JP4442539B2 - Spatial information detection device - Google Patents

Description

  The present invention projects the signal light whose intensity is modulated at a predetermined frequency to the target space, and detects the amplitude of the signal light contained in the light received from the target space, thereby obtaining the reflectance of the object existing in the target space. The present invention relates to a spatial information detection apparatus that obtains spatial information including a distance to an object.

  2. Description of the Related Art Conventionally, there is known an active type spatial information detection device that projects light from a light projecting unit to a target space and images the target space with an image capturing unit. In this apparatus, light that is projected from the light projecting unit to the target space and reflected by the target existing in the target space is received by the imaging unit. Spatial information is information that reflects the reflectance and distance of an object. In order to obtain this type of information, the intensity of light projected from the light projecting means to the target space is modulated with a modulation signal of a predetermined frequency. In addition, it is considered that the imaging means receives light synchronized with two specific intervals of the phase of the modulation signal and obtains the difference between the light reception outputs of both intervals (for example, see Patent Document 1).

  Now, as a waveform of the modulation signal, a period for projecting light from the light projecting means to the target space (referred to as a light project period) and a period for not projecting light from the light projecting means to the target space (referred to as a non-light project period) are alternately provided. Assume that a rectangular wave is used. During the non-projection period, only ambient light such as natural light is incident on the image pickup means, and in the light projection period, signal light, which is light projected from the light projection means, is also incident on the image pickup means. Since light is incident on the imaging means in addition, if the ambient light does not change between the light projection period and the non-light projection period, the difference between the light reception output during the light projection period and the light reception output during the non-light projection period is calculated. By obtaining, a light receiving output corresponding to the signal light can be obtained.

  The received light quantity of the signal light mainly depends on the distance to the object and the reflectance. That is, as the distance increases, the amount of received light decreases, and as the reflectance decreases, the amount of received light decreases. Therefore, by obtaining the light reception output corresponding to the signal light, it is possible to obtain spatial information reflecting the reflectance and distance.

  Here, if signal light does not enter from the background other than the target in the target space, only the signal light reflected by the target is extracted from the light reception output of the imaging means by obtaining the difference as described above. can do. In other words, it is possible to remove only background information and extract only object information.

In the above example, the waveform of the modulation signal is a rectangular wave. However, if the modulation signal has a frequency such that the flight time from light projection to light reception is within the error range of the light reception output, it is a sine wave, triangular wave, or sawtooth. It is also possible to use a sine wave or the like, and even when these waveforms are used, the received light output obtained at the timing synchronized with two specific sections (usually 180 degrees inverted) of the phase of the modulation signal in the imaging means. By using the difference, the amplitude of the received signal light can be obtained. If the amplitude of the signal light on the light emitting side is constant, the amplitude of the signal light on the light receiving side reflects the distance to the object and the reflectance of the object.
JP 2001-148808 A

  By the way, in the imaging means used for the spatial information detection apparatus having the above-described configuration, the received light amount has an upper limit, and the received light output is saturated when the received light amount exceeds the upper limit. When the output is taken out as a light reception output when the imaging means is saturated, the light reception output is the upper limit, so it can be seen that the amount of received light is at least the upper limit, but as described above, the phase of the modulation signal is specified. When the difference between the received light outputs obtained at the timing synchronized with the two sections is obtained, significant spatial information is not included in the difference obtained when one of the received light outputs for which the difference is obtained is saturated. In particular, when both the light receiving outputs are saturated, the difference result is zero and is treated as the background.

  The present invention has been made in view of the above-mentioned reasons, and its purpose is to use an amplitude image obtained by taking a difference so as to eliminate the influence of ambient light, and when the received light output is saturated, the next received light output is saturated. An object of the present invention is to provide a spatial information detection apparatus that suppresses and always obtains a significant amplitude image.

