JP2022176579A - Distance image pickup device and distance image pickup method - Google Patents

Abstract

To provide a distance image pickup device which maintains the sensitivity to the resolution of a photographed image and incident light without increasing the capacity of a charge storage part and suppresses saturation due to increase in the intensity of the incident light.SOLUTION: A distance image pickup device comprises: a light reception unit that includes a plurality of pixel circuits having a photoelectric conversion element which generates a charge according to incident light that is incident from a measurement space of a measurement object, N (N≥3) charge storage units which store the charges in a frame period and a transfer transistor which transfers the charges from the photoelectric conversion element to the charge storage units, and a pixel drive circuit which performs on/off processing of the transfer transistor to the charge storage units in a storage period synchronized with the irradiation of a light pulse and distributes the charges for storage; a measurement control unit which divides the charges generated by the photoelectric conversion element into each of the combinations of the charge storage units in any transfer period of charge storage cycles and distributes the charges for storage; and a distance calculation unit which obtains a distance to a subject in the measurement space as a measurement distance on the basis of the charge amount stored in the charge storage units.SELECTED DRAWING: Figure 1

Description

The present invention relates to a range image capturing device and a range image capturing method.

Conventionally, the time-of-flight (hereinafter referred to as "ToF") method of measuring the distance to an object based on the time of flight of light using the fact that the speed of light is known. There is an imaging device (see Patent Document 1, for example).
The ToF range imaging device consists of a light source unit that emits light and an imaging unit that includes a pixel array in which a plurality of pixel circuits that detect light for measuring distance are arranged in a two-dimensional matrix (array). I have. Each of the pixel circuits has, as a component, a photoelectric conversion element (for example, a photodiode) that generates an electric charge corresponding to the intensity of light.
With this configuration, the ToF range image capturing device can acquire (capture) information about the distance between itself and the subject and an image of the subject in the measurement space (three-dimensional space).

The ToF range image capturing apparatus measures the distance based on the delay time from the timing of emitting the radiation to the timing of receiving the reflected light reflected by the object.
However, since the amount of charge generated by the photosensor changes according to the intensity of the incident light, the intensity of the reflected light increases as the distance to the subject decreases (light intensity is the square of the distance). inversely proportional to ).

As described above, as the intensity of reflected light and the intensity of background light in the environment increase, the amount of charge generated by the photoelectric conversion element increases. The charge storage section may saturate.
On the other hand, since the ToF range image pickup device obtains the delay time based on the charge amount accumulated in the charge accumulation unit, the measurement accuracy improves as the SN ratio between the signal and noise increases.
Therefore, in order not to saturate the charge storage section, it is conceivable to increase the capacity of the charge storage section.

Japanese Patent Application Laid-Open No. 2004-294420

However, when increasing the capacity of the charge storage section, the area of the pixel circuit is increased, and if the capacity of the charge storage section is increased for the same chip size, it is necessary to reduce the number of pixels. Resolution will be reduced.
On the other hand, if the chip size is increased by the amount corresponding to the increase in the area of the pixel circuit, the resolution of the range image pickup device can be maintained, but the unit price of the chip increases.
In addition, if the capacitance of the charge storage portion is increased without changing the area of the pixel circuit, the area of the photoelectric conversion portion must be reduced to compensate for the increase in the area of the charge storage portion. will decrease, and the accuracy of the distance to be obtained will decrease.

The present invention has been made in view of such circumstances, and is capable of increasing the intensity of incident light while maintaining the resolution of a captured image and the sensitivity to incident light without increasing the capacity of the charge storage unit. An object of the present invention is to provide a range image capturing device and a range image capturing method capable of suppressing saturation.

In order to solve the above-described problems, the distance image pickup device of the present invention includes a photoelectric conversion element that generates electric charges according to incident light, which is light that is incident from a measurement space that is a space to be measured, and a plurality of pixel circuits each including N (N≧3) charge storage units that store charges; and transfer transistors that transfer the charges from the photoelectric conversion elements to the respective charge storage units; a light-receiving portion having a pixel drive circuit for performing ON/OFF processing of each of said transfer transistors in each of said charge storage portions in a synchronous predetermined accumulation period and distributing and storing said charges; and said charges generated by said photoelectric conversion elements. is divided and distributed to each of the combinations of the charge accumulators in any transfer period of the charge accumulator cycle, and based on the amount of charge accumulated in each of the charge accumulators, and a distance calculator that obtains a distance to a subject existing in the measurement space as the measurement distance.

In the distance image pickup device of the present invention, the measurement control unit simultaneously turns on the transfer transistors corresponding to each of the plurality of charge storage units of the combination in the transfer order for each storage period in the capacity increase mode, The charge generated by the photoelectric conversion element is transferred to each of the charge storage units of the combination, and the charge generated by the photoelectric conversion element is divided and stored in each of the charge storage units of the combination. and

In the distance image pickup device of the present invention, the measurement control unit divides each of the plurality of charge accumulation units in the combination by multiplying the number of accumulations in the frame period by a predetermined ratio in the capacity increase mode. setting the number of accumulations, turning on the transfer transistors in the order of transfer in different accumulation cycles for each of the charge accumulation units of the combination, and dividing the number of accumulations for each of the charge accumulation units of the combination; The charge generated by the photoelectric conversion element is divided and accumulated in each of the charge storage units of the combination by transferring the charge generated by the photoelectric conversion element.

In the range image pickup apparatus of the present invention, in the capacity increase mode, the transfer transistor is repeatedly turned on for each different accumulation cycle, and the charge accumulation units are alternately charged to each of the plurality of charge accumulation units of the combination. The charge generated by the photoelectric conversion element is distributed and accumulated, and the charge generated by the photoelectric conversion element is divided and accumulated.

The distance image pickup device of the present invention is characterized in that, in the capacity increase mode, a plurality of combinations of two or more charge accumulation units are provided.

In the distance image pickup device of the present invention, the measurement control unit transfers the charge generated by the photoelectric conversion element to each of the charge accumulation units in a transfer order set in each accumulation period in the accumulation period of the frame period. and a normal mode in which the transfer transistor is turned on to store and transfer the charge generated by the photoelectric conversion element in one of the transfer periods of the charge storage cycle, divided and distributed to each of the combinations of the charge storage units and stored. It is characterized by switching between the capacity increase mode and the capacity increase mode according to a predetermined condition.

In the distance image pickup device of the present invention, the predetermined condition is a case where the charge amount of the charge accumulated in the charge storage unit exceeds a preset ratio with respect to the maximum capacity of the charge storage unit. and said combination includes a charge storage portion exceeding said ratio.

A distance image capturing method according to the present invention includes a plurality of pixel circuits each composed of a photoelectric conversion element, a plurality of charge storage units, and a transfer transistor, a pixel drive circuit, a distance calculation unit, and a measurement control unit. In the distance image capturing method for controlling an image capturing device, the pixel driving circuit converts the electric charges generated by the photoelectric conversion element according to the incident light from the measurement space into N a step of performing ON/OFF processing of each of the transfer transistors for transferring the charge from the photoelectric conversion element to the charge storage unit in each of the charge storage units (N≧3), distributing the charge to the charge storage unit, and storing the charge; However, the charge generated by the photoelectric conversion element is divided and distributed to each of the combinations of the charge storage units in one of the transfer periods of the charge storage cycle, and the distance calculation unit performs the above-described determining a distance to an object existing in the measurement space as a measurement distance based on the amount of charge accumulated in each of the charge accumulation units.

As described above, according to the present invention, saturation due to an increase in the intensity of incident light is suppressed while maintaining the resolution of a captured image and the sensitivity to incident light without increasing the capacity of the charge storage unit. It is possible to provide a range image capturing device and a range image capturing method capable of

1 is a block diagram showing a schematic configuration of a distance image pickup device according to a first embodiment of the present invention; FIG. 3 is a circuit diagram showing an example of a configuration of a pixel circuit 321 arranged in a range image sensor 32 in the range image pickup device according to the first embodiment of the present invention; FIG. FIG. 10 is a diagram showing a timing chart for transferring charges generated by the photoelectric conversion element PD in the normal mode to each of the charge storage units CS; FIG. 10 is a timing chart for transferring charges generated by photoelectric conversion element PD to each of charge storage units CS in a capacity increase mode when charge storage amount Q2 of charge storage unit CS2 exceeds a capacity threshold; 3 is a timing chart for transferring charges generated in the photoelectric conversion element PD to each of the charge storage units CS in the capacity increase mode when the charge storage amount Q2 of the charge storage unit CS2 exceeds the capacity threshold value in the first embodiment; FIG. 4 is a diagram showing; 5 is a flow chart showing an operation example of processing for calculating a distance between a distance image sensor 32 and a subject S by the distance image capturing device 1 of the first embodiment. FIG. 10 is a timing chart for transferring charges generated in the photoelectric conversion element PD to each of the charge storage units CS in the capacity increase mode when the charge storage amount Q2 of the charge storage unit CS2 exceeds the capacity threshold in the second embodiment; FIG. 4 is a diagram showing; FIG. 10 is a timing chart showing transfer of charges generated by the photoelectric conversion element PD to each of the charge storage units CS in a capacity increase mode in an environment in which the influence of background light can be ignored in the third embodiment;

<First embodiment>
A first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a distance image pickup device according to a first embodiment of the present invention. A distance image pickup device 1 having the configuration shown in FIG. Note that FIG. 1 also shows a subject S, which is an object whose distance is to be measured in the distance image pickup device 1 . The distance image pickup device is, for example, a distance image sensor 32 (described later) in the light receiving section 3 .

The light source unit 2 irradiates a light pulse PO to a shooting target space in which a subject S whose distance is to be measured in the range image pickup device 1 exists, under the control of the range image processing unit 4 . The light source unit 2 is, for example, a surface emitting semiconductor laser module such as a vertical cavity surface emitting laser (VCSEL: Vertical Cavity Surface Emitting Laser). The light source unit 2 includes a light source device 21 and a diffuser plate 22 .

