JP4416206B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus provided with illumination means, and more particularly to illumination control thereof.
[0002]
[Prior art]
In recent years, monitoring devices using an imaging device such as an industrial television camera (ITV camera) have been installed in various places, and are effective for intruder detection and abnormality detection. Such a monitoring apparatus acquires an image of a monitoring target area with an ITV camera installed on a ceiling or the like. Even now, there are monitoring systems in which a monitoring person monitors a monitoring image to detect an abnormality or the like, but in recent years, an image recognition device is combined to automatically detect an image of a detection target appearing in the monitoring image. Monitoring devices to detect have been developed.
[0003]
The automatic monitoring device is often used for monitoring a room at night or turned off. For this reason, there has conventionally been a monitoring device to which some sort of lighting means is added. As this illuminating means, generally, an LED (Light Emission Diode) having a long life and good electro-optical conversion efficiency is used. By the way, since each LED does not emit a large amount of light, a plurality of LEDs are used as the illumination means of the monitoring device, and they cover the angle of view of the camera, for example, in the immediate vicinity of the monitoring camera or with the monitoring camera. To be arranged. In a bright environment where the conventional monitoring device is turned on in the daytime or indoor lighting, it is detected from the overall brightness of the image and the LED is turned off by itself, while it is dark at night or when the room is turned off. In the environment, the brightness of the image is secured by turning on the LED.
[0004]
[Problems to be solved by the invention]
Conventionally, a plurality of LEDs have been used because the light quantity of the LEDs is small as described above, but they are uniformly turned ON / OFF, and it can be said that they are functionally one illumination means.
[0005]
Now, since the monitoring apparatus has various installation locations, various structures can exist in the imaging region. This is particularly noticeable indoors. For example, considering a normal room, there are structures such as pillars, desks, lockers, partitions, etc., and many monitoring devices are installed on the ceiling, so that the protruding parts of the ceiling (for example, fluorescent lights, smoke detectors, etc.) ) Can also enter the image of the monitoring device. Depending on the distance between these structures and the monitoring device, the direction of the structures, the reflectance, etc., the amount of light emitted from the LEDs returns to the camera changes.
[0006]
As an example of a simple situation, there may be a structure in front of the camera. In this case, the reflected light from the structure located in front becomes stronger. For this reason, on the image, the region where the structure is reflected is photographed very brightly, but the region where the structure is not present and the rear is reflected is photographed darkly.
[0007]
When monitoring a long and narrow space such as a corridor, in order to obtain a good image with a reduced dynamic range, it is preferable to focus the irradiation light in the depth direction, while monitoring a large room. It is preferable that the light distribution is even and wide. However, such different situations cannot be handled by the same illumination means provided in the conventional monitoring device.
[0008]
In the conventional monitoring apparatus provided with the illumination means described above, there is a problem that there are cases where an image having an appropriate luminance distribution cannot be obtained in various situations in which it is used. In particular, when a captured image is processed to detect the presence or absence of an object, the brightness of the obtained image may change due to a change in the situation of the installation location of the monitoring device, and appropriate monitoring may not be performed.
[0009]
The present invention has been made to solve the above problems, and an object thereof is to provide an imaging apparatus capable of obtaining an image with an appropriate luminance distribution suitable for visual recognition and automatic image recognition even under various usage conditions. To do.
[0010]
[Means for Solving the Problems]
An image pickup apparatus according to the present invention is a light source that illuminates a photographing region, and a plurality of illuminating means capable of individually controlling a light emission amount, and a light amount control means for controlling light emission of each of the illumination means with an individual light emission amount, The imaging means for acquiring the image of the photographing area, the response storage means for storing the illumination means and the information on the image area affected by the illumination means in association with each other, and the light quantity control means The luminance dispersion value obtained for the image area is obtained by performing a process for obtaining the luminance dispersion value of the image area of interest when the light emission amount of the illuminating unit corresponding to the image area to be emitted is controlled. and wherein the image processing means to be stored before the sharp Suponsu storage means the relationship between the light emission amount of the illumination means corresponding to the image area of the focus when asked for it, before The light quantity control means refers to the response storage means, determines a light emission amount that maximizes the luminance dispersion value for the illumination means, and the illumination corresponding to the image area of interest with the determined light emission amount The light emission control of the means is performed.
