JP2011022089A - Spatial information detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent misdetection by making spatial information detected, when a distance up to an object lies outside the measurable range ineffective, regardless of the reflectance of the object. <P>SOLUTION: Light is projected to an object space by a light-emitting source 1, and at a light-receiving sensor 2 the charge in a prescribed light reception period is accumulated. Moreover, charge accumulated over an accumulation period longer than the light reception period is extracted. The optical output of the light-emitting source 1 is modulated by a square-wave signal generated randomly in the accumulation period so that continuation periods of binary signal values become periods which are integral number of times the unit period, respectively. The light reception period of the light receiving sensor 2 is prescribed by a timing signal generated on the basis of a modulation signal. A distance computing section 6 computes the distance up to the object by using a charge amount corresponding to the timing signal. A true or false determining section 7 normalizes the difference between two kinds of charge amounts acquired by using two kinds of timing signals and uses it as an evaluation value, and invalidates the spatial information, when it is determined by using the evaluation value that the distance up to the object lies outside the measurable range. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention projects light from a light source to a target space and receives light from the target space, thereby measuring the distance to the object existing in the target space, measuring the reflectance or absorption rate of the object, and the medium in the target space. The present invention relates to an active type spatial information detection device that detects spatial information such as measurement of reflectance or absorption rate and detection of the presence or absence of an object in a target space.

  Conventionally, an active type spatial information detection device that detects spatial information by projecting light from a light source to a target space and receiving light from the target space has been proposed. This type of spatial information detection device is used for purposes such as measuring the distance to an object in the target space, measuring the reflectance of the object, measuring the transmittance of the medium in the target space, and detecting the presence or absence of the object in the target space. Those configured accordingly are known.

  For measuring the distance to an object, the time of flight is used to measure the distance to the object by measuring the time it takes for the light reflected from the object to be received after being emitted from the light source. There are distance measuring devices that use the principle of law. This type of distance measuring device projects intensity-modulated light whose intensity changes at a constant cycle, such as a sine waveform, and measures the phase difference of the modulated waveform between the time when the intensity-modulated light is projected and the time when it is received. A configuration for measuring the distance to an object has been proposed (see, for example, Patent Document 1). Specifically, the charge amount corresponding to the received light intensity (actually, the received light amount) is obtained at different timings synchronized with the period of the intensity-modulated light, and the light projection time and the light reception time point are determined based on the relationship between the charge amounts. The phase difference of the modulation waveform at and is obtained by calculation.

  Since the obtained phase difference corresponds to a time difference until the projected intensity modulated light is reflected after being reflected by the object, the period of the intensity modulated light is T [s], the speed of light is c [m / s], When the phase difference of the modulation waveform is ψ [radian], the time difference r from light projection to light reception is r = T (ψ / 2π), and the distance L to the object is L = (1/2) c · r = (½) c · T (ψ / 2π). For example, if the frequency of intensity-modulated light is 10 MHz, the period T is 100 [ns], so the maximum measurable distance (hereinafter referred to as “measurement maximum distance”) is 15 [m]. That is, since intensity-modulated light whose intensity changes at a constant period is used, the upper limit of the measurable range is a distance (half-wavelength distance) corresponding to a half-period of intensity-modulated light.

  On the other hand, in the spatial information detection device used for measuring the reflectance and absorptance of an object, measuring the reflectance and absorptivity of a medium, and detecting the presence or absence of an object, By providing a non-light-projecting period during which light is not projected from the light-emitting source to the target space, and using the change in the amount of light received between the light-projecting period and the non-light-projecting period, the influence of ambient light or ambient light is eliminated, An intensity detection device that detects only a component of reflected light corresponding to signal light projected into a target space is considered (see, for example, Patent Document 2).

  In other words, the amount of light received during the non-projection period corresponds to only the ambient light or ambient light component, but the amount of light received during the light projection period is the signal light emitted from the ambient light or ambient light component and the light source. Therefore, in the intensity detection device, the component corresponding to the signal light is extracted based on the received light amount during the light projection period and the received light amount during the non-light projection period, and the target is obtained from the component corresponding to the signal light. The spatial information is extracted. In other words, a grayscale image corresponding to the signal light component is generated.

JP 2004-45304 A JP 2006-121617 A

  By the way, in the distance measuring apparatus described in Patent Document 1, since intensity-modulated light whose intensity changes at a constant period is used, even if the distance to the object exceeds the above-described maximum measurement distance, reflection is performed. If the light can be received, it is erroneously recognized as a distance within the measurable range. That is, the time difference from light projection to light reception is detected based on the phase difference of the modulation waveform, and the amount of light received is the same when the phase difference is ψ and when (ψ + 2nπ) (n is a positive integer). When the maximum measurement distance is Lmax and the measurable range is 0 to Lmax, it is difficult to distinguish the range [0, Lmax] from the range [n · Lmax, (n + 1) · Lmax]. Have.

  This type of problem can be solved by taking advantage of the fact that the received light intensity of reflected light decreases as the distance to the object increases. May not be determined only by the received light intensity, so there is an object with a high reflectivity at a distance exceeding the maximum allowable measurement distance, and when the intensity of reflected light from the object is relatively high, There is still the possibility of misrecognizing distance.

  In particular, for an object that exists near the boundary of the measurable range, the received light intensity of the reflected light is relatively high, so it is difficult to distinguish whether the light intensity is within the measurable range or outside the measurable range.

  Moreover, in the intensity | strength detection apparatus described in patent document 2, since it is not assumed that a measurable range is prescribed | regulated, a measurable range cannot be restrict | limited. However, even in the intensity detection device, if the measurable range can be limited, it is not necessary to obtain spatial information about an object that does not exist within the measurable range, and wasteful processing is suppressed when obtaining spatial information. become. Therefore, in the intensity detection apparatus, it is desired to limit the measurable range with respect to the distance to the object.

  The present invention has been made in view of the above reasons, and its purpose is to invalidate spatial information detected when the distance to an object is outside the measurable range regardless of the reflectance of the object. An object of the present invention is to provide a spatial information detection device that prevents detection.

  In order to achieve the above object, the present invention provides a light emitting source that projects light into a target space, and a photoelectric conversion unit that generates and accumulates an amount of electric charge according to the received light intensity received and instructed from the target space. A charge accumulator that accumulates the charges accumulated in the photoelectric conversion unit over a predetermined accumulation period longer than the light receiving period, a charge extraction unit that extracts the charges accumulated in the charge accumulator, and the light output of the light source A timing control unit that outputs a modulation signal and a timing signal that defines a light reception period and determines an accumulation period; a spatial information detection unit that detects spatial information of a target space by using the charge extracted by the charge extraction unit; A correct / incorrect determination unit that determines whether the reflected light from the object existing in the target space is within the allowable measurable range by using the electric charge extracted by the electric charge extraction unit; The signal is a square wave signal in which the duration of each binary signal value is an integral multiple of the unit period and the duration varies randomly in the accumulation period, and the timing control unit Generates multiple types of timing signals that have a defined relationship between the inverted signal or the inverted signal and the modulation signal in the time axis direction, and the photoelectric conversion unit generates the duration of one of the signal values in each timing signal as the light receiving period The spatial information detection unit detects the spatial information using the charge amount obtained by accumulating the charge accumulated in the light receiving period based on each timing signal in the accumulation period, and the correctness determination unit The difference that increases or decreases with the increase in the distance to the object among the difference between the two kinds of charge amounts obtained by using the two kinds of timing signals corresponds to the sum of the charge amounts. Normalize by dividing by the value, use the normalized difference as the evaluation value, the evaluation value that increases with the increase of the distance to the object is greater than the specified threshold, or with the increase of the distance to the object A configuration is adopted in which when the decreasing evaluation value is smaller than a prescribed threshold value, it is determined that it is outside the measurable range, and when it is determined that it is outside the measurable range, the spatial information detected by the spatial information detection unit is invalidated.