According to the first aspect of the present invention, there is provided light projecting means for projecting signal light, the intensity of which is modulated with a modulation signal having a predetermined frequency, into the target space, and signal light reflected by an object that includes a plurality of pixels and exists in the target space. Imaging means for obtaining a light reception output corresponding to a change in the amount of received light for each pixel, a difference calculation means for obtaining a difference between light reception outputs synchronized with two different sections in the phase of the modulation signal for each pixel, Amplitude image generation means for generating an amplitude image having the pixel value of the difference of each pixel obtained by the difference calculation means, and the magnitude of the received light output obtained at the timing synchronized with at least one of the two sections and the prescribed saturation threshold a saturation determination means for comparing the, e Bei and correction means the light receiving output in the saturation determining means to perform the following correction processing to reduce the light output of the are the imaging unit determined to be larger than the saturation threshold The correction unit is a correction execution unit that adjusts the light reception output of the imaging unit according to the instructed operation amount, and obtains the operation amount of the correction execution unit using the comparison result by the saturation determination unit, and the operation amount is stored in the correction execution unit. Correction calculation means for instructing, the correction calculation means for signal light using an area designating means for designating a region of interest in the amplitude image, and the difference regarding the pixels in the region of interest designated by the region designating means. A luminance detection unit that evaluates the corresponding light reception output; and a correction processing unit that obtains the operation amount so that the light reception output corresponding to the signal light evaluated by the luminance detection unit approaches a predetermined standard. In association with the representative value of the light reception output of the region of interest, a coefficient that increases as the light reception output decreases is set. And comparing said effective threshold after multiplied by the coefficient.

According to this configuration, it is possible to suppress the saturation of the received light output by correcting so that the next received light output is reduced when the received light output is saturated. Make spatial information available. For example, when the distance to the target object existing in the target space is too small or when the reflectivity of the target object is higher than the assumed reflectivity, the received light output is used because the received light output is once saturated. Significant spatial information cannot be obtained from the amplitude image, but thereafter, the received light output is corrected so as not to be saturated, and significant spatial information can be obtained from the amplitude image.
Further, in the configuration in which the amplitude image is obtained using the difference between the light reception outputs, the operation amount of the correction execution unit is determined using the comparison result between the light reception output by the saturation determination unit and the saturation threshold value. When determined, a difference can be obtained for the light reception output that is not saturated, and a significant amplitude image can be obtained.
In addition, by specifying an area where the object is highly likely to exist as the target area, the difference obtained from the pixels in the target area among the differences obtained by the difference calculation means has information on the signal light. Become. Therefore, by correcting the light reception output so that the light reception output by the signal light is close to the reference, the amplitude image is corrected so that an amplitude image having an appropriate value with respect to the object can be obtained.
In addition, when the received light output obtained from the region of interest is small, the range specified as the region of interest can be expanded by multiplying the difference by a large coefficient. For example, if the target is located a little far away or if the reflectivity of the target is lower than the expected reflectivity, the target area may contain only a part of the target. By expanding the region of interest using, the region of interest is corrected so as to include the entire object, and as a result, an amplitude image including the entire object can be generated.

According to a second aspect of the present invention, in the first aspect of the invention, the saturation determining means outputs a prescribed value instead of the difference obtained by the difference calculating means when the received light output is larger than a saturation threshold in the comparison result. And

  According to this configuration, the determination result in the saturation determination unit is not directly reflected in the correction execution unit, but the determination result in the saturation determination unit is reflected in the correction execution unit using the difference output from the difference calculation unit. In spite of adopting the configuration, it is possible to know the presence or absence of saturation of the received light output by the output of the difference calculation means, and to reflect the result on the correction execution means. That is, it can be determined from the received light output whether the difference is saturated when the difference reaches the specified value. In addition, by selecting a prescribed value that reduces the difference between the difference corresponding to the pixel and the difference between the peripheral portions when the light reception output corresponding to any pixel is saturated, The uncomfortable feeling at the saturated site can be reduced.

According to a third aspect of the present invention, in the second aspect of the present invention, the specified value is a maximum value of a difference output from the difference calculating means.

  According to this configuration, by giving the maximum value that the difference can take to the pixels in the saturated portion, it is possible to reliably cause the correction calculation means to recognize the saturation of the light reception output. Further, in the amplitude image, a portion where the light reception output is saturated can be distinguished from the background.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the area designating unit compares the difference obtained by the difference calculating unit with a prescribed effective threshold value, and the difference is determined in the amplitude image. A region where pixels exceeding the effective threshold are present is designated as the region of interest.

