JP2010008088A - Spatial information detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spatial information detection device capable of preventing light from a light emitting section from being buried in noise such as disturbance light, and preventing detection of spatial information from being difficult. <P>SOLUTION: A light detection section 8 detects the amount of light of the light emitting section 2 with an emitted-light-amount detection means 8a arranged at a position which is irradiated with direct light from the emitting section 2. A lighting controller 9 performs individual on-off control of switching elements SW inserted respectively between individual light emitting elements 2a and resistors RL forming the emitting section 2, according to the output of the detection section 8, and changes the number of emitting elements 2a which is turned on actually to emit light. When the amount of light of the emitting section 2 detected by the detection section 8 is smaller than a predetermined bottom value, the lighting controller 9 increases the number of switching elements SW to be turned on and increases the number of emitting elements 2a to be turned on. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a spatial information detection device that detects spatial information of a target space using light projected from a light emitting unit to the target space.

  Conventionally, as this type of spatial information detection device, a light emitting unit using an LED (light emitting diode) and a light receiving unit that receives reflected light from a target space are received, and light is received after the light is projected by the light emitting unit. There is known one that detects a distance to an object existing in a target space as spatial information based on the time until the light is received by the unit. Here, since the time from when the light is projected to when it is received is very short, the intensity-modulated light that is modulated so that the intensity changes at a constant period is used as the light that is projected into the target space. The time is obtained from the phase difference between the light output from the light and the light received by the light receiving unit (see, for example, Patent Document 1).

By the way, since the light quantity of a light emission part (LED) is dependent on the magnitude | size of the electric current which flows through a light emission part, in order to obtain the stable light quantity, it is possible to perform constant current control. However, in constant current control, it takes time for the current to stabilize, and the rise of the light emitting unit is delayed. Therefore, when high-speed driving of the light emitting unit is performed, it is necessary to perform constant voltage control in which a constant voltage VDD is applied to the series circuit of the light emitting unit 2 and the resistor RL as shown in FIG. 10 (see, for example, Patent Document 2). ). In the example of FIG. 10, the light emitting unit 2 is a series circuit of a plurality of light emitting elements (LED) 2a, and the light emitting unit 2 is controlled by controlling a driving transistor (FET) Tr inserted in series in the series circuit. Output intensity modulated light.
JP 2004-45304 A JP 2007-149874 A

  However, in the constant voltage control, the light amount of the light emitting unit 2 may change due to the temperature characteristics of the light emitting element (LED) 2a, aging deterioration, or the like. When the light amount of the light emitting unit 2 decreases, the light projected from the light emitting unit 2 is buried in noise such as disturbance light (environmental light), and it may be difficult to detect spatial information.

  The present invention has been made in view of the above-described reasons, and provides a spatial information detection device in which light from a light emitting unit is buried in noise such as ambient light and detection of spatial information does not become difficult. Objective.

  The invention according to claim 1 includes a light emitting unit that has a plurality of light emitting elements and projects light into a target space, and a light emission driving circuit that controls the magnitude of a current flowing through the light emitting element in a state where a constant voltage is applied to the light emitting part. A light receiving unit that receives light from the target space, an evaluation calculation unit that detects spatial information of the target space using the output of the light receiving unit, a light detection unit that detects at least the light amount of the light emitting unit, and a light detection unit And a lighting control unit that controls the number of light emitting elements to be lit so that the light amount of the light emitting unit is within a predetermined range based on the light amount detected in step (b).

  According to this configuration, the lighting control unit controls the number of light emitting elements to be lit based on the light amount detected by the light detection unit so that the light amount of the light emitting unit is within a predetermined range. Even if the light quantity of the light emitting unit decreases due to the influence of temperature characteristics, aging deterioration, etc., the light quantity of the light emitting unit can be maintained within a predetermined range by increasing the number of light emitting elements to be lit. Therefore, it can be avoided that the light emitted from the light emitting unit is buried in noise such as disturbance light and the spatial information is difficult to be detected by reducing the light amount of the light emitting unit.

  According to a second aspect of the present invention, in the first aspect of the invention, the light emission driving circuit emits intensity-modulated light whose intensity changes periodically from the light emitting section by periodically changing a current flowing through the light emitting element. And the evaluation calculation unit detects the spatial information of the target space using a phase relationship between the intensity modulated light from the light emitting unit and the light received by the light receiving unit.