The light source device 21 is a light source that emits a laser beam in a near-infrared wavelength band (for example, a wavelength band of 850 nm to 940 nm) as a light pulse PO to irradiate the subject S. FIG. The light source device 21 is, for example, a semiconductor laser light emitting element. The light source device 21 emits pulsed laser light under the control of the timing control section 41 .
The diffuser plate 22 is an optical component that diffuses the laser light in the near-infrared wavelength band emitted by the light source device 21 over a surface on which the subject S is irradiated. The pulsed laser light diffused by the diffusion plate 22 is emitted as a light pulse PO, and the subject S is irradiated with the light pulse PO.

The light receiving unit 3 receives the reflected light RL of the light pulse PO reflected by the subject S whose distance is to be measured in the distance image pickup device 1, and outputs a pixel signal corresponding to the received reflected light RL. The light receiving section 3 includes a lens 31 and a distance image sensor 32 .
The lens 31 is an optical lens that guides the incident reflected light RL to the range image sensor 32 . The lens 31 emits the incident reflected light RL to the distance image sensor 32 side and causes the pixel circuits provided in the light receiving area of the distance image sensor 32 to receive the light (incident).

The distance image sensor 32 is an image pickup device used in the distance image pickup device 1 . The distance image sensor 32 includes a plurality of pixel circuits 321 in a two-dimensional light receiving area and a pixel driving circuit 322 that controls each of the pixel circuits 321 .
The pixel circuit 321 includes one photoelectric conversion element (for example, a photoelectric conversion element PD to be described later) and a plurality of charge storage units (for example, charge storage units CS1 to CS4 to be described later) corresponding to the one photoelectric conversion element. , and components for distributing charges to the respective charge storage units.

The distance image sensor 32 distributes the charges generated by the photoelectric conversion elements to the respective charge storage units according to control from the timing control unit 41 . Also, the distance image sensor 32 outputs a pixel signal corresponding to the amount of charge distributed to the charge storage section. In the range image sensor 32, a plurality of pixel circuits are arranged in a two-dimensional matrix, and pixel signals for one frame corresponding to each pixel circuit are output.

The distance image processing unit 4 controls the distance image capturing device 1 and calculates the distance to the subject S. FIG.
The distance image processing section 4 includes a timing control section 41 , a distance calculation section 42 and a measurement control section 43 .
The timing control section 41 controls the timing of outputting various control signals required for distance measurement under the control of the measurement control section 43 . The various control signals here include, for example, a signal for controlling the irradiation of the light pulse PO, a signal for distributing the reflected light RL to a plurality of charge storage units, a signal for controlling the number of distributions per frame, and the like. The number of distributions is the number of times the process of distributing charges to the charge storage section CS (see FIG. 2) is repeated.

The distance calculation unit 42 outputs distance information obtained by calculating the distance to the subject S based on the pixel signals output from the distance image sensor 32 under the control of the measurement control unit 43 . The distance calculation unit 42 calculates the delay time Td from the irradiation of the light pulse PO to the reception of the reflected light RL based on the charge amounts accumulated in the plurality of charge accumulation units CS. The distance calculator 42 calculates the distance (measured distance) from the distance image capturing device 1 to the subject S according to the calculated delay time Td.

The measurement control unit 43 distributes the charge generated by the photoelectric conversion element PD due to incident light to each of the charge storage units in accordance with the amount of charge stored in the charge storage unit CS in frames that are repeated at the frame cycle. In this case, either the normal mode (used when the charge storage section is not saturated) or the capacity increase mode (used when the charge storage section is saturated) is selected for the distribution algorithm, and the timing control section 41 , distance calculation unit 42 and pixel drive circuit 322 .
That is, the measurement control unit 43 controls the timing in the timing control unit 41, controls the calculation in the distance calculation unit 42, and controls the charge accumulation unit CS by the pixel drive circuit 322, corresponding to each of the normal mode and the capacity increase mode. charge from the photoelectric conversion element PD is distributed (described in detail later).

With such a configuration, in the distance image capturing device 1, the light receiving unit 3 receives the reflected light RL that is reflected by the subject S from the light pulse PO in the near-infrared wavelength band that the light source unit 2 irradiates the subject S, The distance image processing unit 4 outputs distance information obtained by measuring the distance between the subject S and the distance image capturing device 1 .
Although FIG. 1 shows the distance image pickup device 1 having a configuration in which the distance image processing unit 4 is provided inside, the distance image processing unit 4 is a component provided outside the distance image pickup device 1. may

That is, the distance image capturing apparatus according to this embodiment calculates the distance between the object and the distance image sensor 32 based on the charges accumulated in the charge accumulation unit CS.
Therefore, in the calculation of the measurement distance, when the intensity of the reflected light or the background light is high, the intensity of the incident light is high, and the charge generated in the photoelectric conversion element is the maximum capacity that can store the charge in the charge storage section CS. If the storage capacity is exceeded, the amount of charge generated by the photoelectric conversion element cannot be obtained accurately, and the distance is calculated using the amount of charge in the charge storage unit, so that the measured distance between the distance image pickup device 1 and the subject S is calculated. cannot be determined precisely.

In addition, as the distance from the distance imaging device 1 to the subject S decreases, and as the reflectance of the subject S increases, the intensity of the reflected light generated by the light pulse PO reflected by the subject S increases. Therefore, the amount of charge generated by the reflected light increases in the photoelectric conversion element.
For this reason, the maximum storage capacity of the charge storage unit is exceeded, and the distance between the distance image capturing device 1 and the object S cannot be obtained accurately by calculating the distance using the charge amount of the charge storage unit.

Auto-exposure processing is performed to control the number of times of accumulation or the number of times of emission of light pulses PO, depending on the amount of charge accumulated in the charge storage section.
Here, when the intensity of the reflected light increases, by reducing the number of charge accumulations generated by the photoelectric conversion element due to the reflected light, the amount of charge necessary for calculating the measurement distance is accumulated in the charge accumulation element. The accuracy of the measured distance is improved.

However, it is generally rare for the reflectance of each object to be the same, and the reflectance of each object is different from each other. When the number of times of accumulation is set according to , the amount of electric charge generated by reflected light from a subject with low reflectance at a distance from the distance image capturing device is reduced, the S/N ratio is lowered, and the accuracy of the measured distance is reduced. descend.

On the other hand, when the number of times of accumulation is set according to the subject at a long distance in order to improve the accuracy of the measurement distance, the distance from each subject other than the subject at a long distance to the distance image capturing device is unknown. When an object exists at a short distance in 1, the intensity of the reflected light from the object at the short distance is greater than that from the object at a long distance, and the electric charge generated by the reflected light from the object at the short distance causes charge accumulation. part becomes saturated.
For this reason, in the present embodiment, as will be described later, the measurement controller 43 controls charge accumulation of charges generated by incident light in the photoelectric conversion element PD via the timing control unit 41 so that the charge accumulation unit is not saturated. At the time of distribution to each section, control is performed by selecting either the normal mode or the capacity increase mode for the distribution algorithm.

Next, the configuration of the pixel circuit 321 in the distance image sensor 32 will be described.
FIG. 2 is a circuit diagram showing an example of the configuration of the pixel circuit 321 arranged in the range image sensor 32 in the range image pickup device according to the first embodiment of the present invention. The pixel circuit 321 in FIG. 2 is a configuration example including, for example, four pixel signal readout units RU1 to RU4. The configuration of the pixel circuit 321 in the present embodiment is an example, and has a configuration of a plurality of pixel signal reading units of 3 or more, that is, n (n≧3).

The pixel circuit 321 includes one photoelectric conversion element PD, a charge discharge transistor GD, and four pixel signal readout units RU (RU1 to RU4) that output voltage signals from corresponding output terminals O. As shown in FIG. Each pixel signal readout unit RU includes a transfer transistor G, a floating diffusion FD, a charge storage capacitor C, a reset transistor RT, a source follower transistor SF, and a select transistor SL. The floating diffusions FD (FD1, FD2, FD3, FD4) and the charge storage capacitors C (C1, C2, C3, C4) constitute a charge storage section CS (CS1, CS2, CS3, CS4).

In the pixel circuit 321 shown in FIG. 2, the pixel signal readout unit RU1 that outputs a voltage signal from the output terminal O1 includes a transfer transistor G1 (transfer MOS transistor), a floating diffusion FD1, a charge storage capacitor C1, and a reset transistor RT1. , a source follower transistor SF1, and a selection transistor SL1. In the pixel signal readout unit RU1, the charge storage unit CS1 is composed of the floating diffusion FD1 and the charge storage capacitor C1. The pixel signal readout units RU2, RU3 and RU4 also have the same configuration.

The photoelectric conversion element PD is an embedded photodiode that photoelectrically converts incident light, generates electric charges corresponding to the incident light (incident light), and accumulates the generated electric charges. In this embodiment, incident light is incident from the space to be measured.
In the pixel circuit 321, the charges generated by the photoelectric conversion element PD photoelectrically converting incident light are distributed to the four charge storage units CS (CS1 to CS4), respectively, and the respective charges corresponding to the charge amounts of the distributed charges are distributed. A voltage signal is output to the distance image processing unit 4 .
Further, the configuration of the pixel circuits arranged in the distance image sensor 32 is not limited to the configuration including the four pixel signal readout units RU (RU1 to RU4) as shown in FIG. A pixel circuit having a configuration in which the readout unit RU includes one or more pixel signal readout units RU may be used.

In driving the pixel circuit 321 of the distance image pickup device 1, the light pulse PO is emitted for the irradiation time To, and the reflected light RL is received by the distance image sensor 32 after the delay time Td. Under the control of the timing control unit 41, the pixel driving circuit 322 transfers charges generated in the photoelectric conversion elements PD to the transfer transistors G1, G2, G3, and G4 in synchronization with the irradiation of the light pulse PO as accumulation drive signals. TX1 to TX4 are supplied and switched according to respective timings, and are accumulated in the order of the charge accumulation units CS1, CS2, CS3, and CS4.