  According to this configuration, since the region of interest is designated by the pixel value (that is, the difference) of the amplitude image, it is possible to designate an object existing at a short distance as the region of interest if the object has the same reflectance. it can. In other words, when a person who is present at a relatively short distance, such as a camera used in a door phone slave unit, is used as a target, a person who is passing far away can be excluded from the region of interest. Only the region can be designated as the region of interest.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the imaging means accumulates charges generated separately in two sections having different phases in the modulation signal over a plurality of periods of the modulation signal. An image sensor is provided that takes out as a received light output after being accumulated over time, and the correction execution unit changes the accumulation time according to the operation amount.

  In this configuration, since the light reception output is adjusted by adjusting the accumulation time of the image sensor, if there is a large amount of light received by the imaging means, the accumulation time can be shortened to increase the responsiveness. If the amount of received light is small, the accumulation time becomes long and the responsiveness decreases, but the noise level due to shot noise generated in the image sensor can be suppressed. The accumulation time is a product of one time of each section and the number of cycles (number of accumulations).

According to the configuration of the present invention, when the light reception output is saturated, the next light reception output is reduced to suppress the saturation of the light reception output. Therefore, even when used outdoors such as where there is a lot of ambient light, the light reception output There is an advantage that the saturation of the light can be suppressed and significant spatial information can be obtained from the difference between the received light outputs. In addition, when the received light output obtained from the region of interest is small, there is an advantage that the range designated as the region of the region of interest can be expanded by multiplying the difference by a large coefficient.

  FIG. 1 shows a configuration of the present invention. An imaging unit 1 having a plurality of pixels and capable of obtaining a light reception output corresponding to the amount of received light for each pixel, and signal light is projected to a target space to be imaged by the imaging unit 1. And a light projecting means 2 for emitting light.

  The imaging unit 1 includes a light receiving optical system 11 including an iris diaphragm and a lens, an image sensor 12 in which a large number of pixels are arranged in a two-dimensional plane, and light from a target space is incident on the pixels through the light receiving optical system 11, and an image sensor The AD converter 13 converts the output of 12 into a digital signal. Various structures can be adopted for the light receiving optical system 11, and when an iris diaphragm is used, an aperture that can be adjusted by an external signal is used. In addition to the iris diaphragm and the lens, it is possible to prepare a plurality of neutral density filters having different transmittances and to select which neutral density filter to use according to an external signal. Alternatively, it is also possible to use a neutral density filter using liquid crystal that changes the transmissivity by an external signal. In the lens provided in the light receiving optical system 11, the direction in which the object space is viewed from the image sensor 12 is associated with each pixel of the image sensor 12.

  The light projecting unit 2 includes a light irradiating unit 21 having a light source that irradiates light to the target space, and a modulating unit 22 that outputs a modulation signal having a predetermined frequency for modulating the intensity of light irradiated from the light irradiating unit 21. Consists of. As the light irradiation means 21, for example, a plurality of light emitting diodes arranged on one plane or a combination of a semiconductor laser and a diverging lens can be used. In addition to visible light, infrared light can also be used. A rectangular wave is used for the modulation signal output from the modulation means 22. A configuration is adopted in which light is projected from the light irradiation means 21 to the target space during the rectangular wave on period, and light is not projected from the light irradiation means 21 during the rectangular wave off period. That is, the light irradiation means 21 repeats light projection (lighting) and non-light projection (light extinction) alternately at a predetermined frequency (10 to 100 kHz). Hereinafter, a period during which light is projected from the light irradiation means 21 is referred to as a lighting period, and a period during which light is not projected from the light irradiation means 21 is referred to as a light extinction period.

  The imaging means 1 is controlled to synchronize with the modulation signal, and the light receiving output during the lighting period and the light receiving output during the extinguishing period are taken out separately. However, if it is attempted to take out the light reception output in each lighting period and each extinguishing period in synchronization with the modulation signal, the light reception output has to be taken out tens of thousands of times per second, so that the imaging means 1 having a high response speed is required. . Generally, since a moving image can move smoothly if it is 30 frames per second, it is desirable that the response speed of the image pickup means 1 is also set to this level. Therefore, the image pickup means 1 does not take out the electric charge generated by the light irradiation as it is, but accumulates the charge during the lighting period and the electric charge during the extinction period inside the image sensor 12 constituting the image pickup means 1, respectively. A structure is adopted in which the charge for a predetermined period is accumulated and then taken out as a light reception output. This type of image sensor 12 is realized by making it possible to adjust the light receiving sensitivity in units of pixels.

