JP5215547B2 - Spatial information detection device - Google Patents

Description

  The present invention relates to a spatial information detection device for projecting light into a target space, receiving light from the target space, and detecting spatial information regarding the target space from a change in the received light with respect to the projected light. .

  Conventionally, in order to detect spatial information such as the presence of an object in the target space, the transmittance of the medium, the position of the object, the distance to the object, etc., light is projected into the target space and the reflected light is received, and the target A technique for detecting a change in intensity and a phase change between light projected into space and received light is known.

  There is a limit to the dynamic range of a light receiving element used in an active type sensor that projects and receives this type of light. Therefore, if the received light output is taken out from the light receiving element so that it does not saturate even when reflected light from a short distance or reflected light from an object with high reflectivity is received, it is from reflected light from a long distance or an object with low reflectivity. The light reception output with respect to the reflected light becomes minute, and it becomes difficult to detect spatial information at a long distance or to detect spatial information on an object with low reflectivity. On the other hand, if the received light output is extracted so that spatial information at a long distance can be detected or spatial information can be easily obtained for an object with low reflectance, reflected light from a short distance or reflected light from an object with high reflectance The light detection element is likely to be saturated.

In order to solve this type of problem, the length of the light detection period in the light detection element is set in plural, and the detection period in which the received light output obtained in each detection period becomes the maximum within the allowable range is set. It is considered that the spatial information is obtained using the received light output during this detection period (see, for example, Patent Document 1). In other words, incident light to the photodetection element is received by changing the length of the detection period with one photodetection element multiple times, and using the maximum photodetection output without saturation among the photodetection outputs from the multiple light receptions. If the intensity of light is small, a light reception output with a long detection period is adopted, and if the intensity of incident light to the light detection element is large, a light reception output with a short detection period is adopted. By this operation, it is possible to obtain a light receiving output that is appropriate (that is, SNR is sufficiently high but not saturated) over a wide range of the intensity of incident light to the light detection element.
JP 2006-844300 A

  However, in the above-described technique, the same light detection element changes the length of the detection period and receives light a plurality of times, takes out the received light output for each received light, and stores the received light output for each received light to compare the magnitude of the received light output. It is necessary. Accordingly, there is a relatively large time difference in the light reception output for each detection period, and there arises a problem that correct spatial information cannot be detected when the state of the target space is constantly changing. In particular, the target space is imaged using an image sensor as a light detection element, and the light reception output of each pixel of the image sensor is compared with the light reception output at the same position with different detection periods. If the light reception outputs of pixels satisfying the above are combined, there arises a problem that spatial information obtained by light reception outputs at different times is included in one image.

  The present invention has been made in view of the above reasons, and its object is to obtain spatial information using an appropriate light receiving output over a wide range of the intensity of incident light by selecting from a plurality of light receiving outputs. An object of the present invention is to provide a spatial information detection device that can reduce the time difference between the light reception outputs.

The invention of claim 1 includes a light emitting source for projecting infrared target space, and a plurality of light detecting elements receiving output corresponding to each light receiving quantity receives light is obtained from the same spatial region of the target space , the optical path control element is disposed on the optical path from the object space to the light detection element distributes the incoming light from the target space to each of the light detecting element, the upper limit of the light receiving output of the light receiving output of each of the light detection element and a evaluation unit for detecting the spatial information about the object space using the saturation threshold is proper range defined by the dead threshold as the lower limit of the light-receiving output light receiving output of said light detecting element as the optical path control element, the comprises a prism incident light is incident, the light branching unit comprising an optical path from the partial transmission mirror that 2 branch is configured to include one less than the number of the light detection element, anti of the optical branching section Has a function of Ru was different from each other received light amount of each of the light detecting element by a predetermined distribution ratio set by the rate and transmittance distributing each said incident light to the light detection element, wherein the prism is arranged on one side An optical path is formed in which the reflected light reflected by the light branching unit is totally reflected on the other surface, which is an incident surface from the target space, and then incident on one of the light detection elements .

According to a second aspect of the present invention, in the first aspect of the present invention, the exposure times of the respective light control elements are substantially the same.

The inventions of claim 3, the light emitting source for projecting infrared target space and the plurality of light receiving output in accordance with the respective amount of light received by receiving light from the same spatial region of the target space is obtained photodetecting element An optical path control element that is arranged on an optical path from the target space to the light detection element and distributes incident light from the target space for each of the light detection elements, and a light reception output of light reception outputs for each of the light detection elements An evaluation unit that detects spatial information about the target space using a light reception output of the light detection element that is in an appropriate range determined by a saturation threshold as an upper limit and a deadness threshold as a lower limit of the light reception output, and the optical path control element comprises a state that reflects a state for transmitting light a selectable optical branching unit for switching the optical path into two systems one less than the number of the light detection element, said light in said optical branching part Inspection Wherein the distributing each of the light detection element incident light at a predetermined distribution ratio by the exposure time per element.