Then, the pixel driving circuit 322 controls the reset transistor RT and the selection transistor SL with the drive signals RST and SEL, respectively, and converts the charge accumulated in the charge storage section CS into an electric signal with the source follower transistor SF. , and outputs the generated electric signal to the distance calculator 42 via the output terminal O. FIG.
In addition, the pixel drive circuit 322 discharges (erases) the charge generated in the photoelectric conversion element PD by flowing it to the power supply VDD according to the drive signal RSTD under the control of the timing control unit 41 .

FIG. 3 is a diagram showing a timing chart for transferring charges generated by the photoelectric conversion element PD in the normal mode to each of the charge storage units CS.
In the timing chart of FIG. 3, the vertical axis indicates the pulse level and the horizontal axis indicates time. FIG. 3 also shows an accumulation period that is repeated during the charge accumulation period in a frame. The relative relationship on the time axis between the light pulse PO and the reflected light RL in the normal mode, the timings of the storage drive signals TX1 to TX4 supplied to the transfer transistors G1 to G4, and the drive signal RSTD supplied to the charge discharge transistor GD. timing.

The timing control unit 41 causes the light source unit 2 to irradiate the measurement space with the light pulse PO. As a result, the light pulse PO is reflected by the subject and received by the light receiving section 3 as reflected light RL. Then, the photoelectric conversion element PD generates charges corresponding to each of the background light and the reflected light RL. The pixel driving circuit 322 controls on/off of each of the transfer transistors G1 to G4 in order to transfer the charge generated by the photoelectric conversion element PD to each of the charge storage units CS1 to CS4.
That is, the pixel drive circuit 322 converts each of the accumulation drive signals TX1 to TX4 into an "H" level signal with a predetermined time width (the irradiation time To, that is, the same width as the pulse width), and the transfer transistors G1 to G4, respectively. supply to

The pixel drive circuit 322, for example, turns on the transfer transistor G1 provided on the transfer path for transferring the charge from the photoelectric conversion element PD to the charge storage unit CS1. As a result, charges photoelectrically converted by the photoelectric conversion element PD are accumulated in the charge accumulation unit CS1 via the transfer transistor G1. After that, the pixel drive circuit 322 turns off the transfer transistor G1. As a result, transfer of charges to the charge storage section CS1 is stopped. In this manner, the pixel drive circuit 322 accumulates charges in the charge accumulation section CS1. The same applies to the other charge storage units CS2, CS3 and CS4.

At this time, each of the accumulation drive signals TX1, TX2, TX3, and TX4 corresponds to the accumulation cycle in the charge accumulation period (the period in which charges are accumulated in each of the charge accumulation sections CS in a frame) in which charges are distributed to the charge accumulation sections CS. , transfer cycles T1, T2, T3, and T4 (cycle for accumulating and integrating charges, transfer order) supplied to transfer transistors G1, G2, G3, and G4, respectively, are repeated.
Here, for example, charges generated by incident light (background light only) in the transfer period T1 are accumulated in the charge accumulation section CS1, and charges generated by incident light (background light+reflected light) in the transfer period T2 are accumulated in the charge accumulation section CS1. The charge accumulated in CS2 and generated by incident light (background light+reflected light) in transfer period T3 is accumulated in charge accumulation section CS3, and the charge generated by incident light (background light+reflected light) in transfer period T4 becomes charge. It is accumulated in the accumulation unit CS4.

Charges corresponding to the incident light are transferred from the photoelectric conversion element PD to the charge storage units CS1, CS2, CS3, and CS4 via the transfer transistors G1, G2, G3, and G4, respectively. That is, in the charge accumulation period of each frame period, a plurality of accumulation cycles are repeated in which charges are transferred in each transfer order of the charge accumulation units CS1, CS2, CS3, and CS4.
As a result, charges are stored in the charge storage units CS1, CS2, CS3, and CS4 in each of the transfer cycles T1, T2, T3, and T4 for each storage cycle of the charge storage units CS1, CS2, CS3, and CS4 in the charge storage period. is accumulated.

Further, when repeating the accumulation cycle of each of the charge storage units CS1, CS2, CS3, and CS4, the pixel drive circuit 322 transfers the charge from the photoelectric conversion element PD after the transfer (distribution) of the charge to the charge storage unit CS4 is completed. The "H" level drive signal RSTD is supplied to the charge discharging transistor GD provided on the discharging path to turn it on.
As a result, the charge discharge transistor GD discards the charge generated in the photoelectric conversion element PD after the immediately preceding transfer cycle T4 of the charge storage unit CS4 before the transfer cycle T1 for the charge storage unit CS1 is started (that is, reset the photoelectric conversion element PD).

Then, the pixel drive circuit 322 sequentially applies voltage signals from all the pixel circuits 321 arranged in the light-receiving unit 3 in units of rows (horizontal arrangement) of the pixel circuits 321 to A/D conversion processing and the like. signal processing.
After that, the pixel drive circuit 322 causes the voltage signals after the signal processing to be output to the distance calculation section 42 sequentially in the order of the columns arranged in the light receiving section 3 .

The accumulation of charges in the charge accumulation unit CS by the pixel drive circuit 322 and the discarding of the charges photoelectrically converted by the photoelectric conversion elements PD as described above are repeatedly performed over one frame. As a result, charges corresponding to the amount of light received by the distance image pickup device 1 during a predetermined time interval are accumulated in each of the charge accumulation units CS. The pixel drive circuit 322 outputs to the distance calculation section 42 an electrical signal corresponding to the amount of charge for one frame accumulated in each of the charge accumulation sections CS.

Due to the relationship between the timing of irradiating the light pulse PO and the timing of accumulating electric charge in each of the charge accumulating units CS (CS1 to CS4), the charge accumulating unit CS1 receives light such as background light before irradiation of the light pulse PO. A charge amount corresponding to the external light component is held. Further, the charge amounts corresponding to the reflected light RL and the external light component are distributed and held in the charge storage units CS2, CS3, and CS4. The distribution (distribution ratio) of the amount of charge distributed to the charge storage units CS2 and CS3 or to the charge storage units CS3 and CS4 is the delay time until the light pulse PO is reflected by the object S and is incident on the distance image pickup device 1. It becomes a ratio according to Td.

Returning to FIG. 1, the distance calculator 42 uses this principle to calculate the delay time Td by the following equation (1) or (2).
Td=To×(Q3-Q1)/(Q2+Q3-2×Q1) (1)
Td = To + To x (Q4 - Q1) / (Q3 + Q4 - 2 x Q1) (2)
Here, To is the period during which the light pulse PO is irradiated, Q1 is the amount of charge accumulated in the charge storage section CS1, Q2 is the amount of charge accumulated in the charge storage section CS2, and Q3 is the amount of charge accumulated in the charge storage section CS3. A charge amount Q4 indicates the charge amount accumulated in the charge accumulation section CS4. For example, when Q4=Q1, the distance calculation unit 42 calculates the delay time Td using equation (1), and when Q2=Q1, calculates the delay time Td using equation (2).

In the formula (1), charges generated by reflected light are accumulated in the charge accumulation units CS2 and CS3, but are not accumulated in the charge accumulation unit CS4. On the other hand, in the formula (2), charges generated by reflected light are accumulated in the charge accumulation units CS3 and CS4, but are not accumulated in the charge accumulation unit CS2.
Note that, in the formula (1) or the formula (2), among the charge amounts accumulated in the charge accumulation units CS2, CS3, and CS4, the component corresponding to the external light component is the charge amount accumulated in the charge accumulation unit CS1. It is assumed that the amounts are the same.

The distance calculator 42 multiplies the delay time obtained by formula (1) or formula (2) by the speed of light (velocity) to calculate the measured distance to the object S in the round trip.
Then, the distance calculation unit 42 halves the calculated round-trip distance (delay time Td×c (light speed)/2), so that the distance image sensor 32 (that is, the distance image capturing device 1) to the object S is obtained.

Further, the time Trs is the time when the charge generated by the input light does not remain in the photoelectric conversion element PD after the charge distribution from the photoelectric conversion element PD to the charge storage section CS4 in one cycle of the accumulation period in FIG. ), the drive signal RSTD supplied to the charge discharge transistor GD is set to "H" level.

FIG. 4 is a block diagram showing a configuration example of the measurement control section 43 in the distance image pickup device of the first embodiment. 4, the measurement control unit 43 includes a normal mode operating condition setting unit 431, a mode determination unit 432, a capacity increase mode operating condition setting unit 433, an operation control unit 434, a mode determination condition storage unit 435, and an operating condition combination storage unit 436. Each of the

The normal mode operating condition setting unit 431 reads from the operating condition combination storage unit 436 the control setting of the timing control unit 41 in the normal mode of the timing chart shown in FIG.
Then, the normal mode operation condition setting unit 431 supplies the read normal mode settings to the operation control unit 434 .
The operation control unit 434 controls the operation of the timing control unit 41, the distance calculation unit 42, and the pixel driving circuit 322 by setting the normal mode, and causes the operation in the normal mode shown in FIG.

The mode determination unit 432 determines whether to operate the timing control unit 41 in either the normal mode or the capacity increase mode.
Here, when the charge storage unit CS1 stores charges generated by background light, the mode determination unit 432 determines that the charge storage amount Q2 of the charge storage unit CS2, the charge storage amount Q3 of the charge storage unit CS3, and the charge storage amount Q3 of the charge storage unit CS4 The number of pixel circuits 321 each having a charge accumulation amount Q4 exceeding a preset capacity threshold is extracted.

The mode determination unit 432 reads the capacity threshold value from the mode determination condition storage unit 435, and compares it with each of the charge storage amount Q2, the charge storage amount Q3, and the charge storage amount Q4.
This first threshold value is set, for example, as an amount of charge that is 80% of the maximum storage capacity of the charge storage section CS, or 80% or more.
Here, in actual operation, as the capacitance threshold, considering the variation of the charge generated by the reflected light accumulated in the charge accumulation section CS, the empirical range is, for example, about 90% to 95% of the maximum accumulation capacity. is set to

However, when the capacity threshold is set to 90% to 95% of the maximum storage capacity, the photoelectric conversion element PD generates charges not only by reflected light but also by incident light including background light. , it is assumed that the charge storage section CS is saturated depending on the change in the intensity of the background light.
For this reason, experimentally, it has been found to be desirable to have a margin of 60% or more for variation in the amount of charge due to incident light generated by the photoelectric conversion element PD due to changes in background light.

