JP2010025906A - Distance image sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distance image sensor achieving a suitable detecting distance range for a wide variety of applications. <P>SOLUTION: A light adjusting part 7 controls a light quantity which is received at a light receiving part 3, by adjusting the light quantity which is projecting into an object space from a light projecting part 2. A manual set part 8 is mounted in the distance image sensor 1, the light quantity which is adjusted in the light adjusting part 7 is set according to the operation of the manual set part 8. Here, when the detecting distance range is to be shifted into a near distance side, the light quantity from the light projecting part 2 is to be decreased so as to avoid a saturation of the light receiving part 3, and when the detecting distance range is to be shifted into a remote distance range, the light quantity from the light projecting part 2 is to be increased so as to avoid lack of sensitivity of the light receiving part 3, by doing these procedures, the detecting distance range of the distance image sensor 1 can be varied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a distance image sensor that generates a distance image using a distance value to the object as a pixel value using reflection of light from the object existing in the object space.

  Conventionally, as this type of distance image sensor, based on the time difference (hereinafter referred to as flight time) from when light is projected toward the target space until the light is reflected by the target object in the target space and returned. It is known to obtain three-dimensional information (distance image) using a TOF (Time Of Flight) method for calculating the distance to the object (for example, see Patent Document 1).

  For example, as shown in FIG. 19, the distance image sensor 1 includes a light projecting unit 2 including a light emitting element such as an LED (light emitting diode), and a light receiving unit 3 including an imaging element such as a CCD (Charge Coupled Device). A control unit 4 that controls the drive timing of the light projecting unit 2 and the light receiving unit 3, and a signal processing unit 5 that determines a distance value to an object existing in the target space from the flight time and generates the distance image. I have. Here, if the time required for the light to reciprocate in the space between the distance image sensor 1 and the object is Δt and the speed of light is c, the distance L between the distance image sensor 1 and the object is , L = c · Δt / 2. The detection result (distance image) is output from the detection result output unit 6 to the outside.

  Thus, the distance image sensor 1 using the TOF method observes an object with two cameras and performs distance measurement according to the principle of triangulation, or when the object is irradiated with slit-like light. Compared with the case of adopting the light cutting method that measures the distance by capturing the object shape based on the principle of triangulation by observing the change of reflected light corresponding to the shape of the object There is an advantage that downsizing is easy.

By the way, in the distance image sensor 1 using the TOF method, even if the amount of light projected from the light projecting unit 2 is constant, the amount of light received by the light receiving unit 3 depends on the distance from the distance image sensor 1 to the object. Change (the amount of received light increases as the distance to the object decreases). Here, the light receiving unit 3 saturates the image sensor if the received light amount is too large, and conversely, if the received light amount is too small, the light cannot be detected due to insufficient sensitivity. Hereinafter, the detection distance range) is greatly affected by the performance of the light receiving unit (imaging device) 3 and is limited to a specific range (a range in which saturation or insufficient sensitivity does not occur).
JP 2006-153773 A

  However, depending on the application using the output of the distance image sensor 1, the distance to the target object to be detected may be different, so that there is a problem that a wide variety of applications cannot be handled within a limited detection distance range. Although it is conceivable to increase the amount of received light when the image sensor is saturated, for example, by increasing the accumulated charge capacity of the image sensor, the detection distance range that can be expanded by this method is limited. Cannot handle various applications.

  The present invention has been made in view of the above reasons, and an object thereof is to provide a distance image sensor capable of realizing an appropriate detection distance range for various applications.

  The invention according to claim 1 is a distance image sensor that generates a distance image having a pixel value as a distance value to an object existing in the target space by imaging the target space, and projects light into the target space. A light projecting unit, a light receiving unit each having a plurality of photosensitive elements corresponding to each pixel of the distance image, each receiving light from the target space by each photosensitive element, and controlling the drive timing of the light projecting unit and the light receiving unit The distance between the control unit and the light projecting unit after projecting light is converted into a distance value for each pixel after the light is reflected by the object in the target space and received by the light receiving unit. A signal processing unit that generates an image, and a light amount adjusting unit that adjusts the amount of light projected from the light projecting unit and received by the light receiving unit are provided.

  According to this configuration, since the light amount adjusting unit that adjusts the amount of light emitted from the light projecting unit and received by the light receiving unit is provided, the light amount is adjusted so that saturation or insufficient sensitivity does not occur in the light receiving unit. By doing so, the detectable distance range can be changed. That is, when shifting the detection distance range to the short distance side, the light amount may be reduced so as to avoid saturation of the light receiving unit, and when the detection distance range is shifted to the long distance side, What is necessary is just to increase the said light quantity so that the lack of sensitivity of a light-receiving part may be avoided. As a result, it is possible to easily realize an appropriate detection distance range for various applications.

  According to a second aspect of the present invention, in the first aspect of the invention, the light amount adjusting unit adjusts a light amount of light projected from the light projecting unit to the target space.

  According to this configuration, the amount of light received by the light receiving unit is adjusted by adjusting the amount of light projected from the light projecting unit. It is possible to change the ratio (SN ratio) between the signal component projected from the light projecting unit and the noise component such as disturbance light. Therefore, even when the detection distance range is shifted to the far distance side, there is an advantage that the detection distance range can be changed while securing the distance measurement performance by improving the SN ratio by increasing the light amount.

  According to a third aspect of the present invention, in the second aspect of the invention, the light projecting unit includes a plurality of light emitting elements, and the light amount adjusting unit adjusts the light amount by switching the number of light emitting elements to be lit. Features.

  According to this configuration, it is possible to adjust the amount of light emitted from the light projecting unit with a relatively simple configuration that only switches the number of light emitting elements to be lit.

  According to a fourth aspect of the present invention, in the second aspect of the invention, the light amount adjusting unit adjusts the light amount by changing a resistance value of a resistance element that limits a current supplied to the light projecting unit. Features.

  According to this configuration, the amount of light emitted from the light projecting unit can be adjusted with a relatively simple configuration that only changes the resistance value of the resistance element.

  According to a fifth aspect of the present invention, in the second aspect of the invention, the lighting section in which the light projecting section projects light and the light-out period in which the light is stopped are periodically repeated, and the light quantity adjusting section is turned on. The amount of light is adjusted by adjusting the ratio between the period and the extinguishing period.

  According to this configuration, the light amount adjusting unit adjusts the light amount by adjusting the ratio between the lighting period and the extinguishing period, and thus, without adding a component to the conventional configuration without the light amount adjusting unit. The function of the light amount adjusting unit can be added by simply changing the control content, and the increase in the number of parts can be suppressed.

  According to a sixth aspect of the present invention, in the second aspect of the present invention, the lighting section in which the light projecting section projects light and the extinguishing period in which the projection is stopped are periodically repeated, and the light quantity adjusting section is turned on. In the period, the current is intermittently supplied to the light projecting unit, and the light amount is adjusted by adjusting the duty ratio of the current.

