JP4321540B2 - Object detection device - Google Patents

Description

  The present invention relates to an object detection apparatus, and more particularly to an object detection apparatus that accumulates a signal corresponding to the amount of received light as an electric charge and performs at least one of object detection and information output for object detection.

  Conventionally, the detection range is irradiated with light, the light reflected by an object existing within the detection range is received by a two-dimensional image sensor, and the phase of the received light varies depending on the distance from the reflected object. 2. Description of the Related Art A distance image sensor is known that can calculate and output a distance from an object by detecting each pixel and generate and output an image within a detection range for each distance range. In order to detect the phase of the received light, this distance image sensor performs intensity modulation by repeatedly causing the light source to emit light for a fixed period of time and charges the received light signal obtained by photoelectrically converting the received light with a light receiver. Accumulation as charge in the accumulation means is performed for each of a plurality of periods having different phases with respect to the light emission timing of the light source, and the phase of the received light is detected based on the amount of charge accumulated in each period. (For example, refer to Patent Document 1).

In Patent Document 2, in the distance image sensor described above, residual charges that are not used as signal charges out of the charges generated in the photosensitive portion are discarded, so that noise components are prevented from being mixed into the signal charges, and spatial information is obtained. Has been disclosed that makes it possible to detect a high S / N ratio.
JP 2004-45304 A JP 2004-356594 A

  The inventors of the present application conducted an experiment for measuring a distance to an object using an existing distance image sensor. As a result, it has been clarified that the distance to the object cannot be measured or the measurement accuracy is extremely lowered particularly when the object to be detected is present at a position close to the distance image sensor. This is because when the distance to the object to be detected is small, the intensity of the reflected light that is emitted from the light emitter, reflected by the object to be detected, and incident on the light receiver becomes excessive. This is presumably because the stored charge amount is saturated in the light receiving cell. In the light receiving cell where the accumulated charge amount is saturated, the relationship between the received light intensity and the accumulated charge amount is broken (the actual accumulated charge amount is smaller than the received light intensity), so the distance from the object is calculated from the accumulated charge amount. In this case, the calculation accuracy is also lowered.

  It is also conceivable to reduce the sensitivity of the image sensor or increase the capacity of the charge storage means in order to prevent saturation of the stored charge amount. However, the intensity of the reflected light from the object decreases as the distance to the object increases, so if the sensitivity of the image sensor is reduced, the detection accuracy of an object existing relatively far will be reduced. When a problem arises and the capacity of the charge storage means is increased, there arises a problem that the device configuration becomes complicated and the cost increases.

  The present invention has been made in consideration of the above facts, and an object of the present invention is to obtain an object detection apparatus that can accurately detect an object regardless of the intensity of reflected light from the object.

In order to achieve the above object, an object detection apparatus according to a first aspect of the present invention is a two-dimensional array of light emitting means that emits light while changing the light emission intensity over time, and a direction that intersects the incident direction of light. by a plurality of light receiving means for outputting a light receiving signal corresponding to the amount of received light, a charge storage means provided in a plurality to correspond to each of the plurality of light receiving means, a light reception signal output from said light receiving means, wherein In the accumulation period that is shorter than the light emission period of the light emitting means and in which the phase with respect to the light emission timing of the light emitting means is constant, the charge accumulation means accumulates the charge as a predetermined number of times for each of a plurality of types of accumulation periods having different phases. Detecting means for performing at least one of object detection and information output for object detection on the basis of accumulated charge amounts for each of a plurality of types of phases in the charge storage means; and the phase Together is different from at least one of the luminous intensity and the charge storage times of said light emitting means when performing accumulation of charges to the plurality of charge storage means in a different storage period, accumulated charge at a particular phase in the plurality of charge storage means When a region having a lightness equal to or greater than a first predetermined value exists in the image represented by the amount or the corrected image represented by the accumulated charge amount after the correction in the specific phase, the specific phase Control means for reducing at least one of the light emission intensity of the light emitting means and the number of times of charge accumulation when accumulating charges in the charge accumulating means during the accumulation period .

In the first aspect of the present invention, the light emitting means emits light while temporally changing the light emission intensity, and the plurality of light receiving means are arranged two-dimensionally along the direction intersecting the light incident direction, and according to the amount of light received. The received light signal is output. The light receiving means is arranged at a position / orientation where light (reflected light) emitted from the light emitting means and reflected by the object can be received. The invention according to claim 1 further comprises a plurality of charge storage means provided corresponding to each of the plurality of light receiving means, and the detection means outputs the light reception signal output from the light receiving means to the light emission of the light emitting means. The charge accumulating means causes the charge accumulating means to accumulate a predetermined number of times as charges in an accumulating period shorter than the cycle and having a constant phase with respect to the light emission timing, for each of a plurality of accumulation periods having different phases. At least one of object detection and information output for object detection is performed based on the accumulated charge amount for each of a plurality of types of phases.

  The phase of the light emitted from the light emitting means, reflected by the object, and received by the light receiving means (phase with respect to the light emission timing of the light emitting means) differs depending on the distance from the object that reflected the light. In the charge accumulation means, the light reception signals output from the light reception means are accumulated as charges in the charge accumulation means during a plurality of types of accumulation periods that are shorter than the light emission period of the light emission means and have different phases with respect to the light emission timing of the light emission means. The amount of accumulated charge for each of the multiple types of phases differs depending on the phase of the received light, that is, the distance from the object that reflected the light (for example, the phase where the accumulated charge amount is maximum or the accumulation at each phase) The ratio of the charge amount and the like vary depending on the distance from the object that reflects the light). Accordingly, output of object detection (for example, detection of distance from an object, etc.) and information for object detection (for example, accumulated charge amount for each of a plurality of types of phases) based on the accumulated charge amount for each of a plurality of types of phases. It can be carried out.

  By the way, in the above configuration, the intensity of the light received by the light receiving unit varies greatly depending on the distance from the object that reflects the light emitted from the light emitting unit. For example, when the distance from the object is small, the light received by the light receiving unit There is a possibility that the strength becomes excessive and the charge accumulation means saturates the accumulated charge. Further, if the light emission intensity in the light emitting means is reduced to avoid this, the intensity of light received by the light receiving means when the distance to the object is large becomes too small. There is a problem that the detection accuracy of the object is lowered due to being too small.

In addition, the intensity of the light received by the light receiving means varies greatly depending on the light reflectance of the object in addition to the distance from the object reflecting the light emitted from the light emitting means, and the phase difference from the light emission timing of the light emitting means. Even if the emission intensity of the light emitting means and the number of charge accumulations are uniformly controlled according to the distance range of the object to be detected, depending on the light reflectance of the object that reflects the light emitted from the light emitting means, the charge accumulation There is a possibility that the accumulated charge is saturated by the means, or the accumulated charge amount becomes excessively small.

On the other hand, according to the first aspect of the present invention, in the configuration in which charges are accumulated in the charge accumulating means for each of a plurality of types of phases as described above, the phase of the light received by the light receiving means depends on the distance from the object. Focusing on the fact that the charge accumulation in each phase is the object to be detected based on the difference, the control means applies the charge accumulation means to the charge accumulation means during the accumulation periods with different phases. At least one of the light emission intensity of the light emitting means and the number of charge accumulations during charge accumulation is made different, and an image represented by the accumulated charge amount in a specific phase in a plurality of charge storage means or after correction in a specific phase Light emitting means for accumulating charges in the charge accumulating means during the accumulation period of the specific phase when the correction image represented by the accumulated charge amount includes a lightness area equal to or greater than the first predetermined value. Light emission And reducing at least one of the degrees and the charge storage times.