The mode determination unit 432 determines, for each pixel circuit 321, a charge storage amount Q2, a charge storage amount Q3, a charge storage amount, which are the amounts of charge stored in each of the charge storage unit CS2, the charge storage unit CS3, and the charge storage unit CS4. Each Q4 determines whether or not it exceeds a preset capacity threshold.
Then, the mode determination unit 432 counts the number of each of the charge storage units CS2, CS3, and CS4 whose storage capacitance exceeds the capacitance threshold in all the pixel circuits 321. FIG.
Here, the mode determination unit 432 extracts the charge storage unit CS having the largest number of storage capacities exceeding the capacity threshold among each of the charge storage units CS2, CS3, and CS4.
Note that the method for extracting the charge storage portion is not limited to the method described above. For example, when the ratio of saturated pixels to the total number of pixels (for example, 20% of the total number of pixels) is predetermined as an extraction threshold, and the saturated pixels of each charge storage unit are counted and saturated beyond the extraction threshold, , the charge storage portion may be extracted.

At this time, the mode determination unit 432 distributes the charges generated by the photoelectric conversion element PD in the transfer period T2 (transfer order) in the accumulation period (charge accumulation cycle) in the normal mode only to the charge accumulation unit CS2.
However, for example, when the charge storage amount Q2 of the charge storage unit CS2 exceeds the capacity threshold, the mode determination unit 432 selects the capacity increase mode to transfer the charge generated by the photoelectric conversion element PD in the transfer period T2 to the charge storage unit CS2. and stored in the charge storage unit CS3.
Also, the mode determination unit 432 causes the charge storage unit CS4 to store the charge generated by the photoelectric conversion element PD in the transfer period T3.
Note that the charge storage unit to be combined with the charge storage unit CS2 is not limited to the charge storage unit CS3. For example, by combining the charge storage section CS4 with the charge storage section CS2 at the timing of the transfer period T2, assigning the charge storage section CS3 to the transfer period T3 and the charge storage section CS1 to the transfer period T1, the same operation as described above can be performed. It is possible.
That is, the mode determination section 432 divides and distributes the charge generated by the photoelectric conversion element PD due to incident light to each of the combinations of the charge storage sections CS in any transfer period of the charge storage cycle. process to cause

FIG. 5 shows transfer of charges generated in the photoelectric conversion element PD to each of the charge storage units CS in the capacity increase mode when the charge storage amount Q2 of the charge storage unit CS2 exceeds the capacity threshold in the first embodiment. It is a figure which shows the timing chart which carries out.
In the timing chart of FIG. 5, the vertical axis indicates the pulse level (“H” level/“L” level), and the horizontal axis indicates time. In addition, FIG. 5 shows the order of transfer in an accumulation period that is repeated during the charge accumulation period in a frame. The timing of each of the storage drive signals TX1 to TX4 supplied to the transfer transistors G1 to G4 in the capacity increase mode and the timing of the drive signal RSTD supplied to the charge discharge transistor GD are shown.

The timing control unit 41 causes the light source unit 2 to irradiate the measurement space with the light pulse PO. As a result, the light pulse PO is reflected by the subject and received by the light receiving section 3 as reflected light RL. Then, the photoelectric conversion element PD generates charges corresponding to each of the background light and the reflected light RL. The pixel driving circuit 322 controls on/off of each of the transfer transistors G1 to G4 in order to transfer the charge generated by the photoelectric conversion element PD to each of the charge storage units CS1 to CS4.

That is, the pixel drive circuit 322 converts each of the accumulation drive signals TX1 to TX4 into an "H" level signal with a predetermined time width (the irradiation time To, that is, the same width as the pulse width), and the transfer transistors G1 to G4, respectively. supply to
The pixel drive circuit 322, for example, turns on the transfer transistor G1 provided on the transfer path for transferring the charge from the photoelectric conversion element PD to the charge storage unit CS1. As a result, charges photoelectrically converted by the photoelectric conversion element PD are accumulated in the charge accumulation unit CS1 via the transfer transistor G1. After that, the pixel drive circuit 322 turns off the transfer transistor G1. As a result, transfer of charges to the charge storage section CS1 is stopped.

Further, in the case of the capacity increase mode, the pixel drive circuit 322 outputs the accumulation drive signals TX2 and TX3 at the same timing (at the same timing) in the transfer period T2 for accumulating the charge in the charge accumulation section CS2 under the timing control of the timing control section 41 . ) at the same time in the order of transfer, and set to "H" level.
Then, each of the transfer transistors G2 and G3 divides and distributes the charge generated by the photoelectric conversion element PD to the charge storage section CS2 and the charge storage section CS3, respectively.
As a result, the charge amount saturated only in the charge storage section CS2 is divided and accumulated in each of the charge storage sections CS2 and CS3, thereby suppressing saturation of the accumulated charge amount exceeding the maximum storage capacity. be able to.

Further, in the normal mode, the accumulation drive signal TX4 is set to "H" level in the transfer period T4 in the normal mode.
However, in the capacity increase mode, the charge storage section CS4 has the function of the charge storage section CS3 in the normal mode, so the pixel drive circuit 322 sets the storage drive signal TX4 to "H" level in the transfer cycle T3.
As a result, the charge generated by the photoelectric conversion element PD in the transfer period T3 is distributed and accumulated in the charge accumulation unit CS4 via the transfer transistor G4.

Charges corresponding to the incident light are transferred from the photoelectric conversion element PD to the charge storage units CS1, CS2, CS3, and CS4 via the transfer transistors G1, G2, G3, and G4, respectively. A plurality of storage cycles consisting of transfer cycles T1 to T3 and Trs are repeated during the charge storage period.
As a result, the charge storage units CS1, CS2, and CS4 (transfer cycle T3) are transferred for each transfer cycle of the charge storage units CS1 (transfer cycle T1), CS2 and CS3 (transfer cycle T2), and CS4 (transfer cycle T3) in the charge storage period. Charges are accumulated in each of CS3 and CS4.

In addition, the pixel drive circuit 322 transfers (divides) charges to the charge storage section CS4 when repeating transfer cycles for transferring charges from the photoelectric conversion element PD to each of the charge storage sections CS1, CS2, CS3, and CS4. is completed, the "H" level drive signal RSTD is supplied to turn on the charge discharge transistor GD provided on the discharge path for discharging the charge from the photoelectric conversion element PD.

As a result, the charge discharge transistor GD discards the charge generated in the photoelectric conversion element PD after the immediately preceding transfer cycle T3 of the charge storage unit CS4 before the transfer cycle T1 for the charge storage unit CS1 is started (that is, reset the photoelectric conversion element PD).
In the case of the capacity increase mode, the transfer periods T2 and T3 are substantially integrated and the transfer period T4 is eliminated. Therefore, as shown in FIG. It is turned on by supplying the driving signal RSTD of "H" level.

Then, after the accumulation period in the frame period is completed, the pixel driving circuit 322 outputs voltage signals from each of all the pixel circuits 321 arranged in the light receiving section 3 to the row (horizontal arrangement) of the pixel circuits 321 . Signal processing such as A/D conversion processing is sequentially performed in units. The process of reading the charge storage amounts Q1, Q2, Q3, Q4 from the charge storage units CS1, CS2, CS3, CS4 of the pixel circuit 321 is the same as in the normal mode.
After that, the pixel drive circuit 322 causes the voltage signals after the signal processing to be output to the distance calculation section 42 sequentially in the order of the columns arranged in the light receiving section 3 .

Here, the distance calculation unit 42 adds the digital charge accumulation amount Q2 and the charge accumulation amount Q3 supplied from the pixel drive circuit 322 (handled as the charge amount accumulated in one charge accumulation unit CS2), Using the addition result Q2+Q3, the charge accumulation amount Q1, and the charge accumulation amount Q4, the delay time Td is calculated by equation (4) described later, and the distance between the object S and the distance image pickup device 1 is calculated. Ask for
Further, an adder for adding the charge accumulation amount Q2 and the charge accumulation amount Q3 of analog values is provided in the preceding stage of the A/D conversion process, and the addition result Q2+Q3 by the adder is A/D converted to obtain The addition result Q2+Q3 of the digital values may be output to the distance calculator 42. FIG.

The accumulation of charges in the charge accumulation unit CS by the pixel drive circuit 322 and the discarding of the charges photoelectrically converted by the photoelectric conversion elements PD as described above are repeatedly performed over one frame. As a result, charges corresponding to the amount of light received by the distance image pickup device 1 during a predetermined time interval are accumulated in each of the charge accumulation units CS. The pixel drive circuit 322 outputs to the distance calculation section 42 an electrical signal corresponding to the amount of charge for one frame accumulated in each of the charge accumulation sections CS.

Due to the relationship between the timing of irradiating the light pulse PO and the timing of accumulating electric charge in each of the charge accumulating units CS (CS1 to CS4), the charge accumulating unit CS1 receives light such as background light before irradiation of the light pulse PO. A charge amount corresponding to the external light component is held. Further, the charge amounts corresponding to the reflected light RL and the external light component are distributed and held in the charge storage units CS2, CS3, and CS4.
Here, in FIG. 5, the distribution (distribution ratio) of the amount of charge distributed to the charge storage units CS2 and CS3 and the charge storage unit CS4 is determined by the light pulse PO reflected by the object S and incident on the distance image pickup device 1. It becomes a ratio according to the delay time Td until it is completed.