In the invention of claim 4, in the invention of claim 3, wherein the optical path control element, alternatively to be incident either before Symbol photodetector light from the target space, for each of the light detecting element 1 and wherein each other thereby continuously period for light to each of the light detection element in a period in which the incidence of light by times.
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the optical path control element can obtain an appropriate received light output when the intensity of incident light is large among the light detection elements. The light detecting element is characterized in that the distribution ratio of incident light is set smaller than that of the light detecting element that can obtain an appropriate received light output when the intensity of incident light is small.

According to a sixth aspect of the invention, in the invention according to any one of the first to fifth aspects, the selection condition in the evaluation unit is to select a maximum received light output within a range below a prescribed saturation threshold, serial photodetector is generated in the photosensitive portion by imaging the object space has a plurality of photosensitive unit generating an electric charge according to the amount of light received by receiving light from each of the target space charge is an image sensor that a light receiving output, the evaluation unit, the said selection criteria received light output of the light receiving output obtained by the light-sensitive portion associated with the same position of the target space in the light detection element and selecting for each position of the target space.

According to a seventh aspect of the present invention, in the first to fifth aspects of the present invention, the light emitting source irradiates the target space with light whose intensity is modulated with a modulation signal having a predetermined period, and the selection condition in the evaluation unit is defined as the method comprising the selecting the maximum of the light receiving output in the range below the saturation threshold, before Symbol light detecting element, a plurality of photosensitive generating a charge according to the amount of light received by receiving light from each of the target space is an image sensor that a light receiving output the generated in the photosensitive unit charges by imaging the object space has a section, the evaluation unit is associated in the light detection element at the same position of the target space said one of the light-receiving output obtained by the photosensitive unit, using the selected satisfying the received light output seek distance to the object, the distance image to the pixel value distance for each position of the target space associated with said photosensitive portion Generate a And wherein the Rukoto.

According to the configuration of the first aspect of the present invention, a plurality of light detection elements that receive light from the same space region of the target space are provided, and an optical path control element is provided on the optical path from the target space to each light detection element. Since the amount of light received by each light detection element is different, the intensity of incident light to the light path control element changes over a wide range by appropriately adjusting the light distribution ratio to each light detection element by the light path control element. also, either the amount of light received by the light detecting element likely to become the proper range, is possible to obtain the spatial information using an appropriate light output over a wide range of intensity as a result, the incident light It becomes possible. In addition, since the incident light to the optical path control element is distributed to a plurality of light detection elements, each light detection element is incident with light at the same time or slightly shifted in time. The time difference between the light receiving outputs of the detection elements is reduced.

This is, for example, an image sensor in which each photodetecting element includes a plurality of photosensitive portions, and the light reception output is compared for each photosensitive portion associated with the same position in the target space, and an appropriate light reception output is obtained for each position. Even in the case of selecting, it is possible to use the light receiving output obtained from each photosensitive portion without special consideration. In addition, since the maximum received light output is used for detecting spatial information in a range where saturation does not occur, the influence of shot noise of the light detection element can be reduced, and as a result, the detection accuracy of spatial information can be increased.
In addition, the optical path control element is provided with a light branching unit configured by a partial transmission mirror, and the light distribution ratio to each photodetecting element is set by the reflectance and transmittance of the light branching part. When viewed from each light detection element, it functions in the same way as a neutral density filter having a different light attenuation rate, and the sensitivity of each light detection element can be made different without performing special control. In addition, since light from the same region of the target space is simultaneously incident on each photodetecting element, it is possible to simultaneously obtain each light reception output without a time difference.

According to the configuration of the second aspect of the invention, since the exposure time of each light control element is substantially the same, it is possible to obtain a light reception output at the same time from each light detection element, and a plurality of light detection elements The spatial information at substantially the same time can be detected using any of the received light outputs.

According to the configuration of the invention of claim 3, the optical branching unit capable of selecting a light transmitting state and a reflecting state as the optical path control element is provided, and the exposure time of each photodetecting element is adjusted by the light branching unit. Thus, the light distribution ratio to each photodetecting element is adjusted, so that the optical path control element functions in the same manner as a shutter having a different exposure time when viewed from each photodetecting element, and makes the sensitivity of each photodetecting element different. be able to. In this configuration, light from the same region of the target space does not necessarily enter each photodetecting element at the same time. However, since the light reception output from the photodetecting element can be extracted simultaneously, one photodetecting element is used. Thus, the time difference between a plurality of light receiving outputs can be reduced as compared with the case where light receiving outputs having different exposure times are obtained.