  According to this configuration, since the light amount adjustment unit adjusts the light amount by adjusting the duty ratio of the current, the control content can be changed without adding any components to the conventional configuration without the light amount adjustment unit. It is possible to add the function of the light quantity adjustment unit simply by doing so, and to suppress the increase in the number of parts.

  A seventh aspect of the invention is characterized in that, in the first aspect of the invention, the light amount adjusting unit adjusts the amount of light incident on the light receiving unit from the target space.

  According to this configuration, since the amount of light received by the light receiving unit is adjusted by adjusting the amount of light incident on the light receiving unit, the light received by the light receiving unit even if the amount of received light is adjusted. The ratio (SN ratio) between the signal component projected from the light projecting unit and the noise component such as disturbance light does not change. Therefore, even when the detection distance range is shifted to the short distance side, the SN ratio does not decrease due to the decrease in the light amount, and the detection distance range can be changed while ensuring the distance measurement performance. is there.

  The invention of claim 8 is the invention of claim 7, wherein the light amount adjusting unit adjusts the light amount by changing a diaphragm of a lens provided between the light receiving unit and the target space. And

  According to this configuration, the amount of light incident on the light receiving unit can be adjusted with a relatively simple configuration in which the lens aperture is changed.

  A ninth aspect of the invention is characterized in that, in the seventh aspect of the invention, the light amount adjusting unit adjusts the light amount by changing an exposure time of the light receiving unit.

  According to this configuration, since the light amount adjusting unit adjusts the light amount by changing the exposure time of the light receiving unit, the control content can be changed without adding any components to the conventional configuration without the light amount adjusting unit. It is possible to add the function of the light amount adjusting unit simply by changing, and to suppress an increase in the number of parts.

  In a tenth aspect of the present invention, in the first aspect of the present invention, the light amount adjusting unit is configured to emit light of both light projected from the light projecting unit to the target space and light incident from the target space to the light receiving unit. It is characterized by adjusting.

  According to this configuration, the adjustment range of the received light amount at the light receiving unit is larger than the configuration in which the light amount of only one of the light projected from the light projecting unit and the light incident on the light receiving unit is adjusted. It is possible to widen the adjustment range of the detection distance range.

  The invention of claim 11 is characterized in that in any one of the inventions of claims 1 to 10, a manual setting unit operated to set a light amount adjusted by the light amount adjusting unit is provided.

  According to this configuration, the amount of light adjusted by the light amount adjustment unit is set by the operation of the manual setting unit, so the detection distance range is adjusted by arbitrarily adjusting the amount of light received by the light receiving unit with a relatively simple configuration. can do.

  According to a twelfth aspect of the present invention, there is provided an automatic setting unit according to any one of the first to tenth aspects, wherein the light amount adjusted by the light amount adjusting unit is automatically set according to the output of the signal processing unit. It is characterized by that.

  According to this configuration, the amount of light adjusted by the light amount adjusting unit is automatically set according to the output of the signal processing unit, so that the user can save the trouble of adjusting the amount of light and automatically set the optimum amount of light. Can be flexibly adapted to various applications.

  According to a thirteenth aspect of the present invention, in the twelfth aspect of the present invention, the automatic setting unit is derived from the distance value obtained by the signal processing unit so that the light amount is decreased as the distance to the object is closer. The amount of light is set according to the amount.

  According to this configuration, an appropriate light amount is set according to the feature amount derived from the distance value. Therefore, when the detection distance range is shifted to the short distance side, the light amount decreases and the light receiving unit is saturated. In addition, when the detection distance range is shifted to the far distance side, the light quantity is increased, and insufficient sensitivity of the light receiving unit can be avoided.

  According to a fourteenth aspect of the invention, in the thirteenth aspect of the invention, the automatic setting unit sets the amount of light according to an average value of the distance values for at least some of the pixels of the distance image.

  According to this configuration, the amount of light is set according to the average value of the distance values for at least some of the pixels of the distance image, so the distance to the target object that is frequently detected during operation, for example, is changed. Even in an application, an appropriate detection distance range can be set every time the distance to an object to be detected is changed based on a simple process of obtaining an average value of distance values.

  According to a fifteenth aspect of the invention, in the thirteenth aspect of the invention, the automatic setting unit sets the amount of light according to the minimum value of the distance value for at least some of the pixels of the distance image.

  According to this configuration, the amount of light is set according to the minimum value of the distance value for at least some of the pixels of the distance image, so the distance to the target object that is frequently detected during operation, for example, is changed. Even if it is an application, it can set to the suitable detection distance range whenever the distance to the target object used as a detection target is changed based on the simple process of calculating | requiring the minimum value of a distance value.

  According to a sixteenth aspect of the invention, in the twelfth aspect of the invention, the signal processing unit obtains a received light amount at the light receiving unit for each pixel of the distance image as a gray value, and the automatic setting unit has a large gray value. The amount of light is set according to the feature amount derived from the gray value obtained by the signal processing unit so as to reduce the amount of light.

  According to this configuration, an appropriate light amount is set according to the feature amount derived from the gray value, and therefore, when the detection distance range is shifted to the short distance side, the light amount is decreased and the light receiving unit is saturated. In addition, when the detection distance range is shifted to the far distance side, the light quantity is increased, and insufficient sensitivity of the light receiving unit can be avoided. In addition, even when the distance value fluctuates greatly, there is an advantage that the light amount can be set using a stable gray value.

  According to a seventeenth aspect of the present invention, in the sixteenth aspect, the automatic setting unit sets the light amount according to an average value of the gray values for at least some of the pixels of the distance image.

  According to this configuration, the amount of light is set according to the average value of the gray values for at least some of the pixels of the distance image, so the distance to the target object that is frequently detected during operation, for example, is changed. Even in an application, an appropriate detection distance range can be set every time the distance to an object to be detected is changed based on a simple process of obtaining the minimum value of the gray value.

  According to an eighteenth aspect of the invention, in the invention of the sixteenth aspect, the automatic setting unit sets the light amount according to the maximum value of the gray value for at least some of the pixels of the distance image.

  According to this configuration, since the light amount is set according to the maximum value of the gray value for at least some of the pixels of the distance image, for example, the distance to the target object that is frequently detected during operation is changed. Even in an application, an appropriate detection distance range can be set every time the distance to an object to be detected is changed based on a simple process of obtaining the maximum value of the gray value.

  According to a nineteenth aspect of the present invention, in the twelfth aspect of the invention, the signal processing unit obtains a received light amount at the light receiving unit for each pixel of the distance image as a gray value, and the automatic setting unit determines whether or not to the object. The light amount is set according to the feature amount derived from both the distance value and the gray value obtained by the signal processing unit so that the light amount is decreased as the distance becomes shorter and the light amount is decreased as the gray value becomes higher. It is characterized by.

