JP5190721B2 - Distance image generator - Google Patents

Description

  The present invention relates to a distance image generation device, and more particularly to a distance image generation device capable of generating a distance image with higher accuracy.

  2. Description of the Related Art Conventionally, an apparatus that generates a so-called distance image using a distance image sensor (there is a CCD type or a CMOS type) is known (for example, Patent Document 1).

  The distance image generation device described in Patent Document 1 emits light whose intensity is modulated at a predetermined light emission frequency into a space, receives a reflected light of light emitted from the light source, and receives a signal level corresponding to the received light intensity. And an image sensor as a distance image sensor including a plurality of photoelectric conversion units that output the received light signal. In the distance image generating device described in Patent Document 1, reflected light is received and converted into electric charges within a modulation period, and a predetermined calculation is performed based on the converted electric charges. A phase difference is calculated and a distance image is generated.

JP 2004-32682 A

  However, in the distance image generation device described in Patent Document 1, since the light amount of the light emission source is constant, there is a possibility of greatly affecting the accuracy of the distance image.

  For example, when the modulated light source is too dark, the ratio of the modulated light from the modulated light source becomes extremely smaller than the background light other than the modulated light source, so that the SN ratio is lowered and the measurement distance error is increased. On the other hand, if the modulated light source is too bright, the charge accumulated in the image sensor is saturated and distance measurement cannot be performed.

  In addition, since light attenuates in inverse proportion to the square of the distance from the light source, the light quantity of the modulated light source is constant when the distance to the object is relatively close, such as indoors, and the measurement distance range is limited. Even so, the measurement results are unlikely to fluctuate greatly. However, when measuring the distance in the outdoors, for example, in front of the vehicle, the objects are roads, landscapes, pedestrians, preceding vehicles, oncoming vehicles, and the like, and their distances change from several meters to infinity. Therefore, it is considered that the optimum light amount of the modulated light source is different between the object at a short distance and the object at a long distance, so it is desirable that the light amount of the modulated light source is dynamically changed.

  Furthermore, even when measuring the distance of an object existing at the same distance, the intensity of the reflected light varies depending on the reflectance of the object, so it is desirable to change the light amount of the modulated light source.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a distance image generation apparatus capable of generating a distance image with higher accuracy by changing the light amount of a light emitting source. To do.

  In order to solve the above problems, the present invention provides a light source that emits modulated light that is modulated onto a target space, and a reflection that is irradiated from the light source and reflected by an object in the target space. A plurality of photoelectric conversion elements that receive light and convert it into charges, a plurality of charge storage units provided for each of the photoelectric conversion elements, and converted by the photoelectric conversion elements in synchronization with modulation of the light emission source An image sensor comprising: means for distributing charges to the plurality of charge storage units; and performing a predetermined calculation based on the charges stored in the plurality of charge storage units to generate a distance image in which pixel values are distance values A distance image generating unit, a light amount adjusting unit that adjusts the amount of modulated light of the light source, and an object in the target space that is irradiated from the light source based on charges accumulated in the plurality of charge storage units Of reflected light component reflected by Calculating means, and a counting means for counting the number of the photoelectric conversion elements for which the amplitude value of the reflected light component outside the range predetermined by the calculating means is calculated, the light amount adjusting means, When the number of photoelectric conversion elements counted by the counting means exceeds a certain number, adjustment is made so as to reduce the amount of modulated light of the light emitting source.

  According to the first aspect of the present invention, the light amount of the modulated light from the light source can be adjusted (increased or decreased) by the light amount adjusting means. By adjusting the amount of modulated light from the light source, the amount of reflected modulated light can be optimally maintained even when the distance of the object changes or when objects with various reflectivities are targeted. Thus, it is possible to improve the distance detection accuracy and generate a more accurate distance image. In addition, since the amount of modulated light from the light source is not always constant, it is possible to suppress unnecessary light emission power (particularly when the amount of light is adjusted to decrease).

  According to the first aspect of the present invention, the amount of modulated light from the light source is adjusted based on the number of photoelectric conversion elements counted by the counting means. For example, if the number of photoelectric conversion elements for which the amplitude value of the reflected light component exceeding a predetermined range is calculated exceeds a certain number, it is determined that the amount of modulated light from the light source is too bright and the modulated light from the light source Adjust to reduce the amount of light. Also by this, the amount of reflected modulated light can be kept optimal, so that it is possible to improve distance detection accuracy and generate a more accurate distance image.

  The invention according to claim 2 further includes an extraction means for extracting an object other than a background from the distance image generated by the distance image generation unit according to the invention according to claim 1, wherein the counting means The counting process is performed on the photoelectric conversion element corresponding to the object extracted by the extraction unit.

  According to the second aspect of the present invention, based on the number of photoelectric conversion elements obtained by extracting only the objects other than the background and counting the photoelectric conversion elements corresponding to the extracted objects, Adjust the amount of modulated light. As a result, the amount of modulated light of the light source that is optimal for the object can be maintained, so that it is possible to improve distance detection accuracy and generate a more accurate distance image.

  The invention described in claim 3 is the invention described in claim 1, further comprising an extracting means for extracting an object within a predetermined distance range from the distance image generated by the distance image generating unit. The counting means performs the counting process on the photoelectric conversion element corresponding to the object extracted by the extraction means.