Further, in the case of the combination of the charge storage units CS shown in FIG. 5 in the capacity increase mode, the distance calculation unit 42 calculates the delay time Td by the following equation (4).
Td=To×(Q4-Q1)/(Q2+Q3+Q4-3×Q1) (4)
At this time, the distance calculator 42 multiplies the delay time Td obtained by the above equation (4) by the speed of light (velocity) to calculate the round trip distance to the subject S.
Then, the distance calculation unit 42 halves the calculated round-trip distance (delay time Td×c (light speed)/2), so that the distance image sensor 32 (that is, the distance image capturing device 1) to the object S is obtained.

Further, the charge storage units CS3 and CS4 are used in combination for the capacity increase mode when the charge storage amount Q3 of the charge storage unit CS3 exceeds the capacity threshold.
That is, for example, when the charge storage amount Q3 of the charge storage section CS3 exceeds the capacity threshold in the capacity increase mode, the pixel drive circuit 322 causes the charge storage section CS1 to store charges under the timing control of the timing control section 41. In period T1, it is set to "H" level at the timing of accumulation drive signal TX1.
The pixel driving circuit 322, under the timing control of the timing control section 41, sets the accumulation driving signal TX2 to "H" level at the timing of the accumulation drive signal TX2 in the transfer period T2 in which the electric charge is accumulated in the electric charge accumulation section CS2.

Then, the pixel drive circuit 322 sets the accumulation drive signals TX3 and TX4 to "H" level at the same timing in the transfer period T3 in which the charge accumulation section CS3 accumulates the charge under the timing control of the timing control section 41. FIG.
Here, each of the transfer transistors G3 and G4 divides and distributes the charge generated by the photoelectric conversion element PD to the charge storage section CS3 and the charge storage section CS4, respectively.
As a result, the charge amount saturated only in the charge storage section CS3 is divided and accumulated in each of the charge storage sections CS3 and CS4, thereby suppressing saturation of the accumulated charge amount exceeding the maximum storage capacity. be able to.

Further, in the normal mode, the accumulation drive signal TX4 is set to "H" level in the transfer period T4 in the normal mode.
However, in the capacity increase mode, the charge storage section CS4 has the function of the charge storage section CS3 in the normal mode. ” level.
As a result, in the case of the capacity increase mode, the transfer periods T2 and T3 are substantially integrated and the transfer period T4 is eliminated. drive signal RSTD to turn it on.

Due to the relationship between the timing of irradiating the light pulse PO and the timing of accumulating electric charge in each of the charge accumulating units CS (CS1 to CS4), the charge accumulating unit CS1 receives light such as background light before irradiation of the light pulse PO. A charge amount corresponding to the external light component is held. Further, the charge amounts corresponding to the reflected light RL and the external light component are distributed and held in the charge storage units CS2, CS3, and CS4.
Here, when the charge storage amount Q3 of the charge storage section CS3 exceeds the capacity threshold, the distribution (distribution ratio) of the charge amount distributed to the charge storage section CS2 and the charge storage sections CS3 and CS4 is The ratio is determined according to the delay time Td until the light is reflected by the object S and enters the range image pickup device 1 .

Therefore, in the case of a combination of charge storage units CS in which the charge storage amount Q3 of the charge storage units CS3 in the capacity increase mode exceeds the capacity threshold, the distance calculation unit 42 calculates the delay time Td by the following equation (5). do.
Td=To×(Q3+Q4-2×Q1)/(Q2+Q3+Q4-3×Q1) (5)
At this time, the distance calculator 42 multiplies the delay time Td obtained by the above equation (5) by the speed of light (velocity) to calculate the round trip distance to the object S. FIG.
Then, the distance calculation unit 42 halves the calculated round-trip distance (delay time Td×c (light speed)/2), so that the distance image sensor 32 (that is, the distance image capturing device 1) to the object S is obtained.

Here, the distance calculation unit 42 adds the digital charge accumulation amount Q3 and the charge accumulation amount Q4 supplied from the pixel driving circuit 322 (handled as the charge amount accumulated in one charge accumulation unit CS3), Using the addition result Q3+Q4, the charge storage amount Q1 and the charge storage amount Q2, the delay time Td is calculated by the above equation (5).

In addition, an adder for adding the charge accumulation amount Q3 and the charge accumulation amount Q4 of analog values is provided in the preceding stage of performing the A/D conversion processing in the pixel drive circuit 322, and the addition result Q3+Q4 by the adder is A/D converted. Then, the addition result Q3+Q4 of the obtained digital values may be output to the distance calculation unit 42. FIG.

FIG. 6 is a flowchart showing an operation example of processing for calculating the distance between the distance image sensor 32 and the subject S by the distance image pickup device 1 of the first embodiment. When the distance image pickup device 1 is activated, distance measurement processing is started from step S1 below.
Step S1:
The normal mode operating condition setting unit 431 in the measurement control unit 43 receives from the operating condition combination storage unit 436 normal mode operating conditions (timing control unit 41, distance calculation unit 42 and pixel driving circuit 322 in normal mode) that are normal mode settings. control information).
Then, the normal mode operating condition setting unit 431 supplies the read normal mode operating conditions to the operation control unit 434 .
The operation control unit 434 controls the operation of the timing control unit 41, the distance calculation unit 42, and the pixel driving circuit 322 according to the normal mode operation conditions, and causes the normal mode operation shown in FIG. 3 to be performed.

Step S2:
The pixel drive circuit 322 sequentially supplies the storage drive signals TX1, TX2, TX3, and TX4 to the transfer transistors G1, G2, G3, and G4, respectively, and stores the charge generated by the photoelectric conversion element PD in the charge storage section CS1. , CS2, CS3, and CS4.
Then, the pixel drive circuit 322 performs distance calculation on the amounts of charge Q1, Q2, Q3, and Q4 accumulated in the charge accumulation units CS1, CS2, CS3, and CS4 in a predetermined number of accumulation cycles during one frame. Output to the unit 42 and the measurement control unit 43 .
As a result, the distance calculation unit 42 obtains the distance from the distance image pickup device 1 to the subject S by the formula (1).

Step S3:
The mode determination unit 432 reads, from the mode determination condition storage unit 435, a preset capacity threshold to be compared with the storage capacity of each of the charge storage units CS.
Then, when the current operation is the normal mode, the mode determination unit 432 determines the amount of charge accumulated in each of the charge storage unit CS1, the charge storage unit CS2, the charge storage unit CS3, and the charge storage unit CS4 for each pixel circuit 321. , charge storage amount Q1, charge storage amount Q2, charge storage amount Q3, and charge storage amount Q4 each exceed a preset capacity threshold.

In addition, the mode determination unit 432 determines the number of the charge storage units CS whose storage capacity exceeds the capacity threshold for each type of the charge storage unit CS2, the charge storage unit CS3, and the charge storage unit CS4 in all the pixel circuits 321. Aggregate to
After this counting, the mode determination unit 432 selects the charge storage unit CS having the largest number of storage capacities exceeding the capacity threshold among the types of the charge storage units CS2, CS3, and CS4. Extract.

On the other hand, when the current operation is the capacity increase mode, the mode determination unit 432 operates two (or three or more) charge storage units CS in combination for each pixel circuit 321 and operates alone. It is determined whether or not the amount of charge accumulated in each of the charge accumulation units CS that are being operated exceeds a preset capacity threshold.

For example, when the combination of the charge storage units CS2 and CS3 operates as one charge storage and the charge storage unit CS4 operates alone, the mode determination unit 432 determines the addition value of the charge storage amount Q2 and the charge storage amount Q3. Then, it is determined whether or not each of the charge storage amounts Q4 exceeds a preset capacity threshold. That is, the mode determination unit 432 compares each of the charge storage amount Q2+Q3 in the combination of the charge storage units CS2 and CS3 and the charge storage amount Q4 in the charge storage unit CS with the capacity threshold.

In addition, in all of the pixel circuits 321, the mode determination unit 432 causes the number of charge storage units CS whose storage capacity exceeds the capacity threshold to be operated in combination with the two charge storage units CS operated alone. are counted for each type of the charge accumulating portion CS.
After this counting, the mode determination unit 432 determines that the storage capacity is the capacity threshold value among the types of each of the two charge storage units CS operated in combination and the charge storage units CS operated independently. is extracted.

Here, when the combination of the charge storage units CS2 and CS3 operates as one charge storage and the charge storage unit CS4 operates alone, the mode determination unit 432 determines whether the combination of the charge storage units CS2 and CS3 and the charge The number (that is, the number of pixels) of which the storage capacity exceeds the capacity threshold is counted for each type of the storage section CS4.
Then, mode determination unit 432 sets the number of types having the greater total number as the maximum number, and extracts either the combination of charge storage units CS2 and CS3 or charge storage unit CS4 as the corresponding type.

Step S4:
The mode determination unit 432 compares the number of charge storage units CS (or a combination of two charge storage units) with the largest number of storage capacities exceeding the capacity threshold value, that is, the preset set number ( number) is read from the mode determination condition storage unit 435 .
Then, the mode determination unit 432 determines whether or not the extracted maximum number exceeds the set number.
At this time, if the maximum number exceeds the set number, the mode determination unit 432 advances the process to step S5. On the other hand, when the maximum number is equal to or less than the set number, mode determination unit 432 advances the process to step S6.

Step S5:
The mode determination unit 432 outputs to the capacity increase mode operating condition setting unit 433 the type of the maximum number of charge storage units CS, that is, which of the charge storage units CS2, CS3, and CS4 has the maximum number.
The capacity increase mode operating condition setting unit 433 sets the capacity increase mode operating conditions (the timing control unit 41 in the capacity increase mode, the distance calculation 42 and pixel drive circuit 322) is read out from the operating condition combination storage unit 436.

Here, the capacity increase mode operation condition of the capacity increase mode corresponding to the charge storage section CS2 is, as already described, a setting in which the charge storage sections CS2 and CS3 are used as one charge storage section CS.
Therefore, in the transfer cycle T2 under this capacity increase mode operating condition, the pixel drive circuit 22 sets the accumulation drive signals TX2 and TX3 to the "H" level at the same timing, and divides and oscillates the transfer transistors G2 and G3 respectively. Perform the process of dividing.

