JP2012198337A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of performing optimal exposure control, because an accurate photometric amount is obtained.SOLUTION: The imaging apparatus according to the embodiment sets a three-dimensional area as a photometric area and performs exposure control based on the photometric amount of the photometric area.

Description

  Embodiments described herein relate generally to an imaging apparatus that images a subject in an imaging area.

  In general, exposure control of an imaging apparatus is performed based on the luminance of a monitoring target (subject). However, when an object other than the monitoring target enters the same area as the monitoring target, photometry is performed including that object, so that there is a problem that an accurate photometric value cannot be obtained and optimal exposure control cannot be performed. .

  Specifically, referring to FIG. 23, as shown in FIG. 23A, when imaging the monitoring target 2 in the imaging area 1, a screen is used to keep the brightness in the imaging area 1 constant. Is controlled (exposure control is performed). However, as shown in FIG. 23 (b), for example, if an object 3 having a high light reflectance is entered into the imaging area 1, light measurement is performed including the object 3, so that an accurate photometric value cannot be obtained. Since the optimum exposure control cannot be performed, the entire screen becomes dark as shown in FIG.

JP 2006-119454 A JP 2008-128792 A

  The problem to be solved by the present invention is to provide an imaging apparatus capable of obtaining an accurate photometric amount and capable of optimal exposure control.

  In order to achieve the above object, the imaging apparatus according to the embodiment is characterized in that a three-dimensional region is set as a photometric area and exposure control is performed based on the photometric amount of the photometric area.

1 is a block diagram schematically showing the configuration of an imaging apparatus according to a first embodiment. The schematic diagram explaining the illumination part and light-receiving part which concern on 1st Embodiment. The schematic diagram explaining operation | movement of the light-receiving part which concerns on 1st Embodiment. The figure explaining operation | movement of the light-receiving part which concerns on 1st Embodiment. The figure explaining the photometry area which concerns on 1st Embodiment. The figure explaining the other example of the photometry area which concerns on 1st Embodiment. The figure explaining the LED drive circuit which concerns on 1st Embodiment. The flowchart explaining the gain correction of the illumination part which concerns on 1st Embodiment. 6 is a flowchart for explaining the operation of the imaging apparatus according to the first embodiment. FIG. 5 is a schematic diagram illustrating an application example according to the first embodiment. The figure explaining the photometry area with respect to the application example of FIG. 10 which concerns on 1st Embodiment. The figure which shows typically an example of the distance image acquired with respect to the application example of FIG. 10 which concerns on 1st Embodiment. The figure which shows typically an example of the amplitude image of the reflected light which concerns on 1st Embodiment. The figure which shows typically the photometry area of the amplitude image which concerns on 1st Embodiment. The schematic diagram explaining the example which objects other than the monitoring target approached into the photometry area which concerns on 1st Embodiment. The figure which shows typically an example of the distance image acquired with respect to FIG. 15 which concerns on 1st Embodiment. The figure which shows typically the photometry area of the amplitude image with respect to FIG. 15 which concerns on 1st Embodiment. The block diagram which shows roughly the structure of the imaging device which concerns on 2nd Embodiment. The schematic diagram explaining the visual field range of the distance image camera and area camera which concern on 2nd Embodiment. 9 is a flowchart for explaining gain correction of an area camera according to a second embodiment. 9 is a flowchart for explaining the operation of the imaging apparatus according to the second embodiment. The figure explaining the step of shutter speed correction of the area camera concerning a 2nd embodiment. The schematic diagram explaining the conventional problem.

Hereinafter, an imaging apparatus according to an embodiment will be described with reference to the drawings.
First, the first embodiment will be described.
FIG. 1 schematically shows a configuration of an imaging apparatus according to the first embodiment. The imaging apparatus according to the first embodiment includes a distance image camera 11, a photometric area information storage unit 12, a photometric amount calculation unit 13, a CPU (Central Processing Unit) 14 that controls the entire control, a gain correction unit 15, In addition, a data bus and an address bus 16 are connected to enable communication therebetween.

Hereinafter, each part will be described in detail.
The range image camera 11 is configured by, for example, a TOF (Time of Flight) type range image camera. A distance image camera of the TOF type is one that can simultaneously acquire distance information as an image by integrating a signal charge detection function corresponding to the flight time of light in each pixel of the light receiving unit. Obtain the distance image by irradiating the output pulsed light toward the object and calculating the distance to the object from the time until the reflected light from the object is received by the light receiving unit and the speed of the light. It is based on the principle of doing.