[0011]
According to the present invention, based on the luminance distribution detected by the image processing means, it is possible to determine a control target such as a portion in the image where the luminance should be increased, a portion where the luminance should be decreased, and a required luminance change amount. For example, it is determined that the brightness of an extremely bright part in the image should be lowered. The light quantity control unit individually controls the light emission amounts of the plurality of illumination units according to the control target, and brings the luminance distribution of the image close to a desired state.
[0012]
According to the present invention, the response storage means holds information as to which part of the image the light emission of each lighting means affects and how much it influences as an illumination response relationship. This illumination response relationship can be determined for each individual illumination means, or for each of several illumination means. On the other hand, it can be determined as a relationship such as which illumination means influences a predetermined area of an image and how much the influence degree is. Based on the illumination response relationship, the light amount control unit identifies one or more illumination units related to the target image region whose luminance is to be controlled, and changes the light emission amount of the illumination unit according to the control target, for example. In addition, when the illumination response relationship includes information on the degree of influence of the illumination unit on the target image area, the light amount control unit can determine the variation amount of the light emission amount of the illumination unit in consideration thereof.
[0014]
In a preferred aspect of the present invention, the light amount control unit includes a plurality of light amounts including a maximum light amount and a minimum light amount of the illumination unit corresponding to the image area of interest in the process of obtaining a luminance dispersion value of the image area of interest . The light emission is controlled by the light emission amount .
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment in which an imaging apparatus according to the present invention is applied to an intruder monitoring apparatus will be described with reference to the drawings.
[0017]
1 and 2 are diagrams illustrating the structure of an imaging device used in the intruder monitoring device of the present invention. FIG. 1 is a top view of the camera substrate 2. A solid-state image sensor such as a CCD image sensor is mounted on the central portion of the substrate, and an optical image is formed on the light receiving surface of the image sensor by a camera lens 4 mounted thereon. A plurality of LEDs 8 are arranged on the substrate 2 around the imaging unit 6 constituted by the imaging element and the camera lens. Here, a total of twelve LEDs 8 (L _ij , where i = 1 to 3, j = 1 to 4) are attached to the camera substrate 2 in a matrix form on each of the left and right sides of the imaging unit 6.
[0018]
A lens array 10 is mounted on these LEDs 8. FIG. 2 is a schematic cross-sectional view of the camera substrate 2 including the lens array 10. This figure shows a cross section along the line AA 'shown in FIG. Each lens of the lens array 10 is provided corresponding to the LED 8. Each lens is a plano-convex lens, and the flat end surface is directed to the LED 8 and the convex surface is directed outward. The lens focuses the light emitted from the LED 8 within a certain angle range. Further, the direction of the optical axis 11 of the light from the LED 8 can be changed by inclining the end face of the lens with respect to the LED 8. By tilting the end face in the column direction of the array of the LEDs 8, for example, the four LEDs 8 (L _{11 to} L ₁₄ ) belonging to the upper row have an optical axis that is 20 ° higher when the imaging region is viewed from the camera substrate 2. Directed in the direction. The four LEDs 8 (L _{21 to} L ₂₄ , L _{31 to} L ₃₄ ) in the middle and lower rows are respectively directed in the upper 10 ° direction and the lower 10 ° direction. Similarly, by tilting the end face in the row direction of the LED 8 array, the optical axis of the light from the LED can be made different in the row direction of the LED array. For example, the direction of the optical axis of each column of the LED array is in the order of 25 ° to the right, 5 ° to the right, and 5 ° to the left when viewing the imaging region from the camera substrate 2 in order from the left column toward the camera substrate 2. It can be directed to the left 25 ° direction.
