JP2021021867A - Illumination control device, illumination control method, and imaging device - Google Patents

Abstract

To provide an illumination control device which suppresses luminance unevenness of a taken image with a simple configuration.SOLUTION: An illumination control device includes: control means for controlling an irradiation angle of an illumination part which illuminates an object to be imaged by imaging means; acquisition means for acquiring information on luminance unevenness of an image taken by the tilt-driven imaging means; and determination means for determining whether or not the luminance unevenness is a predetermined value or more on the basis of the information on the luminance unevenness acquired by the acquisition means. When the determination means determines that the luminance unevenness is the predetermined value or more, the control means controls the irradiation angle of the illumination part to make the luminance unevenness less than the predetermined value.SELECTED DRAWING: Figure 1

Description

The present invention relates to a lighting control device, a lighting control method, and an imaging device.

Conventionally, in an imaging apparatus, when an image is taken by illuminating the inside of the imaging range with light from an illumination unit (light source), the light irradiation range is controlled according to the focal length of the lens.
By the way, when an imaging device is used for purposes such as surveillance, the subject is often imaged from diagonally above. In this case, a distance difference from the illumination unit occurs within the imaging range on the subject according to the tilt angle (depression angle) with respect to the subject surface, the illuminance is lower at a position farther from the illumination unit within the imaging range, and the illuminance is lower at a position closer to the subject surface. A phenomenon such as high illuminance (illuminance unevenness) occurs. Therefore, simply controlling the light irradiation range according to the focal length of the lens causes uneven brightness in the captured image.
Patent Document 1 discloses a camera lighting device including a drive mechanism that changes the irradiation direction of light from the lighting unit relative to the imaging direction according to the imaging direction of the camera. In this camera lighting device, uneven brightness of an image is suppressed by changing the irradiation direction according to the zoom operation of the camera and the image information obtained from the camera.

JP-A-2007-134784

However, when a drive mechanism for changing the light irradiation direction is provided as in the technique described in Patent Document 1, the device configuration becomes complicated and the size increases.
Therefore, an object of the present invention is to suppress uneven brightness of a captured image with a simple configuration.

In order to solve the above problems, one aspect of the illumination control device according to the present invention is an image pickup by a control means for controlling an irradiation angle of an illumination unit that illuminates an object to be imaged by the image pickup means and the tilt-driven imaging means. The control includes an acquisition means for acquiring information on the luminance unevenness of the image, and a determination means for determining whether or not the luminance unevenness is equal to or greater than a predetermined value based on the information on the luminance unevenness acquired by the acquisition means. When the determination means determines that the luminance unevenness is equal to or greater than the predetermined value, the means controls the irradiation angle of the illumination unit so that the luminance unevenness becomes less than the predetermined value.

According to the present invention, it is possible to suppress uneven brightness of a captured image with a simple configuration.

It is a parameter explanatory drawing which concerns on lighting control in this embodiment. It is a block diagram of the image pickup apparatus. It is an illuminance distribution map of each lighting part. This is an example of the hardware configuration of the image pickup device. It is a flowchart which shows the lighting control processing procedure of 1st Embodiment. It is a parameter explanatory diagram which concerns on illuminance calculation. This is an example of the light illuminance reaching the subject surface in the first embodiment. It is an image diagram of brightness unevenness. It is a flowchart which shows the lighting control processing procedure of the 2nd Embodiment. It is a figure which shows the electric power ratio in each angle of view. This is an example of the light illuminance reaching the subject surface in the second embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
The embodiments described below are examples of means for realizing the present invention, and should be appropriately modified or modified depending on the configuration of the device to which the present invention is applied and various conditions. It is not limited to the embodiment of.

In the present embodiment, an image pickup apparatus that illuminates the inside of the image pickup range with light from an illumination unit to take an image will be described. The image pickup apparatus in the present embodiment is an image pickup apparatus that images images from diagonally above the subject surface, and can be, for example, a network camera used in a surveillance system or the like. The network camera can image a predetermined monitoring area and deliver the captured image (video) to the client device via the network. In this case, the user can view the image (video) distributed from the imaging device using the client device.
The image pickup apparatus in the present embodiment controls the irradiation angle of the illumination unit that illuminates the object to be imaged. Specifically, the imaging device determines whether or not the luminance unevenness is equal to or greater than a predetermined value based on the information regarding the luminance unevenness of the captured image, and when it is determined that the luminance unevenness is equal to or greater than the predetermined value, The irradiation angle of the illumination unit is controlled so that the brightness unevenness becomes less than a predetermined value.

In the present embodiment, the imaging device controls the lighting of the illumination unit using the focal length information of the lens, the distance information indicating the shortest distance between the imaging device and the subject surface, and the angle information indicating the imaging direction of the imaging device as parameters. Do. Specifically, the image pickup apparatus includes a plurality of illumination units capable of irradiating light having different irradiation angles (light distribution characteristics) with respect to the subject surface with the image pickup direction as the irradiation direction. Then, the imaging device illuminates the imaging range by alternately selecting an irradiation angle from a plurality of irradiation angles and lighting the illumination unit based on the above parameters. As described above, in the present embodiment, the case where the imaging device operates as an irradiation control device that controls the lighting of the irradiation unit will be described. In addition, instead of a plurality of illumination units having different irradiation angles, one illumination unit provided with a zoom optical system may be adopted. In this case, the irradiation angle can be selectively selected by changing the focal length of the zoom optical system of the illumination unit.