  According to this configuration, the evaluation calculation unit detects the distance to the object existing in the target space as the spatial information based on the time taken from when the light is emitted by the light emitting unit to when it is received by the light receiving unit. Can do.

  According to a third aspect of the present invention, in the first aspect of the invention, the light emission driving circuit alternately repeats a lighting period for turning on the light emitting unit and a light extinguishing period for turning off the light emitting unit. The spatial information of the target space is detected using a difference between the received light amount during the lighting period and the received light amount during the extinguishing period.

  According to this configuration, the evaluation calculation unit detects, as spatial information, the reflectance of light at an object existing in the target space from the difference between the received light amount during the lighting period and the received light amount during the extinguishing period. Can do.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the light detection unit is also used as a light emission amount detection unit that detects a light amount of the light emission unit. Features.

  According to this configuration, since the light receiving portion is also used as the light emission amount detecting means, there is an advantage that the number of parts can be reduced as compared with the case where the light emission amount detecting means is provided separately from the light receiving portion. .

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the light detection unit includes disturbance light detection means for detecting the amount of disturbance light, and the predetermined range is disturbance light. The lower limit is determined based on the amount of light.

  According to this configuration, since the lower limit value of the predetermined range is determined based on the amount of disturbance light, the lighting control unit can adjust the light amount of the light emitting unit within a predetermined range corresponding to the amount of disturbance light. . Therefore, even in an environment in which the amount of disturbance light changes, it is possible to reliably avoid detection of spatial information because the light projected from the light emitting unit is buried in the disturbance light.

  The invention of claim 6 is characterized in that, in the invention of claim 5, the light detection unit also serves as the light receiving unit for the disturbance light detection means.

  According to this configuration, since the light receiving unit is also used as the disturbance light detection unit, there is an advantage that the number of parts can be reduced compared to the case where the disturbance light detection unit is provided separately from the light reception unit. .

  In the present invention, since the number of light emitting units to be lit is controlled by the lighting control unit so that the light amount of the light emitting unit is within a predetermined range, the light from the light emitting unit is buried in noise such as disturbance light and spatial information. There is an advantage that it is possible to avoid that it is difficult to detect.

(Embodiment 1)
As shown in FIG. 2, the spatial information detection apparatus 1 according to the present embodiment includes a light emitting unit 2 that projects light onto a target space, a light emission driving circuit 3 that drives the light emitting unit 2 at a constant voltage, and reflected light from the target space. The light receiving unit 4 that receives the light and the evaluation calculation unit 5 that detects the spatial information of the target space. The evaluation calculation unit 5 calculates the distance to the object 6 existing in the target space based on the time (hereinafter referred to as a round trip time) taken from when the light is emitted by the light emitting unit 2 to when it is received by the light receiving unit 4. In this embodiment, a distance image is generated with a pixel value as a distance value to the object 6 existing in the target space. Further, in FIG. 2, a control unit 7 that determines the drive timing of the light emission drive circuit 3 and determines the light reception timing at the light receiving unit 4 is provided. The control unit 7 also instructs the evaluation calculation unit 5 to calculate timing.

  As shown in FIG. 1, the light emitting unit 2 includes a plurality of light emitting elements 2 a made up of LEDs (light emitting diodes), and is configured to irradiate light from each light emitting element 2 a toward a target space. . Here, each light emitting element 2a forms a series circuit together with a current limiting resistor RL and a driving transistor Tr, and a constant voltage VDD is applied to each of the series circuits.

  The light receiving unit 4 is composed of a CCD (Charge Coupled Device) imaging device in which a plurality of photosensitive elements (not shown) are two-dimensionally arranged on a semiconductor substrate (not shown), and the target space is passed through an imaging lens (not shown). Receives light from. In addition, it is good also as a structure which uses infrared LED which outputs infrared rays as the light emitting element 2a, and injects the light from object space into the light-receiving part 4 through an infrared permeation | transmission filter. In this configuration, it is possible to suppress the light in the visible light region from entering the light receiving unit 4 and to easily distinguish the light from the light emitting unit 4 from the disturbance light in the visible light region.