According to the configuration of the invention of claim 4 , the exposure time of each photodetecting element can be individually controlled. In this configuration, each light detection element does not simultaneously receive light from the same region of the target space, and there is a time difference in the light reception output extracted from each light detection element, but exposure is performed using one light detection element. Compared with the case where light reception outputs having different times are obtained, the time difference between the plurality of light reception outputs can be reduced. In addition, since the period in which light is incident on each photodetecting element is continuous with each other in the period in which light is incident on each photodetecting element, the time difference between the light reception outputs of the respective photodetecting elements is small.
According to the configuration of the fifth aspect of the invention, since the distribution ratio of the light to each light detection element by the light path control element is made different, the sensitivity of each light detection element is adjusted by the light path control element. This is equivalent to the arrangement of photodetection elements with multiple levels of sensitivity. Therefore, even if the intensity of light incident on the optical path control element changes in a wide range, there is a high possibility that an appropriate received light output can be obtained with any of the light detection elements.

According to the configuration of the sixth aspect of the invention, spatial information is detected from information obtained by imaging the target space by using an image sensor as the light detection element, and each light detection element is associated with each position in the target space. Since the optimum light receiving output is selected according to the selection condition for the light receiving output obtained by the photosensitive section, a wide dynamic range can be secured with respect to the light intensity at any part in the image obtained by the image sensor.

According to the configuration of the seventh aspect of the invention, the intensity-modulated light is used and an image sensor is used as the light detection element to obtain a distance image related to the target space from information obtained by imaging the target space. Since the distance obtained using the maximum light receiving output that is not saturated among the light receiving outputs corresponding to each photosensitive part obtained from each photodetecting element is used as the pixel value, it can be used in a wide distance range from a short distance to a long distance. It is possible to measure the distance over the distance.

  In the embodiment described below, a distance to an object existing in the target space is obtained as spatial information. In addition, the spatial information detection device described below generates a distance image in which a distance for each position in the target space is associated with each pixel by capturing an image of the target space.

  Before describing the embodiment, first, the principle of measuring the distance will be briefly described. As shown in FIG. 5, the spatial information detection device includes a light emitting source 2 that projects light into a target space, and receives a light from the target space and obtains an output that reflects the amount of received light. Is provided. As the light emitting source 2, one having a single wavelength is used, and it is desirable to use invisible infrared rays rather than using visible light. The distance to the object Ob existing in the target space is the time from when light is projected from the light emission source 2 to the target space until the reflected light from the object Ob enters the light detection element 1 (referred to as “time of flight”). ) In order to obtain the time of flight, intensity-modulated light, which is modulated so that the intensity of the light projected into the target space changes periodically at a constant period, is projected from the light source 2 into the target space, and the light intensity modulation component A phase difference between light transmission and reception is obtained for, and this phase difference is converted into a flight time. That is, the unit of the phase difference ψ of light transmission / reception is [rad], the distance to the object Ob is L [m], the speed of light is c [m / s], and the angular frequency of the intensity modulated light is ω [rad / s]. For example, L = ψ · c / 2ω.

  The phase difference ψ can be calculated by using received light amounts detected at a plurality of timings synchronized with the waveform of a modulation signal that modulates the light projected from the light source 2 into the target space. Now, the received light amounts obtained in the four phase sections in which the phase of the modulation signal is 0 to 90 degrees, 90 to 180 degrees, 180 to 270 degrees, and 270 to 360 degrees are A0, A1, A2, and A3, respectively. That is, the received light amounts A0, A1, A2, and A3 in each phase section are values obtained by integrating the intensity of the light incident on the light detection element 1 during a period of 90 degrees synchronized with the modulation signal.

Now, while obtaining the received light amounts A0, A1, A2, and A3, the phase difference ψ does not change (that is, the distance to the object Ob does not change), and the reflectance of the object Ob does not change. To do. Further, it is assumed that the intensity of light emitted from the light emitting source 2 is modulated by a sine wave, and the intensity of light received by the light detection element 1 at time t is represented by A · sin (ωt + δ) + B. However, A is an amplitude, B is a direct current component (an average value of an ambient light component and a reflected light component), ω is an angular frequency (ω = 2πf; f is a modulation frequency) of intensity-modulated light, and δ is an initial phase. When these conditions are satisfied, the phase difference ψ can be expressed by the following equation, for example.
ψ = tan ⁻¹ (A2−A0) / (A1−A3)
The above equation changes the sign or the phase differs by 90 degrees depending on how to take the interval to be integrated (for example, the phase width of one section is 90 degrees in the above example, but may be 180 degrees). The phase difference ψ can be obtained by using the received light amounts A0, A1, A2, and A3 in the four phase sections.