  According to this configuration, since the light amount is set according to the feature amount derived from both the distance value and the gray value, the light amount is determined according to the feature amount derived from only one of the distance value and the gray value. As compared with the case where is set, more appropriate light quantity can be set.

  A twentieth aspect of the invention is characterized in that, in any of the twelfth to nineteenth aspects of the invention, the automatic setting unit sets a light amount using a value obtained by averaging the feature amount over a predetermined time. To do.

  According to this configuration, the amount of light is set using a value obtained by averaging feature quantities over a certain period of time, so that when the detection target is an object that moves rapidly, or the distance value or the gradation value varies due to noise or the like. Even when is large, there is an advantage that an appropriate light amount can be set stably.

  Since the present invention includes a light amount adjustment unit that adjusts the amount of light projected from the light projecting unit and received by the light receiving unit, the light amount is adjusted so that saturation or insufficient sensitivity does not occur in the light receiving unit. The detectable distance range can be changed, and there is an advantage that an appropriate detection distance range can be realized for various applications.

(Embodiment 1)
As shown in FIG. 1, the distance image sensor 1 according to the present embodiment includes a light projecting unit 2 including a light emitting element L (see FIG. 2) including an LED (light emitting diode), and an imaging element including a CCD (Charge Coupled Device). A distance image having a pixel value as a distance value to a target object (not shown) in the target space, and a control unit 4 that controls drive timing of the light projecting unit 2 and the light receiving unit 3. A signal processing unit 5 to be generated, a detection result output unit 6 that outputs a distance image to the outside using a general-purpose interface such as a USB, a light amount adjustment unit 7 and a manual setting unit 8 to be described later are provided.

  The basic configuration and basic operation of the distance image sensor 1 are the same as those of the conventional configuration shown in FIG. That is, in the signal processing unit 5, a time difference from the time when light is projected from the light projecting unit 2 toward the target space until the light is reflected by the object in the target space and received by the light receiving unit 3 (hereinafter referred to as “light receiving unit 3”) 3D information (distance image) is acquired using a TOF (Time Of Flight) method for calculating the distance to the object based on the flight time).

  More specifically, in the light receiving unit 3, a plurality of photosensitive elements (not shown) each corresponding to each pixel of the distance image are two-dimensionally arranged (for example, arranged in a matrix) on a semiconductor substrate (not shown). An image sensor (CCD) is provided, and light from the target space is received by each photosensitive element through a lens 9 (see FIG. 11). Here, the lens 9 has a one-to-one correspondence between the line-of-sight direction when viewing the target space from the light receiving unit 3 and each photosensitive element, and thereby, the range in which light is incident on each photosensitive element through the lens 9 is as follows. The center of the lens 9 can be regarded as a conical field of view having a small apex angle set for each photosensitive element. Therefore, if the reflected light projected from the light projecting unit 2 and reflected by the object existing in the target space enters the photosensitive element, the optical axis of the lens 9 is determined based on the position of the photosensitive element that has received the reflected light. The direction in which the object exists can be specified.

  Thus, the signal processing unit 5 can generate a distance image by obtaining the distance to the target existing in the target space for each pixel. Further, the signal processing unit 5 has a function of obtaining the received light amount at the light receiving unit 3 for each pixel as a gray value and generating a gray image having the gray value as the pixel value. The grayscale image generated in this way is also output to the outside from the detection result output unit 6 in the same manner as the distance image.

  Note that an infrared LED that outputs infrared light may be used as the light emitting element L, and light from the target space may be incident on the light receiving unit 3 through an infrared transmission filter. In this configuration, the light in the visible light region is prevented from entering the light receiving unit 3, and the light from the light projecting unit 2 can be easily distinguished from the disturbance light in the visible light region.

  Here, since the above-described flight time is very short, in the present embodiment, the light projecting unit 2 uses the intensity-modulated light that is modulated so that the intensity periodically changes at a constant period. The time of flight is obtained from the phase difference between the light output from the light and the light received by the light receiving unit 3. Therefore, the light projecting unit 2 does not continuously output the output light with a constant intensity, but periodically repeats a lighting period in which the light emitting element L is turned on and a light-out period in which the light emitting element L is turned off (see FIG. 4). Switching on / off of the light emitting element L is controlled by a control port output of a microcomputer 10 to be described later.

  That is, when the light intensity (light projection intensity) output from the light projecting unit 2 is modulated by a rectangular wave having a predetermined modulation frequency (for example, 10 MHz), the light projection intensity and the light intensity received by the light receiving unit 3 (light reception intensity) are modulated. Can be regarded as a phase difference between a modulation signal for driving the light projecting unit 2 and light incident on the light receiving unit 3 (each photosensitive element thereof). Therefore, it is considered that the light reception intensity of the incident light to the light receiving unit 3 is obtained for a plurality of different phases of the modulation signal, and the phase difference φ between the incident light and the modulation signal is obtained from the relationship between the obtained phases and the light reception intensity. . Specifically, the light receiving unit 3 detects the amount of received light for each phase section having a predetermined phase width (time width), and uses this received light amount for calculating the phase difference φ.

For example, the phase of the intensity modulated light from the light projecting unit 2 is 0 to 180 degrees (0 to π), 90 to 270 degrees (π / 2 to 3π / 2), 180 to 360 degrees (π to 2π), 270 to 270 degrees. The received light amount in each section of 90 degrees (3π / 2 to π / 2) is A0, A1, A2, A3 (see FIG. 8), and the phase difference φ is obtained while the received light amounts A0, A1, A2, A3 are obtained. Is not changed (that is, the distance to the object is not changed) and the reflectance of the object is not changed, the phase difference φ is φ = tan ⁻¹ {(A3−A1) / (A0-A2)}. The phase width of each phase section is not limited to 180 degrees and can be set as appropriate.

  Using the phase difference φ [deg] thus obtained and the modulation frequency f [Hz] of the intensity-modulated light, the flight time Δt [s] can be expressed as Δt = φ / (360 · f) [s]. it can. By using the flight time Δt [s] and the speed of light c [m / s], the distance value L from the distance image sensor 1 to the object can be expressed as L = c · Δt / 2 [m]. it can.

  By the way, the distance image sensor 1 of the present embodiment includes the light amount adjusting unit 7 so that the light amount of the light projected from the light projecting unit 2 and reflected by the object in the target space and received by the light receiving unit 3 is obtained. As adjustable. In the present embodiment, as described below, a light amount adjusting unit 7 configured to adjust the light amount of light projected from the light projecting unit 2 to the target space is employed.