  The light emission driving circuit 3 controls the driving transistor Tr in the series circuit of the light emitting element 2a to which a constant voltage is applied as described above, the resistor RL, and the driving transistor Tr, thereby outputting the output of each light emitting element 2a. Control light intensity periodically. That is, since the round-trip time described above is very short, in this embodiment, the intensity-modulated light that is modulated so that the intensity periodically changes at a constant period is used as the light projected to the target space, and output from the light emitting unit 2. The round trip time is obtained from the phase difference between the received light and the light received by the light receiving unit 4. Therefore, the light emission driving circuit 3 drives the driving transistor Tr at the predetermined period, thereby periodically changing the current flowing through the light emitting element 2a to realize the intensity-modulated light.

  Here, as shown in FIG. 3A, when the light intensity (projection intensity) output from the light emitting unit 2 is modulated by a sine wave having a predetermined modulation frequency (for example, 10 MHz), the light projection intensity and the light receiving unit 4 The phase difference φ between the received light intensity (received light intensity) can be regarded as the phase difference between the modulation signal for driving the light emitting unit 2 and the light incident on the light receiving unit 4 (each photosensitive element thereof). Therefore, it is considered that the light reception intensity of incident light to the light receiving unit 4 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 4 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 received light amounts in the respective sections of 0 to π / 2, π / 2 to π, π to 3π / 2, and 3π / 2 to 2π of the phase of the intensity modulated light from the light emitting unit 2 are respectively A0, A1, A2 , A3 (corresponding to the area of each region indicated by the hatched portion in FIG. 3B), and the phase difference φ does not change during the determination of the received light amounts A0, A1, A2, A3 (that is, the distance to the object 6). If the reflectance of the object 6 does not change, the phase difference φ [rad] is expressed as φ = tan ⁻¹ {(A0−A2) / (A1−A3)}. Can do. In the example shown in FIG. 3, each phase section is set to a phase width of π / 2 [rad], but the phase width can be set as appropriate.

  By using the phase difference φ [rad] thus obtained and the modulation frequency f [Hz] of the intensity-modulated light, the round trip time Δt [s] can be expressed as Δt = φ / 2πf [s]. Then, by using the round trip time Δt [s] and the speed of light c [m / s], the distance value L from the spatial information detecting device 1 to the object 6 is expressed as L = c · Δt / 2 [m]. Can do.

  By the way, in addition to the structure mentioned above, the spatial information detection apparatus 1 of this embodiment is based on the light detection part 8 which detects at least the light quantity of the light emission part 2, and the detected light quantity in the light detection part 8 as shown in FIG. And a lighting control unit 9 for controlling the number of light emitting elements 2a to be lit.

  The light detection unit 8 is disposed at a position where direct light from the light emitting unit 2 is irradiated, and includes a photoelectric conversion element such as a photodiode that converts output light of the light emitting unit 2 into an electric signal as the light emission amount detecting means 8a. The light quantity of the light emission part 2 is comprised so that detection is hardly received by the influence of disturbance light. The light quantity here is an integrated value of the light intensity per unit time and corresponds to the average value of the light intensity.

  The lighting controller 9 is configured to individually turn on / off the switching elements SW inserted between the light emitting elements 2a and the resistors RL in accordance with the output of the light detector 8. That is, according to the number of switching elements SW that are turned on, the number of light emitting elements 2a that actually emit light (hereinafter referred to as the number of lighting) can be changed with the number of light emitting elements 2a constituting the light emitting unit 2 as an upper limit. When the light intensity of the light emitting unit 2 detected by the light detecting unit 8 is less than a certain reference value (hereinafter referred to as a lower limit value), the lighting control unit 9 increases the number of switching elements SW that are turned on to emit light. The number of lighting of the element 2a is increased. Further, when the light intensity of the light emitting unit 2 exceeds a certain value (hereinafter referred to as the upper limit value), the lighting control unit 9 reduces the number of switching elements SW to be turned on and turns on the light emitting element 2a. Decrease the number.

  Accordingly, the light amount of the light emitting unit 2 falls within a predetermined range between the lower limit value and the upper limit value. Even if the light amount of the light emitting unit 2 decreases for some reason and falls below the lower limit value, the lighting control unit 9 By increasing the number of lighting of the light emitting element 2a, it is possible to suppress a decrease in the light amount of the light emitting unit 2. In the present embodiment, the lower limit value and the upper limit value are set in advance in consideration of the dynamic range of the light receiving unit 4 and are stored in a register (not shown) in the lighting control unit 9.