Accordingly, at least one of the light emission intensity of the light emitting means (the light receiving intensity of the light receiving means that changes according to the light intensity) and the number of charge accumulations when the charge is accumulated in the charge accumulating means during the accumulation period of each phase is determined. It is possible to optimize according to the distance range of the object to be detected by charge accumulation, and in charge accumulation in each phase, the accumulated charge is saturated or the accumulated charge amount is different depending on the distance range of the object to be detected. It is possible to prevent the occurrence of being too small. In addition, since there is a highly reflective object with high light reflectance within the distance range of the detection target in charge accumulation at a specific phase, light reflected by the highly reflective object among the plurality of light receiving means Even when the received light intensity at a part of the light receiving means that receives light becomes excessive and the corresponding charge storage means is saturated or close to saturation, this state is the image of the specific phase or the corrected image. At least one of the emission intensity of the light emitting means and the number of charge accumulations when the charge is accumulated in the charge accumulating means during the accumulation period of the specific phase. Is reduced.

According to the first aspect of the present invention, the phase at which the accumulated charge amount becomes maximum, the ratio of the accumulated charge amount at each phase, and the like correlate with the distance to the object as the control unit performs the above control. However, the light emission intensity of the light emitting means and the number of charge accumulations are known because the control means controls, and the accumulated charge amount in each phase is corrected according to the above light emission intensity and the number of charge accumulations. By using the later value as the amount of accumulated charge for each of multiple types of phases, the accuracy of object detection can be improved due to the synergistic effect of preventing the accumulated charge from being saturated or the amount of accumulated charge from becoming too small. Can do. Therefore, according to the first aspect of the present invention, it is possible to accurately detect an object regardless of the intensity of reflected light from the object, and when a highly reflective object exists within the distance range of the detection target. In addition, at least one of the light emission intensity of the light emitting means and the number of charge accumulations can be optimized.

In the first aspect of the present invention, when correcting the accumulated charge amount according to the third or fourth aspect described later, a plurality of the above-mentioned “regions having a brightness not less than the first predetermined value” are included. The lightness on the image (original image) represented by the amount of accumulated charge in the specific phase in the charge storage means is greater than or equal to the first predetermined value and is represented by the amount of accumulated charge after correction in the specific phase. It is preferable that the brightness reduction amount on the corrected image be an area having a third predetermined value or less. If a high brightness area in the original image has a significant decrease in brightness on the corrected image, it can be estimated that the area has a high brightness on the original image due to ambient light. On the other hand, when a high brightness area in the original image does not decrease much in the corrected image, the area is likely to be an area corresponding to a high reflectance object. Therefore, as described above, the lightness on the image represented by the accumulated charge amount in the specific phase in the plurality of charge accumulation means is equal to or higher than the first predetermined value, and the accumulated charge amount after correction in the specific phase. When there is a region where the amount of decrease in lightness on the corrected image shown is equal to or smaller than the third predetermined value, the light emitting means when the charge is accumulated in the charge accumulation means during the accumulation period of the specific phase By reducing at least one of the emission intensity and the number of charge accumulations, even when there is a highly reflective object within the distance range of the detection target, at least one of the emission intensity and the number of charge accumulations of the light emitting means is more accurate. It can be optimized well.

The object detection apparatus according to claim 2 is arranged two-dimensionally along the direction intersecting the light incident direction, with the light emitting means for emitting light while changing the light emission intensity over time, and the amount of received light A plurality of light receiving means for outputting a corresponding light receiving signal, a plurality of charge accumulating means corresponding to each of the plurality of light receiving means, and a light receiving signal output from the light receiving means as a light emission period of the light emitting means. Shorter than that and the phase with respect to the light emission timing of the light emitting means is constant, the charge accumulation means accumulates the charge as a predetermined number of times for each of a plurality of types of accumulation periods with different phases, and the charge Detecting means for performing at least one of object detection and information output for object detection based on the accumulated charge amount for each of a plurality of types of phases in the storage means; An image represented by the amount of accumulated charges in a specific phase in the plurality of charge storage units, while differentiating at least one of the light emission intensity and the number of times of charge storage of the light emitting units when storing the charges in the charge storage unit Alternatively, the charge accumulation is performed during the accumulation period of the specific phase when there is no region having a brightness of a second predetermined value or more in the corrected image represented by the accumulated charge amount after the correction at the specific phase. Control means for increasing at least one of the light emission intensity of the light emitting means and the number of times of charge accumulation when the charge is accumulated in the means.

The invention described in claim 2 includes light emitting means, a plurality of light receiving means, charge storage means, and detection means having the same configuration as that of the invention described in claim 1. The control means according to the invention described in claim 2 is configured to make at least one of the emission intensity and the number of charge accumulations of the light emitting means different from each other during the accumulation of charges in the charge accumulation means during accumulation periods having different phases. In the image represented by the accumulated charge amount at the specific phase or the corrected image represented by the accumulated charge amount after the correction at the specific phase in the charge storage means, there is a region having a lightness greater than or equal to the second predetermined value. If not, at least one of the light emission intensity of the light emitting means and the number of times of charge accumulation during charge accumulation in the charge accumulation means during the accumulation period of the specific phase is increased. The second predetermined value in the invention described in claim 2 is a value that is significantly smaller than the first predetermined value in the invention described in claim 1, for example, the minimum brightness that enables post-processing such as distance detection. Corresponding values can be used.

As a result, since there is a low-reflectance object with low light reflectivity within the distance range of the detection target in charge accumulation at a specific phase, light reflected by the low-reflectance object among the plurality of light receiving means Even when the received light intensity in a part of the light receiving means that receives light is too low and the amount of stored charge in the corresponding charge storage means is too low, this state is also included in the second predetermined image in the image of the specific phase or the corrected image. Even when the region of lightness exceeding the value is not present, it is detected that at least one of the light emission intensity of the light emitting means and the number of times of charge accumulation when the charge is accumulated in the charge accumulating means during the accumulation period of the specific phase is increased. The Therefore, according to the second aspect of the present invention, it is possible to accurately detect an object regardless of the intensity of reflected light from the object, and when a low-reflectance object exists within the distance range of the detection target. In addition, at least one of the light emission intensity of the light emitting means and the number of charge accumulations can be optimized.

By the way, the object detection device according to the first or second aspect of the present invention provides the original reflected light (emitted from the light source and reflected by the object) when the detection range is illuminated with strong ambient light such as sunlight. High intensity ambient light is received by the light receiving means even during a period when the light is not received, and accordingly, the proportion of the amount of charge corresponding to the ambient light in the amount of charge accumulated in the charge storage means is high. As a result, there is a problem that accurate detection becomes difficult. In consideration of the above, in the first or second aspect of the invention, the detecting means may be a light receiving signal output from the light receiving means in a state in which the light emitting means stops emitting light, as described in claim 3, for example. In addition, the charge accumulation means accumulates charges in the accumulation period of an arbitrary phase, and a plurality of types are obtained by subtracting the accumulated charge amounts in a state where the light emitting means stops light emission from the accumulated charge amounts for each of the plurality of phases. It is preferable that the accumulated charge amount for each phase is corrected and at least one of object detection and information output for object detection is performed based on the accumulated charge amount after correction for each of a plurality of types of phases. . Thereby, even in an environment where the light receiving means receives light including ambient light, accurate object detection with reduced influence of ambient light can be performed.