  In order to achieve the above object, a light emitting source that projects light into the target space, a photoelectric conversion unit that generates and accumulates an amount of charge according to the received light intensity received and instructed from the target space, A charge accumulator that accumulates the charges accumulated in the converter over a predetermined accumulation period longer than the light receiving period, a charge extraction unit that extracts the charges accumulated in the charge accumulator, and a modulation that modulates the light output of the light source A timing control unit that outputs a timing signal that defines a signal and a light receiving period and determines an accumulation period; a spatial information detection unit that detects spatial information of a target space by using the charge extracted by the charge extraction unit; and a charge extraction And a correct / incorrect determination unit that determines whether the reflected light from the object existing in the target space is within the allowable measurable range by using the electric charge extracted by the unit. Is a square wave signal in which the duration of each binary signal value is an integral multiple of the unit period and the duration varies randomly in the accumulation period, and the timing control unit A plurality of types of timing signals having a prescribed relationship with the modulation signal in the time axis direction of the signal or the inverted signal, and a light projection period in which the modulation signal is output and projected from the light source to the target space; and the modulation signal The photoelectric conversion unit integrates the charge generated using the duration of one of the signal values in each timing signal for the light receiving period. The spatial information detection unit detects the spatial information using the amount of charge obtained by accumulating the charges accumulated in the light receiving period based on each timing signal in the accumulation period, and the correctness determination unit The light component other than the signal light projected by the light source is extracted using the amount of charge accumulated during the light period, and the distance to the object is the difference between the two types of charge amount obtained using the two types of timing signals. Normalization is performed by dividing the difference that increases or decreases with the increase by the value obtained by subtracting the charge amount corresponding to the light component other than the signal light from the sum of the charge amounts, and the normalized difference is used as the evaluation value. When the evaluation value that increases as the distance to the object increases is larger than the prescribed threshold value, or the evaluation value that decreases as the distance to the object increases is smaller than the prescribed threshold value, It is also possible to adopt a configuration in which the spatial information detected by the spatial information detection unit is invalidated when it is determined to be outside the measurable range.

  The correctness determination unit is an evaluation value obtained from two types of charge amounts obtained by using a first timing signal that is a non-inverted signal of the modulation signal and a second timing signal that is an inverted signal of the first timing signal. May be used.

  In addition, the correctness / incorrectness determination unit obtains from two types of charge amounts obtained using a first timing signal that is a non-inverted signal of the modulation signal and a second timing signal that is an inverted signal of the first timing signal. A first evaluation value, a third timing signal obtained by delaying a non-inverted signal of the modulated signal by a unit period in the time axis direction, and a fourth timing obtained by delaying an inverted signal of the modulated signal by a unit period in the time axis direction. A second evaluation value obtained from two kinds of charge amounts obtained using the timing signal, a condition that the first evaluation value is smaller than the first threshold value, and the second evaluation value is the second value. You may make it judge that it is outside a measurable range, when at least one of the conditions of being smaller than a threshold value is materialized.

  When the correctness determination unit uses the first timing signal and the second timing signal as evaluation values, the correctness determination unit delays the non-inverted signal of the modulation signal by a unit period in the time axis direction. A difference between two types of charge amounts obtained by using two types of timing signals of the timing signal and a fourth timing signal obtained by delaying the inverted signal of the modulation signal by a unit period in the time axis direction is used as a determination value. The threshold value may be switched according to the magnitude of the determination value.

  Further, in this case, the correctness / incorrectness determination unit selects the threshold value from two levels, a small threshold value when the determination value is larger than a specified reference value, and the determination value is lower than the specified reference value. If it is small, a large threshold value may be selected.

  Alternatively, the correct / incorrect determination unit may include a third timing signal obtained by delaying the non-inverted signal of the modulated signal by a unit period in the time axis direction and a fourth timing signal obtained by delaying the inverted signal of the modulated signal by a unit period in the time axis direction. The difference between two types of charge amounts obtained using two types of timing signals and the first timing signal is used as a first determination value, and the third timing signal and the fourth timing signal are defined to be shorter than the unit period. The difference between the two types of charge amounts obtained by using the two types of timing signals, the fifth timing signal and the sixth timing signal delayed by the delay time, is used as the second determination value, and the threshold value is set in two levels. When the second determination value is smaller than the first determination value, a small threshold is selected, and when the second determination value is larger than the first determination value, a large threshold is selected. It can be formed.

  According to the configuration of the present invention, the light modulated by the modulation signal, which is a square wave signal generated randomly, is projected onto the target space, and the light receiving period at a timing according to the timing signal generated based on the modulation signal And an evaluation value corresponding to the distance to the object existing in the target space is generated by using the amount of charge obtained by accumulating the charges accumulated during the light receiving period, and this evaluation value is used as the specified judgment condition. In this case, it is determined whether or not the object is within the measurable range, and is used as effective information when it is within the measurable range, so that erroneous measurement can be prevented.

  That is, since the period of each signal value of the modulation signal is set to a period that is an integral multiple of the unit period, the charge amount is a linear function of the time difference from light projection to light reception up to the maximum measurement distance determined by the unit period. When the maximum measurement distance is exceeded due to the randomness of the modulation signal, the value becomes almost constant. By utilizing this property, it is possible to determine whether or not the distance to the object is within the measurable range by setting the evaluation value using the amount of charge obtained corresponding to the timing signal.

  In addition, the correctness determination unit uses the normalized value obtained by dividing the difference between the two types of charge amounts obtained by using the two types of timing signals by the value corresponding to the sum of the amount of charges. Evaluation that eliminates the influence of the attenuation factor of light in the path from light reception to light reception becomes possible, and in particular, it is possible to determine whether or not it is within the measurable range regardless of the reflectance of the object.

  Also, it defines a light projection period in which light is projected from the light source to the target space and a non-light projection period in which light is not projected into the target space, and corresponds to light components other than signal light using the amount of charge accumulated during the non-light projection period. In the configuration in which the charge amount difference is normalized by the value obtained by subtracting the charge amount corresponding to the light component other than the signal light from the sum of the two types of charge amounts, not only the reflectance of the object but also the external Since the evaluation value obtained by removing the influence of the light component can be obtained, it is determined whether the distance to the object is within the measurable range without being influenced by the reflectance of the object in an environment where ambient light or ambient light exists. It becomes possible.

  As the timing signal, a first timing signal that matches the modulation signal and a second timing signal in which the signal value of the first timing signal is inverted are used, and the first timing signal, the second timing signal, If the evaluation value is defined using two types of charge amounts corresponding to, the time difference from the light projection to the light reception changes in the distance range within the unit period and does not change in other distance ranges. Can be set within the measurable distance.

  If the correct / incorrect determination unit adopts a configuration in which the first evaluation value and the second evaluation value are used together for the evaluation of whether or not the measurement is within the measurable range, the theoretical value of the first evaluation value depends on the unit period. If the upper limit of the measurable range specified is exceeded, it becomes 0, and the theoretical value of the second evaluation value becomes 0 if it exceeds the distance obtained by adding the upper limit of the measurable range and the distance specified by the unit period. Determining that the measurement value is out of the measurable range when at least one of the condition that the first evaluation value is smaller than the first threshold and the condition that the second evaluation value is smaller than the second threshold is satisfied. This makes it possible to more reliably determine whether or not the measurement range is met. That is, even if one of the first evaluation value and the second evaluation value indicates that it is within the measurable range due to the influence of shot noise, etc. Therefore, the possibility of employing invalid spatial information is reduced, and the reliability of detected spatial information is increased.

  In the configuration in which the threshold value to be compared with the evaluation value is switched by the magnitude of the determination value determined using the charge amount obtained in the light receiving period at a timing different from the charge amount for which the evaluation value is obtained in the correctness / incorrectness determination unit, Set the threshold appropriately according to the distance to the object, increase the accuracy when the distance to the object is within the measurable distance, and switch the threshold when the distance to the object is outside the measurement range Therefore, the possibility of misjudgment as being within the measurable range can be reduced.