Here, as shown in FIG. 1, when the subject surface S is the ground and the imaging device 100 performs imaging from diagonally above the subject surface S, the distance information is obtained from the imaging unit 110 included in the imaging device 100. It can be height information indicating the height H from the subject surface S. As shown in FIG. 1, when the image pickup apparatus 100 is imaging from diagonally above the subject surface S and the imaging direction of the imaging unit 110 can be changed to the tilt direction, the angle information is based on the imaging apparatus. The tilt angle can be 100. The tilt angle of the image pickup apparatus 100 is the angle θ ₀ that the image pickup unit 110 faces when the subject surface S, which is a horizontal plane, is facing, that is, when the image pickup device 100 is facing directly below is 0 degrees.

FIG. 2 is a block diagram showing a configuration example of the image pickup apparatus 100 according to the present embodiment.
The image pickup apparatus 100 is connected to a client apparatus (not shown) via a network 200 in a communicable state.
The image pickup device 100 includes an image pickup unit 110, illumination units 121A and 121B, an illumination control unit 122, a height information acquisition unit 130, a tilt drive unit 140, a calculation unit 150, and a network processing unit 160. The image pickup unit 110 includes a lens unit 111, an image sensor unit 112, and an image processing unit 113.

The lens unit 111 includes a lens group including a zoom lens for adjusting the angle of view, a focus lens for focusing on the subject, and a drive system for driving them. The drive system of the lens unit 111 can realize the zoom function by moving the zoom lens along the optical axis according to the zoom information (focal length information) transmitted from the image processing unit 113. Further, the drive system of the lens unit 111 can realize the focus function by moving the focus lens along the optical axis according to the focus information transmitted from the image processing unit 113.
The zoom function of the lens unit 111 may be manually realized by the user. In this case, the lens unit 111 transmits the zoom position to the image processing unit 113. Further, in the configuration example shown in FIG. 2, the image pickup device 100 is a lens-integrated image pickup device having the lens portion 111 integrally, but the image pickup device 100 is a lens-interchangeable image pickup device in which the lens portion 111 can be exchanged. It may be.

The image sensor unit 112 includes an image sensor (not shown), an AGC circuit, an A / D conversion circuit, and the like. The image sensor outputs the subject image imaged by the lens unit 111 as an electric signal (analog signal). The analog signal output from the image sensor is gain-adjusted by the AGC circuit, converted into a digital signal by the A / D conversion circuit, and then transmitted to the image processing unit 113 as an image signal.
The image processing unit 113 performs predetermined image processing on the image signal output from the image sensor unit 112. The image processing includes, for example, development processing, filter processing, sensor correction (for example, gain correction processing), noise removal processing, and the like. Further, the image processing unit 113 controls the zoom function and the focus function of the lens unit 111, and holds each setting information. The image processing unit 113 transmits zoom information to the calculation unit 150, focus information to the height information acquisition unit 130, and image signals after image processing to the network processing unit 160, respectively.

Each of the illumination units 121A and 121B has a light emitting element that irradiates light according to the current supplied from the illumination control unit 122. The light emitting element may be used alone or may be used with a secondary lens for setting the irradiation angle of light. The illuminance distribution of the light emitted from the illumination units 121A and 121B shall follow the Gaussian distribution as shown in FIG.
The type of light source used for the illumination units 121A and 121B is not particularly limited, and any light source such as a HID lamp, an LED, or a halogen lamp can be used. Moreover, the wavelength of the light source does not matter.

In FIG. 3, the illuminance distribution shown by the solid line is the illuminance distribution of the illumination unit 121A, and the illuminance distribution indicated by the broken line is the illuminance distribution of the illumination unit 121B. In the present embodiment, the irradiation angle of the illumination unit 121A is wider than the irradiation angle of the illumination unit 121B. Here, the irradiation angle is an irradiation angle that is half the peak value of the illuminance distribution. In the case of the illumination unit 121A, since the peak value of the illuminance distribution is 0.6 as shown in FIG. 3, the irradiation angle is 120 °, which is the irradiation angle at 0.3, which is half of the peak value. Similarly, in the case of the illumination unit 121B, the irradiation angle is 70 °, which is the irradiation angle at 0.5, which is the half value of the peak value.
Further, in the present embodiment, it is assumed that the center of the angle of view of the imaging unit 110 and the center of the illuminance distribution (positions that become peak values) by the illumination units 121A and 121B are infinitely coincident with each other. That is, the imaging direction of the imaging unit 110 and the irradiation directions of the irradiation units 121A and 121B are infinitely coincident with each other.

The lighting control unit 122 controls the current supplied to the lighting units 121A and 121B according to the lighting control information received from the calculation unit 150. There is an upper limit to the total current value that can be supplied to the illumination units 121A and 121B, and the illumination control unit 122 performs current control based on the illumination control information in which the amount of current supplied to each and the total value thereof are added.
The height information acquisition unit 130 acquires the height H of the image pickup unit 110 shown in FIG. 1 and transmits this as height information to the calculation unit 150. In the present embodiment, the height information acquisition unit 130 calculates the height H of the image pickup unit 110 based on the focus information received from the image processing unit 113.

The tilt drive unit 140 has a tilt mechanism that supports each element surrounded by a broken line including the image pickup unit 110 and the illumination units 121A and 121B in FIG. 2 and directs the image pickup unit 110 and the illumination unit 120 in a designated direction. For example, the illumination units 121A and 121B may be housed in the same housing together with the image pickup unit 110. In this case, the tilt drive unit 140 can drive the image pickup unit 110 and the illumination units 121A and 121B by driving the image pickup unit 110 in the tilt direction, and can change the image pickup direction and the irradiation direction in the tilt direction. The lighting units 121A and 121B may be externally attached to a housing that houses the imaging unit 110.
The tilt drive unit 140 includes a drive motor for driving the image pickup unit 110. The drive motor can be, for example, an ultrasonic motor or a stepping motor. The tilt drive unit 140 drives and controls the drive motor according to the tilt angle information received from the calculation unit 150, and changes the image pickup direction of the image pickup unit 110.