  According to the third aspect of the present invention, based on the number of photoelectric conversion elements obtained by extracting only the objects within the distance range to be detected and counting the photoelectric conversion elements corresponding to the extracted objects. The amount of modulated light from the light source is adjusted. As a result, the amount of modulated light of the light source that is optimal for the object can be maintained, so that it is possible to improve distance detection accuracy and generate a more accurate distance image.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the light amount adjusting means changes a light amount of the modulated light of the light source every frame time.

  According to the fourth aspect of the present invention, since the amount of modulated light of the light source is changed every frame time, an object in a wide distance range, an object in a plurality of distance ranges, and a plurality of objects having different reflectances Can be detected with high accuracy. Moreover, it becomes possible to measure the distance of a several target object with sufficient precision. Thereby, it is possible to improve the distance detection accuracy and to generate a distance image with higher accuracy.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the light emission source includes a plurality of light emitters that irradiate modulated light onto a target space, and the plurality of light emitters includes a plurality of light emitters. The plurality of photoelectric conversion elements are divided into a plurality of photoelectric conversion element areas corresponding to the plurality of areas, and the light amount adjusting means is divided into the divided photoelectric conversion element areas. Each time, the amount of modulated light of the illuminant that irradiates an area corresponding to the divided photoelectric conversion element area is adjusted based on the number of the photoelectric conversion elements counted by the counting means. .

  According to the fifth aspect of the present invention, the amount of modulated light of the light source can be optimally adjusted for each photoelectric conversion element area (image region), so that it is possible to improve the distance detection accuracy and improve the accuracy of the distance image. Generation is possible. In addition, since the amount of modulated light from the light source is not always constant, it is possible to suppress unnecessary light emission power (particularly when the amount of light is adjusted to decrease).

  According to the fifth aspect of the present invention, the amount of modulated light of the light source is adjusted for each divided photoelectric conversion element area based on the number of photoelectric conversion elements counted by the counting means. For example, in a certain divided photoelectric conversion element area, if the number of photoelectric conversion elements for which the amplitude value of the reflected light component exceeding a predetermined range is calculated exceeds a certain number, the amount of modulated light from the light source is bright. Therefore, it is determined that the amount of modulated light of the light emitter in the irradiation area corresponding to the photoelectric conversion element area is lowered. This also makes it possible to optimally adjust the amount of modulated light from the light source for each photoelectric conversion element area (image region), thereby improving the distance detection accuracy and generating a more accurate distance image.

  The invention described in claim 6 further comprises an extracting means for extracting an object other than a background from the distance image generated by the distance image generating section in the invention according to claim 5, wherein the counting means The counting process is performed on the photoelectric conversion element corresponding to the object extracted by the extraction unit.

  According to the sixth aspect of the present invention, based on the number of photoelectric conversion elements obtained by extracting only the objects other than the background and counting the photoelectric conversion elements corresponding to the extracted objects, Adjust the amount of modulated light. As a result, the amount of modulated light of the light source that is optimal for the object can be maintained, so that it is possible to improve distance detection accuracy and generate a more accurate distance image.

  The invention according to claim 7 is the invention according to claim 5, further comprising an extraction means for extracting an object within a predetermined distance range from the distance image generated by the distance image generation unit. The counting means performs the counting process on the photoelectric conversion element corresponding to the object extracted by the extraction means.

  According to the invention described in claim 7, based on the number of photoelectric conversion elements obtained by extracting only objects within a distance range to be detected and counting the photoelectric conversion elements corresponding to the extracted objects. The amount of modulated light from the light source is adjusted. As a result, the amount of modulated light of the light source that is optimal for the object can be maintained, so that it is possible to improve distance detection accuracy and generate a more accurate distance image.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the distance image generation apparatus which can produce | generate a distance image with higher precision by changing the light quantity of the modulated light of a light emission source.

1 is a block diagram of a distance image generation apparatus that is a first embodiment of the present invention. FIG. It is a figure for demonstrating the principle which produces | generates a distance image. It is a figure showing the relationship between modulated light and incident light which may occur when there is almost no disturbing light, the object is far away, or the reflectance of the object is extremely small. It is a flowchart for demonstrating the operation example 1 of the distance image generation apparatus which is 1st embodiment of this invention. It is a figure showing the relationship between modulated light and incident light which can occur when there is much disturbance light and the reflectance of a target object is high. It is a flowchart for demonstrating the operation example 2 of the distance image generation apparatus which is 1st embodiment of this invention. It is a figure showing the relationship between modulated light and incident light which may occur when disturbance light is relatively large, the object is far away, or the reflectance of the object is extremely small. It is a flowchart for demonstrating the operation example 4 of the distance image generation apparatus which is 1st embodiment of this invention. It is a flowchart for demonstrating the operation example 5 of the distance image generation apparatus which is 1st embodiment of this invention. It is a flowchart for demonstrating the operation example 5 of the distance image generation apparatus which is 1st embodiment of this invention. It is a flowchart for demonstrating the operation example 6 of the distance image generation apparatus which is 1st embodiment of this invention. It is a flowchart for demonstrating the operation example 6 of the distance image generation apparatus which is 1st embodiment of this invention. It is a flowchart for demonstrating the operation example 7 of the distance image generation apparatus which is 1st embodiment of this invention. It is a front view of the light source of the distance image generation apparatus which is 2nd embodiment of this invention. It is the example of an image imaged by the distance image generation device of the second embodiment mounted in front of the automobile.