  That is, the light projecting unit 2 includes first and second light emitting element groups in which a plurality (four in this case) of light emitting elements L made of LEDs are connected in series, as shown in FIG. It is comprised so that the light from a group may be irradiated toward object space. Here, each of the first and second light emitting element groups forms a series circuit together with current limiting resistors R1 and R2 and driving transistors TR1 and TR2, and a constant voltage Vcc is applied to each series circuit. The

  The light amount adjusting unit 7 has a function of controlling on / off of the driving transistors TR1 and TR2. Here, the first and second control ports are control terminals (bases) of the driving transistors TR1 and TR2, respectively. It consists of the microcomputer 10 connected to. Therefore, the light amount adjusting unit 7 outputs both H-level voltage signals from both control ports and turns on both drive transistors TR1 and TR2, thereby turning on both the first and second light emitting element groups. In this state, the intensity of light projected from the light projecting unit 2 is increased (hereinafter referred to as a high output mode), and the output of one control port is set to L level, and one driving transistor TR1 (or TR2) is turned on. By turning off, it is possible to switch between a state in which only one of the light emitting element groups is fully lit and the intensity of light projected from the light projecting unit 2 is kept low (hereinafter referred to as a low output mode). In short, the light quantity adjusting unit 7 switches the number of the light emitting elements L that are actually lit among the plurality of light emitting elements L constituting the light projecting unit 2 by on / off control of the driving transistors TR1 and TR2, and the light projecting unit 2 Adjust the amount of light emitted from.

  Further, the distance image sensor 1 according to the present embodiment includes a manual setting unit 8 including a dip switch, and the light amount adjusted by the light amount adjusting unit 7 described above is set according to the operation of the manual setting unit 8. That is, the user operates the manual setting unit 8 so as to select either the high output mode or the low output mode, thereby switching the output of the control port of the light amount adjusting unit 7 and projecting from the light projecting unit 2. The amount of light emitted can be adjusted.

  In the distance image sensor 1 of the present embodiment described above, the light amount adjusting unit 7 is provided, thereby adjusting the light amount projected from the light projecting unit 2 and consequently adjusting the light amount received by the light receiving unit 3. can do. Therefore, the distance that can be detected by the distance image sensor 1 is set by setting the amount of light projected from the light projecting unit 2 in the manual setting unit 8 so that the light receiving unit 3 does not saturate the image sensor or lack sensitivity. A range (hereinafter referred to as a detection distance range) can be changed. That is, when the detection distance range is shifted to the short distance side, the amount of light from the light projecting unit 2 is reduced so that saturation of the light receiving unit 3 is avoided (that is, only one of the first and second light emitting element groups is reduced). When the detection distance range is shifted to the far side, the amount of light from the light projecting unit 2 is increased so as to avoid insufficient sensitivity of the light receiving unit 3 (that is, the first and first light sources). The two light emitting element groups 2 may be turned on. As a result, when dealing with various applications having different distances to the object to be detected, it is possible to realize an appropriate detection distance range for each application.

  Here, the light received by the light receiving unit 3 includes not only a desired signal component irradiated from the light projecting unit 2 and reflected by an object, but also a noise component due to disturbance light such as sunlight or illumination light. However, since the distance image sensor 1 controls the intensity of light emitted from the light projecting unit 2, it is received by the light receiving unit 3 by increasing the amount of light emitted from the light projecting unit 2. It is possible to improve the ratio (SN ratio) of signal components in the light. That is, when the intensity of light emitted from the light projecting unit 2 is constant, the signal component received by the light receiving unit 3 decreases due to light diffusion or the like when the distance to the object to be detected increases, but the noise component Does not depend on the distance to the object, and as a result, the SN ratio decreases as the distance to the object to be detected increases. On the other hand, in this embodiment, since the SN ratio can be improved by increasing the amount of light emitted from the light projecting unit 2, the SN ratio is reduced even if the distance to the object to be detected is long. Can be suppressed. Therefore, even when the detection distance range is shifted to the far distance side, there is an advantage that sufficient distance measurement performance (SN ratio) can be ensured.

  Moreover, in this embodiment, in order to adjust the light quantity projected from the light projection part 2, the comparatively simple structure of switching the number of the light emitting elements L to light is employ | adopted, and also in order to set a light quantity Since the manual setting unit 8 including a dip switch is employed, the above-described invention can be realized with a comparatively simple configuration. In this configuration, it is necessary to set the detection distance range by operating the manual setting unit 8 in advance before projecting light from the light projecting unit 2 and actually measuring the distance. The distance image sensor 1 is particularly useful for an application or the like that does not need to change the distance to an object that is frequently detected during operation.

  In the above embodiment, the light amount adjusting unit 7 switches the light amount from the light projecting unit 2 in two steps (high output mode and low output mode), but a set of light emitting element groups that can be controlled by the control port. The number of light quantity switching steps may be increased by increasing the number. In this case, the number of modes that can be selected by the operation of the manual setting unit 8 is increased according to the number of light quantity switching steps.

(Embodiment 2)
In the distance image sensor 1 of the present embodiment, as shown in FIG. 3, the current limiting resistors connected in series with the first and second light emitting element groups are variable resistors (resistance elements) VR1 and VR2, respectively. The difference from the distance image sensor 1 of the first embodiment is that the variable resistors VR1 and VR2 are used as the light amount adjusting unit 7. In the present embodiment, the control terminals of both the driving transistors TR 1 and TR 2 are connected to one control port of the microcomputer 10.

  With this configuration, if the current flowing through the light emitting element L is reduced as shown in FIG. 4B by increasing the resistance values of the variable resistors VR1 and VR2 with the state shown in FIG. The intensity of light projected from the light unit 2 is reduced, and the amount of light is reduced. On the contrary, if the current flowing through the light emitting element L is increased by reducing the resistance values of the variable resistors VR1 and VR2, the intensity of the light projected from the light projecting unit 2 increases and the amount of light increases. FIG. 4 shows the supply current to the light projecting unit 2 with the horizontal axis as the time axis.

  In the configuration of the first embodiment, the light amount adjusting unit 7 discretely adjusts the light amount by changing the number of light emitting elements L to be lit. In the configuration of the present embodiment, the variable resistors VR1 and VR2 are provided. The light quantity can be continuously adjusted by continuously changing the resistance value. Therefore, it is possible to set a more appropriate detection distance range for each application with a relatively simple configuration in which the variable resistors VR1 and VR2 are employed.

  In the present embodiment, since the variable resistors VR1 and VR2 as the light amount adjusting unit 7 also function as the manual setting unit 8, it is not necessary to provide a dip switch or the like separately as in the first embodiment.

  Other configurations and functions are the same as those of the first embodiment.