  For example, when an IT-type CCD image sensor is used, the charge generated during the target period of the lighting period and the extinguishing period is moved to the transfer region, and the charge generated during the non-target period is discarded. If controlled to this, the charge in the target period is accumulated in the transfer region. In the case of this configuration, it is possible to adjust a charge accumulation period (hereinafter referred to as “accumulation time”). The accumulation time is a product of one time for accumulating charges and the number of accumulations (accumulation number). It is also possible to use a configuration specialized for this type of application for the image sensor 12. If the frequency of the modulation signal is set to one half of the number of times the light receiving output is taken out from the image sensor 12 per second, a normal CCD image sensor can be used. For example, the frequency of the modulation signal may be 30 Hz, and the light reception output from the imaging unit 1 may be taken out 60 times per second (that is, the lighting period and the extinguishing period are 30 times each). Hereinafter, the unit of the light reception output taken out once from the image sensor 12 is referred to as one frame. That is, if the light reception outputs of the lighting period and the extinguishing period are extracted once, two frames of data are extracted.

  The light reception output taken out as a digital signal from the imaging means 1 is temporarily stored in the frame memory 3. The frame memory 3 only needs to have a capacity of two frames at a minimum, and the received light output of the lighting period and the extinguishing period is stored as one set. If there is no change in the amount of ambient light (sunlight or illumination light) received by the imaging means 1 within one period of the modulation signal, the difference in the received light output between the lighting period and the extinguishing period is determined from the light irradiation means 21. The signal light projected on the space reflects the amplitude of the reflected light reflected by the object Ob existing in the target space.

  In the present embodiment, there is provided a difference calculation means 4 for obtaining a difference between the light reception outputs for two frames stored in the frame memory 3, and the difference calculation means 4 of the imaging means 1 obtained by the lighting period and the extinction period. The difference of the received light output is obtained. The frame memory 3 stores the light reception output during a period in which the light reception output is taken out from the image pickup unit 1, and data is read out during a period in which the image pickup unit 1 accumulates charges due to light irradiation.

  The difference value obtained by the difference calculating means 4 is input to the amplitude image generating means 5 to generate a difference image having the pixel value as the difference for each pixel in the lighting period and the extinguishing period. The value of each pixel in this difference image ideally corresponds to the received light intensity of the signal light, and a difference image reflecting the amplitude of the signal light received by the imaging means 1 is obtained. This is called an amplitude image. For example, assuming that a light reception output corresponding to the image P1 in FIG. 2A is obtained in the lighting period and a light reception output corresponding to the image P2 in FIG. 2B is obtained in the lighting period, the amplitude image P3 is as shown in FIG. As shown in (c). In the amplitude image, the background other than the object Ob that reflects the signal light in the object space is erased, and only the object Ob exists in the amplitude image (the pixel value other than the object Ob is 0 and black). Become a pixel). In addition, if the difference calculation means 4 does not obtain the difference between the light reception output between the lighting period and the light extinction period, and passes only one light reception output between the lighting period and the light extinction period, a gray image including the background can be obtained. it can.

  By the way, a saturation determination unit 6 is provided between the frame memory 3 and the difference calculation unit 4, and the saturation determination unit 6 determines the magnitude of the saturation threshold defined for each pixel with respect to the light reception output during the lighting period and the extinction period. Compare Now, assuming that the light reception output Aa for each pixel in the lighting period and the light reception output for each pixel in the light-off period are Ab, Aa> Ab within a short time when it can be considered that a change in environmental light does not substantially occur. Therefore, if the light reception output Aa does not exceed the prescribed saturation threshold Th1, it can be guaranteed that the light reception output Ab does not exceed the saturation threshold Th1. Therefore, the saturation determination means 6 compares the light reception output Aa during the lighting period with the saturation threshold Th1 (see S3 in FIG. 3). The saturation threshold Th1 is a threshold for determining the saturation of the light reception output Aa. The saturation determination means 6 determines that the light reception output Aa is saturated when the light reception output Aa exceeds the saturation threshold Th1. Here, Aa> Ab is generally established, but in some cases, this relationship may not be established. Therefore, the comparison between the saturation threshold Th1 and the light reception output Ab may be performed together.