  As the light emitting source 2, for example, a light emitting diode in which a large number of light emitting diodes are arranged on one plane or a combination of a semiconductor laser and a diverging lens is used. The modulation signal for driving the light emission source 2 is, for example, a 20 MHz sine wave and is output from the timing control unit 3. The intensity of light emitted from the light source 2 is modulated by this modulation signal. As the waveform of the modulation signal, a triangular wave, a sawtooth wave, or the like can be used in addition to a sine wave.

  The photodetection element 1 may be a single photoelectric conversion element such as a photodiode, but an image sensor having a plurality of photosensitive portions such as a CCD image sensor is used to obtain a distance image. However, the image sensor is not limited to a two-dimensional image sensor, and may be a one-dimensional image sensor. A light receiving optical system 5 is arranged on the light incident path to the photosensitive portion, and each position of the target space is associated with each photosensitive portion by the light receiving optical system 5. Here, the amount of received light is the product of the intensity of light incident on the photosensitive portion and the time that the light is incident on the photosensitive portion (that is, the integrated value of the light intensity at the incident time), and the range where the photosensitive portion is not saturated. Then, each photosensitive part generates electric charge according to the amount of received light. Further, the photosensitive portions 11 are arranged on the lattice points of the planar lattice, and are arranged in a matrix in which, for example, a plurality are arranged at equal intervals in the vertical direction (that is, the vertical direction) and the horizontal direction (that is, the horizontal direction). Is done.

  As described above, in order to obtain the distance to the object Ob, the received light amounts A0, A1, A2, and A3 of the four phase sections synchronized with the modulation signal are obtained, so that the desired received light amounts A0, A1, A2, and A3 are obtained. Control of the timing to obtain is necessary. In the case of an IT (interline transfer) type CCD image sensor, for example, this operation can be realized by controlling the movement of charges from the photosensitive section to the vertical transfer section and the timing of discarding charges by the overflow drain. Can do. Further, in the case of an FT (frame transfer) type CCD image sensor, for example, by using an overflow drain for discarding charges, the discard timing is controlled so as to discard charges other than the target phase section. Can be realized.

  However, since the intensity of the light incident on the photosensitive portion of the light detection element 1 after being projected from the light source 2 into the target space and reflected by the object Ob is small, the received light amounts A0, A1, A2, A3 of each section described above. Is accumulated within one period of the modulation period of the intensity-modulated light, a sufficient difference in the received light amounts A0, A1, A2, A3 cannot be obtained, and the distance measurement accuracy is lowered. Therefore, in practice, the timing control unit 3 so that the charge generated corresponding to each section is accumulated over a plurality of periods (for example, 10,000 periods) of the intensity-modulated light and then the accumulated charge is taken out from the light detection element 1. The light detection element 1 is controlled by the output of.

  The light reception output output from the light detection element 1 is given to the distance calculation unit 4 as an evaluation unit, and the distance calculation unit 4 corresponds to the charges corresponding to the received light amounts A0, A1, A2, and A3 in the above four phase sections. The received light output is received and applied to the above-described equation for obtaining the phase difference ψ, or is applied to a table corresponding to the equation to obtain the phase difference ψ, and further the distance from the phase difference ψ to the object Ob is obtained. Since the distance calculation unit 4 obtains distances in a plurality of directions of the target space, it can obtain three-dimensional information about the target space, and can generate a distance image in which distance values are associated with pixel values.

(Embodiment 1)
In the present embodiment, a plurality of (three in the illustrated example) photodetecting elements 1a, 1b, and 1c are used as shown in FIG. Each of the light detection elements 1a, 1b, and 1c is an image sensor having a plurality of photosensitive portions, and has the same configuration as the light detection element 1 described above. Each photodetecting element 1 has the same specifications. On the optical path from the target space to each of the light detection elements 1a, 1b, and 1c, an optical path control element 11 that distributes incident light from the target space to each of the light detection elements 1a, 1b, and 1c and enters it.