As described above, the mode determination unit 432 selects the capacity increase mode for each of the charge storage units CS2, CS3, and CS4 in accordance with the type of the charge storage units CS extracted as the maximum number. Each operating condition is read from the operating condition combination storage unit 436 .
Then, the capacity increase mode operating condition setting unit 433 outputs the read capacity increase mode operating condition to the operation control unit 434 .
As a result, the operation control unit 434 controls the operation of the timing control unit 41, the distance calculation unit 42, and the pixel driving circuit 322 according to the capacity increase mode operating conditions corresponding to each of the charge storage units CS, thereby performing the capacity increase mode operation. to do
It should be noted that the drive may be performed in the capacity increase mode in advance without being limited to the steps described above.

Step S6:
The mode determination unit 432 determines whether the current operation mode is the normal mode, that is, whether it is the normal mode or the capacity increase mode.
At this time, if the current operation mode is the normal mode, mode determination unit 432 advances the process to step S2.
On the other hand, when the current operation mode is not the normal mode (it is the capacity increase mode), mode determination unit 432 advances the process to step S1.

As described above, according to the present embodiment, when the number of pixels at which the charge storage section CS is saturated exceeds a preset number, a plurality of (for example, two) charge storage sections CS are combined to form a single charge storage section. For example, when the number of charge storage units CS2 whose capacity (storage capacity) of stored charges exceeds the capacity threshold exceeds a set number, the charge storage units CS2 and CS3 are combined to store the charge generated by the photoelectric conversion element PD. By dividing and distributing, the charge storage unit CS2 is saturated and the accuracy of the calculation result of the distance measurement is prevented from being lowered. Also, it is possible to suppress saturation due to an increase in the intensity of incident light while maintaining sensitivity to incident light.

<Second embodiment>
A second embodiment of the present invention will be described below with reference to the drawings.
A distance image pickup device according to the second embodiment of the present invention has the same configuration as the distance image pickup device 1 according to the first embodiment shown in FIG. 1, which has already been described.
Only the operations of the second embodiment that differ from those of the first embodiment will be described below.

As described above, the range image pickup apparatus of the first embodiment simultaneously turns on the transfer transistors G corresponding to the combined charge storage units CS in the same transfer cycle in the same storage cycle in the capacity increase mode. , a process of dividing and distributing the charge generated in the photoelectric conversion element PD by incident light to each of the charge storage units CS of the combination.
However, in the second embodiment, in each of the same transfer cycles in the different accumulation cycles (in each of the same transfer order in the different accumulation cycles) in the capacity increase mode, the transfer corresponding to the combined charge storage section CS Each of the transistors G is turned on, and the charge generated in the photoelectric conversion element PD by incident light is divided and allocated to each of the combined charge storage units CS.

FIG. 7 shows transfer of charges generated in the photoelectric conversion element PD to each of the charge storage units CS in the capacity increase mode when the charge storage amount Q2 of the charge storage unit CS2 exceeds the capacity threshold in the second embodiment. It is a figure which shows the timing chart which carries out. In the timing chart of FIG. 7, the vertical axis indicates the pulse level (“H” level/“L” level), and the horizontal axis indicates time. FIG. 7 also shows an accumulation period that is repeated during the charge accumulation period in the frame period. The timing of each of the storage drive signals TX1 to TX4 supplied to the transfer transistors G1 to G4 in the capacity increase mode and the timing of the drive signal RSTD supplied to the charge discharge transistor GD are shown.

The timing control unit 41 causes the light source unit 2 to irradiate the measurement space with the light pulse PO, as in the description of FIG. As a result, the light pulse PO is reflected by the subject and received by the light receiving section 3 as reflected light RL. Then, the photoelectric conversion element PD generates charges corresponding to each of the background light and the reflected light RL. The pixel driving circuit 322 controls on/off of each of the transfer transistors G1 to G4 in order to transfer the charge generated by the photoelectric conversion element PD to each of the charge storage units CS1 to CS4.

That is, the pixel drive circuit 322 converts each of the accumulation drive signals TX1 to TX4 into an "H" level signal with a predetermined time width (the irradiation time To, that is, the same width as the pulse width), and the transfer transistors G1 to G4, respectively. supply to
The pixel drive circuit 322, for example, turns on the transfer transistor G1 provided on the transfer path for transferring the charge from the photoelectric conversion element PD to the charge storage unit CS1. As a result, charges photoelectrically converted by the photoelectric conversion element PD are accumulated in the charge accumulation unit CS1 via the transfer transistor G1. After that, the pixel drive circuit 322 turns off the transfer transistor G1. As a result, transfer of charges to the charge storage section CS1 is stopped.

Further, when measuring the distance to the object S in the normal mode shown in FIG. 3, the mode determination unit 432 detects that the number of pixels in which the charge accumulation amount Q2 of the charge accumulation unit CS2 exceeds the capacity threshold exceeds the set number. In this case, the capacity increase mode operating condition setting unit 433 reads from the operating condition combination storage unit 436 the capacity increase mode operating condition for operating the charge storage units CS2 and CS3 in combination.
Then, the capacity increase mode operating condition setting unit 433 outputs the read capacity increase mode operating condition to the operation control unit 434 .
The operation control unit 434 controls the operations of the timing control unit 41, the distance calculation unit 42, and the pixel driving circuit 322 according to the capacity increase mode operating conditions corresponding to each of the charge storage units CS, and causes the capacity increase mode operation to be performed. .

As a result, in the case of the capacity increase mode, the pixel drive circuit 322 controls the timing control of the timing control unit 41 so that when there are, for example, m accumulation periods in the accumulation period for accumulating charges in the frame period, the first 1 in the accumulation period From the th accumulation period to the m/2th accumulation period, the accumulation drive signal TX2 is set to the "H" level in the transfer period T2, and the transfer transistor G2 is turned on to accumulate charges in the charge accumulation section CS2.
In addition, the pixel drive circuit 322 sets the accumulation drive signal TX3 to "H" level in the transfer period T2 from the (m/2)+1th accumulation period to the mth accumulation period, and turns on the transfer transistor G3. Charge is accumulated in the charge accumulation unit CS3.

That is, in the capacity increase mode when the charge storage amount Q2 of the charge storage unit CS2 exceeds the capacity threshold, the incident light causes the photoelectric conversion element PD to move in the same transfer cycle in a different storage cycle in the storage period of each frame cycle. The generated charges are not distributed to one charge storage section CS2, but are divided and distributed to a plurality of charge storage sections CS2 and CS3, respectively.
As a result, the charge amount saturated only in the charge storage section CS2 is divided and accumulated in each of the charge storage sections CS2 and CS3, thereby suppressing saturation of the accumulated charge amount exceeding the maximum storage capacity. be able to.

Further, in the normal mode, the accumulation drive signal TX4 is set to "H" level in the transfer period T4 in the normal mode.
However, in the capacity increase mode, the charge storage section CS4 has the function of the charge storage section CS3 in the normal mode. Accumulation drive signal TX4 is set to "H" level.
As a result, the charge generated by the photoelectric conversion element PD in the transfer period T3 is distributed and accumulated in the charge accumulation unit CS4 via the transfer transistor G4.

Further, under the above-described capacity increase mode operating conditions, if there are m accumulation cycles, for example, charges are stored in the charge accumulation unit CS2 from the first accumulation cycle to the m/2th accumulation cycle in the accumulation period. The charge is accumulated in the charge accumulation section CS3 from the (m/2)+1th accumulation period to the mth accumulation period.
However, in the transfer period T2 of the odd-numbered accumulation period, the accumulation drive signal TX2 is set to "H" level, and for example, in the transfer period T2 of the even-numbered accumulation period, the accumulation drive signal TX3 is set to "H" level. and CS3 alternately, the charge generated by the photoelectric conversion unit PD may be divided and distributed.
In addition to the configuration described above, for example, a configuration may be employed in which the number of accumulation periods in the accumulation period of the frame period is randomly distributed so as to divide the charge accumulation section CS2 and the charge accumulation section CS3 by half.

Also, the number of accumulation periods in the accumulation period of the frame period is halved (equally), and the charge generated by the photoelectric conversion section PD is divided and distributed to each of the charge accumulation sections CS2 and CS3.
However, the number of accumulation periods in the accumulation period of the frame period may be set to a predetermined ratio, and the charge generated by the photoelectric conversion section PD may be divided and allocated to each of the charge accumulation sections CS2 and CS3. That is, even if the amount of charge divided into each of the charge storage units CS2 and CS3 is not uniform and has a predetermined ratio, there is an effect of reducing saturation as in the case of only one charge storage unit CS2. can get.

Charges corresponding to the incident light are transferred from the photoelectric conversion element PD to the charge storage units CS1, CS2, CS3, and CS4 via the transfer transistors G1, G2, G3, and G4, respectively. A plurality of accumulation cycles consisting of transfer cycles T1 to T3 and time Trs are repeated during the charge accumulation period.
As a result, in each of the transfer period T1 in the charge accumulation period, the transfer period T2 having a different accumulation period, and the transfer period T3, the charge accumulation unit CS1, the charge accumulation units CS2 and CS3, and the charge accumulation unit A charge is accumulated in each of CS4 and CS4.

In addition, the pixel driving circuit 322 transfers (distributes) the charge to the charge storage section CS4 when repeating each transfer cycle for transferring the charge from the conversion element PD to each of the charge storage sections CS1, CS2, CS3, and CS4. ) is completed, the drive signal RSTD of "H" level is supplied to the charge discharge transistor GD provided on the discharge path for discharging the charge from the photoelectric conversion element PD to turn it on.
As a result, the charge discharge transistor GD discards the charge generated in the photoelectric conversion element PD after the immediately preceding transfer cycle T3 of the charge storage unit CS4 before the transfer cycle T1 for the charge storage unit CS1 is started (that is, reset the photoelectric conversion element PD).
In the case of the capacity increase mode, the transfer periods T2 and T3 are substantially integrated and the transfer period T4 is eliminated. Therefore, as shown in FIG. It is turned on by supplying the driving signal RSTD of "H" level.