(Embodiment 3)
The distance image sensor 1 of the present embodiment is that the control terminals of both driving transistors TR1 and TR2 are connected to one control port of the microcomputer 10 as the light amount adjusting unit 7 as shown in FIG. 1 and the distance image sensor 1. Here, the configuration itself shown in FIG. 5 is the same as the conventional configuration, and only the first and second light emitting element groups cannot be lit by the output of the control port of the microcomputer 10, so that the first embodiment Thus, the number of light emitting elements L to be lit cannot be switched.

  In the present embodiment, the light amount adjusting unit 7 adjusts the amount of light projected from the light projecting unit 2 by adjusting the ratio between the lighting period and the extinguishing period of the light projecting unit 2 as shown in FIG. . FIG. 6 shows the supply current to the light projecting unit 2 with the horizontal axis as the time axis.

  More specifically, during a period in which an H level voltage signal is output from the control port of the microcomputer 10, the driving transistors TR1 and TR2 are turned on to enter a lighting period, and an L level voltage signal is output from the control port. Since the driving transistors TR1 and TR2 are turned off during the period when the signal is output, the light quantity adjusting unit 7 changes the duty ratio of the rectangular wave voltage signal output from the control port. Thus, the ratio between the lighting period and the extinguishing period is adjusted.

  With this configuration, if the ratio of the lighting period is reduced as shown in FIG. 6B with reference to the state shown in FIG. 6A (lighting period: extinguishing period = 1: 1), the light projecting unit 2 projects light. The amount of light emitted is reduced. Conversely, if the ratio of the lighting period is increased, the amount of light projected from the light projecting unit 2 increases.

  In short, the configuration of the present embodiment can be achieved by making a software change (change of control content of the microcomputer 10) without adding hardware changes to the conventional configuration as shown in FIG. An appropriate detection distance range can be realized for each application. In addition, since the light quantity of the light projected from the light projecting unit 2 can be reduced as much as possible by reducing the ratio of the lighting period, this configuration is particularly suitable when the detection distance range is shifted to the short distance side. Useful.

  By the way, as another configuration example of the present embodiment, as shown in FIG. 7, the amount of light is adjusted by causing the current to flow intermittently through the light projecting unit 2 during the lighting period and adjusting the duty ratio of the intermittent current. Is also possible. FIG. 7 shows the current supplied to the light projecting unit 2 with the horizontal axis as the time axis. That is, in this configuration example, the ratio between the lighting period and the extinguishing period is not changed (lighting period: extinguishing period = 1: 1), and the microcomputer 10 is controlled with a period sufficiently shorter than the repeating period of the lighting period and the extinguishing period. The amount of light projected from the light projecting unit 2 is adjusted by changing the duty ratio of the rectangular wave voltage signal output from the general port. In this case, the signal processing unit 5 performs integration processing on the output of the light receiving unit 3.

  Specifically, if the duty ratio is reduced as shown in FIG. 7B with reference to the state where the duty ratio is 50% as shown in FIG. On the contrary, if the duty ratio is increased as shown in FIG. 7C, the amount of light projected from the light projecting unit 2 is increased.

  According to this configuration, the light emitting element L is blinked in a short period as if amplitude modulation was performed on a high frequency carrier wave with a low frequency signal, but the light emitting element L is not blinked by performing integration processing after light reception. It is possible to obtain a similar received light waveform. That is, the distortion of the waveform restored by the integration process is small, and there is an advantage that the degradation of the ranging performance can be suppressed.

By the way, in the configuration of the present embodiment, since the waveform of the intensity modulated light from the light projecting unit 2 changes, even if the phase difference φ between the incident light to the light receiving unit 3 and the modulated signal is constant, FIG. As shown, there may be variations in the phase difference φ determined by the equation of φ = tan ⁻¹ {(A3−A1) / (A0−A2)}. That is, for example, when the phase difference φ = 45 degrees, from the above calculation formula, when the lighting period: extinguishing period = 1: 1 as in FIG. 8A, the phase difference is the same as in the first embodiment. Whereas φ is obtained as “45 degrees”, the lighting period is shorter than the extinguishing period as shown in FIG. 8B (here, the lighting period is reduced to 1/8 wavelength compared with FIG. 8A). When the duty ratio of the intermittent current is 50% as shown in FIG. 8C, the phase difference φ is obtained as “0 degree”. . FIG. 8 shows the light projecting intensity and the light receiving intensity with the horizontal axis as the time axis.

  Therefore, in the present embodiment, the signal processing unit 5 uses the true value of the phase difference φ as a true value of the phase difference φ obtained by converting the phase difference φ (hereinafter referred to as a “calculated value”) obtained by the above calculation formula from the true value. The distance value shall be calculated. Here, a conversion formula or data table showing the correspondence between the calculated value of the phase difference φ and the true value is set in advance, and the conversion formula or the data table is used to convert the calculated value into the true value. The correspondence between the calculated value of the phase difference φ and the true value is as shown in the graph of FIG. In FIG. 9, the horizontal axis represents the true value, the vertical axis represents the calculated value, the one corresponding to FIG. 8A is represented by “A”, the one corresponding to FIG. 8B is represented by “B”, Items corresponding to 8 (c) are represented by “c”.

  Other configurations and functions are the same as those in the first embodiment.

(Embodiment 4)
The distance image sensor 1 of the present embodiment is different from the distance image sensor 1 of the first embodiment in that the light amount adjusting unit 7 is configured to adjust the amount of light incident on the light receiving unit 3 as shown in FIG. .

  More specifically, as shown in FIG. 11, a diaphragm unit 11 is provided in a lens 9 disposed between the light receiving unit 3 and the target space, and the amount of light incident on the light receiving unit 3 is reduced by operating the diaphragm unit 11. It can be adjusted. The diaphragm unit 11 is a device attached to the light receiving unit 3 side of the lens 9 to reduce the amount of light by blocking part of the light incident on the light receiving unit 3 from the lens 9, and the size of the opening provided in the center. The aperture value is adjusted by changing. Here, the diaphragm unit 11 functions as the light amount adjusting unit 7 and the manual setting unit 8.

  According to this configuration, with the state shown in FIG. 11A as a reference, the amount of light received by the light receiving unit 3 is reduced by reducing the amount of light incident on the light receiving unit 3 by the stop 11 as shown in FIG. Can be reduced and saturation of the image sensor can be prevented. On the other hand, if the aperture 11 is opened, the amount of light received by the light receiving unit 3 increases, and the lack of sensitivity of the image sensor can be resolved.

  In the configuration described above, the light amount adjusting unit 7 adjusts the amount of light incident on the light receiving unit 3 from the detection space. Therefore, even if the light amount is changed, the light component received by the light receiving unit 3 has a signal component and a noise component. Are increased or decreased at the same rate, and the SN ratio (ratio of signal component to noise component) can be kept constant. That is, when the light amount is reduced by the light amount adjusting unit 7 in order to avoid saturation of the image sensor, not only the signal component but also the noise component is reduced in the light received by the light receiving unit 3. Therefore, even when the detection distance range is shifted to the short distance side, there is an advantage that saturation of the image sensor can be avoided while ensuring sufficient distance measurement performance (SN ratio).