The calculation unit 150 generates lighting control information from the zoom information received from the image processing unit 113, the height information received from the height information acquisition unit 130, and the tilt angle information transmitted to the tilt drive unit 140. It is transmitted to the lighting control unit 122.
The network processing unit 160 includes an interface connected to the network 200, compresses and encodes the image signal received from the image processing unit 113, and distributes the image signal to a client device (not shown) via the network 200.

The network 200 includes a plurality of routers, switches, cables, and the like that satisfy communication standards such as Ethernet (registered trademark). The network 200 may have any communication standard, scale, and configuration as long as it can communicate between the image pickup device 100 and the above client device. For example, the network 2000 may be configured by the Internet, a wired LAN (Local Area Network), a wireless LAN (Wireless LAN), a WAN (Wide Area Network), or the like.
Further, the image pickup apparatus 100 in the present embodiment may be compatible with PoE (Power Over Ethernet), or may be configured such that power is supplied via a LAN cable or the like.

FIG. 4 is a hardware configuration example of the image pickup apparatus 100.
The image pickup apparatus 100 includes a CPU 11, a ROM 12, a RAM 13, an external memory 14, an image pickup unit 15, an illumination unit 16, and a communication unit 17. The CPU 11, ROM 12, RAM 13, external memory 14, imaging unit 15, lighting unit 16, and communication unit 17 are connected to the internal bus 18.
The CPU 11 comprehensively controls the operation of the image pickup apparatus 100. The ROM 12 is a non-volatile memory that stores programs and data necessary for the CPU 11 to execute processing. The RAM 13 functions as a main memory, a work area, and the like of the CPU 11. The CPU 11 loads a program or the like required from the ROM 12 into the RAM 13 when executing the process, and executes the program or the like to realize various functional operations.

The external memory 14 is a non-volatile storage device typified by an HDD (hard disk drive), a flash memory, an SD card, or the like, and may have a removable configuration. The imaging unit 15 corresponds to the imaging unit 110 shown in FIG. Further, the lighting unit 16 corresponds to the lighting units 121A and 121B shown in FIG. The communication unit 17 corresponds to the network processing unit 160 shown in FIG.
It should be noted that at least a part of the functions of each element of the image pickup apparatus 100 shown in FIG. 2 can be realized by the CPU 11 executing the program.

Next, the illumination control method in the image pickup apparatus 100 will be described.
FIG. 5 is a flowchart showing a procedure of the illumination control process executed by the image pickup apparatus 100. The process of FIG. 5 is started at the timing when, for example, the image pickup apparatus 100 is installed on a wall or the like as shown in FIG. However, the start timing of the process of FIG. 5 is not limited to the above timing. The image pickup apparatus 100 can realize each process shown in FIG. 5 by reading and executing a program required by the CPU 11. Hereinafter, the alphabet S shall mean a step in the flowchart.

In S1, the height information acquisition unit 130 acquires the focus information from the image processing unit 113 and calculates the height information of the image pickup unit 110 (the shortest distance between the image pickup unit 110 and the subject surface). Specifically, the height information acquisition unit 130 swings the focus position from infinity to the front in a state where the image pickup unit 110 is oriented substantially perpendicular (directly below) to the subject surface (a state in which the tilt angle is 0 °). Then, the position (focus position) when the focus is achieved is acquired from the image processing unit 113. Then, the height information acquisition unit 130 calculates the distance to the subject by applying the acquired focus position to the conversion table for the distance to the subject, and acquires this as height information.

In the present embodiment, the case where the height information is calculated using the focus information will be described, but the method for acquiring the height information is not limited to the above. For example, the height information acquisition unit 130 may be equipped with a distance measuring sensor, or may be provided with a mechanism for giving height information to the user via a network. Further, the height H of the imaging unit 110 may be stored in a storage unit such as the ROM 12 of the imaging device 100 or the external memory 14 in advance, and the height information acquisition unit 130 may read it. Calculated in S1. The height information is used when calculating the brightness unevenness prediction value in S6 described later. In the present embodiment, the case where the processing of S1 is performed only once at the timing when the image pickup apparatus 100 is installed will be described, but in the case of an environment where the installation height of the imaging apparatus 100 can change, S1 is periodically performed. The sequence that performs the processing of is preferable.

In S2, the imaging device 100 starts imaging. In this S2, the lighting is not turned on.
In S3, the calculation unit 150 determines whether or not the lighting needs to be turned on. The conditions that require lighting include, for example, the time when the time specified by the user has come, and the case where the imaging environment illuminance detected by using an illuminance sensor or the like falls below the threshold value. When the calculation unit 150 determines that the lighting needs to be turned on, it shifts to S4, and when it determines that the lighting does not need to be turned on, it returns to S2 and continues imaging.