According to the first or second aspect of the present invention, charge accumulation at different phases is targeted for detection of objects existing in different distance ranges, and charge accumulation at phases where accumulation periods do not overlap each other. Then, it is very unlikely that the same object is detected repeatedly. In consideration of this, in the invention according to claim 1 or 2, the detection means, as described in claim 4, for example, from the accumulated charge amount in the first phase, to the accumulation period of the first phase Correction of the accumulated charge amount in the first phase by subtracting the accumulated charge amount in the second phase that does not overlap is performed for each accumulated charge amount in each phase, and correction for each of a plurality of types of phases is performed. It may be configured to perform at least one of object detection and information output for object detection based on the amount of accumulated charge later. Also in this case, in the environment where the light receiving means receives light including ambient light, it is possible to perform accurate object detection with reduced influence of the environmental light. Since charge accumulation in the state where light emission is stopped is not necessary, the processing speed can be improved (the object detection cycle can be shortened).

In addition, in the invention according to any one of claims 1 to 4, the detection means specifically includes, for example, as described in claim 5, the accumulated charge amount for each of a plurality of types or a plurality of types. Based on the accumulated charge amount after correction for each phase, the detection of the distance from the object reflecting the light emitted from the light emitting means can be performed as the object detection. As described above, the accumulated charge amount for each of the plurality of types of phases in the charge storage means differs depending on the phase of the received light, that is, the distance from the object that reflected the light. The distance from the object reflecting the light can be detected from the amount or the accumulated charge amount after correction for each of a plurality of types of phases.

Further, in the invention according to claim 5, a plurality of light receiving means are provided, each light receiving means is two-dimensionally arranged along the direction intersecting the light incident direction, and the charge storage means is each light receiving means. For example, as described in claim 6, the detection means calculates the distance to the object for each individual light receiving means, and the corresponding charge among the individual light receiving means. The light receiving means in which the accumulated charge amount in the accumulation means or the accumulated charge amount after correction indicates a value corresponding to the saturation of the accumulated charge may be excluded from the calculation target of the distance to the object.

As described above, the present invention is applied to a configuration in which a plurality of light receiving means and charge accumulating means are provided, and the light emission intensity and charge accumulation of the light emitting means when accumulating charges in the charge accumulating means during accumulation periods having different phases. Even if at least one of the numbers of times is made different, depending on the distance to the object, the light reflectivity of the object described later, and the phase of the accumulation period, the accumulated charge may be saturated in some charge accumulating means. On the other hand, in the invention described in claim 6, since the light receiving means corresponding to the charge accumulating means in which the accumulated charge is saturated is excluded from the calculation target of the distance to the object, a calculation result with low accuracy is output. Can be prevented. Instead of excluding the calculation target, another process may be performed such as, for example, sounding an alarm or clearly indicating that the accumulated charge is saturated when the calculation result is displayed as an image.

Further, in the invention according to any one of claims 1 to 4, a plurality of light receiving means are provided, and each light receiving means is arranged two-dimensionally along a direction intersecting the light incident direction, In the case where a plurality of storage means are provided corresponding to each light receiving means, the detection means specifically includes a plurality of charge storage means as information for object detection as described in claim 7, for example. The accumulated charge amount for each of a plurality of types of phases or the corrected accumulated charge amount for each of a plurality of phases can be output as an image having a different distance range for each phase.

As described above, the amount of charge accumulated in each phase differs depending on the phase of the light received by the light receiving means, that is, the distance from the object that reflected the light, but the plurality of light receiving means intersect the light incident direction. When the light receiving elements are arranged two-dimensionally along the direction of the light, each light receiving unit receives light reflected at different points in the detection range (different objects or different points of the same object). The magnitude relationship of the accumulated charge amount for each of the plurality of types of phases also differs for each light receiving unit depending on the distance from the location where the light incident on each light receiving unit is reflected. Therefore, when the accumulated charge amount for each of a plurality of phases or the accumulated charge amount after correction for each of a plurality of phases is visualized for each phase as an image in which the luminance changes according to the accumulated charge amount, each image is Since the images have different distance ranges (only the objects that exist within the distance ranges of the individual images are clearly shown as subjects on the individual images: distance images), multiple types of phases are used as described above. By outputting the accumulated charge amount for each phase or the corrected accumulated charge amount for each of a plurality of types of phases, the output accumulated charge amount or the accumulated charge amount after correction can be used for object detection.

Further, in the invention according to any one of claims 1 to 4, the control means, as described in claim 8, for example, the phase of the accumulation period during which charge is accumulated is the same as the light emission timing of the light emitting means. As the phase difference becomes smaller, at least one of the light emission intensity of the light emitting means and the number of charge accumulations can be reduced. Accordingly, at least one of the light emission intensity of the light emitting means (the light receiving intensity of the light receiving means that changes according to the light intensity) and the number of charge accumulations when the charge is accumulated in the charge accumulating means during the accumulation period of each phase is determined. It can be optimized according to the distance range of the object to be detected by charge accumulation.

As described above, according to the present invention, the light receiving signals output from the plurality of light receiving means arranged two-dimensionally along the direction intersecting the light incident direction are shorter than the light emitting period of the light emitting means and the light emitting means. In the accumulation period where the phase with respect to the light emission timing is constant, the charge accumulation means corresponding to each of the plurality of light receiving means accumulates a predetermined number of times as charge for each of a plurality of types of accumulation periods having different phases. When at least one of object detection and output of information for object detection is performed based on accumulated charge amounts for each of a plurality of types of phases in the accumulation means, and charge is accumulated in the charge accumulation means during accumulation periods having different phases It is the difference of at least one of the luminous intensity and the charge storage times of the light emitting means and the image also represented by the amount of charges stored in the specific phase in the plurality of charge storage means In the corrected image represented by the amount of accumulated charge after correction in a specific phase, if there is a region with a brightness greater than or equal to the first predetermined value, the charge stored in the charge storage means during the accumulation period of the specific phase because it reduces at least one of the luminous intensity and the charge storage times of the light emitting means when performing accumulation, can accurately detect objects regardless of the intensity of the reflected light from the object and Do Ri, the detected distance range even when a high reflectance object is present within, it has an emission intensity and at least one of Ru can be optimized, that excellent effects of the charge accumulation times of the light emitting means.
In the present invention, the light reception signals output from the plurality of light receiving means arranged two-dimensionally along the direction intersecting the light incident direction are shorter than the light emission period of the light emitting means and the phase with respect to the light emission timing of the light emitting means. Is stored in a plurality of charge storage means corresponding to each of the plurality of light receiving means for a predetermined number of times for each of a plurality of types of storage periods having different phases. At least one of object detection and output of information for object detection is performed based on the accumulated charge amount for each phase of the seed, and the light emitting means for storing charge in the charge accumulation means during accumulation periods having different phases At least one of the emission intensity and the number of charges accumulated, and an image represented by the amount of accumulated charges in a specific phase in a plurality of charge storage means or in a specific phase When accumulating charges in the charge accumulating means during an accumulation period of a specific phase when there is no region having a lightness greater than or equal to the second predetermined value in the corrected image represented by the amount of accumulated charge immediately before Since at least one of the light emission intensity of the light emitting means and the number of times of charge accumulation is increased, the object can be accurately detected regardless of the intensity of the reflected light from the object, and the low reflectance object within the distance range of the detection target Even in the case where there is, there is an excellent effect that at least one of the light emission intensity of the light emitting means and the number of charge accumulations can be optimized.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an object detection apparatus 10 according to the present embodiment. The object detection device 10 is a device that functions as a distance image sensor, and includes a light emitter 12, a light receiver 14, and a control unit 16. The light emitter 12 includes a light source composed of an LED or the like and a control circuit that controls light emission of the light source. The light emitter 12 is connected to the control unit 16 via the light receiver 14, and the control circuit of the light emitter 12 is instructed to emit the light source by a control signal input from the control unit 16 via the light receiver 14. Then, as shown in FIG. 4A, the light source is intermittently emitted by repeating the light emission of the light source for a certain period of time at a certain period. The light emitter 12 corresponds to the light emitting means according to the present invention.