Then, as in the first embodiment, the pixel drive circuit 322 outputs voltage signals from each of all the pixel circuits 321 arranged in the light receiving section 3 after the accumulation period in the frame cycle is completed. Signal processing such as A/D conversion processing is sequentially performed in units of 321 rows (horizontal array). The process of reading the charge storage amounts Q1, Q2, Q3, Q4 from the charge storage units CS1, CS2, CS3, CS4 of the pixel circuit 321 is the same as in the normal mode.
After that, the pixel drive circuit 322 causes the voltage signals after the signal processing to be output to the distance calculation section 42 sequentially in the order of the columns arranged in the light receiving section 3 .

Here, the distance calculation unit 42 adds the digital charge accumulation amount Q2 and the charge accumulation amount Q3 supplied from the pixel drive circuit 322 (handled as the charge amount accumulated in one charge accumulation unit CS2), Using this addition result Q2+Q3, the charge accumulation amount Q1, and the charge accumulation amount Q4, the delay time Td is calculated in the same manner as in the first embodiment, and the distance between the object S and the distance image pickup device 1 is calculated. Ask for
Further, an adder for adding the charge accumulation amount Q2 and the charge accumulation amount Q3 of analog values is provided in the preceding stage of the A/D conversion process, and the addition result Q2+Q3 by the adder is A/D converted to obtain The addition result Q2+Q3 of the digital values may be output to the distance calculator 42. FIG.

The accumulation of charges in the charge accumulation unit CS by the pixel drive circuit 322 and the discarding of the charges photoelectrically converted by the photoelectric conversion elements PD as described above are repeatedly performed over one frame. As a result, charges corresponding to the amount of light received by the distance image pickup device 1 during a predetermined time interval are accumulated in each of the charge accumulation units CS. The pixel drive circuit 322 outputs to the distance calculation section 42 an electrical signal corresponding to the amount of charge for one frame (frame period) accumulated in each of the charge accumulation sections CS.

Due to the relationship between the timing of irradiating the light pulse PO and the timing of accumulating electric charge in each of the charge accumulating units CS (CS1 to CS4), the charge accumulating unit CS1 receives light such as background light before irradiation of the light pulse PO. A charge amount corresponding to the external light component is held. Further, the charge amounts corresponding to the reflected light RL and the external light component are distributed and held in the charge storage units CS2, CS3, and CS4.
Here, in FIG. 7, the distribution (distribution ratio) of the amount of charge distributed to the charge storage units CS2 and CS3 and the charge storage unit CS4 is determined by the light pulse PO reflected by the object S and incident on the distance image pickup device 1. It becomes a ratio according to the delay time Td until it is completed.

In the capacity increase mode when the charge storage amount Q3 of the charge storage section CS3 exceeds the capacity threshold, the charge storage section CS2 is used alone (one) and the charge storage sections CS3 and CS4 are used in combination.
That is, when measuring the distance to the object S in the normal mode shown in FIG. 3, the mode determination unit 432 detects that the number of pixels in which the charge accumulation amount Q3 of the charge accumulation unit CS3 exceeds the capacity threshold exceeds the set number. In this case, the capacity increase mode operating condition setting unit 433 reads from the operating condition combination storage unit 436 the capacity increase mode operating condition for operating the charge storage units CS3 and CS4 in combination.

Then, the capacity increase mode operating condition setting unit 433 outputs the read capacity increase mode operating condition to the operation control unit 434 .
The operation control unit 434 controls the operations of the timing control unit 41, the distance calculation unit 42, and the pixel driving circuit 322 according to the capacity increase mode operating conditions corresponding to each of the charge storage units CS, and causes the capacity increase mode operation to be performed. .

As a result, in the case of the capacity increase mode, the pixel drive circuit 322 controls the timing control of the timing control unit 41 so that when there are, for example, m accumulation periods in the accumulation period for accumulating charges in the frame period, the first 1 in the accumulation period From the th accumulation period to the m/2th accumulation period, in the transfer period T3, the accumulation drive signal TX3 is set to the "H" level, the transfer transistor G3 is turned on, and charges are accumulated in the charge accumulation section CS3.
In addition, the pixel drive circuit 322 sets the accumulation drive signal TX4 to "H" level and turns on the transfer transistor G4 in the transfer period T3 from the (m/2)+1th accumulation period to the mth accumulation period. Charge is accumulated in the charge accumulation unit CS4.

That is, in the capacity increase mode when the charge storage amount Q3 of the charge storage unit CS3 exceeds the capacity threshold, the incident light causes the photoelectric conversion element PD to move in the same transfer cycle in a different storage cycle in the storage period of each frame cycle. The generated charges are not distributed to one charge storage section CS3, but are divided and distributed to a plurality of charge storage sections CS3 and CS4, respectively.
As a result, the charge amount saturated only in the charge storage section CS3 is divided and accumulated in each of the charge storage sections CS3 and CS4, thereby suppressing saturation of the accumulated charge amount exceeding the maximum storage capacity. be able to.

In the normal mode, accumulation drive signal TX2 is set to "H" level in transfer period T2 as in the normal mode.
As a result, the charges generated by the photoelectric conversion elements PD in the transfer cycle T2 are distributed and accumulated in the charge storage unit CS2 via the transfer transistor G2, as in the normal mode.

7 in the capacity increase mode, when the charge accumulation units CS3 and CS4 are combined in the transfer period T3, the distance calculation unit 42 calculates the delay time Td by the following equation (6).
Td=To×(Q3+Q4-2×Q1)/(Q2+Q3+Q4-3×Q1) (6)
At this time, the distance calculator 42 multiplies the delay time Td obtained by the above equation (6) by the speed of light (velocity) to calculate the round trip distance to the subject S.
Then, the distance calculation unit 42 halves the calculated round-trip distance (delay time Td×c (light speed)/2), so that the distance image sensor 32 (that is, the distance image capturing device 1) to the object S is obtained.

In addition, under the above-described capacity increase mode operation conditions, if there are m accumulation periods, for example, charges are stored in the charge accumulation section CS3 from the first accumulation period to the m/2th accumulation period in the accumulation period. The charge is accumulated in the charge accumulation section CS4 from the (m/2)+1th accumulation period to the mth accumulation period.
However, for example, the accumulation drive signal TX3 is set to "H" level in the transfer period T3 of the odd-numbered accumulation period, and the accumulation drive signal TX4 is set to "H" level in the transfer period T3 of the even-numbered accumulation period. and CS4 alternately, the charge generated by the photoelectric conversion unit PD may be divided and distributed.

Also, the number of accumulation periods in the accumulation period of the frame period is halved (equally), and the charge generated by the photoelectric conversion section PD is divided and distributed to each of the charge accumulation sections CS3 and CS4.
However, the number of accumulation periods in the accumulation period of the frame period may be set to a predetermined ratio, and the charge generated by the photoelectric conversion section PD may be divided and allocated to each of the charge accumulation sections CS3 and CS4. That is, even if the amount of charge divided into each of the charge storage units CS3 and CS4 is not equal and has a predetermined ratio, there is an effect of reducing saturation as in the case of only one charge storage unit CS3. can get.

Charges corresponding to the incident light are transferred from the photoelectric conversion element PD to the charge storage units CS1, CS2, CS3, and CS4 via the transfer transistors G1, G2, G3, and G4, respectively. A plurality of storage cycles consisting of transfer cycles T1 to T4 are repeated during the charge storage period.
As a result, the charge storage unit CS1, the charge storage unit CS2, and the charge storage units CS3 and CS4 are charged for each transfer cycle of the transfer cycle T1, the transfer cycle T2, and the transfer cycle T3 having a different storage cycle in the charge storage period. charge is accumulated in each of

As described above, according to the present embodiment, as in the first embodiment, when the number of pixels at which the charge storage section CS is saturated exceeds a preset number, a plurality of (for example, two) charge storage sections CS are combined to operate as one charge storage unit. For example, when the number of charge storage units CS2 whose capacity of stored charges (accumulation capacity) exceeds the capacity threshold exceeds a set number, the charge storage units CS2 and CS3 are combined, By dividing and distributing the charge generated by the photoelectric conversion element PD, the charge storage section CS2 is saturated and the accuracy of the calculation result of the distance measurement is prevented from deteriorating. It is possible to suppress saturation due to an increase in the intensity of incident light while maintaining the resolution of the captured image and the sensitivity to incident light without increasing the intensity.

<Third Embodiment>
A third embodiment of the present invention will be described below with reference to the drawings.
A distance image pickup device according to the second embodiment of the present invention has the same configuration as the distance image pickup device 1 according to the first embodiment shown in FIG. 1, which has already been described.
Only the operations of the second embodiment that differ from those of the first embodiment will be described below.

As described above, the range image pickup apparatus of the first embodiment simultaneously turns on the transfer transistors G corresponding to the combined charge storage units CS in the same transfer cycle in the same storage cycle in the capacity increase mode. , a process of dividing and distributing the charge generated in the photoelectric conversion element PD by incident light to each of the charge storage units CS of the combination.
However, the third embodiment has a capacity increasing mode that assumes an environment in which the influence of background light is negligible, for example, a state in which there is almost no background light in the dark environment.
Note that the driving in the present embodiment described above is for a pixel having 4 taps (four charge storage portions), and in a pixel having charge storage portions of 5 taps (five charge storage portions) or more, the driving of the background light is performed. It becomes a capacity increase mode considering the influence.

FIG. 8 is a diagram showing a timing chart for transferring charges generated by the photoelectric conversion element PD to each of the charge storage units CS in the capacity increase mode in the case of an environment in which the influence of background light can be ignored in the third embodiment. is. In the timing chart of FIG. 8, the vertical axis indicates the pulse level (“H” level/“L” level), and the horizontal axis indicates time. Also, FIG. 8 shows an accumulation period that is repeated during the charge accumulation period in the frame period. The timings of the storage drive signals TX1 to TX4 supplied to the transfer transistors G1 to G4 and the timing of the drive signal RSTD supplied to the charge discharge transistor GD in the capacity increase mode are shown.