In S4, the calculation unit 150 acquires the tilt angle information held by the image processing unit 113. In the present embodiment, as shown in FIG. 1 described above, the tilt angle is set to 0 ° when the imaging unit 110 is facing directly below (toward the ground).
In S5, the calculation unit 150 acquires the angle of view. Since the angle of view is determined by the zoom position of the lens, the calculation unit 150 acquires the zoom information held by the image processing unit 113 and calculates the angle of view from the acquired zoom information. Then, the calculation unit 150 selects, among the irradiation units 121A and 121B, an irradiation unit having an irradiation angle corresponding to the calculated angle of view as a candidate for the irradiation unit to be lit. The calculation unit 150 selects a candidate for the lighting unit to be turned on by using the association information in which the angle of view and the lighting unit to be turned on are associated with each other stored in the storage unit. In the present embodiment, when the angle of view is 70 ° or less, which is the irradiation angle of the illumination unit 121B, the illumination unit 121B is selected as a candidate, and when the angle of view exceeds 70 °, the illumination unit 121A is selected as a candidate. It shall be.

In S6, the calculation unit 150 determines the brightness unevenness of the captured image when the irradiation unit corresponding to the angle of view is turned on. Specifically, the calculation unit 150 calculates the predicted value of the brightness unevenness of the captured image when the irradiation unit corresponding to the angle of view is turned on, and the brightness unevenness occurs when the predicted brightness unevenness value is equal to or more than a predetermined value. Is determined. This predetermined value is an upper limit value of the permissible luminance unevenness of the captured image, and can be given to the calculation unit 150 in advance by the user.

Hereinafter, the method of calculating the predicted luminance unevenness value will be described in detail.
First, using the height H calculated in S1, the distance D from the imaging unit 110 to the subject surface corresponding to each imaging angle θ within the imaging range is calculated. Here, the imaging angle θ is an angle formed by a main ray corresponding to each object point on the subject surface and a perpendicular line drawn on the subject surface. The distance D is the distance from the image pickup unit 110 to the point on the subject surface, and is expressed by the following equation (1).
D = H / cos (θ) ……… (1)
As shown in FIG. 6, when the tilt angle is θ ₀ and the angle of view (total angle of view) is θ ₁ , the lower end of the captured image corresponds to the object point A on the subject surface S, and the upper end corresponds to the object surface S. Corresponds to the object point B of, and the center corresponds to the object point C on the subject surface S. Here, the imaging angle theta _A object point A, is _{θ A = θ 0 -θ 1/} 2 ( i.e., the angle obtained by subtracting the half angle from the tilt angle theta _0). The imaging angle theta _B object point B is _{θ B = θ 0 + θ 1} /2 ( i.e., the angle obtained by adding the half angle in the tilt angle theta _0). Further, the imaging angle theta _C object points C, is θ _C = θ ₀ (i.e., tilt angle itself). Therefore, it is possible to calculate using these imaging angle theta _A through? _C, the distance D _A to D _C from the imaging unit 110 to the object point A~ object point C on the object surface S, respectively.

Further, as described above, the center of the angle of view and the center of the illuminance distribution by the illumination units 121A and 121B coincide with each other. Thus, illuminance of the light irradiated toward the irradiation unit 121A, the 121B to the point C, that is, the intensity of light in the last (D _C = 0) of the image pickup apparatus 100, as shown in FIG. 3, the irradiation angle 0 It is the intensity of light at ° (C'). When the angle of view θ ₁ = 60 °, the illuminance of the light emitted from the irradiation units 121A and 121B toward the point A is the intensity of the light at the irradiation angle −30 ° (A ′). Similarly, the illuminance of the light emitted from the irradiation units 121A and 121B toward the point B is the intensity of the light at the irradiation angle of 30 ° (B').

The illuminance of the light emitted from the irradiation units 121A and 121B is attenuated in inverse proportion to the square of the distance and reaches the subject surface. Therefore, assuming that the illuminance of the light reaching the subject surface is E and the function of the illuminance distribution shown in FIG. 3 is E'(θ), the following equation can be obtained using the above equation (1).
E = E'(θ) / D ²
= E'(θ) × cos (θ) ² / H ² ……… (2)
By giving the imaging angle θ of the above equation (2) in the range of the angle of view θ ₁ (the range of the imaging angles θ _{A to} θ _B ), the illuminance distribution on the subject surface S within the imaging range can be obtained. The calculation unit 150 defines the difference between the maximum value and the minimum value of the illuminance distribution on the subject surface S within the imaging range as the luminance unevenness prediction value, and calculates the luminance unevenness prediction value.

Specifically, what kind of brightness unevenness prediction value will be obtained when a value is assigned to each parameter will be described below.
First, each parameter is as follows.
Height H = 10m, tilt angle θ ₀ = 48 °, angle of view θ ₁ = 60 °
Further, for the irradiation intensities of the illumination units 121A and 121B, in order to simplify the calculation, a value normalized by setting the peak value of the illumination unit 121B shown in FIG. 3 to 100 is used.
When the illuminance E1c reaching the point C from the irradiation unit 121B is calculated using the above equation (2), it can be obtained as follows.
E1c = E'(48 °) x cos (48 °) ² / H ²
= 100 × 0.67 ^{2/10 2}
≒ 0.45

By the same method, the illuminance reaching the subject surface from the illumination units 121A and 121B is obtained for all the object points on the subject surface within the imaging range, and the result is as shown in FIG. 7A. In FIG. 7A, E0 (solid line) is the illuminance distribution (luminance unevenness prediction value) by the illumination unit 121A, and E1 (broken line) is the illuminance distribution (luminance unevenness prediction value) by the illumination unit 121B. The illuminances at the imaging angles a to e in FIG. 7A are shown in FIG. 7B.
Here, the imaging angle a is an imaging angle = 18 ° (= 48 ° −30 °) at the end of the imaging range (object point A in FIG. 6). Further, the imaging angle b is an imaging angle = 19 ° at which the illuminance E0 is the maximum value, and the imaging angle c is an imaging angle = 30 ° at which the illuminance E1 is the maximum value. Further, the imaging angle d is the imaging angle = 48 ° at the center of the imaging range (point C in FIG. 6), and the imaging angle e is the imaging angle = 78 ° (= 48) at the end of the imaging range (point B in FIG. 6). ° + 30 °).