  The distance image camera 11 includes an illumination unit 17 and a light receiving unit 18. For example, as shown in FIG. 2, the illumination unit 17 includes a plurality of LEDs (light emitting diodes) 22,... Arranged at a predetermined interval on a support substrate 21, and modulates the plurality of LEDs 22,. Lighting control is performed with a frequency signal (that is, pulsed light).

  The light receiving unit 18 is composed of, for example, a CMOS (complementary metal oxide semiconductor) image sensor or a CCD (charge coupled device) image sensor, and is disposed integrally with the illumination unit 17 as shown in FIG. In other words, in the example of FIG. 2, the light receiving unit 18 is disposed at a substantially central portion on the support substrate 21, and a plurality of LEDs 22,.

  As shown in FIGS. 3 and 4, the distance image camera 11 irradiates the subject 19 with the emitted light 17 a from the illumination unit 17, receives the reflected light 17 b with the light receiving unit 18, and emits the emitted light 17 a and the subject 19. A distance image from each pixel of the light receiving unit 18 to the subject 19 is calculated by calculating the time delay of the reflected light 17b by the internal arithmetic circuit. Further, coordinate values (x, y, z) with the camera as the origin are output by performing known appropriate correction. Furthermore, the characteristic is that the amplitude (I) of the reflected light 17b can also be acquired at the same time.

  The photometric area information storage unit 12 is realized by, for example, a RAM (Random Access Memory) and stores information for setting a three-dimensional area as a photometric area for the imaging area.

  For example, a three-dimensional area as shown in FIG. 5 is designated by three-dimensional coordinates. In the example of FIG. 5, the case where the area 23 surrounded by eight points a to h is set as the photometric area is shown. Note that, as shown in FIG. 6, the spherical area 24 may be set as a photometric area by the center coordinate i and the radius j.

  The photometric quantity calculation unit 13 is realized by the CPU 14 executing a program preset in the photometric quantity calculation unit 13, and the luminance value of each pixel of the distance image in the photometric area obtained from the range image camera 11 is obtained. The average value is calculated and output as the photometric quantity. Here, the photometric quantity may be a peak value or a mode value instead of the average value.

  The illumination gain correction unit 15 performs gain correction of the illumination unit 17 (exposure control of the distance image camera 11) based on the light measurement amount obtained by the light measurement amount calculation unit 13. For example, as shown in FIG. 7, the gain correction is performed by controlling the gain value 52 of the LED drive circuit 51 that drives the LED 22.

Hereinafter, gain correction of the illumination unit 17 (exposure control of the distance image camera 11) will be described with reference to a flowchart shown in FIG. First, it is determined whether or not the photometric quantity obtained by the photometric quantity calculation unit 13 is within a preset normal value (standard value having a predetermined range) (step S1). finish. If the photometric amount is not within the normal value, it is determined whether the photometric amount is not less than the normal value (step S2). If the photometric amount is not less than the normal value, the gain value 52 of the LED drive circuit 51 in the illumination unit 17 is set. Decreasing the amount by a predetermined amount (for example, -1 and step S3), and increasing the gain value 52 of the LED drive circuit 51 by a predetermined amount (for example, +1) (step S4) if the photometric quantity is not the normal value or more Adjust brightness automatically.
That is, the concept of automatic adjustment is to increase the brightness by increasing the drive voltage of the LED 22 when it is dark, and lower the brightness by decreasing the drive voltage of the LED 22 when it is bright. .

Next, the operation of the imaging apparatus according to the first embodiment having the above configuration will be described with reference to the flowchart shown in FIG.
In the following description, for example, a case where the entrance / exit of the automobile 27 around the gate of the parking lot 25 as shown in FIG.

  First, in the photometric area information storage unit 12, a three-dimensional photometric area 28 as shown in FIG. 11 is set so as to include the broken line area (imaging area) 26 of FIG.

  As described above, distance information of each pixel is obtained from the distance image camera 11 from the reflected light from the object in the broken line area 26 (step S11). FIG. 12 shows an example of the distance image obtained. This example corresponds to FIG. 11 and shows a distance image in a form in which the gray value of the image becomes smaller (darker) as it goes deeper. For example, A part is 0 to 2 m, and B part is 2 to 4 m. The C part corresponds to 4 to 6 m, and the D part corresponds to 6 m or more.