[First embodiment]
Hereinafter, a distance image generating apparatus according to a first embodiment of the present invention will be described with reference to the drawings.

[Configuration of Distance Image Generation Device]
First, the configuration of the distance image generation apparatus according to the first embodiment will be described.

  FIG. 1 is a block diagram of a distance image generation apparatus according to the first embodiment. As shown in FIG. 1, the distance image generation device 1 includes an optical time-of-flight distance image sensor 10 (hereinafter referred to as a distance image sensor 10). The distance image sensor 10 includes a light source 11, an image sensor 15, a control unit 16, a distance image generation unit 17, and the like.

  The light source 11 is a light emitting source that irradiates light modulated in a target space (for example, infrared light or visible light modulated at high speed with a sine wave or a rectangular wave). Used.

  The imaging element 15 receives a plurality of photoelectric conversion elements (also referred to as pixels) that receive incident light 14 including reflected light that is irradiated from the light source 11 and reflected by an object in the target space, and converts the incident light 14 into charges. Provided with a plurality of charge storage units, and means for distributing the charges converted by the photoelectric conversion elements to the plurality of charge storage units in synchronization with the modulation of the light source 11 (all not shown). .

  The control unit 16 is for controlling the light source 11 and the image pickup device 15 in synchronization. The image pickup device 15 rapidly transfers charges converted by the photoelectric conversion elements to a plurality of charge storage units according to the synchronization signal of the control unit 16. Sort out.

  The distance image generation unit 17 performs a predetermined calculation based on the distributed charges, calculates a phase difference with the light emission source, and generates a distance image whose pixel value is a distance value.

[Principle for generating range images]
Next, the principle of generating a distance image will be described.

  FIG. 2 is a diagram for explaining the principle of generating a distance image. In FIG. 2, the sine wave 21 represents the modulated light of the light source 11, and the sine wave 22 represents the incident light of the image sensor 15. The phase difference φ between the sine wave 21 and the sine wave 22 represents a delay caused by the time of flight to the object of light.

  In FIG. 2, one cycle of modulation of the light source 11 is divided into four periods, and the charges are distributed to the four charge storage units. If each period is T1, T2, T3, and T4, and the amount of charge accumulated in each period is C1, C2, C3, and C4, the phase difference φ is expressed by the following equation.

  Since the speed of light is known, the distance to the object can be obtained by obtaining this phase difference φ, and a distance image whose pixel value is a distance value can be generated.

  The charge amount average A used as general image data is expressed by the following equation.

  The amplitude amount B of the modulated light component reflected by the object is expressed by the following equation.

  In general, the modulation frequency of the light source is several tens of MHz, and therefore one period of modulation is about several tens of ns. Therefore, in order to obtain a distance image, a charge accumulation time of several hundred to several hundred thousand cycles is required.

[Operation of Distance Image Generation Device]
Next, the operation of the distance image generating apparatus 1 having the above configuration will be described with reference to the drawings.

[Operation Example 1 of Distance Image Generating Device]
FIG. 3 shows the relationship between the modulated light and the incident light that can occur when there is almost no disturbing light, the object is far away, or the reflectance of the object is extremely small.

  In FIG. 3, since the amount of incident light 32 is very small with respect to the modulated light 31 emitted from the light source 11, the charge accumulated in the image pickup device 15 is also reduced. As the accumulated charge decreases, the influence of photon shot noise and the like increases, and the calculation error of the phase difference φ increases.

  In order to prevent or reduce the calculation error of the phase difference φ due to the small amount of incident light, the distance image generating device 1 operates as shown in FIG. 4 under the situation shown in FIG.

  FIG. 4 is a flowchart for explaining an operation example 1 of the distance image generating apparatus 1. The following processing is mainly performed by the control unit 16 or a control unit (not shown) provided separately from the control unit 16.

  First, the light source 11 irradiates the target space with modulated light according to the synchronization signal of the control unit 16 (step S10). The image sensor 15 receives incident light including reflected light irradiated from the light source 11 and reflected by an object in the target space, converts the incident light into charges by the photoelectric conversion element, and converts the incident light according to the synchronization signal of the control unit 16. The charged charges are distributed to a plurality of charge storage units (step S11). The distance image generation unit 17 performs a predetermined calculation (calculation of the above formula 1) based on the distributed charges, calculates a phase difference φ with the light emission source, and generates a distance image whose pixel value is a distance value. .

  Next, the control unit 16 counts the number of photoelectric conversion elements in which charges equal to or less than a specified value (predetermined value, threshold) are stored in at least one charge storage unit (step S12) (in the present invention). Equivalent to counting means). When the counted number of photoelectric conversion elements exceeds a certain number (step S13: Yes), the control unit 16 determines that the light amount of the light source 11 is dark and performs control to increase the light amount of the light source 11 (step S14). ). Thereafter, the processing from step S10 to step S14 is repeated.

  As described above, in this operation example 1, when the number of photoelectric conversion elements counted in step S12 exceeds a certain number (step S13: Yes), it is determined that the light amount of the light source 11 is dark, and the light amount of the light source 11 (Step S14). Thereby, since the light quantity of incident light (reflected modulated light) can be kept optimal, it is possible to prevent or reduce the calculation error of the phase difference φ due to the small quantity of incident light. Thereby, it is possible to improve the distance detection accuracy and to generate a distance image with higher accuracy.