  Light (irradiation light) emitted from the light emitter 12 by the light source of the light emitter 12 being emitted is reflected and received by an object (for example, the detection object 18 shown in FIG. 1) existing within the irradiation range of the irradiation light. Is incident on the container 14. The light receiver 14 includes a CCD sensor or a CMOS sensor, and includes a plurality of light receiving cells each including a photodiode 20 (see FIG. 2) that photoelectrically converts received light and outputs a light receiving signal at a level corresponding to the amount of light received. An image pickup device arranged in two dimensions is provided, and this image pickup device is arranged so that the arrangement direction of the light receiving cells intersects the incident direction of the light to the light receiver 14. A signal processing circuit 24 shown in FIG. 2 is connected to each light receiving cell of the image sensor. Note that the signal processing circuit 24 may be provided separately from the image sensor, or may be formed integrally with the image sensor on a semiconductor chip that functions as the image sensor. Each light receiving cell (photodiode 20) corresponds to the light receiving means according to the present invention.

  As shown in FIG. 2, the signal processing circuit 24 of the light receiver 14 includes a storage unit 26 as charge storage means according to the present invention. One end of the storage unit 26 is connected to the power supply end, and the other end of the storage unit 26 is connected to the other end of the photodiode 20 which is built in the light receiving cell of the image sensor and connected to the power supply end via the switch 28. Has been. The switch 28 is also connected to the power supply end, and in accordance with an input modulation signal, the first state in which the other end of the photodiode 20 is connected to the power supply end, or the other end of the photodiode 20 is connected to the storage unit 26. It switches to the 2nd state connected to. The switch 28 can be realized by combining semiconductor switching elements such as transistors. When the photodiode 20 outputs a light reception signal of a level corresponding to the amount of light received and the switch 28 is in the second state, the storage unit 26 corresponds to the level of the light reception signal input via the signal line. An amount of charge is accumulated (specifically, an amount of charge corresponding to a value obtained by integrating the level of the received light reception signal with the time during which the switch 28 is in the second state (charge accumulation time) is accumulated. ).

  The other end of the storage unit 26 is connected to an A / D (analog / digital) converter 44 via a switch 40 and an amplifier 42. Note that the switch 40 can also be formed of a semiconductor switching element such as a transistor. The switch 40 is turned on / off in response to an input read signal. When the switch 40 is turned on, the charge accumulated in the storage unit 26 is transferred / input to the amplifier 42 via the switch 40 and amplified by the amplifier 42. After that, the A / D converter 44 converts it into digital data (accumulated charge amount data) representing the accumulated charge amount of the accumulation unit 26 and outputs it. Further, the signal line connecting the storage unit 26 and the switch 40 is branched into two on the way, and the branched signal line is connected to the power feeding end via the switch 46. Note that the switch 46 can also be formed of a semiconductor switching element such as a transistor. The switch 46 is turned on / off in response to the input reset signal. When the switch 46 is turned on, the electric charge accumulated in the accumulating unit 26 is discharged, and the accumulating unit 26 is in an initial state (accumulated charge amount = 0 state). Reset to.

The light receiver 14 operates various parts by inputting various signals (the above-described modulation signal, selection signal, readout signal, and reset signal) to each part of the signal processing circuit 24 in accordance with the control signal input from the control part 16. A control circuit for controlling is also provided. On the other hand, the control unit 16 is composed of a CPU, a memory, a microcomputer having nonvolatile storage means such as an HDD (Hard Disk Drive) or a flash memory, or a DSP (Digital Signal Process ) , and includes a light emitter 12 and a light receiver. 14 is controlled, and processing such as calculation (described later) of the distance to the detected object is performed based on the image data output from the light receiver 14.

  Next, the operation of this embodiment will be described. The control unit 16 according to the present embodiment repeatedly executes the object detection process shown in FIG. In the following, in the series of object detection processes, first, acquisition of a normal phase image for object detection (step 60 to step 76) will be described.

  In step 60, 0 is set to the variable i. In step 62, a predetermined control signal is output to the light emitter 12 via the light receiver 14, thereby starting light emission of the light source of the light emitter 12. As a result, the light source of the light emitter 12 emits light intermittently by repeating light emission for a fixed time at a constant cycle as shown in FIG. 4A, and the light emitted from the light emitter 12 irradiates the detection object. After being reflected by the object, it is received by the light receiver 14 as reflected light. Each light receiving cell (photodiode 20) of the image sensor of the light receiver 14 outputs a light reception signal every time it receives reflected light. The output timing of this light reception signal is as shown in FIG. In addition, the light emission timing in the light emitter 12 is delayed according to the distance from the object that has reflected the light. In the example of FIG. 4A, the light emission time of the light source is set to ½ of the light emission period of the light source, but the present invention is not limited to this.

  In the next step 64, the modulation phase is set to the phase i (in this case, i = 0, so phase 0), and the set modulation phase is notified to the optical receiver 14. In the present embodiment, the phase 0 modulation is shorter than the light emission period of the light emitter 12 in the signal processing circuit 24 corresponding to each light receiving cell, as shown in FIG. Only during a period of phase difference 0 with respect to the light emission period of the light source in the light emitter 12 (charge accumulation period of phase difference 0 to π with respect to the light emission start timing of the light source). The light receiving signal output from the photodiode 20 is subjected to modulation (modulation 0) for accumulating as a charge in the accumulating unit 26. When the modulation phase is notified that the phase is 0, the control circuit of the light receiver 14 The modulation signals for switching the switches 28 of the individual signal processing circuits 24 to the second state (the state in which the other end of the photodiode 20 is connected to the storage unit 26) are input to the individual switches 28 only during the accumulation period. .

  In step 66, the optical receiver 14 is instructed to reset the storage unit 26 of each signal processing circuit 24. As a result, the control circuit of the light receiver 14 inputs a reset signal to each signal processing circuit 24 and turns on the switch 46 for a certain period of time, so that the charge accumulated in the storage unit 26 of each signal processing circuit 24 is obtained. Are discharged (discarded). In the next step 68, it is determined whether or not the number of charges stored in the storage unit 26 has become equal to or greater than the number of charges stored in advance with respect to the phase i, and step 68 is repeated until the determination is affirmed.

  During this time, the photodiode 20 corresponding to each light receiving cell outputs a light receiving signal at a level corresponding to the amount of received light every time it receives reflected light (see also FIG. 4B), but the individual signal processing circuit 24. Then, since the switch 28 is switched to the second state only during the charge accumulation period shown in FIG. 4C, a signal is inputted to the accumulation unit 26 and charges are accumulated only during the period shown by hatching in FIG. Is done. Further, since the charge is accumulated in the accumulator 26 Ni times, Ni is set to a relatively large value even when the charge accumulation period is shorter than the received light intensity of the reflected light in the light receiver 14. As a result, the charge storage amount of the storage unit 26 is multiplied by Ni, so that the substantial sensitivity of the reflected light amount to the received light intensity can be increased.

  When the accumulation of Ni charges in the accumulating unit 26 is completed, the determination in step 68 is affirmed and the process proceeds to step 70, and the accumulated charge amount from the accumulating unit 26 of each signal processing circuit 24 to the photoreceiver 14. Is instructed to read. As a result, the control circuit of the light receiver 14 inputs the readout signal to each signal processing circuit 24 and turns on the switch 40 for a certain period of time, so that the charge accumulated in the storage unit 26 of each signal processing circuit 24 is obtained. The data is transferred to the amplifier 42 (reading of the accumulated charge amount). The accumulated charge transferred to the amplifier 42 is amplified by the amplifier 42, converted into digital accumulated charge amount data by the A / D converter 44, and output to the control unit 16. In the next step 72, the accumulated charge amount data respectively input from the individual signal processing circuits 24 of the light receiver 14 is stored in the memory or the nonvolatile storage unit as the phase image data of the phase i.