  In addition, since the lower limit value that is a criterion for increasing the number of lighting and the upper limit value that is a criterion for decreasing the number of lighting is larger, the upper limit value is set larger (lower limit value <upper limit value). Even if the light quantity of the light emitting unit 2 detected by the light detecting unit 8 is increased by increasing the number of lighting of the light emitting elements 2a in the lighting control unit 9, the lighting control unit 9 decreases the number of lightings at that time. By doing so, the light quantity of the light emitting unit 2 does not fall below the lower limit value again.

  According to the spatial information detecting device 1 having the above-described configuration, the light quantity of the light emitting unit 2 can be maintained within a predetermined range. Therefore, the temperature characteristics and aging deterioration of each light emitting element (LED) 2a constituting the light emitting unit 2 are achieved. Even if the light quantity of the light emitting unit 2 changes due to the influence of the above, the change of the light quantity can be suppressed to such an extent that the detection of the spatial information is not affected. As a result, the amount of light from the light emitting unit 2 is reduced as in the conventional case, and light from the light emitting unit 2 is not buried in noise such as disturbance light (environmental light), so that it is difficult to detect spatial information. There is an advantage that detection can be performed reliably.

  By the way, in the said embodiment, although the space information detection apparatus 1 which acquires the distance (distance image) to the object 6 which exists in object space as space information was illustrated, it is not restricted to this example, For example, the object 6 in object space The present invention can also be used in the spatial information detection device 1 that detects spatial information such as presence or absence and the light reflectance of the object 6. In order to obtain the presence / absence of the object 6 and the light reflectance of the object 6, as shown in FIG. 4A, a lighting period T <b> 1 for turning on the light emitting unit 2 and a light-off period T <b> 2 for turning off the light are set. The difference between the light amount and the received light amount in the extinguishing period T2 is obtained. At this time, the intensity of the output light of the light emitting unit 2 is modulated by a rectangular wave.

  The light receiving unit 4 receives the signal light projected from the light emitting unit 2 during the lighting period T1 and reflected by the object 6 and the environmental light existing in the target space, and only the environmental light enters during the extinguishing period T2. . Therefore, from the difference (C0−C2) between the received light amount C0 in the lighting period T1 and the received light amount C2 in the extinguishing period T2, the influence of ambient light is removed and the degree of reflection (reflectance) of the object 6 is evaluated. can do.

(Embodiment 2)
The spatial information detection device 1 according to the present embodiment is different from the spatial information detection device 1 according to the first embodiment in that the light detection unit 8 detects the light amount of the light emitting unit 2 based on the current value flowing through the light emitting element 2a. That is, the light emission amount detecting means 8a is configured not to directly detect the light output of the light emitting unit 2, but to estimate the light amount of the light emitting unit 2 from the current value flowing through the light emitting element 2a constituting the light emitting unit 2. Yes.

  As a specific configuration, as shown in FIG. 5, a detection resistor RS is inserted between a plurality of drive transistors Tr connected in series with each light emitting element 2a and circuit ground, and the detection resistor A current value flowing through the light emitting element 2a is calculated from a potential difference between both ends of the RS. Here, the potential difference between both ends of the detection resistor RS is extracted using the differential amplifier OP1, and the output of the differential amplifier OP1 is averaged by the low-pass filter 10, which corresponds to the light amount of the light emitting unit 2. The average value of the current is obtained. The current value (average value) obtained in this way is input to the comparator CP1 constituting the lighting control unit 9 and compared with the lower limit value.

  In addition to the comparator CP1, the lighting control unit 9 includes a decoder 11 connected to the output of the comparator CP1, and a D / A converter 12 that converts the output of the decoder 11 into an analog signal. Each switching element SW is controlled to be turned on / off by an output signal (analog signal) of the converter 12. Therefore, when the comparator CP1 determines that the current value (average value) of the light emitting unit 2 is lower than the lower limit value, the number of switching elements SW to be turned on is the number corresponding to the difference between the current value and the lower limit value. The number of lighting of the light emitting element 2a increases.