[Operation Example 2 of Distance Image Generating Device]
FIG. 5 shows the relationship between the modulated light and the incident light that can occur when there is a lot of disturbance light and the reflectance of the object is high.

  In FIG. 5, a sine wave 41 represents modulated light emitted from the light source 11, and a sine wave 42 represents incident light. Here, a straight line 43 represents the amount of light that saturates the charge accumulated in the image sensor 15. In a period in which the sine wave 42 exceeds the straight line 43, the charge accumulated in the image sensor 15 is saturated and does not increase any more, resulting in an error when the phase difference φ is calculated.

  In order to prevent or reduce the calculation error of the phase difference φ due to the saturation of the charge accumulated in the image sensor with a large amount of incident light, the distance image generating device 1 is shown in FIG. The operation is as shown in FIG.

  FIG. 6 is a flowchart for explaining an operation example 2 of the distance image generating apparatus 1. The following processing is mainly performed by the control unit 16 or a control unit (not shown) provided separately from the control unit 16.

  First, the light source 11 irradiates the target space with modulated light according to the synchronization signal of the control unit 16 (step S20). The image sensor 15 receives incident light including reflected light irradiated from the light source 11 and reflected by an object in the target space, converts the incident light into charges by the photoelectric conversion element, and converts the incident light according to the synchronization signal of the control unit 16. The charged charges are distributed to a plurality of charge storage units (step S21). The distance image generation unit 17 performs a predetermined calculation (calculation of the above formula 1) based on the distributed charges, calculates a phase difference φ with the light emission source, and generates a distance image whose pixel value is a distance value. .

  Next, the control unit 16 counts the number of photoelectric conversion elements in which charges equal to or greater than a predetermined value (predetermined value, threshold) are stored in at least one charge storage unit (step S22) (in the present invention). Equivalent to counting means). Alternatively, a predetermined range (predetermined value, threshold) is provided for the amplitude amount B of the modulated light component reflected by the object, and the control unit 16 calculates the amplitude value B of the reflected light component that is equal to or greater than the specified range. The number of photoelectric conversion elements is counted (step S22). When the counted number of photoelectric conversion elements exceeds a certain number (step S23: Yes), the control unit 16 determines that the light amount of the light source 11 is too bright and performs control to decrease the light amount of the light source 11 (step S23). S24). Thereafter, the processing from step S10 to step S14 is repeated.

  As described above, in this operation example 2, when the number of photoelectric conversion elements counted in step S22 exceeds a certain number (step S23: Yes), the light amount of the light source 11 is determined to be too bright. The amount of light is decreased (step S24). As a result, the amount of incident light (reflected modulated light) can be kept optimal, so that the calculation error of the phase difference φ caused by the amount of incident light being large and the charge accumulated in the image sensor 15 being saturated. It is possible to prevent or reduce (that is, improve the distance detection accuracy). Thereby, it is possible to improve the distance detection accuracy and to generate a distance image with higher accuracy.

[Operation Example 3 of Distance Image Generating Device]
FIG. 7 shows the relationship between the modulated light and the incident light that can occur when the amount of disturbance light is relatively large and the object is far away, or the reflectance of the object is extremely small. In FIG. 7, a sine wave 51 represents modulated light emitted from a light source, and a sine wave 52 represents incident light. Since the amount of incident light 52 is sufficient, but the modulated light component reflected by the object is very small, the values of (C1-C3) and (C2-C4) are small when the phase difference φ is obtained by the above equation 1. Become. Therefore, if only a little noise is applied to C1, C2, C3, and C4, the value of the phase difference φ may greatly vary.

  In order to prevent or reduce fluctuations in the value of the phase difference φ due to the fact that the amount of incident light 52 is sufficient, but the modulated light component reflected by the object is very small, the operation is performed under the situation shown in FIG. As in Example 2, the distance image generating apparatus 1 operates as shown in FIG.

  That is, in this operation example 3, when the number of photoelectric conversion elements counted in step S22 exceeds a certain number (step S23: Yes), it is determined that the light amount of the light source 11 is too bright and the light amount of the light source 11 is decreased. (Step S24). As a result, although the amount of incident light 52 is sufficient, it is possible to prevent or reduce the variation in the value of the phase difference φ due to the very small amount of modulated light component reflected by the object (that is, improve the distance detection accuracy). Become. Thereby, it is possible to improve the distance detection accuracy and to generate a distance image with higher accuracy.

[Operation Example 4 of Distance Image Generating Device]
When the object being imaged is constant, the light amount of the light source 11 and the amplitude amount B obtained by the above equation 3 are theoretically proportional. Therefore, the average value or standard deviation of the amplitude amount B of all the photoelectric conversion elements may be calculated, and the light amount of the light source 11 may be increased or decreased so that the value falls within the specified range. In this case, the distance image generating apparatus 1 operates as shown in FIG.

  FIG. 8 is a flowchart for explaining an operation example 4 of the distance image generating apparatus 1. The following processing is mainly performed by the control unit 16 or a control unit (not shown) provided separately from the control unit 16.