  In step 74, it is determined whether or not the variable i is 3. If the determination is negative, the variable i is incremented by 1 in step 76, and then the process returns to step 64. Steps 64 to 76 are repeated until the determination in step 74 is affirmed. In the present embodiment, four types of phases, phase 0 to phase 3, are set as modulation phases, and steps 64 to 76 are repeated as described above, so that the photodiode 20 in each signal processing circuit 24 is repeated. The light reception signals output from the signal are accumulated as charges in the accumulation unit 26 in different charge accumulation periods corresponding to the phases 1 to 3.

  More specifically, in each signal processing circuit 24, in phase 1 modulation, as shown in FIG. 4D as a charge accumulation period, a period having a phase difference of 1 / 2π with respect to the light emission period of the light source in the light emitter 12 Modulation (modulation 1) for accumulating received light signals as charges in the accumulator 26 is performed only during a period of a phase difference of 1 / 2π to 3 / 2π with respect to the light emission start timing of the light source. As shown in FIG. 4E as a charge accumulation period, the light receiving signal is only in the period of phase difference π with respect to the light emission period of the light source in the light emitter 12 (period of phase difference π to 2π with respect to the light emission start timing of the light source). Is modulated as a charge in the storage unit 26 (modulation 2). In the phase 3 modulation, as shown in FIG. Phase difference of 3 / 2π (light emission start of light source Modulation for storing the charges received light signal in the storage unit 26 only during the period) of the phase difference 3 / 2π~5 / 2π (modulation 3) is performed on the timing. Then, when the phase 0 to phase 3 modulation (charge accumulation) described above is sequentially performed, and accumulated charge amount data corresponding to each phase is stored in the memory or the nonvolatile storage unit as phase image data of each phase, The determination of 74 is affirmed.

Next, the principle of distance detection with respect to an object based on the accumulated charge amount for each phase (phase image for each phase) obtained by the above-described phase 0 to phase 3 modulation (charge accumulation) will be described. On the right side of FIGS. 4C to 4F, when the light receiving cell (photodiode 20) receives reflected light at the timing shown in FIG. The delay time (phase difference) of the light reception timing of the reflected light with respect to the light emission timing of the light source of the light emitter 12 changes according to the distance from the object that reflected the light, The delay time of the reflected light reception timing changes in accordance with the change in the distance from the object that reflects the light, and the amount of accumulated charge in each phase modulation also changes in accordance with the change in the delay time. When the accumulated charge amount in the modulation of each phase of phase 0 to phase 3 is A _{0 to} A ₃ , the phase difference φ of the light reception timing of the reflected light with respect to the light emission timing of the light source of the light emitter 12 is
φ = tan ⁻¹ (A ₃ −A ₁ ) / (A ₀ −A ₂ ) (1)
The distance d from the object reflected by the above equation (1) and the object reflecting the light can be obtained by the following equation (2), where f is the emission frequency of the light source of the light emitter 12 and c is the speed of light.

d = (c / 2f) · (φ / 2π) (2)
However, in the above equation (2), the actual phase difference of the light reception timing of the reflected light with respect to the light emission timing of the light source of the light emitter 12 is in the range of 0 to 2π (reflection with respect to the light emission timing of the light source of the light emitter 12). The delay time of the light reception timing is within the light emission cycle of the light source), and if the above assumption is broken when the distance d to the object exceeds (c / 2f), the distance d is obtained correctly. I can't. In order to avoid this, it is only necessary to set the light emission frequency f of the light source of the light emitter 12 based on the maximum distance from the object to be detected so that the above assumption is not lost. By performing the above calculation for each light receiving cell (accumulation unit 26), it is possible to obtain the distances d to the object that reflects the reflected light incident on each light receiving cell.

  When the light source of the light emitter 12 emits a square wave as shown in FIG. 4A, the phase difference φ is calculated according to the following equation (3) instead of the above equation (1). Thus, the phase difference φ can be obtained more accurately.

When the calculation is performed using the above equations (3) to (5), the calculation of tan ^{−1 in} the equation (1) becomes unnecessary, so that the calculation process can be speeded up.

  Further, as described above, the accumulated charge amount in the modulation of each phase changes in accordance with the change in the distance d to the object, and the phase at which the accumulated charge amount becomes maximum also changes in accordance with the distance d from the object. When phase image data of 0 to phase 3 is displayed as an image by visualizing the charge accumulation amount for each pixel (light receiving cell) represented by the phase image data as luminance for each pixel, each image of phase 0 to phase 3 Is an image (this is referred to as a distance image) in which objects that exist in different distance ranges within the imaging range of the imaging device are displayed as high-luminance objects.

  By the way, in the phase 0 to the phase 3, the distance range of the object to be detected (object in which reflected light is accumulated as electric charges) is different. For example, the distance detection range (maximum distance from the object to be detected) is 10 m. In this case, the distance range of an object in which reflected light is accumulated as electric charges by modulation of each phase is as follows: phase 0 is 0 to 5 m, phase 1 is 2.5 to 7.5 m, phase 2 is 5 to 10 m, phase 3 is 7.5 to 10 m, and 0-2.5m. The intensity of the reflected light received by the light receiver 14 varies greatly depending on the distance from the object that reflects the light. For this reason, in the phase 0 modulation for receiving the reflected light from an object present at a relatively short distance, the received light intensity of the reflected light at the light receiver 14 becomes excessive, and the accumulated charge may be saturated in the accumulation unit 26. On the other hand, in the modulation of the phases 2 and 3 for receiving the reflected light from the object existing at a relatively long distance, the received light intensity of the reflected light from the object existing at a long distance in the light receiver 14 becomes too small. As a result, the amount of charge stored in the storage unit 26 is too small, which may reduce the object detection accuracy.

In consideration of the above, in the object detection device 10 according to the present embodiment, the initial value of the charge accumulation number Ni for each phase is set to the phase where the phase difference from the light emission timing of the light emitter 12 becomes smaller. Is set to be smaller. Accordingly, it is possible to prevent the accumulated charge from being saturated in the accumulation unit 26 in the phase 0 modulation or the accumulated charge amount in the accumulation unit 26 from being excessively small in the phase 2 or phase 3 modulation. When the charge accumulation frequency Ni for each phase is made different, the accumulated charge amount A _{0 to} A ₃ for each phase read out from each accumulation unit 26 is divided by the charge accumulation frequency Ni for each phase ( Ai ← Ai / Ni), the difference between the charge accumulation count Ni for each phase is corrected by multiplying the ratio of the charge accumulation count Ni for each phase by the maximum value Nmax of the charge accumulation count (Ai ← Ai · Nmax / Ni). The phase difference φ is obtained by substituting the corrected stored charge amounts A _{0 to} A ₃ into the equations (1) or (3) to (5), and the obtained phase difference φ is represented by the equation (2). By substituting into, the distance d to the object can be obtained.

Note that setting the initial value of the charge accumulation count N for each phase as described above corresponds to the control means according to the present invention (specifically, the control means described in claim 8 ). Further, instead of changing the charge accumulation frequency N for each phase as described above, the emission intensity of the light emitter 12 decreases as the phase difference from the light emission timing of the light emitter 12 becomes smaller. The light emission intensity of the light emitter 12 at the time of modulating each phase may be made different.