  If the correctness / incorrectness determination unit adopts a configuration in which the threshold value for the evaluation value is switched by comparing the determination value obtained using the charge amount obtained in the light receiving period at a timing different from the charge amount for obtaining the evaluation value with a specified reference value. If the evaluation value is small and outside the measurable range, the threshold value is increased to reduce the possibility that the evaluation value fluctuates within the measurable range even if the evaluation value fluctuates due to the effects of shot noise, etc. be able to. In other words, not only the evaluation value but also the judgment value changes according to the distance to the object, so it is roughly judged whether the distance to the object is within the measurable range from the magnitude of the judgment value, and the judgment result is the evaluation value. By reflecting the value on the threshold value, it is possible to improve the certainty of the determination as to whether or not it is within the measurable range.

  Here, the determination value decreases as the distance increases when the distance to the object is between the distance corresponding to the unit period and the distance corresponding to twice the unit period. When the threshold value is larger than the threshold value, the threshold value increases at a distance between a distance corresponding to the unit period and a distance corresponding to twice the unit period. In other words, by increasing the threshold before the distance to the object exceeds the distance corresponding to the unit period and reaches the distance corresponding to twice the unit period, the probability of erroneous determination due to the influence of shot noise or the like is reduced. be able to. In addition, when the threshold value is switched by comparing the determination value with the reference value, a large threshold value is selected even in a section where the distance to the object is relatively small and the evaluation value is relatively large. Since the evaluation value is relatively large in, judgment is not affected if the threshold value is set smaller than the minimum value of the evaluation value in this section.

  On the other hand, in a section where the distance to the object is relatively large and the evaluation value is relatively small, the maximum distance that can be determined to be within the measurable range is increased by selecting a small threshold.

  In the correctness / incorrectness determination unit, two types of determination values are obtained using the charge amount obtained in the light receiving period at a timing different from the charge amount for obtaining the evaluation value, and the increase in the distance to the object due to the magnitude relationship between the two determination values. If it is determined whether the evaluation value increases or decreases and the threshold value for the evaluation value is switched between the increasing interval and the decreasing interval, the threshold is set when the evaluation value is large within the measurable range. By making it smaller, it is easier to make a judgment within the measurable range, and when the evaluation value is outside the measurable range and the evaluation value is small, even if the evaluation value fluctuates due to the influence of shot noise, etc. The possibility of being erroneously determined as being within the measurable range can be reduced. In other words, not only the evaluation value but also the judgment value changes according to the distance to the object, so it is roughly judged whether the distance to the object is within the measurable range from the magnitude of the judgment value, and the judgment result is the evaluation value. By reflecting the value on the threshold value, it is possible to increase the certainty of the determination as to whether or not it is within the measurable range. In addition, since the magnitude relationship between the two types of determination values is used, it is possible to determine whether the evaluation value increases or decreases without being affected by the reflectance of the object.

It is a block diagram which shows embodiment of a distance measuring device. It is a figure which shows an example of the modulation signal used for the same as the above. It is operation | movement explanatory drawing same as the above. It is operation | movement explanatory drawing same as the above. It is a block diagram which shows embodiment of an intensity | strength detection apparatus. It is operation | movement explanatory drawing of embodiment shown in FIG. It is operation | movement explanatory drawing same as the above. It is operation | movement explanatory drawing of the correctness determination part used for this invention. It is explanatory drawing of other operation | movement of the correctness determination part used for this invention. It is explanatory drawing of other operation | movement of the correctness determination part used for this invention.

  In the embodiment described below, as an example of the spatial information detection device, a distance measurement device that measures the distance to an object existing in the target space, and an intensity detection that detects the intensity of reflected light from the object existing in the target space An apparatus is illustrated. Therefore, first, the configuration of the distance measuring device and the intensity detecting device will be described.

(Distance measuring device)
As shown in FIG. 1, the distance measuring device has an active configuration including a light emitting source 1 that projects light into a target space where a distance measuring object 3 is present, and a light receiving sensor 2 that receives light from the target space. And the distance to the object 3 is calculated based on a physical quantity corresponding to the time until the light projected from the light source 1 (hereinafter referred to as “signal light”) is reflected by the object 3 and received by the light receiving sensor 2. Measure. That is, the distance is measured using the principle of the time-of-flight method.

  As the light source 1, a light emitting element capable of modulating the optical output at a high frequency (for example, 10 MHz) such as a light emitting diode or a laser diode is used. On the other hand, as the light receiving sensor 2, a light receiving element capable of detecting a change in received light intensity for a time approximately equal to a time for changing the light output of the light emitting source 1 is used.

  In this embodiment, the light receiving sensor 2 is assumed to use a light receiving element (imaging device) having a large number of light receiving regions (regions corresponding to pixels) like a CCD area image sensor or a CMOS area image sensor. Yes. By using this type of light receiving sensor 2, it is possible to collectively measure the distance to the object 3 existing in the spatial region defined by the field of view of the light receiving sensor 2. That is, it is possible to generate a distance image whose pixel value is a distance value without scanning the signal light projected from the light emitting source 1 or scanning the visual field of the light receiving sensor 2.

  As will be described later, one pixel of the distance image can be associated with one light receiving region of the light receiving sensor 2. First, one pixel of the distance image is associated with four light receiving regions adjacent to the light receiving sensor 2. Explain that it is. If it is set as the structure which extracts the information for 1 pixel of a distance image using the light reception amount in the four adjacent light reception area | regions of the light reception sensor 2, the operation | movement for 1 pixel of a distance image is based on operation | movement of 4 light reception areas. I can explain. Each light receiving area of the light receiving sensor 2 is equivalent to a light receiving element having a single light receiving area such as a photodiode or a phototransistor. That is, the light receiving sensor 2 generates and accumulates an amount of electric charge according to the received light intensity (actually, the amount of received light at a predetermined time). For the four light receiving regions, a shape in which four light receiving regions are arranged on a straight line, a shape in which 2 × 2 light receiving regions are arranged on lattice points, or the like can be adopted.

  If the light receiving sensor 2 is a photodiode or a phototransistor, a gate circuit such as an analog switch is provided after the light receiving sensor 2 so as to extract charges generated during the light receiving period. In the case of using an element, the light receiving period in which charges are accumulated in the imaging element is controlled using the principle of an electronic shutter, and the accumulated charges are accumulated many times (for example, 10,000 times) for each light receiving area and then taken out to the outside. (Hereinafter, a period for accumulating charges is referred to as an “accumulation period”). The light receiving period is set to a short time such that the light receiving intensity in the period may be considered constant. Therefore, the amount of received light during the light receiving period is equivalent to the received light intensity.

  That is, the light receiving sensor 2 generates and accumulates charges corresponding to the amount of received light in the light receiving period, a charge accumulating part that accumulates in a predetermined accumulation period sufficiently longer than the light receiving period, and the accumulated charges externally. And a charge extraction portion to be taken out. In the case of an FT type CCD image sensor, the photoelectric conversion unit corresponds to each pixel in the imaging region, the charge storage unit corresponds to the storage region, and the charge extraction unit corresponds to the horizontal transfer unit. In the case of an IT type CCD image sensor, the photoelectric conversion unit corresponds to a pixel in each imaging region, the charge storage unit corresponds to a vertical transfer unit, and the charge extraction unit corresponds to a vertical transfer unit and a horizontal transfer unit. .

  By accumulating charges in this way, it is possible to increase the amount of charge extracted in association with each light receiving region and increase the signal level, and to reduce the influence of shot noise. In addition, when the light output of the light source 1 is modulated at a frequency of about 10 MHz, the number of times the charge is taken out from the light receiving sensor 2 to the outside even if the number of times of accumulation is about 10,000 may be 30 times or more per second. it can. That is, it is possible to obtain a moving image having a smooth motion with respect to a distance image whose pixel value is a distance value.

  By the way, in this configuration, a signal pattern of a modulation signal that modulates the intensity of the signal light projected from the light source 1 and the object 3 depending on the relationship between the timing of accumulating charges in the light receiving sensor 2 in association with this signal pattern. The distance is detected.

  As shown in FIG. 2, the modulation signal is a square wave signal in which the measurement period of each of the binary signal values of the H level and the L level is changed randomly (“1” in FIG. 2 indicates the H level). "0" indicates the L level), the H level and the L level are generated without periodicity, and the generation probabilities of the H level and the L level are equal.