  First, the light source 11 irradiates the target space with modulated light according to the synchronization signal of the control unit 16 (step S30). The image sensor 15 receives incident light including reflected light irradiated from the light source 11 and reflected by an object in the target space, converts the incident light into charges by the photoelectric conversion element, and converts the incident light according to the synchronization signal of the control unit 16. The charged charges are distributed to a plurality of charge storage units (step S31). The distance image generation unit 17 performs a predetermined calculation (calculation of the above formula 1) based on the distributed charges, calculates a phase difference φ with the light emission source, and generates a distance image whose pixel value is a distance value. .

  Next, the control unit 16 calculates the average value or standard deviation of the amplitude amounts B of all the photoelectric conversion elements (step S32). The control unit 16 increases or decreases the light amount of the light source 11 so that the value falls within a specified range (within a predetermined range) (step S33: No, step S34). Thereafter, the processing from step S30 to step S34 is repeated.

  As described above, in the fourth operation example, the amplitude amount B that affects the accuracy of the distance image can maximize the number of photoelectric conversion elements (also referred to as the number of pixels) in an appropriate range for obtaining the distance image. Thus, it is possible to obtain a distance image with higher accuracy.

[Operation Example 5 of Distance Image Generating Device]
When the distance image generating device 1 is used in a room or the like, the background brightness and distance are often fixed. In detecting the object other than the background in such a situation, it is possible to improve the accuracy of the distance image of the object by extracting only the object other than the background.

  For example, if the reflectance of an object other than the background is very large compared to the reflectance of the background, or if the object is very close to the background, the light amount of the light source 11 when obtaining the background distance image remains as follows: There is a possibility that the reflected light from the object other than the background is large, the charge accumulated in the image pickup device 15 is saturated, and a distance image with high accuracy cannot be obtained. Conversely, when the reflectance of the object other than the background is very small compared to the reflectance of the background, there is a possibility that a highly accurate distance image cannot be obtained.

  Therefore, an object other than the background is extracted from the distance image generated by the distance image generation unit 17, and the photoelectric conversion elements (also referred to as pixels) corresponding to the extracted object are illustrated in FIGS. By performing the same processing and controlling the light quantity of the light source 11, the distance accuracy of the object can be increased. In this case, the distance image generating apparatus 1 operates as shown in FIGS.

  9 and 10 are flowcharts for explaining an operation example 5 of the distance image generating apparatus. The following processing is mainly performed by the control unit 16 or a control unit (not shown) provided separately from the control unit 16.

  First, the light source 11 irradiates the modulated light into the target space according to the synchronization signal of the control unit 16 (step S40). The image sensor 15 receives incident light including reflected light irradiated from the light source 11 and reflected by an object in the target space, converts the incident light into charges by the photoelectric conversion element, and converts the incident light according to the synchronization signal of the control unit 16. The charged charges are distributed to a plurality of charge storage units (step S41). The distance image generation unit 17 performs a predetermined calculation (calculation of the above formula 1) based on the distributed charges, calculates a phase difference φ with the light emission source, and generates a distance image whose pixel value is a distance value. (Step S42).

  Next, the control unit 16 extracts objects other than the background from the distance image generated in step S42 (step S43). As a method for extracting an object other than the background, a background distance image is stored in a memory and sequentially compared with the distance image. And the pixel which calculated the distance value different from a background is considered as a target object. At this time, it is possible to prevent erroneous detection by eliminating an abnormally small or large object.

  Next, the control unit 16 has a predetermined value (predetermined value, threshold) or less in at least one charge storage unit among the photoelectric conversion elements (also referred to as pixels) corresponding to the object extracted in step S43. The number of photoelectric conversion elements in which the charges are accumulated is counted (step S44). When the counted number of photoelectric conversion elements exceeds a certain number (step S45: Yes), the control unit 16 determines that the light amount of the light source 11 is dark and performs control to increase the light amount of the light source 11 (step S46). ). Thereafter, the processing from step S40 to step S46 is repeated.

  Alternatively, as illustrated in FIG. 10, the control unit 16 sets a predetermined value (predetermined in advance) in at least one charge storage unit among the photoelectric conversion elements (also referred to as pixels) corresponding to the target object extracted in step S43. Value.threshold.) The number of photoelectric conversion elements in which the above charges are accumulated is counted (step S47). When the counted number of photoelectric conversion elements exceeds a certain number (step S48: Yes), the control unit 16 determines that the light amount of the light source 11 is too bright and performs control to reduce the light amount of the light source 11 (step S48). S49). Thereafter, the processing from step S40 to step S49 is repeated.

  As described above, in this operation example 5, only the objects other than the background are extracted (step S43), and the counting process is performed on the photoelectric conversion elements corresponding to the extracted objects (steps S44 and S47). Based on the number of the photoelectric conversion elements, the light amount of the light emitting source is adjusted (step S45: Yes, step S46, step S48: Yes, step S49). Thereby, since the light quantity of the light source 11 that is optimal for the object can be maintained, it is possible to improve distance detection accuracy and to generate a distance image with higher accuracy.

[Operation Example 6 of Distance Image Generating Device]
When using the distance image generating device 1 outdoors, or when using the distance image generating device attached to a moving body such as an automobile, the distance to be detected when used in a situation where the distance of the object changes greatly. By setting the range, it is possible to increase the distance detection accuracy of an object within the range.