  The fact that the light reception output Aa exceeds the saturation threshold Th1 means that the light reception output Aa is saturated as described above. Therefore, such light reception output Aa does not reflect spatial information. In other words, an amplitude image cannot be generated even if the difference ΔA is obtained by the difference calculation means 4. Therefore, when the saturation determination unit 6 determines that the value is saturated, the difference calculation unit 4 is instructed to set the output value to a specified value. That is, at the time of saturation, the output of the difference calculation means 4 becomes a specified value.

  As the specified value, the maximum value or median value of the range allowed as the output value of the difference calculation means 4 can be used, or a specific value that is not normally output from the difference calculation means 4 can be adopted. For example, when the light reception outputs Aa and Ab are expressed by 8 bits, that is, in 255 levels, “255” is used when the maximum value is adopted as the specified value. When the maximum value is used as the output value of the difference calculation means 4, a pixel in which the light reception output Aa is saturated can be distinguished from the background. Further, when the median value of the output value range of the difference calculation means 4 is used, the difference between the saturated pixels and the peripheral pixels can be made relatively small, so that an amplitude image without a sense of incongruity can be obtained.

  Also, if the specified value is a value that does not occur in other pixels (for example, the difference ΔA is expressed in 254 steps out of 255 steps, and “255” is a value that does not occur in the difference ΔA), the pixels of the specified value are changed. An invalid pixel in which the light reception output Aa is saturated can be obtained. In this way, if the saturated pixel is distinguished from other pixels as an invalid pixel, the amplitude image generating unit 5 can interpolate the invalid pixel with the values of surrounding pixels. If the interpolated amplitude image is used, it is difficult to generate pixels having abnormal values in the amplitude image, and an image with less sense of discomfort can be obtained.

  By the way, if the light reception output is saturated, the light reception output does not reflect the spatial information, and even if the prescribed value is applied to the pixel as described above, the value is obtained when the amplitude image is displayed. It is only a pseudo value for not giving a sense of incongruity. Therefore, the received light output to be stored next in the frame memory 3 must be corrected so as not to exceed the saturation threshold. In addition, as described above, in the amplitude image, the purpose is to obtain an image of only the object Ob by removing the background. Therefore, if the light reception output of the pixel corresponding to the object Ob is not saturated, the object is obtained. An amplitude image can be obtained.

  In the following, it is determined whether or not the light reception output from the imaging unit 1 is saturated in the designated region of interest, and when there is a light reception output saturated in the region of interest, the next light reception output is saturated for the region. A technique for controlling in a direction to suppress the above will be described. As specific means for controlling in a direction to suppress the saturation, at least one kind of light emission intensity of the light irradiation means 21, transmittance of the light receiving optical system 11, and accumulation time of the image sensor 12 can be used. That is, if the light emission intensity of the light irradiation means 21 is reduced, the transmittance of the light receiving optical system 11 is reduced, or if the accumulation time of the image sensor 12 is shortened, the light reception output of the imaging means 1 is reduced. Can be suppressed. Therefore, the light irradiation means 21, the light receiving optical system 11, and the image sensor 12 function as correction execution means. In this embodiment, when the received light output is saturated, the output of the difference calculating means 4 is set to a specified value, so that not only the amplitude image can be prevented from being strange, but also the received light output is saturated by using this specified value. This is reflected in the correction execution means. That is, setting the specified value is used for two functions.

  A region where the object Ob exists is used as the region of interest. This is because it is only necessary to focus on the object Ob in the amplitude image. Such a region of interest can be determined by using the output of the difference calculation means 4. That is, in the area designating unit 7, an area in which the difference ΔA output from the difference calculating unit 4 exceeds the effective threshold Th2 is set as a focused area (see S7 to S9 in FIG. 3). In this method, the region of interest Da as shown in FIG. 2D can be obtained from the amplitude image P3 as shown in FIG. Further, when the present apparatus is used as a camera attached to a door phone slave unit, for example, the effective threshold Th2 is set so that a person's face existing within a predetermined distance range from the imaging means 1 can be extracted as the object Ob. Set in advance.