  On the other hand, in the above description, it has been described that the ambient light other than the reflected light is not incident on the light receiver 14. However, for example, when the imaging range (object detection range) of the image sensor of the light receiver 14 is outdoors, the light is reflected on the image sensor. As shown in FIG. 5A, for example, the ambient light is output to the light receiving signal output from the photodiode 20 of each light receiving cell, as shown in FIG. Will be included. When the amount of ambient light received is higher than the amount of reflected light received, as shown in FIG. 5B, most of the charge accumulated in the storage unit 26 corresponds to the ambient light. There is a problem that the detection accuracy by the object detection device 10 (the calculation accuracy of the distance d to the object and the accuracy of the distance image) is significantly reduced by the influence of ambient light.

  For this reason, in the object detection process according to the present embodiment, prior to the acquisition of the phase image in steps 60 to 76 described above, the accumulated charge amount during non-light emission is acquired in steps 50 to 58. That is, first, in step 50, the modulation phase is set to an arbitrary phase, and the set modulation phase is notified to the photoreceiver 14, so that the control circuit of the photoreceiver 14 individually sets only the accumulation period corresponding to the notified modulation phase. The switch 28 of the signal processing circuit 24 is switched to the second state. In step 52, the optical receiver 14 is instructed to reset the storage unit 26 of each signal processing circuit 24, and is stored in the storage unit 26 of each signal processing circuit 24 by the control circuit of the light receiver 14. All charges are discharged (discarded). In step 54, it is determined whether or not the number of charges stored in the storage section 26 is equal to or greater than the number of charges stored Nx when no light is emitted, and step 54 is repeated until the determination is positive.

During this time, since the light emitter 12 is not emitting light, the photodiode 20 corresponding to each light receiving cell receives only ambient light, and as an example, a level corresponding to the amount of received ambient light as shown in FIG. The received light signal is output. In each signal processing circuit 24, the switch 28 is switched to the second state only during the charge accumulation period corresponding to the modulation phase notified from the control unit 16, for example, in the period indicated by hatching in FIG. A signal is input to the storage unit 26, and only a charge corresponding to ambient light is stored. Note that the number Nx of charge accumulation during non-light emission is preferably the same as the number of charge accumulation during phase image acquisition. However, in this embodiment, the number of charge accumulation Ni during phase image acquisition is different for each phase. The accumulated charge amount at the time of non-light emission acquired in steps 50 to 58 is used for correcting the accumulated charge amount A _{0 to} A ₃ for each phase (details will be described later). Can adopt “1” or the greatest common divisor of the number of charge accumulations N _{0 to} N ₃ for each phase.

When the accumulation of Nx times of charges in the storage unit 26 is completed, the determination in step 54 is affirmed and the process proceeds to step 56 to read out the stored charge amount from the storage units 26 of the individual signal processing circuits 24. In step 58, the accumulated charge amount data respectively input from the individual signal processing circuits 24 of the light receiver 14 is stored in the memory or the nonvolatile storage unit as non-light emitting image data. In the object detection process according to the present embodiment, when the determination of step 74 is affirmed when the acquisition of the phase image data of phase 0 to phase 3 is completed, in the next step 78, the above process is obtained. Using the non-light-emitting image data, correction is performed to remove the ambient light component from the accumulated charge amounts A _{0 to} A ₃ (phase images for each phase) read from each storage unit 26 for each phase. To generate a difference image.

  In the correction in step 78, first, the accumulated charge amount Ax for each pixel (each light receiving cell / each accumulating unit 26) represented by the image data at the time of non-emission is calculated from the charge accumulation number Nx at the time of non-emission and the charge of phase i. Correction is made according to the difference in the number of accumulations Ni. When the correction is made by dividing the accumulated charge amount Ai of the phase i by the charge accumulation number Ni of the phase i (Ai ← Ai / Ni), similarly, the accumulated charge amount Ax when no light is emitted. (Ax ← Ax / Nx) may be corrected by dividing the charge accumulation number Nx when no light is emitted, and the charge accumulation number Ni of phase i and the maximum value Nmax of the charge accumulation number with respect to the accumulated charge amount Ai of phase i. When the correction is performed (Ai ← Ai · Nmax / Ni), the ratio of the number Nx of charge accumulation during non-light emission and the maximum value Nmax of the number of charge accumulation is multiplied (Ax ← Ax · Nmax / Nx). Correction may be performed. Then, as shown in the following equation (6), the accumulated charge amount Ax of the corresponding pixel in the non-light-emitting image data subjected to the above correction is calculated from the accumulated charge amount Ai of each pixel represented by the phase image data of phase i. The difference charge amount Ai ′ is calculated by subtracting each.

Ai '← Ai-Ax (6)
Note that an image represented by the differential charge amount Ai ′ calculated by the equation (6) is hereinafter referred to as a differential image. As a result of the above correction, as shown in FIG. 5E, the charge amount corresponding to the ambient light component is subtracted from the accumulated charge amount of phase i, and the charge amount (difference charge amount) for each pixel represented by the difference image data. Ai ′) is data that accurately represents the received light intensity of the reflected light in the corresponding light receiving cell. For example, as shown in FIG. 6, even when there is a region in which accumulated charge is saturated due to direct incidence of sunlight as ambient light in the phase image of phase i, Similarly, since the accumulated charge is saturated in the same region in the image, the accumulated charge in the region is removed from the difference image. In step 78, the above correction is performed for each phase, thereby generating a difference image for each phase.

  Further, as described above, the charge accumulation number Ni for each phase is set in advance so that the charge accumulation number Ni becomes smaller as the phase difference from the light emission timing of the light emitter 12 becomes smaller. Thus, it is possible to prevent the accumulated charge amount in the accumulation unit 26 from becoming excessive (saturated) or excessively small due to the difference in the distance range for each phase of the detection target object. The received light intensity of the reflected light greatly varies depending on the light reflectance of the object that reflects the light emitted from the light emitter 12, so that depending on the light reflectance of the object, saturation of the accumulated charge occurs in the accumulation unit 26, Conversely, the amount of stored charge may be too small.

  For this reason, in the object detection processing according to the present embodiment, in the next step 80 to step 118, the light reflectance of the object to be detected in the phase i is estimated based on the difference image of the phase i, and according to the estimation result. The process of adjusting the number of charge accumulations Ni of phase i in the next phase image acquisition is sequentially performed for each phase. That is, in step 80, the brightness value (accumulated charge amount) in the phase 0 difference image is a high brightness area with a brightness TH1 or more or a brightness area with a threshold TH2 or more (the area is a medium to high brightness area, Hereinafter, for convenience, the brightness area is referred to as “medium brightness area”). In order to prevent erroneous determination due to the influence of noise, it is desirable to add a condition that “the area is equal to or greater than a predetermined value” in the high brightness area / medium brightness area. Further, threshold value TH1 >> threshold value TH2, and as the threshold value TH2, a value corresponding to the minimum brightness with which distance detection is possible can be used. In the next step 82, it is determined whether or not a high brightness area has been found by the search in step 80.

For example, when an object having a high light reflectivity exists within the detection target distance range of phase 0, an accumulation unit is included in an image region corresponding to the object as shown in FIG. 7A as an example. 26, an area where accumulated charge is saturated (accumulated charge saturation area) appears. Since this area does not saturate the accumulated charge on the non-light-emitting image, it remains as a high brightness area on the difference image (see also the difference image shown in FIG. 7A). Therefore, when it is found by the search in step 80 that a high brightness area exists on the difference image, the accumulated charge of the accumulation unit 26 corresponding to the phase 0 charge accumulation (when the phase image 0 is acquired) is stored. It can be determined that there is a high possibility that saturation has occurred, and there is a high possibility that an object having a high light reflectance exists within the detection target distance range of phase 0. For this reason, if the determination in step 82 is affirmative, the process proceeds to step 84, and the process proceeds to step 90 after the value of the number of charge accumulations N _{0 in} phase 0 is reduced. As a result, the amount of stored charge in the storage unit 26 at the time of acquiring the next phase image 0 is suppressed, and it is possible to prevent saturation of the stored charge in some of the storage units 26. The calculation accuracy of d improves. Instead of decreasing the value of the charge accumulation count N ₀ of phase 0, the light emission intensity of the light emitter 12 at the next acquisition of the phase image 0 may be decreased.