  Further, in the present embodiment, a relatively simple configuration in which the diaphragm portion 11 is provided in order to adjust the amount of light incident on the light receiving portion 3 is employed, so that the above invention can be realized with a relatively simple configuration. it can.

  Other configurations and functions are the same as those in the first embodiment.

(Embodiment 5)
The distance image sensor 1 of the present embodiment is that the light amount adjusting unit 7 adjusts the amount of light incident on the light receiving unit 3 by adjusting the length of the exposure time of the light receiving unit 3 as shown in FIG. 4 is different from the distance image sensor 1. Here, the exposure time of the light receiving unit 3 is configured to be controllable by the control unit 4. In FIG. 12, the horizontal axis is the time axis, (a) shows the control timing of the light projecting unit 2, and (b), (c) shows the control timing of the light receiving unit 3.

  That is, in the present embodiment, as shown in FIG. 12B, the light receiving unit 3 is driven over the lighting period of the light projecting unit 2, thereby increasing the amount of light received by the image sensor and eliminating the lack of sensitivity. As shown in FIG. 12 (c), by shortening the time (exposure time) for driving the light receiving unit 3 compared to the lighting period of the light projecting unit 2, the amount of light received by the image sensor is reduced and saturation of the image sensor is prevented. You can do it.

  In short, the configuration of the present embodiment is appropriate for each application by making a software change (a change in the control content of the microcomputer) without making a hardware change to the conventional configuration. A simple detection distance range can be realized.

  Other configurations and functions are the same as those in the fourth embodiment.

(Embodiment 6)
In the distance image sensor 1 of the present embodiment, the light amount adjusting unit 7 adjusts the light amount for both the light projected from the light projecting unit 2 to the target space and the light incident on the light receiving unit 3 from the target space. The point which is comprised differs from the distance image sensor 1 of said each embodiment.

  That is, in the present embodiment, the light amount adjusting unit 7 adjusts the light incident side adjusting unit 7a that adjusts the amount of light projected from the light projecting unit 2 and the light amount incident on the light receiving unit 3, as shown in FIG. And a light receiving side adjusting portion 7b. Here, the specific configuration of the light emitting side adjustment unit 7a is the same as that of the light amount adjustment unit 7 shown in any of the first to third embodiments, and the specific configuration of the light receiving side adjustment unit 7b is the fourth embodiment. Or it is set as the structure similar to the light quantity adjustment part 7 shown in Embodiment 5. FIG.

  According to this configuration, both the amount of light projected from the light projecting unit 2 and the amount of light incident on the light receiving unit 3 can be adjusted, so the amount of light projected from the light projecting unit 2 and the amount of light incident on the light receiving unit 3 Compared with the case where only one of the above is adjusted, the adjustment range of the amount of light received by the light receiving unit 3 is widened, and the detection range in the light receiving unit 3 that can prevent saturation of the image sensor and insufficient sensitivity is adjusted widely. There is an advantage that you can.

  Other configurations and functions are the same as those in the first embodiment.

(Embodiment 7)
The distance image sensor 1 of the present embodiment employs an automatic setting unit 12 that automatically sets the light amount adjusted by the light amount adjusting unit 7 instead of the manual setting unit 8 as shown in FIG. 6 is different from the distance image sensor 1 of FIG.

  The automatic setting unit 12 sets the light amount according to the output of the signal processing unit 5. In the present embodiment, the automatic setting unit 12 responds to the feature amount derived from the distance value to the target obtained by the signal processing unit 5. Set the amount of light.

  Hereinafter, operations of the signal processing unit 5 and the automatic setting unit 12 of the present embodiment will be described with reference to a flowchart shown in FIG.

  The signal processing unit 5 calculates the distance value to the object using the flight time as an input (S10, S11), and outputs the calculation result from the detection result output unit 6 (S12). The automatic setting unit 12 derives a feature amount based on the calculation result of the distance value in parallel with the process of step S12 (S13), and the distance to the target is calculated using the feature amount as a short distance and a long distance. (S14, S15). If it is determined that the distance tends to be short (S14: Yes), the light amount adjusted by the light amount adjusting unit 7 is set so that the detection distance range is shifted to the short distance side (S16), and conversely. If it is determined that the distance tends to be long (S15: Yes), the light amount adjusted by the light amount adjusting unit 7 is set so that the detection distance range is shifted to the long distance side (S17). In short, if the distance to the actually detected object is short, the light amount is decreased and the detection distance range is shifted to the near distance side, and if the distance to the object is far, the light amount is increased to increase the detection distance range to the long distance side. Therefore, the distance value of the object can be prevented from deviating from the detection distance range.

  Here, an average value of distance values (pixel values) for the entire frame (all pixels) or a part of pixels of the distance image is used as the feature amount derived from the distance value. In this case, it is determined that the distance to the object tends to be a long distance if the feature amount (average value) is equal to or greater than a predetermined threshold, and a short distance if the feature amount is less than the threshold. That is, since the light amount is set according to the average value of the distance values for at least some of the pixels in the distance image, for example, an application in which the distance to the target object that is frequently detected during operation is changed. However, based on a simple process of obtaining an average value of distance values, an appropriate detection distance range can be set every time the distance to the object is changed. In addition, for example, even if an abnormal value occurs in only one pixel of the distance image, there is an advantage that it is possible to avoid setting the light amount according to the abnormal value.

  According to the configuration described above, the amount of light adjusted by the light amount adjusting unit 7 is automatically set according to the feature value of the distance value obtained by the signal processing unit 5, so that the object to be detected by the user This saves you the trouble of adjusting the light intensity according to the distance. In addition, since the optimal amount of light according to the distance to the target is automatically set, for example, in applications that need to change the distance to the target that is frequently detected during operation, By adjusting the detection distance range each time the distance to the object is changed, it is possible to prevent the image sensor from being saturated or insufficiently sensitive in the light receiving unit 3.

  The feature amount derived from the distance value is not limited to the above-described average value, and is, for example, the minimum value (recent value) of the distance value for the entire frame (all pixels) or a part of the distance image. May be. In this case, if the feature amount (average value) is greater than or equal to a predetermined threshold value, it is determined that the distance tends to be long, and if the feature value (average value) is less than the threshold, it is determined to be close. In this example, since the feature amount can be derived only by performing a sorting process of distance values, even an application in which the distance to the target object that is frequently detected during operation is changed easily. Based on the sorting process, an appropriate detection distance range can be set every time the distance to the object is changed. Furthermore, the feature amount may be, for example, the maximum distance value (farthest value), the number of pixels where the distance value exceeds a certain threshold, the number of pixels whose distance value falls below the threshold, and the like.