  According to the configuration of the present embodiment, since the light amount of the light emitting unit 2 is not directly detected, light (disturbance light) other than the output light of the light emitting unit 2 is incident on the light detecting unit 8 to detect the light detecting unit 8. In this case, there is no change in the detected light amount. As a result, there is an advantage that the light amount of the light emitting unit 2 can be detected without being affected by disturbance light (environmental light).

  As another example, since it is conceivable to estimate the light amount of the light emitting unit 2 from the temperature characteristics of the light emitting element (LED) 2a, a temperature sensor for measuring the temperature of the light emitting element 2a is added, and based on the measured temperature. It is good also as a structure which estimates the light quantity of the light emission part 2. FIG.

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

(Embodiment 3)
The spatial information detection apparatus 1 of the present embodiment is different from the spatial information detection apparatus 1 of the first embodiment in that the light receiving unit 4 is also used as the light emission amount detection means 8a of the light detection unit 8.

  In the present embodiment, as shown in FIG. 6, the output of the light receiving unit 4 ′ composed of a CCD image sensor is digitally output not only by the evaluation calculation unit 5 (not shown in FIG. 6) but also by the A / D converter 13. After being converted to a signal, it is also sent to the lighting control unit 9. The lighting control unit 9 compares the output of the light receiving unit 4 ′ with the lower limit value in the difference circuit 14, and performs on / off control of each switching element SW by the decoder 15 that receives the output of the difference circuit 14. Therefore, when the difference circuit 14 determines that the light amount of the light emitting unit 2 is below the lower limit value, the number of switching elements SW to be turned on increases by the number corresponding to the difference between the light amount of the light emitting unit 2 and the lower limit value. The number of lighting of the element 2a increases.

  According to this configuration, it is not necessary to use a photoelectric conversion element as the light emission amount detecting means 8a separately from the light receiving unit 4 ′, and an amplifier (differential amplifier) is also provided as compared with the case of detecting the current of the light emitting element 2a. Since it becomes unnecessary, the number of components of the spatial information detecting device 1 can be reduced.

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

(Embodiment 4)
The spatial information detection apparatus 1 of this embodiment is different from that of Embodiment 1 in that disturbance light detection means 8b for detecting the amount of disturbance light is added to the light detection unit 8 as shown in FIG.

  The amount of disturbance light detected by the disturbance light detection means is used to determine the lower limit value, and the lower limit value determined in this way is compared with the light amount of the light emitting unit detected by the light emission amount detection means in the lighting control unit. The That is, since the lower limit value varies according to the level of disturbance light (noise level), it is necessary to avoid that the output light of the light emitting unit is buried in noise such as disturbance light and it becomes difficult to detect spatial information. It becomes possible to set the light quantity of the light emitting unit as a lower limit value.

  Specifically, as shown in FIG. 8, the ambient light detection means 8b made of a photodiode, the low pass filter 16 that averages the output of the ambient light detection means 8b, and the output of the low pass filter 16 are converted into digital values. The A / D converter 17 is provided, and the output (digital value) of the A / D converter 17 is output to the lighting control unit 9. In the example of FIG. 8, a CCD imaging device is used as the light emission amount detection means 8 a, and the output of the light emission amount detection means 8 a is input to the lighting control unit 9 through the A / D converter 13. As in the third embodiment, a light receiving unit composed of a CCD image sensor may also be used as the light emission amount detecting means 8a.

  Here, the lighting control unit 9 includes an adder 18 that adds a predetermined reference value to the output of the A / D converter 17 on the disturbance light detection means 8b side and outputs the result as a lower limit value. The light amount is compared with the output (lower limit value) of the adder 18 by the difference circuit 14, and each switching element SW is turned on / off by the decoder 15 that receives the output of the difference circuit 14. Thus, when the difference circuit 14 determines that the light amount of the light emitting unit 2 is below the lower limit value, the number of switching elements SW to be turned on increases by the number corresponding to the difference between the light amount of the light emitting unit 2 and the lower limit value, The number of lighting of the light emitting element 2a increases. Note that the reference value added to the output of the A / D converter 17 by the adder 18 is a value for determining the relationship between the amount of disturbance light and the amount of light of the light emitting unit 2, for example, A / D conversion. Is set to a value that increases the output of the device 17 by 1 bit.

