount over all the photoelectric conversion units. 6. The apparatus for detecting spatial information according to claim 5, wherein the amount of unnecessary charges separated by one weighing operation is reduced and the number of weighing operations is increased. The signal processing unit controls the photodetecting element so as to provide a plurality of disposal periods in the lighting period for separating unnecessary charges calculated in accordance with the amount of received light obtained in the extinguishing period, and in one disposal period The weighing operation is performed a plurality of times, and the number of weighing operations is increased for each specified number of disposal periods, and the specified number of times is discarded by the amount of charge due to noise components generated in one lighting period and one weighing operation. The spatial information detection device according to claim 1, wherein the spatial information detection device is defined by an amount of unnecessary charges. 2. The signal processing unit according to claim 1, wherein when the light receiving output reaches a predetermined saturation level during a lighting period that is a fixed time each time, the signal processing unit increases an amount of unnecessary charges separated in a next lighting period. The spatial information detection device according to claim 4. 9. The spatial information detection device according to claim 8, wherein the signal processing unit increases the amount of unnecessary charges separated in the lighting period by increasing the number of operations for discarding unnecessary charges in the lighting period.   The signal processing unit controls the photodetecting element to perform an operation of discarding unnecessary charges a plurality of times during the lighting period, and sets a time interval for each operation, and the time interval increases as the light receiving output during the light-off period increases. The spatial information detection device according to claim 1, wherein the spatial information detection device is shortened. The said signal processing part selects the time for which a lighting period continues from multiple types, The detection apparatus of the spatial information of any one of Claim 1 thru | or 10 characterized by the above-mentioned. 11. The signal processing unit according to claim 1, wherein the signal processing unit selects a time during which the lighting period continues from a plurality of types, and increases or decreases the number of weighing operations according to the time during which the lighting period continues. The apparatus for detecting spatial information according to item 1.

Images