  However, the difference value may not exceed the effective threshold Th2 even within the range of the object Ob due to a difference in reflectance or a difference in distance due to unevenness (the portion where the light reception output is saturated is replaced with a specified value). Therefore, an expansion process or the like is performed on a region exceeding the effective threshold Th2. With this process, even if a small partial region of the region that exceeds the effective threshold Th2 as a whole does not exceed the effective threshold Th2, the partial region can be taken into the region of interest. For example, when the object Ob is a face, the reflectance of eyes, eyebrows, hair, etc. is low, so the difference obtained by the difference calculation means 4 may be smaller than the effective threshold Th2 for these parts. However, since there are more pixels that exceed the effective threshold Th2 for the entire face, eyes, eyebrows, hair, and the like can be taken into the region of interest by performing the expansion process.

  The correction execution means described above can increase or decrease the light reception output of the entire image, but cannot increase or decrease the light reception output for a partial region. Therefore, the average value of the light reception output of the pixels in the area detected by the area specifying unit 7 is obtained by the luminance detecting unit 8, and the operation amount instructed to the correction performing unit is obtained by the correction processing unit 9 using this average value. That is, a reference value corresponding to the appropriate luminance of the object Ob in the amplitude image is set in advance in the luminance detection means 8, and an error from the average value is obtained using this reference value as a target value. Further, the correction processing unit 9 determines an operation amount of the correction execution unit based on the error given from the luminance detection unit 8.

  In the correction processing means 9, when the average value of the light reception output in the region of interest is larger than the reference value, the operation amount of the correction execution means is determined in the direction in which the light reception output decreases, and conversely, the average value of the light reception output is greater than the reference value. Is smaller, the operation amount of the correction execution means is determined in the direction in which the light reception output increases. However, since the operation range of the correction execution unit is limited, the current state is maintained when the upper or lower limit of the operation range is reached.

  When combining a plurality of types of means as correction execution means, a priority order is determined for each means, and the operation amount of the other means is changed when the upper limit or lower limit of the operation range of any means is reached. It is good. In addition, it is possible to adopt a configuration in which the amount of change in the manipulated variable can be changed according to the magnitude of the error. However, when the amount of change in the manipulated variable is constant and the error is large, the manipulated variable changes several times. It may be configured to reach the reference value in the meantime. By adopting this configuration, it is possible to suppress the disturbance of the amplitude image due to the response to the instantaneous light quantity change. Furthermore, if the reference value has a width and the operation amount of the correction execution unit is not changed when the average value of the received light output in the region of interest is within the range of the reference value, the correction execution unit Useless operation can be prevented. It is desirable that the initial value of the correction execution means at the start of operation is the upper limit of the operating range.

  As described above, the region designating unit 7, the luminance detecting unit 8, and the correction processing unit 9 determine the operation amount of the correction performing unit based on the determination result by the correction determining unit 4, and thus function as a correction calculating unit. . Further, a correction means is constituted by the correction execution means and the correction calculation means. In FIG. 1, the parts other than the imaging means 1 and the light receiving means 2 are realized by executing an appropriate program with a microcomputer.

  The operation of this embodiment will be briefly described with reference to FIG. When the operation of the apparatus is started, first, imaging of the target space is performed by the imaging unit 1 (S1). As described above, imaging is performed in synchronization with the lighting period and the extinguishing period of the light projecting means 2. When the light reception output Aa in the lighting period is obtained (S2), the saturation determination means 6 compares the saturation threshold Th1 with the light reception output Aa (S3). If the light reception output Aa is equal to or less than the saturation threshold Th1, the light reception output is not saturated, and the difference calculation means 4 determines the difference ΔA between the light reception outputs Aa and Ab (S4). On the other hand, when the light reception output Aa exceeds the saturation threshold Th1, the difference ΔA is set as a specified value (S5). The difference ΔA thus obtained is output as an amplitude image through the amplitude image generating means 5 (S6).

  The difference ΔA is also given to the area specifying means 7 for controlling the correction execution unit. In the area designating means 7, the difference ΔA is compared with the effective threshold Th2 (S7), and the pixels exceeding the effective threshold Th2 are stored as pixels of the target area (S8). This process is performed for all the pixels of the amplitude image (S9). When the region of interest is thus determined, the luminance detection means 8 obtains the average value of the differences ΔA for the pixels in the region of interest (S10).