Here, if the amplitude (luminance) image of the reflected light obtained from the distance image camera 11 is as shown in FIG. 13, the photometric quantity calculation unit 13 uses a range 29 (shown in FIG. 11) indicated by a broken line in FIG. The average luminance value (photometric light amount) of the pixels within the range that satisfies the photometric area of FIG. 11 obtained from the distance image is obtained as follows (step S12).
Photometric quantity = Σ _{i <320j <160 ((x, y, z) ∈M)} I (i, j) / (n ((x, y, z) ∈M))
However, i and j are the coordinates of the grayscale image, x, y and z are the orthogonal coordinate values output from the distance image camera 11, M is a set of preset photometric areas, and n () is the M of the grayscale image coordinates. The number of elements included in (photometric area), I (i, j), indicates the luminance value of each pixel of the grayscale image.
In the present embodiment, the number of pixels of the distance image camera 11 is considered as 320 × 160.

Next, for comparison with the conventional example, for example, an example in which an object (truck 30) other than the monitoring object (automobile 27) enters the photometry area 28 is shown in FIG. The obtained distance image is as shown in FIG. In this case, the photometric area 28 includes the area 31 surrounded by the broken line shown in FIG. 17, and the photometric quantity hardly changes even when the track 30 enters the photometric area 28, and thus the LED drive circuit 51. The gain value 52 is automatically adjusted by the illumination gain correction unit 15 to the same extent as when the track 30 is not provided. (Step S13).
Next, a second embodiment will be described.
FIG. 18 schematically illustrates the configuration of an imaging apparatus according to the second embodiment. The difference of the second embodiment from the first embodiment is that an area camera 41, an area camera photometric quantity calculation unit 42, and an area camera gain correction unit 43 are added, and the others are the same. Only differences from the first embodiment will be described.

  The area camera 41 can be realized by a high-resolution monitoring camera. Although it is a function installed in general products, camera parameters (such as shutter speed) can be externally controlled from an external device (such as a personal computer) using an interferus such as USB (Universal Serial Bus). Assume that the area camera 41 is used.

  Further, as shown in FIG. 19, the visual field range 41a of the area camera 41 is set to be substantially the same as the visual field range 11a of the distance image camera 11 described in the first embodiment. By setting the visual field range in this way, exposure control of the area camera 41 using the distance image from the distance image camera 11 becomes possible.

  The area camera photometric quantity calculation unit 42 is realized by the CPU 14 executing a program preset in the area camera photometric quantity calculation unit 42, and each image in the photometric area of FIG. 5 obtained from the area camera 41 is obtained. An average value of luminance values of pixels is calculated and output as a photometric quantity.

In addition, the area camera photometric quantity calculation unit 42 performs processing for associating information of different resolutions between the distance image camera 11 and the area camera 41. For example, if the distance image camera 11 and the area camera 42 have the same spot as the field of view and the resolution differs by 4 times in both the horizontal and vertical directions, the photometry is performed after the resolution of the area camera 41 is reduced based on the following conversion formula: Calculate quantity.
I ′ (i, j) = I (i / 4, j / 4)
Here, I () is the luminance value of the area camera 41, and I ′ () is the luminance value of the area camera 41 with the resolution reduced to ¼. In the above formula, the resolution is reduced by thinning out every four pixels, but the resolution may be reduced by an average value of 4 × 4.

The area camera gain correction unit 43 performs gain correction of the area camera 41 (exposure control of the area camera 41) based on the photometric quantity obtained by the area camera photometric quantity calculation unit 43.
Hereinafter, gain correction of the area camera 41 (exposure control of the area camera 41) will be described with reference to a flowchart shown in FIG. First, it is determined whether or not the photometric quantity obtained by the area camera photometric quantity calculation unit 43 is within a preset normal value (standard value having a predetermined range) (step S21). The process ends. If the photometric amount is not within the normal value, it is determined whether the photometric amount is not less than the normal value (step S22). If the photometric amount is not less than the normal value, the shutter speed of the area camera 41 is set to a predetermined amount (for example, 1 Step) (step S23), and if the photometric quantity is not equal to or higher than the normal value, the gain of the area camera 41 is automatically adjusted by increasing the shutter speed of the area camera 41 by a predetermined amount (for example, one step) (step S24).
Next, the operation of the imaging apparatus according to the second embodiment having the above configuration will be described with reference to the flowchart shown in FIG.
In the following description, it is assumed that the parking lot 25 as shown in FIG. 10 is mainly monitored by the area camera 41 and the distance image camera 11 is used for exposure control of the area camera 41.