  For example, when the vehicle is mounted in front of an automobile and monitoring a front obstacle when traveling, when there is no obstacle at a short distance, the light amount of the light source 11 can be increased to accurately measure a distance to a far object. To. However, when an object is present at a short distance, the amount of light reflected from the object increases, which may affect detection accuracy.

  Therefore, an arbitrary distance range is determined, and an object within the distance range is extracted from the distance image generated by the distance image generation unit 17, and the light quantity of the light source 11 optimum for the object within the distance range to be detected is controlled. By doing so, the measurement distance accuracy can be increased.

  For example, when there is no obstacle ahead in monitoring the front of an automobile, the amount of light from the light source is increased to measure up to a long distance. If there is an obstacle ahead and the obstacle approaches within a certain distance, it is necessary to keep an eye on the obstacle, so adjust the light amount of the light source to a light amount suitable for the distance of the obstacle . In this case, the distance image generating apparatus operates as shown in FIGS.

  FIGS. 11 and 12 are flowcharts for explaining an operation example 6 of the distance image generating apparatus 1. The following processing is mainly performed by the control unit 16 or a control unit (not shown) provided separately from the control unit 16.

  First, the light source 11 irradiates the modulated light into the target space according to the synchronization signal of the control unit 16 (step S50). The image sensor 15 receives incident light including reflected light irradiated from the light source 11 and reflected by an object in the target space, converts the incident light into charges by the photoelectric conversion element, and converts the incident light according to the synchronization signal of the control unit 16. The charged charges are distributed to a plurality of charge storage units (step S51). The distance image generation unit 17 performs a predetermined calculation (calculation of the above formula 1) based on the distributed charges, calculates a phase difference φ with the light emission source, and generates a distance image whose pixel value is a distance value. (Step S52).

  Next, the control part 16 extracts the target object in arbitrary distance ranges predetermined from the distance image produced | generated by step S52 (step S53). As a method for extracting an object within an arbitrary distance range, it is conceivable to consider pixels within an arbitrary predetermined distance range as an object. At this time, it is possible to prevent erroneous detection by eliminating an abnormally small or large object.

  Next, the control unit 16 has a predetermined value (predetermined value, threshold) or less in at least one charge storage unit among the photoelectric conversion elements (also referred to as pixels) corresponding to the object extracted in step S53. The number of photoelectric conversion elements in which the charges are accumulated is counted (step S54). When the counted number of photoelectric conversion elements exceeds a certain number (step S55: Yes), the control unit 16 determines that the light amount of the light source 11 is dark and performs control to increase the light amount of the light source 11 (step S56). ).

  Alternatively, as illustrated in FIG. 12, the control unit 16 sets a predetermined value (a predetermined value) in at least one charge storage unit among the photoelectric conversion elements (pixels) corresponding to the object extracted in step S <b> 53. Threshold value.) The number of photoelectric conversion elements in which the above charges are accumulated is counted (step S57). When the counted number of photoelectric conversion elements exceeds a certain number (step S58: Yes), the control unit 16 determines that the light amount of the light source 11 is too bright and performs control to reduce the light amount of the light source 11 (step S58). S59). Thereafter, the processing from step S50 to step S59 is repeated.

  As described above, in the present operation example 6, the object within the distance range to be detected is extracted (step S53), and the count process is performed on the photoelectric conversion element corresponding to the extracted object (step S54, step S54). Based on the number of photoelectric conversion elements S57), the light amount of the light emitting source is adjusted (Step S55: Yes, Step S56, Step S58: Yes, Step S59). As a result, the light quantity of the light source 11 that is optimal for the object within the distance range can be maintained, so that it is possible to improve the distance detection accuracy and to generate a distance image with higher accuracy.

  Note that if a wide place such as the outdoors is imaged, an object in a wide distance range from a short distance road to infinity is captured. In this case, the target range on the image may be narrowed down in advance, for example, by removing the upper part of the image showing the sky or the lower part of the image showing a part of a car or a road.

  You may make it consider the object in arbitrary target distance ranges from a distance image as a target object. At this time, it is possible to prevent erroneous detection by providing a restriction on the size of the detected object. Moreover, you may provide picture restrictions by a shape.

[Operation Example 7 of Distance Image Generating Device]
When there are a plurality of target distance ranges, or when there are a plurality of objects having different distances and reflectivities, etc., when the amount of light from the light source 11 cannot be measured with high accuracy, the distance between the objects cannot be accurately measured. By sequentially changing the amount of light, it is possible to accurately measure the distance between the plurality of objects.

  For example, when the target measurement range is 0 to 30 m, and the optimal light amount of the light source 11 is different from 0 to 15 m and 15 to 30 m, there is a possibility that accurate distance measurement cannot be performed with the light amount of one type of light source 11. There is. In such a case, it is possible to accurately detect objects in a wide distance range by switching the light amount of the light source 11 suitable for 0 to 15 m and 15 to 30 m for each frame and measuring the distance. Here, one frame is a time for obtaining one distance image. In this case, one distance image is generated in two frame times of 0 to 15 m and 15 to 30 m. In this case, the distance image generating apparatus operates as shown in FIG.