  The optical path control element 11 shown in FIG. 1 is configured by combining three prisms 11a, 11b, and 11c, and a partial transmission mirror is provided on the boundary surface of the portion where the prisms 11a, 11b, and 11c are joined. 12a and 12b are arranged. Although not shown, a light receiving optical system for associating each position in the target space with each photosensitive portion of the light detection elements 1a, 1b, and 1c is disposed between the target space and the optical path control element 11. . Here, the light detection elements 1a, 1b, and 1c are arranged so that the photosensitive portions at the same position correspond to the same position in the target space.

  The first prism 11a into which the light from the target space is directly incident has a triangular cross section, and the light reflected by the light branching portion 12a arranged on the boundary surface with the second prism 11b on the extension line of the incident light. The light is totally reflected on the incident surface, and is emitted from the emission surface, which is the remaining surface of the prism 11a, and is incident on the light detection element 1a.

  Both the second prism 11b and the third prism 11c have a quadrangular cross section, and are arranged on a straight line orthogonal to the incident surface of the first prism 11a. That is, the light incident on the first prism 11a is also introduced into the second prism 11b and the third prism 11c. The light incident on the second prism 11b through the light branching portion 12a is reflected by the light branching portion 12b disposed on the boundary surface with the third prism 11c, and the boundary surface with the first prism 11a and the third prism The light exits from an exit surface different from the boundary surface with the prism 11c and enters the light detection element 1b.

  Further, the light incident on the third prism 11c through the light branching portion 12b formed of a partial transmission mirror disposed on the boundary surface between the second prism 11b and the third prism 11c is transmitted to the third prism 11c by the second prism 11c. The light exits from the exit surface located on the opposite side of the boundary surface with 11b and enters the light detection element 1c.

As described above, the optical path control element 11 has two light branching portions 12a and 12b each composed of a partial transmission mirror that splits the optical path into two (that is, one fewer than the light detection elements 1a, 1b, and 1c ). Thus, the light incident on the optical path control element 11 can be branched into three and distributed to the three photodetectors 1a, 1b, and 1c. The reflectance and transmittance of each of the light branching portions 12a and 12b are set so that the distribution ratios for distributing the light incident on the optical path control element 11 to the respective light detection elements 1a, 1b, and 1c are different from each other. That is, the sensitivity with respect to the intensity of the incident light to the optical path control element 11 can be varied while using the light detection elements 1a, 1b, and 1c having the same specifications.

  In this way, the sensitivity of the light detection elements 1a, 1b, and 1c can be made different from each other, so that the light incident on the light path control element 11 when the amount of light received by each of the light detection elements 1a, 1b, and 1c falls within an appropriate range. The light intensity can be divided into three ranges (hereinafter referred to as intensity ranges). That is, as shown in FIG. 2, the received light output of the light detection elements 1a, 1b, and 1c is in a range from the minimum value that can be distinguished from noise to the saturated received light output, and the received light amount and the received light output are one-to-one. When the corresponding range is the appropriate range Rf, the intensity ranges Sa, Sb, and Sc in which the light reception outputs of the light detection elements 1a, 1b, and 1c become the appropriate range Rf can be made different from each other. Here, if each of the intensity ranges Sa, Sb, and Sc is set to be continuous, when the incident light to the optical path control element 11 has an intensity within the range Si that combines the intensity ranges Sa, Sb, and Sc, An output in the appropriate range Rf is obtained from the light detection elements 1a, 1b, and 1c.

  In other words, the light detection elements 1a, 1b, and 1c are respectively associated with the intensity ranges Sa, Sb, and Sc of the incident light to the optical path control element 11. Here, as the level of the intensity ranges Sa, Sb, Sc is higher, the light detection elements 1a, 1b, 1c associated with the intensity ranges Sa, Sb, Sc must be set to lower sensitivity. Is set to be smaller as the levels of the intensity ranges Sa, Sb, Sc associated with the light detection elements 1a, 1b, 1b are higher.

  In order to accurately obtain the distance in the distance calculation unit 4 as the evaluation unit, it is necessary to alternatively select the light detection elements 1a, 1b, and 1c whose received light output is within the appropriate range Rf. Therefore, the distance calculation unit 4 uses the output determination unit 4a that evaluates the light reception output of each of the light detection elements 1a, 1b, and 1c in accordance with a specified selection condition, and uses any of the detection results of the output determination unit 4a to detect light. A selector 4b for selecting the light reception output of the elements 1a, 1b, 1c is provided.

  The selection condition in the output determination unit 4a is to determine whether or not the light reception output of each of the light detection elements 1a, 1b, and 1c is within the proper range Rf, and further, the light detection elements 1a, 1b, and 1c that have the light reception output within the proper range Rf. Is present, the light detection elements 1a, 1b, and 1c having the maximum light reception output are selected. Whether or not it is within the appropriate range Rf is determined by setting a saturation threshold as an upper limit of the light reception output and a dead threshold as the lower limit of the light reception output, and comparing the light reception output with the saturation threshold Ts and the dead threshold Ti.