  In the correction processing means 9, the average value of the difference ΔA in the region of interest is compared with the reference value (S11), and when the average value of the difference ΔA is larger than the reference value, an operation amount for reducing the light reception output is given to the correction execution unit. When the average value of the differences ΔA is less than or equal to the reference value, an operation amount for increasing the light reception output is given to the correction execution unit (S15). However, since there is an upper limit and a lower limit in the operation amount range of the correction execution unit, the operation amount is minimized in the direction of decreasing the light reception output (S12), or the operation amount is maximized in the direction of increasing the light reception output. If so (S14), the next imaging is performed without changing the operation amount (S1).

  In the above-described operation, every time the difference between the light reception outputs of the lighting period and the extinguishing period is obtained, the correction processing unit 9 gives an instruction to the correction execution unit. Correction is performed when a state in which the average value of the received light output is greater than the reference value occurs continuously for a specified number of times, or a state in which the average value of the received light output obtained in the luminance detection means 8 is continuously generated a specified number of times. You may employ | adopt the structure which gives an instruction | indication to a means.

  Further, in order to prevent hunting by the correction execution means, the correction processing means 9 may have hysteresis. For example, after the average value is larger than the reference value and the correction execution unit is instructed to reduce the light reception output, even if an error occurs in which the average value becomes smaller than the reference value, the absolute value of the error is If the specified value is not exceeded, the instruction to increase the received light output is not given, and conversely, after the average value becomes smaller than the reference value and the correction execution means is given an instruction to increase the received light output, the average value Even if an error that becomes larger than the reference value occurs, an instruction to reduce the received light output is not given unless the absolute value of the error exceeds a specified value.

  Instead of obtaining the average value of the light reception output in the luminance detection means 8, the number of pixels whose light reception output exceeds the reference value in the region of interest may be counted, and the operation amount may be determined according to this number.

  In the above example, the average value of the light reception output of the region of interest is compared with one reference value. However, the reference value is set in a plurality of steps, and the correction amount of the correction execution means is stepwise for each step. You may employ | adopt the structure changed to. In this configuration, the operation amount of the correction execution unit can be determined in a stepwise manner, so that control using a digital signal is easy. When the reference value is set in a plurality of stages, the number of pixels at each stage is counted, and the operation amount can be determined so as to correspond to the stage where the maximum frequency is obtained.

  Further, when the region designating unit 7 extracts the region of interest, the result obtained by multiplying the difference obtained by the difference calculating unit 4 by the coefficient is compared with the effective threshold Th2, and the coefficient to be multiplied by the difference is used as the luminance detecting unit 8. A configuration may be adopted in which the average value of the received light output obtained in step 1 is changed in a plurality of stages. The coefficient is set to be smaller as the average value is larger. If the average value of the light reception output of the target area is small and dark, the coefficient extracted by the difference is increased to widen the range extracted as the target area. To. Here, in order to determine the coefficient, an average value that is a representative value of the received light output obtained by the luminance detecting means 8 is used, but other values such as a maximum value and a mode may be used as the representative value. Is possible.

  That is, when the amplitude of the signal light is small, such as when the object Ob exists in the distance or when the reflectance of the object Ob is low, the object Ob may be included in the region of interest by expanding the region of interest. Can be increased. With this operation, the pixel value corresponding to the object Ob can be kept within a specified range regardless of the distance to the object Ob and the change in the reflectance of the object Ob. An easy-to-view image of the object Ob can be obtained with respect to the amplitude image to be displayed.

  In the above configuration example, the area for obtaining the average value (or the number of pixels satisfying the predetermined condition) of the light reception output in the luminance detection means 8 does not necessarily have to be the area from which the object Ob is extracted. It is possible to set all the pixels in the image as the region of interest, set a predetermined range in the center of the image as the region of interest, or set the region of interest at an appropriate location in the image. How to set the region of interest may be appropriately selected depending on the application. However, if the region of interest is determined in advance, the region designating unit 7 may determine the region of interest regardless of the difference obtained by the difference calculating unit 4. Will be specified.

  The frame memory 3 holds the light reception output for the lighting period and the light extinction period only once, and the difference calculation means 4 obtains the difference in the light reception output between the lighting period and the light extinction period for each time. The received light output for a plurality of times for each of the period and the extinguishing period may be added to the frame memory 3 and held. In this case, the processing in the difference calculation means 4, the saturation determination means 6, and the luminance detection means 8 is a process using a plurality of addition values of the lighting period and the extinguishing period, so that noise included in the light reception output is suppressed. It is done. Alternatively, an average value obtained by dividing the added value by the number of times the received light output is taken out may be used. Furthermore, the difference obtained by the difference calculation means 4 may be added, and the added value of the differences or the average value of the differences may be used.