In the present embodiment, since it is not necessary to obtain background light, in the case of the capacity increase mode, the light source unit 2 outputs the light pulse PO to irradiate.
Also, the mode determination to select the capacity increase mode is performed in the normal mode, as in the first and second embodiments.
Then, the capacity increase mode operating condition setting unit 433 outputs the read capacity increase mode operating condition to the operation control unit 434 .

The operation control unit 434 controls the operations of the timing control unit 41, the distance calculation unit 42, and the pixel driving circuit 322 according to the capacity increase mode operating conditions corresponding to each of the charge storage units CS, and causes the capacity increase mode operation to be performed. .
Since the charge storage section CS1 is not used for accumulating background light, the operating conditions for the capacity increase mode are the combination of the charge storage sections CS1 and CS2 and the combination of the charge storage sections CS3 and CS4. Each one of the storage units CS1 and CS2 is made to operate.

That is, in the case of the capacity increase mode, the pixel drive circuit 322 outputs the accumulation drive signals TX1 and TX2 at the same timing in the transfer period T1 in which charges are accumulated in the charge accumulation section CS1 in normal driving, under the timing control of the timing control section 41. to "H" level.
Each of the transfer transistors G1 and G2 divides and distributes the charge generated by the photoelectric conversion element PD to the charge storage section CS1 and the charge storage section CS2, respectively.
As a result, the charge amount saturated in only the charge storage section CS1 is divided and accumulated in each of the charge storage sections CS1 and CS2, thereby suppressing saturation of the accumulated charge amount exceeding the maximum storage capacity. be able to.

Similarly, in the case of the capacity increase mode, the pixel drive circuit 322 outputs the accumulation drive signals TX3 and TX4 in the transfer period T2 in which charges are accumulated in the charge accumulation section CS2 in normal driving, under the timing control of the timing control section 41. At the same timing, it is set to "H" level.
Then, each of the transfer transistors G3 and G4 divides and distributes the charge generated by the photoelectric conversion element PD to the charge storage section CS3 and the charge storage section CS4, respectively.
As a result, the charge amount saturated only in the charge storage section CS2 is divided and accumulated in each of the charge storage sections CS3 and CS4, thereby suppressing saturation of the accumulated charge amount exceeding the maximum storage capacity. be able to.

Charges corresponding to the incident light are transferred from the photoelectric conversion element PD to the charge storage units CS1, CS2, CS3, and CS4 via the transfer transistors G1, G2, G3, and G4, respectively. A plurality of storage cycles consisting of transfer cycles T1 to T4 are repeated during the charge storage period.
As a result, the charge accumulation units CS1 and CS2 and the charge accumulation units CS1 and CS2 and the charge accumulation units are A charge is accumulated in each of CS3 and CS4.

In addition, the pixel driving circuit 322 transfers (distributes) the charge to the charge storage section CS4 when repeating each transfer cycle for transferring the charge from the conversion element PD to each of the charge storage sections CS1, CS2, CS3, and CS4. ) is completed, the drive signal RSTD of "H" level is supplied to the charge discharge transistor GD provided on the discharge path for discharging the charge from the photoelectric conversion element PD to turn it on.

As a result, before the transfer cycle T1 for the charge storage unit CS1 is started, the charge discharge transistor GD discards the charge generated in the photoelectric conversion element PD after the immediately preceding transfer cycle T2 for the charge storage unit CS4 (that is, the photoelectric conversion element PD). reset the conversion element PD).
In the case of the capacity increase mode, the transfer periods T1 and T2 and the transfer periods T3 and T4 are substantially integrated and the transfer periods T3 and T4 are eliminated. At the time Trs, the "H" level drive signal RSTD is supplied to the charge discharge transistor GD to turn it on.

Also, as in the second embodiment, the capacity increase mode when the charge storage amounts Q2 and Q3 of the charge storage units CS2 and CS3 exceed the capacity threshold is the same in different storage cycles in the storage period of each frame cycle. In the transfer period of , the charges generated by the photoelectric conversion element PD due to incident light are not distributed to the single charge storage units CS2 and CS3, but divided into the two charge storage units CS1 and CS2, respectively. Alternatively, it may be divided and allocated to the two charge storage units CS3 and CS4.

Assuming that the background light is ignored, the combination of the charge storage units CS1 and CS2 in the three charge storage units CS1, CS2, and CS3 is the same as in the configuration of the first embodiment. , the distance measurement may be performed with the charge storage unit CS3, or the distance measurement may be performed with the combination of the charge storage unit CS1 and the charge storage units CS2 and CS3.

As described above, according to the present embodiment, as in the first embodiment, when the number of pixels at which the charge storage section CS is saturated exceeds a preset number, a plurality of (for example, two) charge storage sections CS are combined to operate as one charge storage unit. Alternatively, by combining the charge storage units CS3 and CS4 and dividing and distributing the charge generated by the photoelectric conversion element PD, the charge storage units CS2 and CS3 are saturated and the accuracy of the distance measurement calculation result is lowered. Therefore, it is possible to suppress saturation due to an increase in the intensity of incident light while maintaining the resolution of the captured image and the sensitivity to incident light without increasing the capacity of the charge storage unit. Become.

DESCRIPTION OF SYMBOLS 1... Range image pick-up device 2... Light source part 3... Light-receiving part 21... Light source device 22... Diffusion plate 31... Lens 32... Range image sensor (range image pick-up element)
321... Pixel circuit 322... Pixel drive circuit 4... Distance image processing unit 41... Timing control unit 42... Distance calculation unit 43... Measurement control unit 431... Normal mode operation condition setting unit 432... Mode determination unit 433... Capacity increase mode operation condition Setting unit 434 Operation control unit 435 Mode determination condition storage unit 436 Operation condition combination storage unit CS1, CS2, CS3, CS4 Charge storage unit FD1, FD2, FD3, FD4 Floating diffusion G1, G2, G3, G4... Transfer transistor GD... Charge discharge transistor PD... Photoelectric conversion element PO... Light pulse RL... Reflected light RT1, RT2, RT3, RT4... Reset transistor S... Subject SF1, SF2, SF3, SF4... Source follower transistor SL1, SL2, SL3, SL4... selection transistor

Claims (8)

a photoelectric conversion element that generates charges according to incident light that is light that is incident from a measurement space that is a space to be measured; N (N≧3) charge storage units that store the charges in a frame period; a plurality of pixel circuits each comprising a transfer transistor for transferring the charge from the photoelectric conversion element to each of the charge storage units;
a pixel drive circuit that turns on and off the transfer transistors in each of the charge storage units in a predetermined accumulation cycle synchronized with the irradiation of the light pulse, and distributes and accumulates the charges;
a measurement control unit that divides and distributes and accumulates the charge generated by the photoelectric conversion element to each of the combinations of the charge accumulation units in any transfer period of the charge accumulation cycle;
and a distance calculation unit that calculates a distance to a subject existing in the measurement space as a measurement distance based on the amount of charge accumulated in each of the charge accumulation units. The measurement control unit
In the capacity increasing mode, the transfer transistors corresponding to each of the plurality of charge storage units of the combination are simultaneously turned on in the transfer order for each storage cycle, and the photoelectric conversion is performed for each of the charge storage units of the combination. 2. The distance imaging device according to claim 1, wherein the charge generated by the element is transferred, and the charge generated by the photoelectric conversion element is divided and accumulated in each of the charge storage units of the combination. The measurement control unit
In the capacity increase mode, for each of the plurality of charge storage units in the combination, a divided storage count obtained by multiplying the storage count in the frame period by a predetermined ratio is set, and the charge storage units in the combination are divided. For each, the transfer transistors are turned on in the transfer order in the different accumulation cycles, and the charges generated by the photoelectric conversion elements for the number of divided accumulations are transferred to each of the charge accumulation units of the combination. 2. The range image pickup apparatus according to claim 1, wherein the charge generated by the photoelectric conversion element is divided and accumulated in each of the charge accumulation units of the combination. In the capacity increase mode, the transfer transistor is repeatedly turned on for each different accumulation period, so that the charge generated by the photoelectric conversion element is alternately distributed to each of the plurality of charge accumulation units of the combination. 4. The range image pick-up device according to claim 3, wherein the charge generated by the photoelectric conversion element is divided and accumulated. 5. The distance image pickup device according to claim 1, wherein in the capacity increase mode, a plurality of combinations of two or more charge accumulation units are provided. The measurement control unit
a normal mode in which the charge generated by the photoelectric conversion element is accumulated and transferred by turning on a transfer transistor in a transfer order set in each of the charge accumulation units for each accumulation period in the accumulation period of the frame period; A capacity increase mode in which the charge generated by the conversion element is divided and distributed to each of the combinations of the charge storage units and stored in any transfer period of the charge storage cycle is switched according to a predetermined condition. The range imaging device according to any one of claims 1 to 5. The predetermined condition is
the charge amount of the charge accumulated in the charge storage unit exceeds a preset ratio with respect to the maximum capacity of the charge storage unit, and the combination includes the charge storage unit exceeding the ratio. 7. The range imaging device according to claim 6, characterized by: A range image capturing method for controlling a range image capturing apparatus comprising: each of a plurality of pixel circuits each composed of a photoelectric conversion element, a plurality of charge storage units, and a transfer transistor; a pixel drive circuit; a distance calculation unit; and a measurement control unit. and
The pixel driving circuit stores charges generated by the photoelectric conversion elements in response to incident light from the measurement space in each of N (N≧3) charge storage units in a predetermined storage period synchronized with irradiation of light pulses. a step of turning on and off each of the transfer transistors for transferring the charge from the photoelectric conversion element to the charge storage unit, distributing the charge, and accumulating the charge;
a step in which the measurement control unit divides, distributes, and accumulates the charge generated by the photoelectric conversion element to each of the combinations of the charge accumulation units in one of the transfer cycles of the charge accumulation cycle;
and a distance image capturing method, wherein the distance calculation unit obtains a distance to an object existing in the measurement space as a measurement distance based on the amount of charge accumulated in each of the charge accumulation units. .

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