  This type of modulation signal can be generated using a technique (for example, a Gold code generation circuit) that generates a PN (Pseudorandom Noise) code used in the spread spectrum technique. Similar to the PN code, the modulation signal is generated so that each period of the H level and the L level has a length that is an integral multiple of the unit period. Hereinafter, this unit period is referred to as a chip length following the PN code. The chip length can be set appropriately, but is set to 100 [ns], for example.

  The modulation signal described above is generated in the code generator 4, and the modulation signal output from the code generator 4 is given to the light emission source 1 via the timing control unit 5. The light emitting source 1 is turned on during a period when the modulation signal is at the H level, and is turned off when the modulation signal is at the L level. That is, the light source 1 is turned on / off according to the signal value of the modulation signal, and the signal light whose intensity changes in a rectangular wave shape is projected onto the target space.

  Based on the modulation signal output from the code generator 4, the timing control unit 5 also generates a timing signal that defines a light receiving period in which charges are accumulated in the light receiving sensor 2. In the present embodiment, four types of timing signals having different timings are generated in order to generate one distance image. Further, the timing control unit 5 also outputs a clock signal for determining the timing at which the charge accumulated in the light receiving sensor 2 is taken out and the operation timing of the distance calculation unit 6 and the correctness determination unit 7 described later.

  FIG. 3 shows the relationship between the modulation signal and each timing signal. FIG. 3A shows the modulation signal (the intensity of the projected light), and FIG. 3B shows the intensity of the light received by the light receiving sensor 2. Each timing signal is generated based on the modulation signal as shown in FIGS. That is, the first timing signal that is a non-inverted signal (that is, a signal synchronized with the modulation signal) as shown in FIG. 3C, and the modulation signal as shown in FIG. A second timing signal which is an inverted signal obtained by inverting the level, a third timing signal obtained by delaying the non-inverted signal of the modulation signal by one chip length Tc as shown in FIG. 3E, and FIG. As described above, there are four types of timing signals of the fourth timing signal in which the inverted signal of the modulation signal is delayed by one chip length Tc and the H level and the L level are inverted. That is, each timing signal is generated by setting a non-inverted signal or an inverted signal of the modulation signal in a predetermined relationship with the modulation signal in the time axis direction.

  Since there is a time difference between signal light reflected from the object 3 after being projected from the light emitting source 1 and received by the light receiving sensor 2, each timing signal described above from each of the four light receiving areas of the light receiving sensor 2 is H. When charge is taken out during a period of level, the amount of charge obtained from each light receiving region becomes an amount corresponding to the area of the portion indicated by the hatched portion in FIGS.

  Here, as described above, the charge is taken out from the light receiving sensor 2 after the charge is accumulated many times for each light receiving region (after the charge is accumulated for many times the chip length Tc). The amount of charge extracted corresponding to each light receiving region converges to a value represented by a linear function of the time difference τ from light projection to light reception due to the randomness of the modulation signal. If the charge amounts extracted for each light receiving region at timings corresponding to FIGS. 3C to 3F are A0, A2, A1, and A3, respectively, the time difference τ is 0 ≦ τ ≦ as shown in FIG. In the range of Tc, the charge amounts A0 and A3 decrease as the time difference τ increases, and the charge amounts A1 and A2 increase as the time difference τ increases. If Tc <τ ≦ 2Tc, the charge amounts A0 and A2 are constant, the charge amount A1 decreases as the time difference τ increases, and the charge amount A3 increases as the time difference τ increases. Further, if 2Tc <τ, all the charge amounts A0 to A3 are constant.

  The charge amounts A0 to A3 ideally have a relationship of A0 + A2 = A1 + A3 = constant. Furthermore, the charge amount A0 when the time difference τ is 0 is a charge amount that is a half of the charge amount when light is received over the entire accumulation period. Similarly, the charge amount A1 when the time difference τ is one chip length Tc is a charge amount that is one half of the charge amount when light is received over the entire accumulation period.

Therefore, as shown in FIG. 4, when (A0 + A2) / 2 = (A1 + A3) / 2 = B, the charge amount A0 when the time difference τ is 0 is A + B, and the above relation is summarized, 0 ≦ τ ≦ Tc In this range, each charge amount A0 to A3 can be expressed as follows.
A0 = -α · τ + A + B
A1 = α ・ τ + B
A2 = α · τ + BA
A3 = -α · τ + B
However, α is a constant representing the rate of change of charge with respect to the time difference τ, and α = A / Tc.

  The values of the constants A and B depend on the intensity of ambient light or ambient light and the light attenuation rate in the path from the light source 1 to the light receiving sensor 2 that receives the signal light projected from the light source 1 to the target space. To do. This attenuation factor includes the reflectance of the object 3 and the transmittance of the medium through which light passes as parameters. Therefore, the change rate α also includes the intensity, reflectance, and transmittance of ambient light or ambient light as parameters. If the light attenuation rate changes, the charge amount change rate α changes as shown by the broken line in FIG. Usually, since the transmittance of the medium may be considered to be constant, it can be said that the change rate α depends on the reflectance of the object 3.

By the way, when the time difference τ [s] is obtained from the above equation, it is as follows.
τ = (A1−A3) Tc / {(A0−A2) + (A1−A3)}
If the distance to the object 3 is L [m] and the speed of light is c [m / s], the distance L can be expressed as L = c · τ / 2 using the time difference τ.

  For example, if 1 chip length Tc is 100 [ns], 0 ≦ τ ≦ 100 [ns], so 0 ≦ L ≦ 15 [m], and 15 [m] is the upper limit of the measurable range. 3 distances can be measured. That is, the distance calculation unit 6 as the spatial information detection unit obtains the distance to the object 3 by performing the above-described calculation using the charge generated during the period defined by the timing signal generated by the timing control unit 5. .

  Further, as apparent from the equation for obtaining the time difference τ, the difference between the charge amounts A0 and A2 and the difference between the charge amounts A1 and A3 are used, so the component of the constant B is removed and further includes the constant A. By dividing the components, the constant A component is also removed. That is, by obtaining the time difference τ by the above equation, the time difference τ can be obtained without being affected by the ambient light component or the ambient light component caused by the ambient light and the light attenuation rate in the light transmission / reception path.

  As is clear from the above equation, the time difference τ [s] can be obtained without being affected by the external light component and the light attenuation factor even if only three of the four types of charge amounts A0 to A4 are used. it can. For example, since A1-A2 = A and A1-A3 = 2α · τ, τ = (Tc / 2) (A1-A3) / (A1-A2).

  Alternatively, by using the fact that A = B under the condition that there is no ambient light or ambient light, and determining any two types of charge amounts A0 to A3 at a known distance (known time difference τ), Constants α, A, B can be determined. That is, the time difference τ [s] can be obtained by combining two types of charge amounts among the four types of charge amounts A0 to A4.

  Further, A = B under the condition that there is no ambient light or ambient light, and α = constant if the reflectance of the object 3 is constant (invariable), so that it is a known distance (known time difference τ). When any one of the charge amounts A0 to A3 is obtained, the constants α, A, and B (in reality, any one constant) can be determined. That is, by obtaining one type of charge amount A0, the time difference τ [s] is set to τ = 2 {1- (A0 / A)} Tc or the like, and only the charge amount corresponding to one of the charge amounts A0 to A3. It can be calculated from

  As described above, in order to obtain the charge amounts A0 to A3 corresponding to the four types of timing signals by the image sensor, four adjacent light receiving regions (four in one row or two in two rows) may be provided. Charges corresponding to the timing signals may be accumulated in each light receiving region included in the group, and the charges may be accumulated in the image sensor. That is, one distance value is obtained using four light receiving regions, and the resolution is lowered, but four charge amounts A0 to A3 can be read out from the image sensor at one time. By reducing the number of times of reading of charges for generating a distance image of a screen, the time required to obtain a distance image of one screen can be shortened. That is, a smooth moving image can be generated for the distance image.