  The comparison of the received light output is performed for each photosensitive unit associated with the same position in the target space in each of the light detection elements 1a, 1b, and 1c. That is, the light reception output is compared with respect to information obtained from the same position in the target space, and an appropriate light reception output is selected by performing the above-described determination. Therefore, the light detection elements 1a, 1b, and 1c used for calculating the distance are determined for each position in the target space.

  Although it is desirable to set the dead threshold Ti, it is not always necessary. In addition, when the light reception output of the light detecting element 1c associated with the highest intensity range Sc exceeds the saturation threshold Ts, the distance cannot be normally calculated, so the distance is not calculated. Processing is performed when measurement is impossible. In this process, a notification that measurement is impossible or a determination based on the previous measurement value is performed. Similarly, when the insensitive threshold Ti is set, the distance measurement is impossible even when the light reception output of the light detecting element 1a associated with the lowest intensity range Sa is below the insensitive threshold Ti. Process the case.

  Compared with the case where each of the light detection elements 1a, 1b, and 1c is used alone by using the three light detection elements 1a, 1b, and 1c, the intensity range of the incident light to the optical path control element 11 can be obtained. And the distance can be obtained by using a light receiving output having a large SNR with respect to a wide range of intensity changes of light incident on the optical path control element 11. That is, the range of the distance that can be measured can be increased, and the corresponding range for the difference in reflectance of the object Ob existing in the target space is also widened. In the illustrated example, the intensity ranges Sa, Sb, and Sc are made different without overlapping, but it is desirable to partially overlap them. This is because a part of the intensity range Sa, Sb, Sc is overlapped to reduce the change in the light reception output when the photodetection elements 1a, 1b, 1c to be selected are switched, and as a result, the change in the SNR is reduced. Because it can.

  By the way, in the structure of this embodiment, since the optical path control element 11 is static and the reflectance and transmittance of the light branching portions 12a and 12b do not change, the light detection elements 1a, 1b and 1c have the same target space. Spatial information can be obtained simultaneously from the region. That is, there is no time difference in the spatial information obtained by the light detection elements 1a, 1b, 1c. In the present embodiment, the exposure times of the light detection elements 1a, 1b, and 1c are substantially the same, but light absorption occurs in each of the light branching portions 12a and 12b. Can't get. Therefore, means for adjusting the exposure time may be provided as necessary.

  As an example, it is assumed that each of the light branching portions 12a and 12b reflects 2/3 of incident light and transmits 1/3. In addition, the exposure time Pe of each of the light detection elements 1a, 1b, and 1c is 18 ms, and the read time Pr required for reading the received light output is 8 ms. In this setting, the sensitivity of each of the light detection elements 1a, 1b, and 1c is substantially set to 2/3, 2/9, and 1/9 when the sensitivity when the optical path control element 11 is not used is 1. It will be. Since the exposure time Pe is equal, the amount of received light is proportional to the ratio of sensitivity, and a charge corresponding to the amount of received light at the exposure time obtained by multiplying the actual exposure time Pe by the ratio of sensitivity is generated. In short, in the light detection elements 1a, 1b, and 1c, light reception outputs corresponding to exposure times of 18 ms × (2/3) = 12 ms, 18 ms × (2/9) = 4 ms, and 18 ms × (1/9) = 2 ms, respectively. Is obtained.

  If the exposure time Pe is changed to 12 ms, 4 ms, and 2 ms using one photodetecting element, a light-receiving output with the same exposure time Pe can be obtained, but one readout time Pr is 8 ms. Therefore, as shown in FIG. 3B, it takes 42 ms to obtain three types of light reception outputs. On the other hand, in the configuration of the present embodiment, three kinds of received light output amounts can be obtained in 26 ms as shown in FIG. 3A, and the present embodiment generates one distance image. The time required for this can be shortened, resulting in an increase in the amount of information obtained within a unit time. In addition, in the present embodiment, since there is no time difference between the three types of light reception outputs, the distance to the object Ob can be measured under the same conditions while using the light reception outputs of the three light detection elements 1a, 1b, and 1c. That is, the distance at the same time can be obtained even when the object Ob moves relatively.