  On the other hand, if the determination in step 82 is negative, the process proceeds to step 86, and it is determined whether or not a medium lightness area has been found by the search in step 80. For example, when the light reflectance of an object existing within the detection target distance range of phase 0 is low, the received light intensity of the reflected light from the object becomes low, and as an example, the phase image shown in FIG. As described above, in the storage unit 26 corresponding to the light receiving cell that receives the reflected light from the portion corresponding to the background of the object, the accumulated charge amount in the storage unit 26 corresponding to the light receiving cell that receives the reflected light from the object is The image area corresponding to the object on the difference image after subtracting the charge amount corresponding to the ambient light component, which is almost the same as the accumulated charge amount (in FIG. 7, the accumulated charge amount is replaced with lightness). Becomes unclear and the entire image has low brightness (see also the difference image shown in FIG. 7B). Therefore, if even the middle lightness region is not found on the difference image by the search in step 80, the accumulated charge amount in the accumulation unit 26 corresponding to the phase 0 charge accumulation (when the phase image 0 is acquired) is too small. Therefore, it can be determined that there is a high possibility that an object having a low light reflectance exists within the detection target distance range of phase 0.

Therefore, if the determination in step 86 is negative, the process proceeds to step 88, and after increasing the value of the charge accumulation count N _{0 in} phase 0, the process proceeds to step 90. As a result, the amount of accumulated charge in the accumulation unit 26 at the time of acquiring the next phase image 0 is increased, and reflected light from an object having a low light reflectance can be accumulated as a sufficient amount of accumulated charge. The calculation accuracy of the distance d with respect to the object is improved. Note that instead of increasing the value of the charge accumulation count N ₀ of phase 0, the light emission intensity of the light emitter 12 at the next acquisition of the phase image 0 may be increased.

In the object detection processing according to the present embodiment, processing similar to the processing performed for phase 0 in steps 80 to 88 described above is performed for phase 1 in the next steps 90 to 98, and steps 100 to 100 are performed. Step 108 is performed for phase 2, and steps 110 to 118 are performed for phase 3. As a result, the number of charge accumulations Ni when acquiring the next phase image is optimized for each phase in accordance with the light reflectance of the object existing within the detection target distance range for each phase. Become. The above-described processing is processing corresponding to the control means according to the present invention. More specifically, steps 82, 84, 92, 94, 102, 104, 112, 114 are added to the control means according to claim 1 . Steps 86, 88, 96, 98, 106, 108, 116, 118 correspond to the control means described in claim 2 .

  As described above, when the number of charge accumulations Ni for each phase in the next phase image acquisition is adjusted, in the next step 120, the control unit 16 determines whether the previous (1 ) Or (3) to (5) is used to calculate the phase difference φ, and the distance d to the object is calculated using the above equation (2) for each light receiving cell of the image sensor. Outputs the calculation result to the outside. By referring to the calculation result of the distance d to the object, it is possible to recognize the distance to each object existing in the imaging range by the imaging device of the light receiver 14.

When calculating the distance d to the object, it is desirable to exclude pixels / regions in which accumulated charge is saturated in any of the phase 0 to phase 3 difference images from the calculation target of the distance d (claims). (Equivalent to the invention described in item 6 ), according to the object detection processing according to the present embodiment, even when there is a region where the accumulated charge is saturated on the phase image due to the influence of environmental light, By calculating the difference from the image, the above area is removed from the difference image, and the accumulated charge is saturated in some areas on the difference image because the object to be detected is a highly reflective object. Since the value of the charge accumulation count Ni is adjusted so that the accumulated charge is not saturated when the next phase image is acquired, the pixel / region excluded from the calculation target of the distance d is also next time. In the subsequent object detection process, the distance d is Will be calculated.

In step 122, based on the difference image data of phase 0 to phase 3, the detection target distance corresponding to each phase in which the charge accumulation amount for each pixel represented by each difference image is replaced with the corresponding brightness (density). Distance image data for each range) is generated, the generated distance image data is output to the outside, and the object detection process is terminated. By displaying the image represented by the distance image data on a display or the like, it is possible to visually recognize what object exists for each distance range within the imaging range of the imaging device of the light receiver 14. Can do. Steps 120 and 122 described above correspond to the detection means according to the present invention (specifically, the detection means according to claims 3 and 5 to 7 ) together with steps 50 to 78 described above.

In the above description, the charge amount obtained by removing the charge amount corresponding to the ambient light component by subtracting the accumulated charge amount Ax (non-light-emitting image) when not emitting light from the accumulated charge amount Ai (phase image) for each phase. Although the aspect of obtaining Ai ′ (difference image) has been described, the present invention is not limited to this, and the charge accumulation period does not overlap with phase i from the accumulated charge amount Ai of phase i for each pixel. By subtracting the accumulated charge amount Aj of phase j for each phase (see the following formula: However, if Ai ′ <0 in the following formula, it is replaced with Ai ′ = 0).
A ₀ '← A ₀ -A ₂ A ₁ ' ← A ₁ -A ₃ A ₂ '← A ₂ -A ₀ A ₃ ' ← A ₃ -A ₁
A charge amount Ai ′ (difference image) from which the charge amount corresponding to the ambient light component is removed may be obtained (see also FIG. 8).

For example, when the distance detection range (maximum distance from the object to be detected) is 10 m and objects exist at distances of 1 m and 7 m as shown in FIG. 8, phase image 2 is subtracted from phase image 0. When the calculation is performed, since the distance range of the detection target object is 0 to 5 m for phase 0 and 5 to 10 m for phase 2, an object existing at a distance of 1 m appears brightly on the phase image 0 (7 m Since the object existing at the distance appears brightly on the phase image 2), even if the calculation of subtracting the phase image 2 from the phase image 0 is performed, the object existing at the distance of 1 m remains on the difference image 0. On the other hand, a region where accumulated charge is saturated due to direct incidence of sunlight is removed, and it is possible to avoid a decrease in the accuracy of object detection due to the influence of ambient light. In the above processing, it is not necessary to obtain the accumulated charge amount Ax when no light is emitted, so that the processing speed can be improved (the object detection cycle can be shortened). The above aspect corresponds to the invention described in claim 4 .

  In the above description, the mode in which the value of the number of charge accumulations Ni at the phase i is reduced when the brightness (accumulated charge amount) is higher than the threshold TH1 in the difference image at the phase i has been described. The present invention is not limited to this, and the brightness on the phase image of phase i is equal to or higher than the threshold TH1, and the brightness on the difference image of phase i with respect to the brightness on the phase image of phase i is A region where the amount of decrease is equal to or less than the threshold TH3 is searched, and when the corresponding region exists, the value of the charge accumulation count Ni of phase i is decreased (or the light emitting device 12 at the time of acquiring the phase image of phase i). (The emission intensity may be reduced). Accordingly, it is possible to more accurately detect whether or not an object having a high light reflectance exists within the detection target distance range of the phase i. When the object exists, the distance d to the object is determined. The calculation accuracy can be further improved.