From the results shown in FIGS. 7 (a) and 7 (b), the maximum value of the illuminance E0 on the subject surface S within the imaging range when the illumination unit 121A is turned on is 0.45 at the imaging angle b. It can be seen that the minimum value of the illuminance E0 is 0.01 at the imaging angle e. Therefore, the predicted brightness unevenness value (difference between the maximum value and the minimum value of the brightness) of the captured image when the illumination unit 121A is turned on can be calculated as 0.44.
Similarly, the maximum value of the illuminance E1 on the subject surface S within the imaging range when the illumination unit 121B is turned on is 0.63 at the imaging angle c, and the minimum value of the illuminance E1 is at the imaging angle e. It turns out that it is 0.02. Therefore, the predicted brightness unevenness value of the captured image when the illumination unit 121B is turned on can be calculated as 0.61.

In this way, the calculation unit 150 calculates the brightness unevenness prediction value of the captured image when the candidate of the illumination unit corresponding to the angle of view is turned on in S6 of FIG. 5, and the calculated brightness unevenness prediction value and the user Compare with the set predetermined value. That is, when the candidate of the illumination unit is the illumination unit 121B, the brightness unevenness prediction value = 0.61 is compared with the predetermined value. Then, when the calculation unit 150 determines that the luminance unevenness predicted value is equal to or greater than the predetermined value, it determines that the luminance unevenness occurs and shifts to S7, and determines that the luminance unevenness predicted value is less than the predetermined value. Moves to S8.

In S7, the calculation unit 150 selects a wide-angle lighting unit from the candidates for the lighting unit corresponding to the angle of view, and transmits the lighting control information to the lighting control unit 122 so as to light the selected lighting unit. That is, when the illumination unit 121B is selected as a candidate for the illumination unit based on the angle of view, the illumination unit 121A having a wider angle is selected and the illumination control is performed so as to turn it on. As described above, since the predicted brightness unevenness value when the illumination unit 121A is turned on is 0.44, the brightness unevenness can be suppressed by 0.17 by lighting the illumination unit 121A instead of the illumination unit 121B. it can. FIG. 8A shows an image of uneven brightness when the illumination unit 121B is turned on, and FIG. 8B shows an image of uneven brightness when the illumination unit 121A is turned on. In this way, uneven brightness can be suppressed.

Although this embodiment is an example in which two lighting units 121A and 121B are provided, three or more lighting units may be provided. In this case, the brightness unevenness is predetermined from the lighting unit other than the lighting unit corresponding to the angle of view selected in S5 (that is, the lighting unit other than the lighting unit determined to have the brightness unevenness of the predetermined value or more in S7). The lighting unit having a value less than the value may be selected. Further, in this case, the illumination unit having the smallest luminance unevenness may be selected from the illumination units having the luminance unevenness less than a predetermined value. Alternatively, the illumination unit having the largest peak brightness may be selected from the illumination units whose brightness unevenness is less than a predetermined value.
That is, the smaller the angle formed by the subject surface S and the imaging direction of the imaging unit 110, the more the arithmetic unit 150 selects and lights the illumination unit having a wider irradiation angle from the plurality of illumination units.

In S8, the calculation unit 150 transmits the lighting control information to the lighting control unit 122 so as to light the candidate lighting unit corresponding to the angle of view.
In S9, the calculation unit 150 determines whether or not the imaging conditions have been changed. Specifically, the calculation unit 150 determines whether or not the tilt angle or the angle of view has been changed as an imaging condition. Then, when it is determined that any of the imaging conditions has been changed, the calculation unit 150 determines that it is necessary to calculate the illuminance E that reaches the subject surface again, and returns to S4. On the other hand, when the calculation unit 150 determines that there is no change in the imaging conditions, it determines that the imaging may be continued as it is, and retains the current setting.

As described above, the image pickup apparatus 100 in the present embodiment includes an image pickup unit 110 that takes an image from diagonally above the subject surface, and controls the irradiation angle of the illumination unit that illuminates the object to be imaged by the image pickup unit 110. .. Specifically, the imaging device 100 acquires information on the luminance unevenness of the image captured by the tilt-driven imaging unit 110, and determines whether or not the luminance unevenness is equal to or greater than a predetermined value based on the acquired information on the luminance unevenness. To do. Then, when it is determined that the luminance unevenness is equal to or more than a predetermined value, the imaging device 100 controls the irradiation angle of the illumination unit so that the luminance unevenness becomes less than the predetermined value. Here, the image pickup apparatus 100 acquires information on the luminance unevenness based on the distance to the object to be imaged by the image pickup unit 110 and the illuminance distribution of the illumination unit.