  According to this configuration, since the lower limit value is dynamically determined according to the amount of disturbance light, even when the spatial information detection device 1 is used in an environment where disturbance light is likely to fluctuate, the lower limit value is optimal. By taking the value, there is an advantage that it is possible to surely avoid that the output light of the light emitting unit 2 is buried in noise such as disturbance light and difficult to detect.

  As another specific example of the present embodiment, as shown in FIG. 9, it is also conceivable to use the light receiving unit 4 ′ formed of a CCD image pickup device as both the light emission amount detecting means 8a and the disturbance light detecting means 8b. . In the configuration of FIG. 9, direct light from the light emitting unit 2, reflected light projected from the light emitting unit 2 and reflected by the object 6 in the target space, and disturbance light are incident on the light receiving unit 4 ′. The output of the light receiving unit 4 ′ is sent not only to the evaluation calculation unit 5 (not shown in FIG. 9) but also to the lighting control unit 9 after being converted into a digital signal by the A / D converter 13.

  Here, the lighting control unit 9 gives the output of the A / D converter 13 obtained during the lighting of the light emitting unit 2 to the difference circuit 14 as the output of the light emitting amount detecting means 8a in the light emission amount acquiring unit 9a. The disturbance light acquisition unit 9b is configured to give the output of the A / D converter 13 obtained while the light emitting unit 2 is turned off to the adder 18 as the output of the disturbance light detection means 8b.

  According to this configuration, the CCD image pickup device (light receiving unit 4 ′) and the A / D converter 13 are shared by the light emission amount detection means 8a and the disturbance light detection means 8b, so that the number of components of the spatial information detection device 1 is increased. There is an advantage that can be reduced.

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

It is a schematic circuit diagram which shows the structure of Embodiment 1 of this invention. It is a schematic block diagram same as the above. It is a wave form diagram which shows operation | movement same as the above. It is a time chart which shows operation | movement same as the above. It is a schematic circuit diagram which shows the structure of Embodiment 2 of this invention. It is a schematic circuit diagram which shows the structure of Embodiment 3 of this invention. It is a schematic circuit diagram which shows the structure of Embodiment 4 of this invention. It is a schematic circuit diagram which shows the specific example same as the above. It is a schematic circuit diagram which shows the other structural example same as the above. It is a schematic circuit diagram which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spatial information detection apparatus 2 Light emission part 2a Light emission element 3 Light emission drive circuit 4 Light reception part 5 Evaluation calculating part 8 Light detection part 8a Light emission amount detection means 8b Disturbance light detection means 9 Lighting control part RL Resistance SW Switching element

Claims (6)

  A light emitting unit that has a plurality of light emitting elements and projects light into the target space, a light emission driving circuit that controls the magnitude of a current flowing through the light emitting element in a state where a constant voltage is applied to the light emitting unit, and light from the target space A light receiving unit that receives light, an evaluation calculation unit that detects spatial information of the target space using the output of the light receiving unit, a light detection unit that detects at least the light amount of the light emitting unit, and a light amount detected by the light detection unit And a lighting control unit that controls the number of light emitting elements to be lit so that the light quantity of the light emitting unit is within a predetermined range.   The light emission driving circuit emits intensity-modulated light whose intensity periodically changes from the light emitting unit by periodically changing a current flowing through the light emitting element, and the evaluation calculation unit has an intensity from the light emitting unit. The spatial information detection apparatus according to claim 1, wherein the spatial information of the target space is detected using a phase relationship between modulated light and light received by the light receiving unit.   The light emission drive circuit alternately repeats a lighting period during which the light emitting unit is turned on and a light extinguishing period during which the light emitting unit is turned off, and the evaluation calculation unit calculates a difference between a light receiving amount during the lighting period and a light receiving amount during the light extinguishing period. The spatial information detection apparatus according to claim 1, wherein the spatial information of the target space is detected using a computer.   4. The spatial information detection according to claim 1, wherein the light detection unit also serves as the light reception unit for a light emission amount detection unit that detects a light amount of the light emission unit. 5. apparatus.   The said light detection part has a disturbance light detection means which detects the light quantity of disturbance light, and the said lower limit is determined for the said predetermined range based on the light quantity of disturbance light. Item 5. The spatial information detection device according to any one of items 4 to 6. 6. The spatial information detection device according to claim 5, wherein the light detection unit also serves as the light reception unit for the disturbance light detection unit.

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