  In addition, in the above, when the high brightness area having the threshold value TH1 or more exists in the difference image of the phase i or even the middle brightness area having the threshold value TH2 or more does not exist, the object to be detected is the high reflectance object. Alternatively, the aspect of changing the charge accumulation number Ni of the phase i by determining that the object is a low reflectivity object has been described, but the present invention is not limited to this, and the brightness difference between the phase image i and the non-light emitting image is calculated. Compared to each pixel, if the area where accumulated charge is saturated on the phase image i (desirably greater than a certain area) is not detected when the accumulated charge is not saturated on the non-light-emitting image When the target object is determined to be a high-reflectance object, the value of the charge accumulation number Ni of the phase i is reduced, and there is no region having a brightness difference between the phase image i and the non-light-emitting image, Number of charge accumulations of phase i when the object to be detected is judged as a low reflectance object It may be the value of i is increased. This aspect has an advantage that it is not necessary to perform an operation such as adjusting the magnitudes of the thresholds TH1 and TH2 so that the determination is appropriately performed.

  Moreover, although the aspect provided with the image pick-up element by which two or more light-receiving cells corresponded to the light-receiving means based on this invention was provided in the above was demonstrated, this invention is not limited to this, The present invention can also be applied to a distance detecting device that includes a single light receiving means and detects a distance from an object that reflects light received by the light receiving means.

  Furthermore, the light emission pattern of the light emitter 12 is not limited to a square wave light emission pattern as shown in FIG. 4A, and may be any light emission pattern having various waveforms such as a sine wave shape, a triangular wave shape, and a sawtooth wave shape. There may be. Further, the light emission pattern of the light emitter 12 is not limited to the constant phase of the light emission period within each cycle as shown in FIG. 4A, and the phase of the light emission period within each cycle is varied. Also good. Further, the light emission pattern of the light emitter 12 is not limited to a constant period as shown in FIG. 4A. For example, the length of the light emission period is constant and the length of the non-light emission period is varied. The period of the light emission pattern may be changed by changing the length of the light emission period or changing the length of the light emission period and the non-light emission period.

It is a block diagram which shows schematic structure of the object detection apparatus which concerns on this embodiment. It is a circuit diagram of the signal processing part connected to each light reception cell of a light receiver. It is a flowchart which shows the content of an object detection process. It is a timing chart which shows accumulation | storage of the electric charge in each phase, and the electric charge amount accumulate | stored in an accumulation | storage part. It is explanatory drawing for demonstrating removal of the environmental light component based on the amount of stored charges at the time of light emitter non-light emission. It is an image figure for demonstrating removal of the environmental light component based on the amount of stored charges at the time of light emitter non-light emission. It is an image figure for demonstrating the case where a high brightness area | region arises on a difference image, and the case where a medium brightness area | region does not arise, respectively. It is an image figure for demonstrating the other method of environmental light component removal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Object detection apparatus 12 Light emitter 14 Light receiver 16 Control part 20 Photodiode 24 Signal processing circuit 26 Accumulation part

Claims (8)

A light emitting means for emitting light while changing the light emission intensity over time;
A plurality of light receiving means arranged in a two-dimensional manner along a direction intersecting the light incident direction and outputting a light reception signal corresponding to the amount of light received;
A plurality of charge storage means provided corresponding to each of the plurality of light receiving means ;
The light receiving signal output from the light receiving means is accumulated a predetermined number of times as charges in the charge accumulating means during an accumulation period shorter than the light emission period of the light emitting means and with a constant phase with respect to the light emission timing of the light emitting means. Detection means for performing each of a plurality of types of accumulation periods having different phases, and performing at least one of object detection and information output for object detection based on a stored charge amount for each of the plurality of types of phases in the charge storage means When,
At least one of the light emission intensity and the number of times of charge accumulation of the light emitting means when charge is accumulated in the plurality of charge accumulation means during the accumulation periods having different phases, and at a specific phase in the plurality of charge accumulation means. In the image represented by the accumulated charge amount or the corrected image represented by the accumulated charge amount after the correction in the specific phase, when there is a region having a brightness greater than or equal to the first predetermined value, Control means for reducing at least one of the light emission intensity of the light emitting means and the number of times of charge accumulation when accumulating charges in the charge accumulating means during an accumulation period of a specific phase ;
An object detection apparatus including: A light emitting means for emitting light while changing the light emission intensity over time;
A plurality of light receiving means arranged in a two-dimensional manner along a direction intersecting the light incident direction and outputting a light reception signal corresponding to the amount of light received;
A plurality of charge storage means provided corresponding to each of the plurality of light receiving means;
The light receiving signal output from the light receiving means is accumulated a predetermined number of times as charges in the charge accumulating means during an accumulation period shorter than the light emission period of the light emitting means and with a constant phase with respect to the light emission timing of the light emitting means. Detection means for performing each of a plurality of types of accumulation periods having different phases, and performing at least one of object detection and information output for object detection based on a stored charge amount for each of the plurality of types of phases in the charge storage means When,
At least one of the light emission intensity and the number of times of charge accumulation of the light emitting means when accumulating charges in the charge accumulating means during the accumulation periods having different phases is made different, and accumulation at a specific phase in the plurality of charge accumulating means In a case where there is no region of lightness equal to or greater than a second predetermined value in the image represented by the charge amount or the corrected image represented by the accumulated charge amount after the correction in the specific phase, the specific phase Control means for increasing at least one of the light emission intensity of the light emitting means and the number of times of charge accumulation when accumulating charges in the charge accumulating means during the accumulation period;
An object detection apparatus including: The detecting means accumulates the light receiving signal output from the light receiving means in a state where the light emitting means stops emitting light in the charge accumulating means during the accumulation period of an arbitrary phase, and the plurality of types of phases. The accumulated charge amount for each of the plurality of phases is corrected by subtracting the accumulated charge amount in a state where the light emitting unit stops light emission from the accumulated charge amount for each of the plurality of phases. 3. The object detection apparatus according to claim 1, wherein at least one of the object detection and the output of information for object detection is performed based on a stored charge amount . The detection means subtracts the accumulated charge amount in the second phase that does not overlap with the accumulation period in the first phase from the accumulated charge amount in the first phase, thereby subtracting the accumulated charge amount in the first phase. Is corrected for each of the accumulated charge amounts for each phase, and based on the corrected accumulated charge amounts for each of the plurality of phases, the object detection and the output of information for object detection are performed. The object detection apparatus according to claim 1, wherein at least one of them is performed . The detection means reflects the light emitted from the light emitting means as the object detection based on the accumulated charge amount for each of the plurality of phases or the corrected accumulated charge amount for each of the plurality of phases. The object detection apparatus according to any one of claims 1 to 4, wherein a distance between the detection object and the object is detected. A plurality of the light receiving means are provided, each of the light receiving means is two-dimensionally arranged along a direction intersecting the light incident direction, and a plurality of the charge storage means are provided corresponding to each of the light receiving means. And
The detection means calculates the distance to the object for each individual light receiving means, and among the individual light receiving means, the accumulated charge amount in the corresponding charge accumulation means or the corrected accumulated charge amount is the accumulated charge amount. 6. The object detection apparatus according to claim 5, wherein the light receiving means showing a value corresponding to saturation is excluded from the calculation target of the distance to the object. A plurality of the light receiving means are provided, each of the light receiving means is two-dimensionally arranged along a direction intersecting the light incident direction, and a plurality of the charge storage means are provided corresponding to each of the light receiving means. And
The detection means uses, as information for detecting the object, the accumulated charge amount for each of the plurality of phases in the plurality of charge accumulation means or the accumulated charge amount after the correction for each of the plurality of phases for each phase. 5. The object detection device according to claim 1, wherein the object detection device outputs an image having a different distance range . The control means reduces at least one of the light emission intensity of the light emitting means and the number of charge accumulations as the phase of the accumulation period for accumulating the charge becomes a phase with a smaller phase difference from the light emission timing of the light emitting means. The object detection device according to claim 1, wherein the object detection device is a device.