  Further, four accumulation periods for each light receiving region of the image sensor are set as one cycle, and charges corresponding to different timing signals for each accumulation period are integrated in one light receiving region, and each image signal corresponds to each timing signal. By accumulating charges, one distance value may be obtained in four accumulation periods. In this configuration, since charges are usually read out every accumulation period, the time required to obtain a one-screen distance image is longer than in the above-described operation, but a distance value is obtained for each light receiving region. Therefore, it is possible to generate a range image with high resolution.

  By the way, among the charge amounts A0 to A3, the charge amounts A0 and A3 are linear functions having a negative slope in the range of 0 ≦ τ ≦ Tc with respect to the time difference τ, but when the time difference τ exceeds one chip length Tc, a constant value is obtained. The charge amounts A1 and A2 are linear functions having a positive slope in the range of 0 ≦ τ ≦ Tc with respect to the time difference τ, and are linear functions having a negative slope in the range of Tc <τ ≦ 2Tc. (Indicated by a broken line in FIG. 4), when the time difference τ exceeds the 2-chip length Tc, the constant value B is obtained.

  That is, when 0 ≦ τ ≦ Tc, A0−A2 = −2α · τ + 2A and A = α · Tc, so that A0−A2 = 2α (Tc−τ)> 0, whereas Tc Since <0, A0−A2 = 0, so the distance to the object 3 cannot be measured. In other words, the distance corresponding to τ = Tc is the upper limit of the measurable range.

  However, since the charges A0 and A2 fluctuate in an environment where shot noise or the like actually occurs, the condition of A0−A2 = 0 is not always satisfied when Tc <τ. From this, Tc <τ In this case, the distance to the object 3 may be erroneously detected. In order to prevent such erroneous detection, the configuration shown in FIG. That is, the correctness / incorrectness determination unit 7 determines whether or not the distance to the object 3 is within the measurable range, and invalidates the spatial information detected by the distance calculation unit 6 as the spatial information detection unit when the distance is outside the measurable range. . The specific operation of the correctness determination unit 7 will be described later.

(Intensity detector)
Next, an intensity detection device that detects the intensity of reflected light from the object 3 will be described. In the intensity detection device, a light projection period in which signal light is projected from the light source 1 to the target space and a non-light projection period in which signal light is not projected from the light source 1 to the target space are provided, and light is received during the light projection period. The intensity of the reflected light is detected by removing the ambient light component or ambient light component detected during the non-projection period from the light.

  As shown in FIG. 6, the intensity detection apparatus has a configuration in which the distance calculation unit 6 of the distance measurement apparatus shown in FIG. 1 is replaced with an intensity calculation unit 8 as a spatial information detection unit. The configuration excluding the intensity calculation unit 8 is the same as that of the distance measuring device, and here, it is assumed that an image sensor is used as the light receiving sensor 2. That is, a grayscale image having the pixel value of the intensity of the reflected light reflected from the object 3 by the signal light projected from the light source 1 is generated. Since the external light component is removed (or reduced), the pixel value of the grayscale image is hereinafter referred to as a “reflection intensity value” in order to distinguish it from a normal density value. Further, in order to distinguish an image having a reflection intensity value as a pixel value from a normal grayscale image, it is hereinafter referred to as a “reflection intensity image”. Note that the use of the image sensor is not essential, and the light receiving sensor 2 having only one light receiving region can also be used.

  Since such an external light component is removed, such a reflection intensity image can be referred to as a grayscale image of the object 3 under a certain illumination condition. For example, as in the case of performing face authentication based on the image, the object In the application of extracting the feature amount 3 from the image, the convenience is enhanced.

  By the way, the light received by the light receiving sensor 2 during the light projection period in which the light source 1 projects the signal light into the target space includes a signal light component (hereinafter referred to as “signal component”) and an external light component. The light received by the light receiving sensor 2 during the non-projection period when the light source 1 does not project the signal light into the target space is only the external light component. Therefore, a light projection period and a non-light projection period are provided, and the charge amount (corresponding to the light reception amount) in the light projection period of the light receiving sensor 2 and the charge amount (corresponding to the light reception amount) in the non-light projection period are used. The signal component can be extracted.

  That is, while the distance measurement device continuously outputs the modulation signal from the timing control unit 5 while measuring the distance, the intensity detection device detects the intensity while A light projection period for outputting a modulation signal from the timing control unit 5 and a non-light projection period for not outputting a modulation signal are provided. As described above, the operation of the timing controller 5 is different between the distance measuring device and the intensity detecting device.

  Hereinafter, in order to simplify the description, as shown in FIG. 7A, a case where the lengths of the light projection period Ta and the non-light projection period Tb are one to one will be described as an example. In this case, if the time when the light projection period Ta and the non-light projection period Tb are combined is short enough that the intensity of the ambient light or the ambient light does not substantially change, ideally, FIG. ), The difference between the charge amount Ba accumulated by the light receiving sensor 2 during the light projection period Ta and the charge amount Bb accumulated by the light reception sensor 2 during the non-light projection period Tb includes only the signal component. become. That is, this difference is detected as an intensity value (or gray value). In other words, the intensity detection device can be said to be an active imaging device that generates a grayscale image having the intensity of reflected light corresponding to the signal light projected from the light source 1.

  The lengths of the light projection period Ta and the non-light projection period Tb do not have to be one-to-one. The length of the light projection period Ta and the non-light projection period Tb is an appropriate ratio, and a coefficient corresponding to the ratio. The charge amount Ba, Bb may be multiplied to calculate the difference. For example, when Ta / Tb = k, the external light component can be removed by obtaining Ba−k · Bb. In this operation, if the light projection period Ta and the non-light projection period Tb are made one-to-one and the length of the light projection period Ta is equal, the light projection period Ta and the non-light projection period Tb are Total time is shortened.

  As apparent from the operation described above, in detecting the intensity of the reflected light, it is sufficient if there is one kind of timing signal for defining the light projection period Ta and the non-light projection period Tb. Since only the signal component is extracted using the difference between the received light amounts Ba and Bb with respect to the non-light projection period Tb, the intensity of the reflected light is not affected by the external light component by using only one type of timing signal. Can be detected.

  By the way, the timing signal in the intensity detection device is generated by the timing control unit 5 based on the modulation signal generated by the code generator 4 as in the distance measurement device. Accordingly, similarly to the distance measuring device, the correctness determination unit 7 is used to determine whether or not the distance to the object 3 is within the measurable range, and when it is outside the measurable range, the intensity calculation unit 8 that is a spatial information detection unit. It is possible to invalidate the spatial information obtained in step. That is, in the intensity detection device, by limiting the distance to the object 3 as in the distance measurement device, it is possible to emphasize and extract target information without extracting useless spatial information.

(Correct / incorrect judgment section)
(Operation example 1)
Below, operation | movement of the correctness determination part 7 is demonstrated. The correctness / incorrectness determination unit 7 uses, as an evaluation value, a value based on a difference between at least two types of charge amounts among the four types of charge amounts A0 to A3 obtained corresponding to each timing signal. The combination of the charge amounts for obtaining the difference is a combination in which the difference increases or decreases as the distance to the object 3 increases. Specifically, (A0, A2) (A1, A3) (A0, A1) ( It is possible to use four combinations of A2, A3). The difference of each combination changes as shown in FIGS. 8A to 8D according to the time difference τ.

  Therefore, any combination of (A1, A3) (A0, A1) (A2, A3) can be adopted as the difference. First, a case where the combination of (A0, A2) is used as the difference will be described. . The difference between the charge amounts A0 and A2 (= A0−A2) is a linear function with the time difference τ as a variable, and decreases as the time difference τ increases. Therefore, a threshold is set for the difference, and the difference is It can be considered that it is determined that it is out of the measurable range when it becomes smaller than the threshold value. In this case, if the threshold is a very small positive number (≈0), the distance range where the time difference τ satisfies 0 ≦ τ <Tc can be set within the measurable range.