At this time, the image pickup apparatus 100 controls lighting of a plurality of illumination units 121A and 121B capable of irradiating light having different irradiation angles with respect to the subject surface with the imaging direction of the image pickup unit 110 as the irradiation direction. The angle can be controlled. The imaging device 100 may control the irradiation angle by controlling the illumination of the irradiation unit, which can selectively select the irradiation angle from a plurality of irradiation angles.
The image pickup apparatus 100 can acquire distance information indicating the shortest distance between the image pickup unit 110 and the subject surface, and angle information indicating the image pickup direction of the image pickup unit 110. Here, the distance information is height information indicating the height of the imaging unit 110 from the subject surface, and can be acquired based on the focus information of the imaging unit 110. Further, the angle information is the tilt angle of the imaging unit 110, and can be set to 0 ° when the imaging unit 110 is facing directly below (toward the ground). Then, the image pickup apparatus 100 can control the lighting of the plurality of illumination units 121A and 121B based on the acquired height information and the tilt angle.

In this way, since the image pickup apparatus 100 performs illumination control according to the angle formed by the subject surface and the illumination optical axis, the image pickup apparatus 100 can be used as compared with the conventional illumination control using only the focal length (angle of view). It is possible to reduce the brightness unevenness of the captured image caused by the distance difference. Further, since a drive mechanism for changing the irradiation direction of light from the illumination unit relative to the imaging direction is not required, it is possible to reduce the uneven brightness of the captured image with a simple configuration.
Further, the image pickup apparatus 100 in the present embodiment can selectively turn on a plurality of illumination units based on the height information and the tilt angle of the image pickup unit 110 during lighting control. Specifically, the smaller the angle between the subject surface and the imaging direction, the more the illumination unit having a wider irradiation angle can be selected and lit from among the plurality of illumination units.
Therefore, it is possible to appropriately reduce the luminance unevenness in the captured image.

Further, the image pickup apparatus 100 selects an illumination unit to be turned on from a plurality of illumination units based on the angle of view of the image pickup unit 110, and determines the brightness unevenness of the captured image when the selected illumination unit is turned on. be able to. Then, when it is determined that the captured image has uneven brightness, the image pickup apparatus 100 can select and turn on the illumination unit having a wider irradiation angle than the selected illumination unit. As a result, when the brightness unevenness of the captured image is within the permissible range, the illumination unit that irradiates the light having the irradiation angle corresponding to the angle of view can be turned on. Therefore, it is possible to suppress the selection and lighting of the illumination unit having an unnecessarily wide irradiation angle, and to suppress the decrease in the average illuminance within the angle of view.
Further, when selecting the illumination unit corresponding to the angle of view, the image pickup apparatus 100 stores the association information in which the angle of view and the illumination unit to be turned on are associated with each other, and lights up using the stored association information. You can select the lighting unit to be used. Therefore, it is possible to easily select a candidate for the lighting unit to be turned on.

(Second embodiment)
Next, a second embodiment of the present invention will be described.
In the first embodiment described above, the case where the lighting units 121A and 121B are alternately lit has been described. In this second embodiment, the case of irradiating the synthetic light while adjusting the ratio of the irradiation intensities of the illumination units 121A and 121B will be described. By controlling the ratio of the irradiation intensity, it becomes possible to keep the brightness unevenness of the captured image within the range required by the user and to acquire the brightest possible image.

The configuration of the image pickup apparatus 100 in the present embodiment is the same as that of the image pickup apparatus 100 in the first embodiment described above.
However, the image pickup apparatus 100 in the present embodiment is different from the first embodiment in that the illumination control process shown in FIG. 9 is executed instead of the illumination control process shown in FIG. In FIG. 9, the steps for performing the same processing as in FIG. 5 are assigned the same step numbers as those in FIG. 5, and the parts having different processing will be mainly described below.

In S11, similarly to S5 in FIG. 5, the calculation unit 150 acquires the zoom information held by the image processing unit 113, and calculates the angle of view θ ₁ from the acquired zoom information. Then, in the present embodiment, the calculation unit 150 determines the ratio of the irradiation intensities (lighting ratio) of the illumination units 121A and 121B based on the calculated angle of view θ ₁ . The calculation unit 150 stores association information in which the angle of view θ ₁ and the ratio of the irradiation intensities of the illumination units 121A and 121B are associated with each other, and the illumination units 121A and 121B are lit by using the association information. Determine the proportion.

An example of the relationship between the angle of view θ ₁ and the lighting ratios of the illumination units 121A and 121B is shown in FIG. The image pickup apparatus 100 has an upper limit on the power consumption that can be used as a whole, and the upper limit of the power consumption is assigned to each component included in the image pickup apparatus 100 according to the upper limit. Therefore, there is an upper limit to the power that can light the lighting units 121A and 121B at the same time. Therefore, as shown in FIG. 10, the power supply of the lighting units 121A and 121B is such that the total power consumption when the lighting units 121A and 121B are turned on at the same time is the power value allocated to the lighting units 121A and 121B. Set a ratio for. In FIG. 10, the solid line is the power ratio of the illumination unit 121A, and the broken line is the power ratio of the illumination unit 121B.

In the present embodiment, when the angle of view θ ₁ is 120 ° or more, which is the irradiation angle of the illumination unit 121A, the power ratio of the illumination unit 121A is set to 100%, and only the illumination unit 121A is selected as a candidate for the illumination unit to be turned on. To do. On the other hand, when the angle of view θ ₁ is 70 ° or less, which is the irradiation angle of the illumination unit 121B, the power ratio of the illumination unit 121B is set to 100%, and only the illumination unit 121B is selected as a candidate for the illumination unit to be turned on. When the angle of view θ ₁ is larger than 70 ° and smaller than 120 °, the lighting units 121A and 121B are selected as candidates for the lighting unit to be turned on, and the larger the angle of view θ ₁ , the larger the lighting ratio of the irradiation unit 121A. Set.