  FIG. 13 is a flowchart for explaining an operation example 7 of the distance image generating apparatus. The following processing is mainly performed by the control unit 16 or a control unit (not shown) provided separately from the control unit 16.

  First, the light source 11 irradiates light modulated in the target space with a light amount suitable for 0 to 15 m in accordance with the synchronization signal of the control unit 16 (steps S60 and S61). The imaging device 15 receives incident light including reflected light reflected by the object in the target space irradiated from the light source 11, converts the incident light into charges by the photoelectric conversion element, and converts the light according to the synchronization signal of the control unit 16. The generated charges are distributed to a plurality of charge storage units (step S62).

  When one frame time has elapsed (step S63: Yes), the light source 11 irradiates the modulated light into the target space with a light amount suitable for 15 to 30 m in accordance with the synchronization signal of the control unit 16 (steps S64 and S65). The imaging device 15 receives incident light including reflected light reflected by the object in the target space irradiated from the light source 11, converts the incident light into charges by the photoelectric conversion element, and converts the light according to the synchronization signal of the control unit 16. The generated charges are distributed to a plurality of charge storage units (step S66).

  And when 1 frame time passes (step S67: Yes), the distance image generation part 17 will be the distance of the target object within 0-15m obtained by performing a predetermined calculation based on the electric charge distributed at step S62. A distance image including a distance value of an object within 15 to 30 m obtained by performing a predetermined calculation based on the value and the charge distributed in step S66 is generated (step S68). Thereafter, the processing from step S60 to step S68 is repeated.

  As described above, in the seventh operation example, by measuring the distance by switching the light amount of the light source 11 suitable for 0 to 15 m and 15 to 30 m for each frame (steps S60 and S64), the object in a wide distance range. Can be detected with high accuracy. Moreover, it becomes possible to measure the distance of a several target object with sufficient precision. Thereby, it is possible to improve the distance detection accuracy and to generate a distance image with higher accuracy.

  In this operation example, the distance is divided into two types of distance ranges, but may be divided into two or more types of ranges. Also, the type of light quantity may be divided not for each distance range but for each object having a plurality of reflectances and each object having a plurality of distances.

  As described above, according to the distance image generation device 1 of the present embodiment, since the light amount of the light source 11 is changed, the distance detection accuracy is improved and the distance image is generated with higher accuracy. It becomes possible. In addition, since the light amount of the light source 11 is not always constant, it is possible to suppress excessive light emission power (particularly when the light amount is adjusted in a direction in which the light amount decreases).

[Second Embodiment]
Next, a distance image generating apparatus according to a second embodiment of the present invention will be described with reference to the drawings.

[Configuration of Distance Image Generation Device]
When measuring the distance in front of the vehicle outside, generally the upper part of the image is taken at a relatively far distance, such as the sky, and conversely the lower part of the image is at a relatively close distance such as a road or part of the host vehicle. Many images are taken. Therefore, it is desirable that the amount of light is variable for each position on the image.

  The distance image generation apparatus of the present embodiment is configured so that the light amount of the light source 11 can be varied for each position on the image, and has a configuration substantially similar to that of the distance image generation apparatus 1 of the first embodiment. The following points are different.

  FIG. 14 is a front view of the light source of the distance image generating apparatus according to the second embodiment of the present invention.

  First, as shown in FIG. 14, the light source 11 is composed of a plurality of light emitters 11 a such as LEDs that irradiate modulated light into the target space (108 light emitters 11 a are illustrated in FIG. 14). Is different. In FIG. 14, the plurality of light emitters 11a are divided into a plurality of regions 61 to 69, and the light emitters 11a in the respective regions 61 to 69 have different irradiation areas.

  The second difference is that the light quantity of the light emitters 11a in the respective regions 61 to 69 can be adjusted independently. In addition, adjustment of this light quantity is mainly performed by the control part 16 or the control part (not shown) provided separately from this similarly to 1st embodiment.

  Third, a plurality of photoelectric conversion elements (also referred to as pixels) are divided into a plurality of photoelectric conversion element areas corresponding to different irradiation areas of the light emitters 11a in the respective regions 61 to 69. FIG. 15 is different in that it is divided into a plurality of photoelectric conversion element areas 71 to 79.

  Fourth, the processing shown in the operation examples 1 to 7 of the distance image generation device 1 described in the first embodiment is performed for each of the photoelectric conversion element areas 71 to 79, and the area corresponding to the photoelectric conversion element areas 71 to 79. The point which controls the light quantity of the light-emitting body 11a independently for every 61-69 differs.

  Other points are the same as in the first embodiment.

  FIG. 15 is an image captured by the distance image generation device of the present embodiment mounted in front of the automobile. In FIG. 15, reference numeral 700 denotes the entire image, and reference numerals 71 to 79 correspond to the irradiation ranges of the divided areas 61 to 69 of the light emitter 11a, respectively. Here, the above-described calculation pixel range for adjusting the light quantity is divided corresponding to the division ranges 71 to 79 in FIG.

  In general, the upper part of the image is picked up from a relatively far distance such as the sky, so the amount of light increases. Conversely, the lower part of the image captures an object at a relatively short distance, such as a road, so that the amount of light is expected to be smaller than the lower part of the image.