  By the way, since the difference is A0−A2 = 2A−2α · τ and α = A / Tc, 2A {1− (τ / Tc)}. That is, each of the charge amounts A0 to A3 includes the constants A and B as described above, and these constants A and B indicate the attenuation rate of the light path from light projection to light reception, the external light component, and the like. Therefore, the constants A and B cannot be removed by only the difference.

  Here, the attenuation rate is affected by parameters such as the reflectance of the object 3, the distance to the object 3, and the medium of the path. However, in order to simplify the description, only the reflectance of the object 3 will be described below. Pay attention. It can be easily estimated from FIG. 5 that the difference (= A0−A2) is influenced by the reflectance of the object 3. Therefore, in order to remove the influence of the reflectance of the object 3 and accurately determine whether or not the distance to the object 3 is within the measurable range, it is necessary to normalize so as to remove the influence of the constants A and B. .

  Here, since only the influence of the reflectance of the object 3 is focused, consider the case where the object 3 exists in an environment where no external light component exists. As described above, since the difference (A0−A2) does not include the constant B, in order to normalize the difference (A0−A2) and use it as the evaluation value, the difference (A0−A2) is normalized to remove the constant A. I understand that

  Since the external light component corresponds to (B−A) in the amount of charge, A = B in an environment where no external light component exists. Further, since A0 + A2 = A + B, A0 + A2 = 2A in an environment where no external light component exists. Therefore, if the difference (A0−A2) is divided by (A0 + A2), {(A0−A2) / (A0 + A1)} = 1− (τ / Tc), and the first order of the time difference τ not including the constants A and B A function can be obtained. Therefore, by using this value as the evaluation value, it is possible to evaluate the distance to the object 3 without being affected by the reflectance in an environment where no external light component exists.

  That is, the correctness / incorrectness determination unit 7 determines that the distance to the object 3 is in the range of 0 to c · τ / 2 when the evaluation value is equal to or greater than the threshold value, and detects the spatial information (distance distance) detected for the object 3. , The reflectance of the object 3, etc.) is treated as effective spatial information. Further, when the evaluation value is smaller than the threshold value, the distance to the object 3 has exceeded c · τ / 2. Therefore, the distance to the object 3 is determined to be out of the measurement distance range and detected. Disable spatial information.

  Here, if the one-chip length Tc is 100 [ns], the measurable range is 0 to 15 [m]. In the correctness determination unit 7, the distance to the object 3 is the upper limit of the measurable range 15 If [m] is exceeded, the detected spatial information (distance value, reflection intensity value) is invalidated.

  Since the image sensor is used for the light receiving sensor 2 and a distance image and a reflection intensity image are obtained, the correctness / incorrectness determination unit 7 determines whether or not each pixel is within the measurement distance range, and spatial information is valid for each pixel. Or invalid. For the distance image, an instruction is given to the distance calculation unit 6 so that the distance value is not output for the pixel for which the distance value is determined to be invalid by the correctness / incorrectness determination unit 7. For the pixel whose value is determined to be invalid, the intensity calculation unit 8 is instructed not to output the reflection intensity value.

  By this operation, the distance value and the reflection intensity value are not given to the pixel for the distant object 3 that exceeds the upper limit of the measurable range, so that erroneous detection of the distance value can be prevented and the distance is limited for the reflection intensity value. can do. That is, a pixel value is obtained for a region where the distance to the object 3 is within the measurable range, and the region outside the measurable range is within the measurable range without adjusting the sensitivity of the light receiving sensor 2. Limits can be given.

  However, in an environment where the amount of charge fluctuation due to shot noise is large, the evaluation value (= A0−A2) does not become 0 and A0−A2> 0 even when the time difference τ exceeds 1 chip length Tc. There is sex. Accordingly, the correctness / incorrectness determination unit 7 gives an appropriate threshold value other than 0 to the evaluation value (= A0−A2). In this case, the upper limit of the measurement distance range is slightly shorter than c · τ / 2, and the lower limit is slightly larger than 0.

(Operation example 2)
In the operation example 1 described above, the charge amounts A0 and A2 are used and normalized by dividing the difference between the charge amounts A0 and A2 by the sum. By providing a light projection period Ta for projecting light and a non-light projecting period Tb for projecting light from the light source 1 to the target space (see FIG. 7), a value corresponding to the constant B is obtained and normalized by this value. It is also possible to do. That is, in the operation example 1, normalization is performed using the fact that A0 + A2 = A + B = 2A in an environment where no external light component exists, but in this operation example, from the amount of charge corresponding to the constant A + B. A charge amount corresponding to the constant A is obtained by removing a charge amount corresponding to the constant B, and normalization is possible even in an environment where an external light component exists.

  Here, it is assumed that the light projection period Ta and the non-light projection period Tb are equal in length, and that the external light component does not change between the light projection period Ta and the non-light projection period Tb. In the non-light projection period Tb, the charge amounts A0 to A3 are constant regardless of the distance to the object 3, and the rate of change α = 0, so it can be seen that the constant A = 0. That is, the sum of the charge amounts A0 and A2 in the non-light projection period Tb is A0 + A2 = A + B = B.

  Since the constant B does not change in the light projection period Ta and the non-light projection period Tb, the sum of the charge quantities A0 and A2 obtained in the non-light projection period Tb from the sum of the charge quantities A0 and A2 obtained in the light projection period Ta. Since A + B−B = A, the difference (A−B) between the charge amounts A0 and A2 obtained in the light projection period Ta is divided by this value to obtain 2A {1− (τ / Tc)}) / A = 1− (τ / Tc). Similar to Operation Example 1, by using this value as an evaluation value, it can be determined whether or not the distance to the object 3 is within the measurable range.

  In this operation, the influence of the external light component is removed by using the charge amount obtained in the light projection period Ta and the non-light projection period Tb, so that it can be used even in an environment where the external light component exists. Can do. Other operations are the same as those in the first operation example. Moreover, although it is necessary to provide the light projection period Ta and the non-light projection period Tb, this operation | movement can be applied to a distance measuring device by calculating | requiring distance as spatial information in the light projection period Ta. Further, the light projection period Ta and the non-light projection period Tb do not necessarily have the same time length, and the sum of the charge amount obtained in the non-light projection period Tb is subtracted from the sum of the charge quantity obtained in the light projection period Ta. When doing so, you may perform correction | amendment according to the time ratio of the light projection period Ta and the non-light projection period Tb.

(Operation example 3)
In the operation example 1 described above, an example is shown in which the evaluation value obtained by combining the two types of charge amounts A0 and A2) is used in the correctness / incorrectness determination unit 7, but by using the four types of timing signals described above, 4 When the types of charge amounts A0 to A4 are obtained, an evaluation value obtained by combining the other two types of charge amounts A1 and A3 may be used in combination.

  Hereinafter, the evaluation value obtained from the charge amounts A0 and A2 is referred to as a first evaluation value, and the evaluation value obtained from the charge amounts A1 and A3 is referred to as a second evaluation value. As can be easily understood with reference to FIGS. 8A and 8B, the first evaluation value becomes 0 when the time difference τ is 1 chip length Tc or more, and the second evaluation value has the time difference τ of It becomes the maximum value (= 2) when the length is 1 chip length Tc, and becomes 0 when the time difference τ is 2 chips length 2Tc or more.

  Using this fact, the first and second evaluation values are set to a threshold value of two levels, a first threshold value and a second threshold value, which are substantially 0, and correct / incorrect determination is made. The unit 7 determines that the time difference τ is 1 chip length Tc or more when the first evaluation value is equal to or less than the first threshold value, and the time difference τ is 2 chips when the second evaluation value is equal to or less than the second threshold value. A configuration in which it is determined that the length is 2 Tc or more can be employed.

  That is, when both the condition that the first evaluation value is smaller than the first threshold and the condition that the second evaluation value is smaller than the second threshold are satisfied, the time difference τ is 2 chips long 2Tc. When the condition that the first evaluation value is smaller than the first threshold is satisfied and the condition that the second evaluation value is larger than the second threshold is satisfied, the time difference τ is 1 It can be seen that the chip length is not less than Tc. Further, when the time difference τ exceeds one chip length Tc due to the influence of shot noise or the like, the first evaluation value may be larger than the first threshold value. If the evaluation value is smaller than the second threshold, it can be determined that the 2-chip length 2Tc is exceeded. That is, the correctness determination unit 7 can determine that the time difference τ exceeds the two-chip length Tc if at least one of the two conditions described above is satisfied. In addition, although the same value can be used for the first threshold value and the second threshold value, different values may be used. Other operations are the same as those in the first operation example. Further, the technical concept of this operation can be applied to the operation example 2.