In S12, the calculation unit 150 calculates the lighting ratios of the illumination units 121A and 121B so that the luminance unevenness is equal to or less than the predetermined value Th and the average illuminance within the imaging range is maximized. Here, the predetermined value Th = 0.50 can be set.
Similar to the first embodiment described above, when the illuminance reaching the subject surface is obtained from the illumination units 121A and 121B for all the object points on the subject surface within the imaging range, the result is as shown in FIG. 11A. (E0, E1). Further, when the light from the illumination units 121A and 121B is combined at a predetermined ratio, the illuminance reaching the subject surface is indicated by the alternate long and short dash line E2. Here, the illuminance E2 is an illuminance distribution (luminance unevenness prediction value) when the combined ratio of the illumination A of the illumination unit 121A and the illumination B of the illumination unit 121B is 4: 6.
FIG. 11B shows the results of obtaining the brightness unevenness and the average illuminance within the imaging range at each composite ratio. Here, in order to simplify the calculation, the composition ratio is only an integer ratio of 10 in total. When the predetermined value Th = 0.50, from the result of FIG. 11B, the composite ratio at which the luminance unevenness is equal to or less than the predetermined value Th and the average illuminance within the imaging range is maximized is Illumination A: Illumination B. It can be seen that = 4: 6.

Then, in S13, the calculation unit 150 transmits the lighting ratio calculated in S12 to the lighting control unit 122 as lighting control information. As a result, the lighting control unit 122 performs lighting control so that the lighting units 121A and 121B are turned on at a rate based on the received lighting control information.
That is, when the calculation unit 150 determines that the captured image has uneven brightness when the illumination unit is turned on at the lighting ratio determined based on the angle of view θ ₁ , the irradiation angle is higher than the determined lighting ratio. Increases the ratio of the irradiation intensity of wide illumination to turn on the illumination unit. In this case, the smaller the angle formed by the subject surface S and the imaging direction of the imaging unit 110, the larger the ratio of the irradiation intensity of the illumination unit having a wide irradiation angle among the plurality of illumination units.

As described above, the image pickup apparatus 100 in the present embodiment can control the ratio of the irradiation intensities of the plurality of illumination units 121A and 121B based on the height information and the tilt angle of the image pickup unit 100. Therefore, as in the first embodiment described above, the image pickup apparatus 100 has a captured image that is caused by a distance difference from the image pickup apparatus 100, rather than the conventional illumination control using only the focal length (angle of view). Brightness unevenness can be reduced.
Further, in the imaging device 100 of the present embodiment, in the lighting control, the smaller the angle formed by the subject surface and the imaging direction, the larger the ratio of the irradiation intensity of the illumination unit having a wide irradiation angle among the plurality of illumination units. it can.
Therefore, it is possible to appropriately reduce the luminance unevenness in the captured image.

Further, the image pickup apparatus 100 determines the ratio of the irradiation intensities of the plurality of illumination units based on the angle of view of the image pickup unit 110, and the brightness unevenness of the captured image when the plurality of illumination units are turned on at the determined ratio. Can be determined. Then, when it is determined that the captured image has uneven brightness, the image pickup apparatus 100 can increase the ratio of the irradiation intensity of the illumination unit having a wider irradiation angle than the determined ratio. Therefore, it is possible to suppress an increase in the ratio of the irradiation intensity of the illumination unit having an unnecessarily wide irradiation angle, and to suppress a decrease in the average illuminance within the angle of view.
Further, at this time, when the imaging device 100 determines that the captured image has uneven brightness, the ratio of the irradiation intensities of the plurality of illumination units is set so that the uneven brightness of the captured image is equal to or less than a predetermined value and is within the imaging range. The ratio can be controlled to maximize the average illuminance. Therefore, it is possible to obtain an image as bright as possible while keeping the luminance unevenness within an allowable range.

(Modification example)
In each of the above embodiments, the case where the subject surface is a horizontal surface such as the ground has been described, but the subject surface may be a vertical surface such as a wall or an inclined surface inclined with respect to the horizontal surface. Good.
Further, in each of the above embodiments, as shown in FIG. 1, the case where the imaging unit 110 images the subject from diagonally above has been described, but the imaging unit 110 may be configured to image the subject from diagonally below. ..
Further, in each of the above embodiments, the case where the tilt angle θ ₀ shown in FIG. 1 is used as the angle information indicating the angle of the imaging unit 110 with respect to the subject surface has been described, but the present invention is not limited to the above. .. The angle information indicating the angle of the imaging direction with respect to the subject surface of the imaging unit 110 may be any angle information indicating the angle formed by the subject surface and the imaging direction (optical axis) of the imaging unit 110, and the pan angle of the imaging unit 110 may be used. There may be.

Further, in each of the above embodiments, the case where the illumination units 121A and 121B are built in the image pickup apparatus 100 has been described. However, the illumination units 121A and 121B may have a configuration in which the irradiation direction can be changed so that the center of the illuminance distribution coincides with the center of the angle of view of the imaging unit 110 as the imaging direction of the imaging unit 110 changes. , May be externally attached to the image pickup apparatus 100.
Further, in each of the above embodiments, the case where the image pickup apparatus 100 includes two illumination units has been described, but the number of illumination units is not limited to the above. As long as the irradiation angle can be changed, the number of illumination units may be one. Further, if the irradiation angles are different, the number of irradiation portions may be three or more.