Steps S11 to S13 are the same as those in FIG.
Next, in step S14, an average luminance value (photometric amount) is obtained based on distance information from the distance image camera 11. Specifically, the area camera photometric quantity calculation unit 42 obtains the range 29 (shown from the distance image in FIG. 12) indicated by the broken line in FIG. 14 of the image obtained from the area camera 41 with reduced resolution as described above. The luminance average value (photometric light amount) of each pixel within a range that satisfies 11 photometric areas is obtained as follows.
Photometric quantity = Σ _{i <320j <160 ((x, y, z) ∈M)} I ′ (i, j) / (n ((x, y, z) ∈M))
However, i and j are the coordinates of the grayscale image, x, y and z are the orthogonal coordinate values output from the distance image camera 11, M is a set of preset photometric areas, and n () is the coordinates of the grayscale image. , M (photometric area), the number of elements, I ′ (i, j) represents the luminance value of each pixel of the grayscale image with the resolution reduced to ¼.
In the present embodiment, it is assumed that the number of pixels of the distance image camera 11 is 320 × 160 and the resolution of the area camera 41 is 1280 × 640.

Next, the area camera gain correction unit 43 performs gain correction of the area camera 41 (exposure control of the area camera 41) based on the photometric quantity obtained by the area camera photometric quantity calculation unit 43 (step S15). Specifically, as described with reference to FIG. 20, the brightness of the monitoring target is set to a constant value by switching the shutter speed of the area camera 41 one step at a time as shown in FIG. Can keep.
According to at least one embodiment described above, a stable distance image can always be obtained from the distance image camera 11 by performing exposure control of the distance image camera 11 based on the photometric amount of a three-dimensional region. And automatic monitoring with high accuracy is possible.

  Further, according to at least one embodiment described above, the exposure control of the area camera 41 is performed based on the photometric amount of the three-dimensional area of the distance image camera 11, so that not only the distance image camera 11 but also the high The brightness of the resolution area camera 41 is also kept optimal, and stable monitoring can always be performed.

  In the above embodiment, a case where a TOF type distance image camera is used as the distance image camera has been described. However, the present invention is not limited to this, and for example, a stereo camera or an ultrasonic camera can be used in the same manner. .

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 11 ... Distance image camera, 12 ... Photometry area information storage part, 13 ... Light measurement amount calculation part, 14 ... CPU, 15 ... Gain correction part for illumination, 16 ... Data bus and address bus, 17 ... Illumination part, 18 ... Light-receiving part , 41... Area camera, 42... Area camera photometric calculation unit, 43... Area camera gain correction unit.

Claims (9)

  An imaging apparatus characterized in that a three-dimensional area is set as a photometric area and exposure control is performed based on the photometric amount of the photometric area. A distance image camera that acquires a distance image indicating a distance to a subject in an imaging area;
Photometric area setting means for setting a three-dimensional area as the photometric area with respect to the imaging area;
A photometric light quantity calculating means for calculating a photometric light quantity based on a distance image in the photometric area set by the photometric area setting means obtained from the distance image camera;
Exposure control means for performing exposure control of the distance image camera based on the photometric quantity calculated by the photometric quantity calculating means;
An imaging apparatus comprising: The distance image camera irradiates the subject with pulsed light output from the illumination unit, and calculates the distance to the subject from the time until the reflected light from the subject is received by the light receiving unit and the speed of light. This is a TOF (time of flight) type distance image camera that acquires distance images.
3. The imaging according to claim 2, wherein the exposure control unit performs exposure control of the range image camera by controlling brightness of the illumination unit based on a photometric amount calculated by the photometric amount calculating unit. apparatus. A distance image camera that acquires a distance image indicating a distance to a subject in an imaging area;
An area camera for imaging a subject in the imaging area;
Photometric area setting means for setting a three-dimensional area as the photometric area with respect to the imaging area;
Based on the distance image in the photometric area set by the photometric area setting means obtained from the distance image camera, a photometric quantity calculating means for calculating the photometric quantity using the image obtained from the area camera;
Exposure control means for performing exposure control of the area camera based on the photometric quantity calculated by the photometric quantity calculating means;
An imaging apparatus comprising:   The imaging apparatus according to claim 4, wherein a field-of-view range of the area camera corresponds to a field-of-view range of the distance image camera.   5. The imaging apparatus according to claim 4, wherein the photometric quantity calculating means calculates the photometric quantity after converting the resolution of the area camera to the resolution of the range image camera.   The distance image camera irradiates the subject with pulsed light output from the illumination unit, and calculates the distance to the subject from the time until the reflected light from the subject is received by the light receiving unit and the speed of light. The imaging apparatus according to claim 4, wherein the imaging apparatus is a TOF (time of flight) type distance image camera that acquires a distance image.   The imaging apparatus according to claim 1, wherein the three-dimensional region is a rectangular parallelepiped region.   The imaging apparatus according to claim 1, wherein the three-dimensional region is a spherical region.

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