(Operation example 4)
In the operation example 3, when it is determined that the spatial information is invalid in at least one of the two types of evaluation values, the detected spatial information is invalidated. In the following, the threshold value for one type of evaluation value is switched. Thus, a technique for improving the reliability of spatial information will be described.

  In this operation example, evaluation values obtained from the charge amounts A0 and A2 are used, and a determination value for determining a condition for switching a threshold value for the evaluation value is defined as a difference (A1−A3) between the charge amounts A1 and A3. As shown in FIG. 8B, the determination value increases when the time difference τ is 1 to Tc, decreases when the time difference τ is Tc to 2Tc, and becomes 0 when the time difference τ exceeds 2Tc.

  As described above, the threshold value for the evaluation value is defined in order to determine that the spatial information is invalid when the distance to the object 3 exceeds the upper limit (c · τ / 2) of the measurable range. Therefore, within the measurable range where the evaluation value is relatively large, the upper limit of the measurable range is set as close to c · τ / 2 as possible by setting the threshold for the evaluation value as small as possible, and the range in which the detected spatial information can be treated as effective It is desirable to spread. On the other hand, outside the measurable range where the evaluation value is small, by setting a relatively large threshold for the evaluation value, the detected spatial information is invalidated even if the evaluation value does not become sufficiently small due to the effects of shot noise, etc. It is desirable to prevent erroneous detection of spatial information.

  That is, as the determination value, it is desirable to use a value that can be used to determine whether or not it is within the measurable range, similarly to the evaluation value. However, it may not be possible to determine whether the determination value is within the measurable range alone. For example, when A1-A3 is adopted as the determination value, one charge amount corresponds to two time differences as shown in FIG. 8B. Therefore, the time difference τ is within one chip length Tc with only the determination value. It is not possible to determine whether there is a range from 1 chip length Tc to 2 chip length 2Tc.

  In this example, as shown in FIG. 9A, a configuration is adopted in which the threshold value for the evaluation value (A0-A2) is selected from threshold values Ths and Thi of two levels. Which threshold Ths or Thi is selected is determined by comparing the determination value (A1-A3) with a prescribed reference value Vt, as shown in FIG. 9B. That is, when the determination value is smaller than the reference value Vt, a large threshold value Ths is selected, and when the determination value is larger than the reference value Vt, a small threshold value Ths is selected. The reference value Vt can be appropriately set as a value between the minimum value and the maximum value of the determination value according to the magnitudes of the threshold values Ths and Thi.

  Specifically, when the time difference τ exceeds one chip length Tc, the evaluation value ideally becomes 0. However, since the evaluation value actually fluctuates due to the influence of shot noise or the like, the threshold Ths that is larger than this fluctuation Is set, it is possible to prevent erroneous determination due to the evaluation value. However, when a large threshold Ths is used for the evaluation value, there arises a disadvantage that the distance determined as the measurable range is significantly shortened than the distance corresponding to one chip length Tc.

  Therefore, in a section where the evaluation value is relatively small in a section where the time difference τ is shorter than one chip length Tc, that is, in a section where the distance to the object is relatively large, a small threshold value Thi is selected to extend the measurable range as much as possible. It is desirable. However, if only the small threshold value Thi is used, the possibility of erroneous determination increases when the evaluation value fluctuates due to the influence of shot noise or the like.

  In this operation example, by selecting a large threshold Ths when the determination value is smaller than the reference value Vt, the distance between the distance corresponding to 1 chip length (unit period) Tc and the distance corresponding to 2 chips length 2Tc is selected. A large threshold value Vt is selected on the far side from the distance. Accordingly, a larger threshold Ths is selected until the distance to the object exceeds the distance corresponding to the one-chip length Tc and reaches the distance corresponding to the two-chip length 2Tc, so that the distance corresponding to the two-chip length 2Tc can be selected. The probability of misjudgment due to the influence of shot noise after a small distance can be reduced.

  That is, by adopting the operation of this example, compared to the configuration in which it is determined whether or not the distance corresponding to the 2-chip length 2Tc is larger as in the operation example 2, it is less susceptible to the influence of shot noise and the like. Is possible.

  On the other hand, since the large threshold Ths is selected when the determination value is smaller than the reference value Vt, the large threshold Ths is selected even in the section where the distance to the object is relatively small and the evaluation value is relatively large. However, as shown in FIG. 9A, since the evaluation value is relatively large in this section, setting the threshold Ths smaller than the minimum value of the evaluation value in this section affects the judgment based on the evaluation value. There is nothing.

  As described above, the large threshold value Ths needs to be set larger than the variation of the evaluation value due to shot noise or the like and smaller than the evaluation value in the section where the distance to the object is short. In addition, it is desirable to set the small threshold Thi as small as possible in order to raise the upper limit of the measurable range. Other configurations and operations are the same as those in the first operation example.

(Operation example 5)
As can be seen from the operation example 3, the determination value (= A1−A3) increases as the time difference τ increases in the time difference τ range of 0 to Tc, and the time difference τ increases in the range of Tc to 2Tc. And decreases to approximately 0 when the time difference τ exceeds 2Tc. If such a characteristic of the determination value is used, it is possible to detect whether or not the distance to the object 3 is within the measurable range based on the determination value.

  Whether the determination value (= A1-A3) increases or decreases as the time difference τ increases can be determined as follows. Hereinafter, a region where the determination value increases as the time difference τ increases is referred to as an increase region, and a region where the determination value decreases is referred to as a decrease region. In the example of FIG. 8B, a region where the time difference τ is 0 to Tc is an increase region, and a region where the time difference τ is Tc to 2Tc is a decrease region.

  Here, the correctness / incorrectness determination unit 7 cooperates with the timing control unit 5, and in addition to the above-described four types of timing signals, the timing signal corresponding to the charge amounts A1 and A3 is transmitted from the timing control unit 5 to a predetermined determination time ΔTd ( A timing signal delayed by << Tc) is also output. The former timing signal and the latter timing signal are output at different times. However, both timing signals are output within a short time such that there is no substantial change in the distance to the object 3, the reflectance of the object 3, the transmittance of the medium, and the external light component.

  Now, as shown by the solid line in FIG. 10, if the obtained determination value (= A1-A3) is Q1, it can be said that the time difference τ is either τ1 or τ2, but the determination value Q1 alone is used. The time difference τ cannot be uniquely determined only by using it. Therefore, the correctness determination unit 7 obtains the determination value Q1, and then instructs the timing control unit 5 to determine the timing signals (see FIGS. 3E and 3F) corresponding to the charge amounts A1 and A3 as the determination time ΔTd. A timing signal delayed by an amount of time is output. Since the timing signals corresponding to the charge amounts A1 and A3 are delayed by one chip length Tc with respect to the timing signals corresponding to the charge amounts A0 and A2, the newly generated timing signals are the charge amounts A0 and A2. Is delayed by (Tc + ΔTd) with respect to the timing signal corresponding to.

  When the charge amounts A11 and A31 corresponding to the charge amounts A1 and A3 are obtained using the timing signal shifted by the determination time ΔTd as described above, and the charge amounts Q11 and Q12 of the difference A11-A13 are obtained, FIG. As indicated by a broken line, the charge amount Q11 is smaller than the determination value Q1 in the increase region, and the charge amount Q12 is larger than the determination value Q1 in the decrease region. That is, when the charge amounts Q11 and Q12 corresponding to the determination value are obtained using the timing signal delayed by the determination time ΔTd, the increase region is determined depending on the change direction with respect to the determination value Q1 obtained using the non-delayed timing signal. It can be identified whether it is a decreasing area.