  Other configurations and functions are the same as those in the sixth embodiment.

(Embodiment 8)
In the distance image sensor 1 of the present embodiment, the automatic setting unit 12 sets the light amount according to the feature amount derived from the gray value obtained by the signal processing unit 5 (that is, the received light amount at the light receiving unit 3 for each pixel). This is different from the distance image sensor 1 of the seventh embodiment.

  Hereinafter, operations of the signal processing unit 5 and the automatic setting unit 12 of the present embodiment will be described with reference to a flowchart shown in FIG.

  The signal processing unit 5 calculates the distance value to the object using the flight time as an input (S20, S21), and outputs the calculation result from the detection result output unit 6 (S22). In the automatic setting unit 12, in parallel with the processing of steps S20 to S22, the grayscale value (shading information) obtained from the light receiving unit 3 is input (S23), and a feature amount based on the grayscale value is derived ( S24) Using the feature amount, it is determined whether the distance to the object tends to be a short distance or a long distance (S25, S26). If it is determined that there is a tendency toward short distance (S25: Yes), the light amount adjusted by the light amount adjusting unit 7 is set so that the detection distance range is shifted to the short distance side (S27), and conversely. If it is determined that the distance tends to be long (S26: Yes), the light quantity adjusted by the light quantity adjusting unit 7 is set so that the detection distance range is shifted to the long distance side (S28). In short, if the amount of light received by the light receiving unit 3 tends to be saturated, it is determined that the distance to the object is short, the amount of light is decreased, the detection distance range is shifted to the near side, and conversely, If the received light amount tends to be insensitive, it is determined that the distance to the object is far, and the detection distance range is shifted to the far side by increasing the light amount, so the distance value of the object is the detection distance range. Can be prevented from coming off.

  Here, the average value of the gray values for the entire frame (all pixels) or a part of the gray image is used as the feature amount derived from the gray values. In this case, if the feature amount (average value) is equal to or greater than a predetermined threshold value, it is determined that there is a tendency to be saturated, and if it is less than the threshold value, it is determined that the sensitivity is insufficient. That is, since the light amount is set according to the average value of the gray value for at least some of the pixels of the gray image, for example, an application in which the distance to the target object that is frequently detected during operation is changed. However, based on a simple process of obtaining the average value of the gray values, it is possible to set an appropriate detection distance range each time the distance to the object is changed. Further, for example, even if an abnormal value occurs only in one pixel of a grayscale image, there is an advantage that it is possible to avoid setting the light amount according to the abnormal value.

  According to the configuration described above, the amount of light adjusted by the light amount adjustment unit 7 is automatically set according to the feature value of the gray value obtained by the signal processing unit 5, so that the object to be detected by the user This saves you the trouble of adjusting the light intensity according to the distance. In addition, since an optimum light amount corresponding to the amount of light received by the light receiving unit 3 is automatically set, for example, an application that needs to change the distance to an object to be detected frequently during operation. However, every time the distance to the object is changed, it is possible to avoid the saturation of the image sensor and the lack of sensitivity in the light receiving unit 3 by adjusting the detection distance range.

  In addition, the feature amount derived from the gray value is not limited to the above-described average value, and may be the maximum gray value of the entire frame (all pixels) or a part of the gray image, for example. In this case, if the feature amount (maximum value) is equal to or greater than a predetermined threshold value, it is determined that there is a tendency to be saturated, and if the feature amount (maximum value) is less than the threshold value, it is determined that the sensitivity is insufficient. In this example, since the feature amount can be derived only by performing grayscale value sorting processing, even an application that frequently changes the distance to the target object to be detected during operation can be easily applied. Based on the sorting process, an appropriate detection distance range can be set each time the distance to the object is changed. Furthermore, the feature amount may be, for example, a minimum gray value, the number of pixels where the gray value exceeds a certain threshold, or the number of pixels whose distance value falls below the threshold.

  As another example of the present embodiment, the automatic setting unit 12 is derived from both the distance value obtained by the signal processing unit 5 and the gray value (that is, the received light amount at the light receiving unit 3 for each pixel). It is good also as a structure which sets light quantity according to quantity. The operations of the signal processing unit 5 and the automatic setting unit 12 in this case will be described below with reference to the flowchart shown in FIG.

  The signal processing unit 5 calculates the distance value to the object using the flight time as an input (S30, S31), and outputs the calculation result from the detection result output unit 6 (S32). In the automatic setting unit 12, in parallel with the processing of steps S30 to S31, the gray value (light / dark information) obtained from the light receiving unit is input (S33), and the feature amount based on the gray value and the distance value. (S34), and using the feature amount, it is determined whether the distance to the object tends to be a short distance or a long distance (S35, S36). If it is determined that there is a tendency toward short distance (S35: Yes), the light amount adjusted by the light amount adjusting unit 7 is set so that the detection distance range is shifted to the short distance side (S37), and conversely. If it is determined that the distance tends to be long (S36: Yes), the light quantity adjusted by the light quantity adjusting unit 7 is set so that the detection distance range is shifted to the long distance side (S38). In short, if it is determined that the distance to the object is close, the amount of light is decreased and the detection distance range is shifted to the near side, and conversely, if it is determined that the distance to the object is far, the light amount Is increased to shift the detection distance range to the far side, so that the distance value of the object can be prevented from deviating from the detection distance range.

  According to this configuration, even when one of the distance value and the gray value is missing, the light amount is set according to the feature amount derived from the other, so either one of the distance value or the gray value is set. There is an advantage that an appropriate detection distance range can be set more reliably as compared with the case of using.

  Other configurations and functions are the same as those in the seventh embodiment.

(Embodiment 9)
The distance image sensor 1 according to the present embodiment is that the automatic setting unit 12 averages the feature amount derived from the distance value over a certain period of time and sets the light amount using the averaged value. 7 is different from the distance image sensor 1 of FIG.

  Hereinafter, operations of the signal processing unit 5 and the automatic setting unit 12 in the present embodiment will be described with reference to a flowchart shown in FIG.

  The signal processing unit 5 calculates the distance value to the object using the flight time as an input (S40, S41), and outputs the calculation result from the detection result output unit 6 (S42). The automatic setting unit 12 derives a feature amount based on the calculation result of the distance value in parallel with the process of step S42 (S43). Thereafter, the same processing (S44 to S47, S48 to S51) as in steps S40 to S43 is repeated a plurality of times (here, twice), and the automatic setting unit 12 determines the feature values derived in steps S43, S47, and S51, respectively. An average value is taken (S52), and the average value is used to determine whether the distance to the object tends to be a short distance or a long distance (S53, S54). Here, if it is determined that there is a tendency toward short distance (S53: Yes), the light amount adjusted by the light amount adjusting unit 7 is set so that the detection distance range shifts to the short distance side (S55). If it is determined that the distance tends to be long (S54: Yes), the light amount adjusted by the light amount adjusting unit 7 is set so that the detection distance range is shifted to the long distance side (S56). In short, if it is determined that the distance to the object is close, the amount of light is decreased and the detection distance range is shifted to the near side, and conversely, if it is determined that the distance to the object is far, the light amount Is increased to shift the detection distance range to the far side, so that the distance value of the object can be prevented from deviating from the detection distance range.