  In the present embodiment, the regions indicated by reference numerals 73, 76, and 79 in FIG. 15 have a relatively short distance, so that there are many reflection components of the modulated light from the light source 11. In this case, for example, the process of FIG. 6 is performed for each of the photoelectric conversion element areas 71 to 79, and the photoelectric conversion element areas in which the counted number of photoelectric conversion elements exceeds a certain number (for example, photoelectric conversion element areas 73, 76, and 70). ) In the region corresponding to (for example, the regions 63, 66, and 69), the light amount of the light emitter 11a is decreased.

  On the other hand, since the areas indicated by reference numerals 71, 74, and 77 in FIG. 15 mainly include objects at a long distance such as the sky, it is necessary to increase the amount of light in the corresponding areas 61, 64, and 67. In this case, for example, the process of FIG. 4 is performed for each of the photoelectric conversion element areas 71 to 79, and the number of photoelectric conversion elements counted exceeds a certain number (for example, photoelectric conversion element areas 71, 74, and 77). ) In the region corresponding to (for example, the regions 61, 64, 67) is increased. For the photoelectric conversion element area in which a traffic light or the like is shown as shown in FIG. 15, the light amount of the light emitter 11a in the corresponding region is adjusted by the processing of FIG. 4 or FIG.

  In the present embodiment, an example in which there are nine divided areas has been described, but the present invention is not limited to this. There may be more than nine divided areas or fewer than nine. Further, the number of divisions of the light source 11 and the number of divisions of the photoelectric conversion element may be different as long as the correspondence between the irradiation region of the light source 11 and the division region of the image sensor is taken.

  As described above, according to the distance image generation apparatus of the present embodiment, the light amount of the light source 11 (light emitter 11a) can be optimally adjusted for each photoelectric conversion element area (image area), so that the distance detection accuracy is improved. Further, it is possible to generate a distance image with higher accuracy. In addition, since the light amount of the light source 11 (light emitter 11a) is not always constant, it is possible to suppress unnecessary light emission power (particularly when the light amount is adjusted in the direction in which the light amount decreases).

  The above embodiment is merely an example in all respects. The present invention is not construed as being limited to these descriptions. The present invention can be implemented in various other forms without departing from the spirit or main features thereof.

  DESCRIPTION OF SYMBOLS 1 ... Distance image production | generation apparatus, 10 ... Optical time-of-flight type distance image sensor (distance image sensor), 11 ... Light source, 11a ... Luminescent body, 14 ... Incident light, 15 ... Image sensor, 16 ... Control part, 17 ... Distance image Generation part, 61-69 ... division | segmentation area, 71-79 ... photoelectric conversion element area, (phi) ... phase difference

Claims (7)

A light source that emits modulated light to the target space;
A plurality of photoelectric conversion elements that receive reflected light irradiated from the light emitting source and reflected by an object in a target space and convert it into charges, a plurality of charge storage units provided for each of the photoelectric conversion elements, and the light emission Means for distributing the charges converted by the photoelectric conversion elements to the plurality of charge storage units in synchronization with the modulation of the source, and
A distance image generation unit that performs a predetermined calculation based on the charges accumulated in the plurality of charge accumulation units and generates a distance image in which a pixel value is a distance value;
A light amount adjusting means for adjusting a light amount of the modulated light of the light source;
An arithmetic means for calculating an amplitude value of a reflected light component irradiated from the light source and reflected by an object in a target space based on the charges accumulated in the plurality of charge accumulating units;
Counting means for counting the number of the photoelectric conversion elements in which the amplitude value of the reflected light component outside the predetermined range is calculated by the calculating means;
With
The distance image generating apparatus according to claim 1, wherein the light amount adjusting unit adjusts the light amount of the modulated light of the light source when the number of photoelectric conversion elements counted by the counting unit exceeds a certain number. An extraction means for extracting an object other than the background from the distance image generated by the distance image generation unit;
The range image generating apparatus according to claim 1, wherein the counting unit performs the counting process on the photoelectric conversion element corresponding to the object extracted by the extracting unit. An extraction means for extracting an object within a predetermined distance range from the distance image generated by the distance image generation unit;
The range image generating apparatus according to claim 1, wherein the counting unit performs the counting process on the photoelectric conversion element corresponding to the object extracted by the extracting unit.   4. The distance image generating apparatus according to claim 1, wherein the light amount adjusting unit changes a light amount of the modulated light of the light emitting source every frame time. 5. The light-emitting source includes a plurality of light emitters that irradiate modulated light in a target space,
The plurality of light emitters are divided into a plurality of regions,
The plurality of photoelectric conversion elements are divided into a plurality of photoelectric conversion element areas corresponding to the plurality of regions,
The light amount adjusting unit emits light for irradiating an area corresponding to the divided photoelectric conversion element area based on the number of the photoelectric conversion elements counted by the counting unit for each divided photoelectric conversion element area. The distance image generating apparatus according to claim 1, wherein the amount of modulated light of the body is adjusted. An extraction means for extracting an object other than the background from the distance image generated by the distance image generation unit;
The distance image generating apparatus according to claim 5, wherein the counting unit performs the counting process on the photoelectric conversion element corresponding to the object extracted by the extracting unit. An extraction means for extracting an object within a predetermined distance range from the distance image generated by the distance image generation unit;
The distance image generating apparatus according to claim 5, wherein the counting unit performs the counting process on the photoelectric conversion element corresponding to the object extracted by the extracting unit.