  By identifying whether the determination value Q1 is an increase region or a decrease region as described above, it is possible to identify whether the time difference τ is shorter or longer than one chip length Tc, and the time difference τ is uniquely determined. can do.

  Therefore, the correctness / incorrectness determination unit 7 decreases the threshold value for the evaluation value to increase the upper limit of the measurable range as much as possible when the determination value (= A1-A3) is in the increase region, and when the determination value is in the decrease region. By increasing the threshold value for the evaluation value, it is possible to prevent erroneous determination due to fluctuations in the evaluation value. If a technology that detects whether the judgment value is an increase region or a decrease region is adopted, it is possible to determine whether it is within the measurable range using only the judgment value, but the upper limit of the measurable range Judgment cannot be made accurately in the vicinity. Therefore, it is used only for switching the threshold value for the evaluation value. Other operations are the same as those in the first and second operation examples.

  In each of the above-described operation examples, the evaluation value is defined by the charge amounts A0 and A2, but as shown in FIG. 8, the difference increases or decreases according to the time difference τ among the four types of charge amounts A0 to A3. Any combination of charge amounts can be used as an evaluation value. A value that can be used as an evaluation value can also be used as a determination value.

DESCRIPTION OF SYMBOLS 1 Light emission source 2 Light reception sensor (a photoelectric conversion part, a charge storage part, a charge extraction part)
3 Object 4 Code Generator 5 Timing Control Unit 6 Distance Calculation Unit 7 Correct / Error Judgment Unit 8 Strength Calculation Unit

Claims (7)

  A light emitting source that projects light into the target space, a photoelectric conversion unit that generates and accumulates an amount of charge according to the light reception intensity received and instructed from the target space, and a charge accumulated in the photoelectric conversion unit from the light reception period A charge accumulating unit that accumulates over a long predetermined accumulation period, a charge extracting unit that extracts charges accumulated in the charge accumulating unit, a modulation signal that modulates the light output of the light emitting source, and a timing signal that defines the light receiving period. The timing control unit that outputs and determines the accumulation period, the spatial information detection unit that detects the spatial information of the target space by using the charge extracted by the charge extraction unit, and the target by using the charge extracted by the charge extraction unit A correct / incorrect determination unit that determines whether reflected light from an object existing in space is within a permissible measurable range, and the modulation signal has a duration of each binary signal value. Each is a square wave signal that is an integral multiple of the unit period and whose duration changes randomly in the accumulation period, and the timing control unit modulates the non-inverted signal or the inverted signal of the modulated signal in the time axis direction. A plurality of types of timing signals having a prescribed relationship with the signal are generated, the photoelectric conversion unit integrates the generated charges using the duration of one signal value in each timing signal as the light receiving period, and the spatial information detection unit Spatial information is detected using the amount of charge obtained by accumulating the charge accumulated during the light receiving period based on each timing signal during the accumulation period, and the correctness determination unit can be obtained using two types of timing signals. The difference between the two types of charge amount, which increases or decreases as the distance to the object increases, is normalized by dividing the difference by the value corresponding to the sum of the charge amounts. The evaluation value that increases as the distance to the object increases is larger than the specified threshold value, or the evaluation value that decreases as the distance to the object increases decreases from the specified threshold value. A spatial information detection device characterized by determining that it is outside the measurable range when it is small, and invalidating the spatial information detected by the spatial information detection unit when it is judged to be outside the measurable range.   A light emitting source that projects light into the target space, a photoelectric conversion unit that generates and accumulates an amount of charge according to the light reception intensity received and instructed from the target space, and a charge accumulated in the photoelectric conversion unit from the light reception period A charge accumulating unit that accumulates over a long predetermined accumulation period, a charge extracting unit that extracts charges accumulated in the charge accumulating unit, a modulation signal that modulates the light output of the light emitting source, and a timing signal that defines the light receiving period. The timing control unit that outputs and determines the accumulation period, the spatial information detection unit that detects the spatial information of the target space by using the charge extracted by the charge extraction unit, and the target by using the charge extracted by the charge extraction unit A correct / incorrect determination unit that determines whether reflected light from an object existing in space is within a permissible measurable range, and the modulation signal has a duration of each binary signal value. Each is a square wave signal that is an integral multiple of the unit period and whose duration changes randomly in the accumulation period, and the timing control unit modulates the non-inverted signal or the inverted signal of the modulated signal in the time axis direction. A plurality of types of timing signals having a prescribed relationship with the signal are generated, a modulation period is output to project light from the light emission source to the target space, and the modulation signal is stopped to emit light from the light source to the target space. A non-projection period in which no light is projected is defined, the photoelectric conversion unit accumulates charges generated using the duration of one signal value in each timing signal as a light reception period, and the spatial information detection unit The spatial information is detected using the charge amount obtained by accumulating the charge accumulated in the light receiving period based on the storage period in the accumulation period, and the correctness determination unit uses the charge amount accumulated in the non-light emitting period. A light component other than the signal light projected by the light source is extracted, and a difference that increases or decreases with an increase in the distance to the object is obtained from the difference between the two types of charge amounts obtained by using the two types of timing signals. Normalize by dividing the sum of the charge amount by the value excluding the charge amount corresponding to the light component other than the signal light, use the normalized difference as the evaluation value, and increase as the distance to the object increases When the evaluation value to be measured is larger than the specified threshold value, or the evaluation value that decreases with the increase in the distance to the object is smaller than the specified threshold value, it is determined to be out of the measurable range, and it is determined to be out of the measurable range A spatial information detection apparatus characterized by invalidating spatial information detected by the spatial information detection unit.   The right / wrong judgment unit evaluates from two types of charge amounts obtained using a first timing signal that is a non-inverted signal of the modulation signal and a second timing signal that is an inverted signal of the first timing signal. The spatial information detection device according to claim 1, wherein a value is used.   The right / wrong judgment unit obtains a first charge signal obtained from two types of charge amounts obtained by using a first timing signal that is a non-inverted signal of a modulation signal and a second timing signal that is an inverted signal of the first timing signal. An evaluation value of 1, a third timing signal obtained by delaying the non-inverted signal of the modulated signal by a unit period in the time axis direction, and a fourth timing obtained by delaying the inverted signal of the modulated signal by a unit period in the time axis direction A second evaluation value obtained from two types of charge amounts obtained using a signal, a condition that the first evaluation value is smaller than the first threshold value, and the second evaluation value is a second threshold value. 3. The spatial information detection device according to claim 1, wherein the spatial information detection device determines that the measurement value is out of a measurable range when at least one of the conditions of smaller than is satisfied.   The correctness determination unit includes a third timing signal obtained by delaying the non-inverted signal of the modulated signal by a unit period in the time axis direction, and a fourth timing obtained by delaying the inverted signal of the modulated signal by a unit period in the time axis direction. 4. The spatial information according to claim 3, wherein a difference between two kinds of charge amounts obtained by using two kinds of timing signals and a signal is used as a judgment value, and the threshold value is switched according to the magnitude of the judgment value. Detection device.   The right / wrong judgment unit selects the threshold value from two levels, a small threshold value when the judgment value is larger than a prescribed reference value, and a large threshold value when the judgment value is smaller than a prescribed reference value. The spatial information detection device according to claim 5, wherein the spatial information detection device is selected.   The correctness determination unit includes a third timing signal obtained by delaying the non-inverted signal of the modulated signal by a unit period in the time axis direction, and a fourth timing obtained by delaying the inverted signal of the modulated signal by a unit period in the time axis direction. The difference between the two types of charge amounts obtained using the two types of timing signals and the signal is used as a first determination value, and the third timing signal and the fourth timing signal are specified delay times shorter than the unit period. A difference between two types of charge amounts obtained by using two types of timing signals, ie, the fifth timing signal and the sixth timing signal delayed by a certain amount, is used as a second determination value, and the threshold value is selected from two levels of magnitude When the second determination value is small with respect to the first determination value, a small threshold is selected, and when the second determination value is large with respect to the first determination value, a large threshold is selected. Spatial information detecting apparatus according to claim 3 wherein.

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