  As described above, when the average value of the received light output or the average value of the difference of the received light output is used, if one of the number of additions and the divisor is changed, the region designating unit 7 is used to detect the region of interest. The same effect as when the coefficient is changed can be expected. If the average value of the received light output or the average value of the difference between the received light outputs is used, the frame rate is reduced as compared with the case where the received light output of the lighting period and the unlit period is used only once, but this occurs in the image sensor 12. Shot noise can be reduced. Therefore, the influence of noise may be reduced by reducing the number of additions in a room with little ambient light and increasing the number of additions in the outdoors where there is a lot of ambient light.

  In the above-described configuration example, the light irradiation means 21 is provided with a lighting period and a light extinction period, but the modulation signal for controlling the light irradiation means 21 is not only a rectangular wave but also a sine wave, a triangular wave, a sawtooth wave, or the like. May be. In this case, the component of the ambient light is removed even if the light reception output synchronized with two different specific sections in the phase of the modulation signal is extracted from the imaging unit 1 and the difference between the light reception outputs of the two sections is obtained. An image similar to the amplitude image can be obtained. The width of the section taken out from the image sensor 1 can be selected as appropriate, but when the phase difference between the two sections is 180 degrees, the operation is substantially the same as when the difference between the lighting period and the extinguishing period is obtained. become. However, the phase difference between both sections may be other than 180 degrees.

It is a block diagram which shows embodiment. It is operation | movement explanatory drawing same as the above. It is operation | movement explanatory drawing same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image pickup means 2 Light projection means 3 Frame memory 4 Difference calculation means 5 Amplitude image generation means 6 Saturation determination means 7 Area designation means 8 Luminance detection means 9 Correction processing means Ob Object

Claims (5)

A light projecting means for projecting signal light, the intensity of which is modulated with a modulation signal of a predetermined frequency, into the target space, and a signal light reflected by an object existing in the target space with a plurality of pixels, and for each pixel The imaging means for obtaining the received light output according to the change in the amount of received light, the difference calculating means for obtaining the difference between the received light outputs synchronized with two different sections in the phase of the modulation signal for each pixel, An amplitude image generating means for generating an amplitude image having the pixel difference as a pixel value; and a saturation determining means for comparing the magnitude of a received light output obtained at a timing synchronized with at least one of the two sections and a specified saturation threshold value. , e Bei and correction means the light output to perform reduced to correction processing for the next light receiving output is the the imaging unit determined to be larger than the saturation threshold in the saturation determining means, correcting means, indicated Correction execution means for adjusting the light reception output of the image pickup means according to the operated amount, and correction calculation means for obtaining the operation amount of the correction execution means using the comparison result of the saturation determination means and instructing the correction execution means The correction calculation means includes a region designation means for designating a region of interest in the amplitude image, and a light reception output corresponding to the signal light using the difference regarding the pixels in the region of interest designated by the region designation means. A luminance detection means for evaluation, and a correction processing means for obtaining the manipulated variable so that a received light output corresponding to the signal light evaluated by the luminance detection means approaches a predetermined standard, and the correction processing means comprises: A coefficient that increases as the light reception output decreases in association with the representative value of the light reception output is set, and the area designation unit multiplies the difference by the coefficient when determining the target area to be designated next. Detection device of spatial information and comparing said effective threshold after. The spatial information detection device according to claim 1 , wherein the saturation determination unit outputs a specified value instead of the difference obtained by the difference calculation unit when the light reception output is larger than a saturation threshold in the comparison result . The spatial information detection device according to claim 2 , wherein the specified value is a maximum value of a difference output from the difference calculation means . The region designating unit compares the difference obtained by the difference calculating unit with a prescribed effective threshold value, and designates, as the region of interest, a region where a pixel whose difference exceeds the effective threshold value exists in the amplitude image. The spatial information detection device according to any one of claims 1 to 3 . The image pickup means includes an image sensor that stores charge generated separately in two sections of different phases in the modulation signal in an accumulation time over a plurality of periods of the modulation signal and then takes out as a light reception output, and the correction execution means detection equipment spatial information according to any one of claims 1 to 4, characterized in that to vary the accumulation time in accordance with the operation amount.

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