  According to this configuration, the amount of light is set using a value obtained by averaging feature amounts over a certain period of time, so that the distance value may change due to the influence of noise or the like when the object moves violently and the distance value fluctuates. Even if it fluctuates violently, it is possible to prevent the light amount setting value from fluctuating significantly, and as a result, it is possible to switch the detection distance range stably.

  In the present embodiment, in order to set the amount of light, an example in which the feature amount derived from the distance value is used in the same manner as in the seventh embodiment has been described. However, as described in the eighth embodiment, A feature amount derived from both the distance value and the distance value may be used.

  Other configurations and functions are the same as those of the seventh embodiment.

It is a schematic block diagram which shows Embodiment 1 of this invention. It is a schematic circuit diagram which shows the principal part same as the above. It is a schematic circuit diagram which shows the principal part of Embodiment 2 of this invention. It is a time chart which shows operation | movement same as the above. It is a schematic circuit diagram which shows the principal part of Embodiment 3 of this invention. It is a time chart which shows operation | movement same as the above. It is a time chart which shows the other operation example same as the above. It is a time chart which shows the operation example same as the above. It is a graph which shows the correspondence of the true value of a phase difference same as the above, and a calculation value. It is a schematic block diagram which shows Embodiment 4 of this invention. It is a schematic plan view which shows the principal part same as the above. It is a time chart which shows operation | movement of Embodiment 5 of this invention. It is a schematic block diagram which shows Embodiment 6 of this invention. It is a schematic block diagram which shows Embodiment 7 of this invention. It is a flowchart which shows operation | movement same as the above. It is a flowchart which shows the operation | movement of Embodiment 8 of this invention. It is a flowchart which shows the other operation example same as the above. It is a flowchart which shows operation | movement of Embodiment 9 of this invention. It is a schematic block diagram which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Distance image sensor 2 Light projection part 3 Light reception part 4 Control part 5 Signal processing part 7 Light quantity adjustment part 8 Manual setting part 9 Lens 11 Aperture part 12 Automatic setting part L Light emitting element VR1, VR2 Variable resistance (resistance element)

Claims (20)

  A distance image sensor that generates a distance image with a pixel value as a distance value to an object existing in the target space by imaging the target space, and a light projecting unit that projects light into the target space, A light receiving unit that has a plurality of photosensitive elements corresponding to each pixel of the distance image and receives light from the target space by each photosensitive element, a light projecting unit, a control unit that controls drive timing of the light receiving unit, and light projection A signal processing unit that generates a distance image by converting a time difference from when the unit projects light to when the light is reflected by an object in the target space and received by the light receiving unit into a distance value for each pixel And a light amount adjusting unit that adjusts the amount of light projected from the light projecting unit and received by the light receiving unit.   The distance image sensor according to claim 1, wherein the light amount adjusting unit adjusts a light amount of light projected from the light projecting unit to the target space.   3. The distance image sensor according to claim 2, wherein the light projecting unit includes a plurality of light emitting elements, and the light amount adjusting unit adjusts the light amount by switching the number of light emitting elements to be lit.   The distance image sensor according to claim 2, wherein the light amount adjusting unit adjusts the light amount by changing a resistance value of a resistance element that limits a current supplied to the light projecting unit.   The light projecting unit periodically repeats a lighting period for projecting light and a light extinguishing period for stopping light projection, and the light amount adjusting unit adjusts the ratio of the lighting period to the light extinguishing period to adjust the light amount. The distance image sensor according to claim 2, wherein the distance image sensor is adjusted.   The light projecting unit periodically repeats a lighting period for projecting light and a light extinguishing period for stopping the light projecting, and the light amount adjusting unit intermittently supplies current to the light projecting unit within the lighting period. The distance image sensor according to claim 2, wherein the light quantity is adjusted by adjusting the duty ratio of the current.   The distance image sensor according to claim 1, wherein the light amount adjusting unit adjusts a light amount of light incident on the light receiving unit from the target space.   The distance image sensor according to claim 7, wherein the light amount adjusting unit adjusts the light amount by changing a diaphragm of a lens provided between the light receiving unit and the target space.   The distance image sensor according to claim 7, wherein the light amount adjusting unit adjusts the light amount by changing an exposure time of the light receiving unit.   2. The distance according to claim 1, wherein the light amount adjusting unit adjusts both the light amount projected from the light projecting unit to the target space and the light incident from the target space to the light receiving unit. Image sensor.   11. The distance image sensor according to claim 1, further comprising a manual setting unit operated to set a light amount adjusted by the light amount adjusting unit.   11. The distance according to claim 1, further comprising an automatic setting unit that automatically sets a light amount adjusted by the light amount adjusting unit according to an output of the signal processing unit. Image sensor.   The automatic setting unit sets the light amount according to a feature amount derived from the distance value obtained by the signal processing unit so as to decrease the light amount as the distance to the object is closer. Item 13. A distance image sensor according to item 12.   The distance image sensor according to claim 13, wherein the automatic setting unit sets a light amount according to an average value of the distance values for at least some of the pixels of the distance image.   The distance image sensor according to claim 13, wherein the automatic setting unit sets a light amount according to a minimum value of the distance value for at least some of the pixels of the distance image.   The signal processing unit obtains the received light amount at the light receiving unit for each pixel of the distance image as a gray value, and the automatic setting unit obtains the gray level determined by the signal processing unit so as to decrease the light amount as the gray value increases. The distance image sensor according to claim 12, wherein the light amount is set according to a feature amount derived from the value.   The distance image sensor according to claim 16, wherein the automatic setting unit sets a light amount according to an average value of the grayscale values for at least some of the pixels of the distance image.   The distance image sensor according to claim 16, wherein the automatic setting unit sets a light amount according to a maximum value of the gray value for at least some of the pixels of the distance image.   The signal processing unit obtains the received light amount at the light receiving unit for each pixel of the distance image as a gray value, and the automatic setting unit decreases the light amount as the distance to the object is closer, and the gray value is 13. The distance image sensor according to claim 12, wherein the light amount is set according to a feature amount derived from both the distance value and the gray value obtained by the signal processing unit so that the light amount is decreased as the value increases. The distance image sensor according to any one of claims 12 to 19, wherein the automatic setting unit sets a light amount using a value obtained by averaging the feature amount over a predetermined time.

Images