Further, in each of the above embodiments, the image pickup apparatus 100 acquires information on the brightness unevenness of the image captured by the image pickup unit based on the distance to the object to be imaged by the image pickup unit and the illuminance distribution of the illumination unit, and obtains the brightness. The case of determining unevenness has been described. However, the brightness unevenness of the image may be determined by analyzing the image captured by the imaging unit. That is, the information regarding the luminance unevenness used for determining the luminance unevenness may be the luminance information of the image captured by the imaging unit.
Further, in each of the above embodiments, the case where the image pickup device 100 operates as a lighting control device has been described, but the image pickup device 100 may have only a part of the functions of the lighting control device, or other devices. May have some or all of the functions of the lighting control device.

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

100 ... Imaging device, 110 ... Imaging unit, 111 ... Lens unit, 112 ... Image sensor unit, 113 ... Image processing unit, 121A, 121B ... Lighting unit, 122 ... Lighting control unit, 130 ... Height information acquisition unit, 140 ... Tilt drive unit, 150 ... calculation unit, 160 ... network processing unit, 200 ... network

Claims (18)

A control means for controlling the irradiation angle of an illumination unit that illuminates an object to be imaged by the image pickup means,
An acquisition means for acquiring information on brightness unevenness of an image captured by the tilt-driven imaging means, and an acquisition means.
It has a determination means for determining whether or not the luminance unevenness is equal to or higher than a predetermined value based on the information regarding the luminance unevenness acquired by the acquisition means.
The control means is characterized in that when the determination means determines that the luminance unevenness is equal to or greater than the predetermined value, the irradiation angle of the illumination unit is controlled so that the luminance unevenness becomes less than the predetermined value. Lighting control device. The lighting control device according to claim 1, wherein the acquisition means acquires information on the luminance unevenness based on the distance to an object to be imaged by the imaging means and the illuminance distribution of the illumination unit. .. The acquisition means
A first acquisition means for acquiring distance information indicating the shortest distance between the imaging means and the subject surface,
A second acquisition means for acquiring angle information indicating the imaging direction of the imaging means is provided.
The control means
The first or second aspect of the present invention, wherein the lighting control of a plurality of the illumination units capable of irradiating the subject surface with light having different irradiation angles is performed with the imaging direction of the imaging means as the irradiation direction. Lighting control device. The control means
The lighting control device according to claim 3, wherein the plurality of lighting units are selectively turned on. The control means
The lighting control device according to claim 4, wherein the smaller the angle formed by the subject surface and the imaging direction is, the wider the illumination angle is selected and lit from the plurality of illumination units. .. A selection means for selecting a lighting unit to be turned on from the plurality of lighting units based on the angle of view of the imaging means is provided.
The determination means determines the brightness unevenness when the illumination unit selected by the selection means is turned on.
The control means is characterized in that when the determination means determines that the luminance unevenness is equal to or greater than the predetermined value, the lighting unit is selected and turned on so that the luminance unevenness is less than the predetermined value. The lighting control device according to claim 4 or 5. Further provided with a storage means for storing associating information in which the angle of view and the lighting unit to be lit are associated with each other.
The lighting control device according to claim 6, wherein the selection means selects the lighting unit to be turned on by using the association information stored by the storage means. The control means
The lighting control device according to claim 3, wherein the ratio of the irradiation intensity of the plurality of lighting units is controlled. The control means
The illumination according to claim 8, wherein the smaller the angle formed by the subject surface and the imaging direction, the larger the ratio of the irradiation intensity of the illumination unit having a wide irradiation angle among the plurality of illumination units. Control device. A determination means for determining the ratio of the irradiation intensities of the plurality of illumination units based on the angle of view of the imaging means is provided.
The determination means determines the brightness unevenness when the plurality of illumination units are turned on at a rate determined by the determination means.
When the determination means determines that the luminance unevenness is equal to or greater than the predetermined value, the control means sets the ratio of the irradiation intensities of the plurality of lighting units to the proportion at which the luminance unevenness becomes less than the predetermined value. The lighting control device according to claim 8 or 9, wherein the lighting control device is controlled. The control means
The ratio of the irradiation intensity of the plurality of lighting units is controlled so that the brightness unevenness determined by the determination means is less than the predetermined value and the average illuminance within the imaging range of the imaging means is maximized. The lighting control device according to claim 10. Further provided with a storage means for storing associating information in which the angle of view and the ratio of the irradiation intensity are associated with each other.
The lighting control device according to claim 10 or 11, wherein the determination means determines the ratio of the irradiation intensity by using the association information stored by the storage means. The imaging means captures images from diagonally above the subject surface.
The first acquisition means according to any one of claims 3 to 12, wherein the first acquisition means acquires height information indicating the height of the imaging means from the subject surface as the distance information. Lighting control device. The lighting control device according to claim 13, wherein the first acquisition means acquires the height information based on the focus information of the imaging means. The lighting control device according to any one of claims 3 to 14, wherein the second acquisition means acquires the tilt angle of the imaging means as the angle information. The lighting control device according to any one of claims 1 to 15.
With the imaging means
With the lighting unit
An imaging device comprising: a driving means capable of changing the imaging direction of the imaging means. A step of acquiring information on brightness unevenness of an image captured by a tilt-driven imaging means, and
Based on the acquired information on the luminance unevenness, a step of determining whether or not the luminance unevenness is equal to or higher than a predetermined value, and
When it is determined that the luminance unevenness is equal to or more than the predetermined value, the step of controlling the irradiation angle of the illumination unit that illuminates the object to be imaged by the imaging means so that the luminance unevenness becomes less than the predetermined value. A lighting control method comprising ,. A program for causing a computer to function as each means of the lighting control device according to any one of claims 1 to 15.

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