As is clear from the relationship shown in FIG. 2, the upper limit values of the intensity ranges Sa, Sb, and Sc increase with a power relationship. That is, if the saturation threshold Ts and the dead threshold Ti are used and the upper limit value of the minimum intensity range Sa is Va, it can be expressed by the relationship of (Ts / Ti) ⁿ · Va. Instead of adjusting the sensitivity to correspond to the exposure time Pe, a relationship corresponding to an exposure time Pe of 8 ms, 4 ms, 2 ms, or an exposure time of 10 ms, 4.4 ms (= 2 × 5 ^0.5 ), 2 ms A relationship corresponding to Pe may be used.

(Embodiment 2)
In the first embodiment, the optical path control element 11 uses the light branching portions 12a and 12b made up of partial transmission mirrors that have a constant transmittance and reflectance and branch the optical path into two branches. However, in the present embodiment, The reflecting state can be selected, and the optical branching units 12a and 12b that switch the optical path to two systems are used. The arrangement of the light branching portions 12a and 12b is the same as that of the first embodiment shown in FIG.

  The light branching portions 12a and 12b used in the present embodiment are known as dimming mirrors (see Japanese Patent Application Laid-Open No. 60-247226), and reflect light by changing the voltage applied to the electric chromic material. The state to be transmitted and the state to be transmitted can be switched.

  In the present embodiment, the timing control unit 3 outputs a signal for selecting transmission and reflection of each of the optical branching units 12a and 12b (not shown). Therefore, it is possible to selectively introduce light into the light detection elements 1a, 1b, and 1c by selecting transmission and reflection of the light branching portions 12a and 12b. Specifically, if the light branching portion 12a is in a reflective state, light is introduced only into the light detection element 1a regardless of the state of the light branching portion 12b, and the light branching portion 12b is set in a transmission state. If the light is reflected, light is introduced only into the light detection element 1b. If both the light branching portions 12a and 12b are in the transmission state, light is introduced only into the light detection element 1c.

  In the first embodiment, the distribution ratio is adjusted with respect to the light intensity with respect to each of the light detection elements 1a, 1b, and 1c by adjusting the reflectance and transmittance in each of the light branching portions 12a and 12b. Since the light branching portions 12a and 12b only select reflection and transmission, and have only a function as a kind of shutter, the distribution ratio cannot be adjusted with respect to the light intensity. However, since the light branching portions 12a and 12b function as shutters, it is possible to adjust the light distribution ratio according to the exposure time.

  Therefore, as shown in FIG. 4, in addition to controlling the light branching portions 12a, 12b so that the exposure times of the light detection elements 1a, 1b, 1c are different, the exposure time Te of the light detection elements 1a, 1b, 1c. Is partially overlapped with the readout time Tr of the other light detection elements 1a, 1b, and 1c. In the illustrated example, as in the first embodiment, the light branching portions 12a and 12b are controlled so that the substantial exposure times Te of the light detection elements 1a, 1b, and 1c are 12 ms, 4 ms, and 2 ms. Since the readout time Tr is 8 ms and the total exposure time Te of the light detection elements 1b and 1c is 6 ms, in this relationship, the exposure time Te of the light detection elements 1b and 1c is equal to the read time Te of the light detection element 1a. finish. That is, the exposure of the photodetecting elements 1b and 1c is completed in 20 ms, which is the sum of the exposure time Te and the reading time Tr of the photodetecting element 1a. However, the time required to read out the light reception outputs of all the light detection elements 1a, 1b, and 1c is 26 ms.

  In the configuration of the present embodiment, since light at different times is incident on each of the light detection elements 1a, 1b, and 1c, there is a time difference in information included in the light reception output of the light detection elements 1a, 1b, and 1c. Compared with the case where the exposure time Te and the readout time Tr are alternately repeated using only the photodetecting elements, the time difference of the information contained in the light receiving outputs of the photodetecting elements 1a, 1b, 1c is small, and all the light The time required to obtain the light reception output from the detection elements 1a, 1b, 1c is also shortened. Further, in the configuration of the first embodiment, even in the light detection element 1a associated with the maximum sensitivity, the intensity of the incident light is attenuated with respect to the incident light to the optical path control element 11, so that the exposure time is equal to the attenuation. In this embodiment, since the intensity of the incident light to the light detection element 1a associated with the maximum sensitivity is substantially equal to the intensity of the incident light to the optical path control element 11, the exposure time No extension is required.

  Note that the number of the optical branching portions 12a and 12b is not limited to two, and may be one or three or more. When three or more are provided, the light branching section may be arranged so that it is further branched after being branched into two. In the configuration example described above, an example in which the optical branching portions 12a and 12b are arranged on the optical axis of the light detection element 1b is shown. However, the optical branching portion may be arranged at a position different from the optical axis. Good. Other configurations and operations are the same as those of the first embodiment.

It is a schematic block diagram which shows embodiment. FIG. 3 is an operation explanatory diagram of the first embodiment. It is operation | movement explanatory drawing same as the above. FIG. 9 is an operation explanatory diagram of the second embodiment. It is a block diagram explaining the principle of operation same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photodetection element 1a, 1b, 1c Photodetection element 2 Light emission source 3 Timing control part 4 Distance calculating part (evaluation part)
4a Output determination unit 4b Selector 5 Light receiving optical system 11 Optical path control element 11a, 11b, 11c Prism 12a, 12b Optical branching unit Ob Object

Claims (7)

A light emitting source for projecting infrared target space, and a plurality of light detecting elements receiving output corresponding to each light receiving quantity receives light is obtained from the same spatial region of the object space, the light from the target space an optical path control element is disposed on the optical path of the detecting element distributes the incoming light from the target space to each of the light detecting element, the saturation threshold and a light receiving output of the upper limit of the light receiving output of the light receiving output of each of the light detection element and a evaluation unit for detecting the spatial information about the object space by using the light receiving output of the light detection element is proper range defined by the dead threshold as the lower limit of the optical path control element, the incident light The optical branching unit includes an incident prism, and includes a light branching portion including a partial transmission mirror that branches the optical path in two, which is smaller than the number of the light detection elements. Ri has a function of Ru was different from each other received light amount of each of the light detecting element by at set predetermined distribution ratio to distribute respectively the incident light on the light detecting element, the light the prism is disposed on one surface An apparatus for detecting spatial information, comprising: forming an optical path for causing the reflected light reflected by the branching part to be totally reflected by the other surface, which is an incident surface from the target space, and then to be incident on one of the light detection elements. . 2. The apparatus for detecting spatial information according to claim 1, wherein the exposure time of each of the light control elements is substantially the same . A light source that emits infrared light into a target space; a plurality of light detection elements that receive light from the same spatial region of the target space and obtain a light reception output corresponding to the amount of received light; and the light from the target space An optical path control element that is arranged on the optical path to the detection element and distributes incident light from the target space for each of the photodetection elements, and a saturation threshold and a photodetection output as an upper limit of the photodetection output among the light reception outputs for each of the photodetection elements An evaluation unit that detects spatial information about the target space using a light reception output of the light detection element that is an appropriate range determined by a dead threshold as a lower limit of the insensitive threshold, and the optical path control element transmits light A light branching section that can select a state and a reflecting state and switches the optical path to two systems is provided by one less than the number of the light detection elements, and exposure is performed for each light detection element in the light branching section. Detector spatial information, characterized in that distributed to each of the light detection element incident light at a predetermined distribution ratio by. The optical path control element selectively makes light from the target space incident on any one of the light detection elements, and for each light detection element within a period in which light is incident once for each light detection element. 4. The spatial information detecting apparatus according to claim 3, wherein the periods during which light is incident are continuous with each other . The optical path control element can obtain a proper light receiving output when the intensity of incident light is large among the light detecting elements, and the light detecting element can obtain a proper light receiving output when the intensity of incident light is small. The spatial information detection device according to claim 1, wherein a distribution ratio of incident light is set smaller than that of the light detection element . The selection condition in the evaluation unit is to select the maximum light reception output within a range equal to or less than a predetermined saturation threshold, and the light detection element receives light from the target space and responds to the light reception amount. An image sensor having a plurality of photosensitive units for generating electric charges and taking the electric charges generated by the photosensitive unit by imaging the target space, and the evaluation unit is configured to detect the target in the light detection element. 6. The light receiving output satisfying the selection condition is selected for each position of the target space from among the light receiving outputs obtained by the photosensitive units associated with the same position in the space. The spatial information detecting device according to claim 1. The light emitting source irradiates the target space with light whose intensity is modulated with a modulation signal having a predetermined period, and the selection condition in the evaluation unit is to select a maximum light receiving output within a range equal to or less than a prescribed saturation threshold. , before Symbol photodetector is generated by the photosensitive unit by imaging the object space has a plurality of photosensitive unit generating an electric charge according to the amount of light received by receiving light from each of the target space and is an image sensor that a light receiving output charge, the evaluation unit, the light associated with the same position of the target space in the detection element and the one of the light-receiving output obtained by the photosensitive unit and the selection criteria received light output obtains the distance to the object using the distance of each position of the target space associated with the photosensitive unit claims 1 and generates a distance image and pixel values either claim 5 Or 1 Detection equipment of the spatial information of the placement.

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