[0019]
In this way, while the emitted light from each LED 8 is focused using the lens array 10, the direction of the optical axis is made different so that each LED 8 irradiates a different partial region of the imaging region. Can do. The configuration in which the optical axis is changed by the lens array 10 is easy to manufacture because the LED 8 itself only needs to be arranged flat on the camera substrate 2 in the same direction.
[0020]
Since this apparatus is exclusively attached to the ceiling obliquely downward, the LED 8 is arranged on the left and right of the imaging unit 6 from the viewpoint of suppressing the apparatus height in the attached state, and the vertical direction of the camera substrate 2 is set. The size is suppressed. Here, the configuration in which the LEDs 8 are arranged symmetrically on both sides of the imaging unit 6 makes it easier to make the illumination conditions for the left and right partial regions of the imaging region uniform than the configuration in which the LEDs 8 are arranged only on one side of the imaging unit 6. In principle, the LEDs 8 may be arranged so as to surround not only the left and right sides of the image pickup unit 6 but also the image pickup unit 6 in, for example, a letter “B”. Such a configuration would be preferable without being restricted by the height of the apparatus when the camera substrate 2 is placed flat on the ceiling and the area directly underneath is monitored.
[0021]
FIG. 3 is a schematic diagram of an image 20 obtained by the present apparatus. As described above, 12 image areas are defined in the image corresponding to the partial areas respectively illuminated by the 12 LEDs 8. In the figure, the boundary of the image area 22 is indicated by a dotted line. Twelve image areas 22 (A _ij , where i = 1 to 3, j = 1 to 4) are arranged in 3 rows and 4 columns corresponding to the arrangement of the LEDs 8. Here, for the sake of convenience, the suffix of A _ij representing each image area 22 is made to coincide with the suffix of L _ij representing the corresponding LED 8. Incidentally, the image 20 shown here shows a room and a rectangular parallelepiped structure 24 placed in the room.
[0022]
FIG. 4 is a schematic block diagram of a monitoring device 30 to which the imaging device according to the present invention is applied. In this apparatus, the imaging unit 6 capable of shooting a moving image and the 12 LED lights 32 configured by the respective LEDs 8 and the drive circuit for each LED 8 are integrally configured on the camera substrate 2 as described above, and the imaging region It is arranged toward.
[0023]
An image output from the imaging unit 6 is input to the image processing unit 34. The image processing unit 34 includes an intruder detection processing unit 36 and a luminance distribution detection processing unit 38. The intruder detection processing unit 36 performs an image recognition process on the input image to detect an intruder, and can adopt a conventional process. The luminance distribution detection processing unit 38 performs processing for obtaining the luminance distribution in the input image. The processing result of the luminance distribution detection processing unit 38 is used by the light amount control unit 40 as described later. The luminance distribution detection processing unit 38 and the light amount control unit 40 perform processing using the illumination response relationship stored in the response storage unit 42.
[0024]
The image processing unit 34 and the light amount control unit 40 can be configured using, for example, a central processing unit (CPU). The response storage unit 42 can use a magnetic recording device such as a hard disk device, but can also increase the processing speed by using a semiconductor memory such as a RAM (Random Access Memory).
[0025]
In the response storage unit 42, which region of the image corresponds to each image area (definition of the image area A _ij ), and which LED 8 (or LED illumination 32) irradiates each image area A _ij ( The correspondence relationship between the image area A _ij and the LED 8) is stored in advance. Here, the correspondence between A _ij and L _ij having the same subscript corresponds to the correspondence between the latter image area A _ij and the LED 8.
[0026]
The luminance distribution detection processing unit 38 classifies the image data for each image area based on the definition information of the image area obtained from the response storage unit 42, and obtains the average luminance and the variance value of each image area.
[0027]
The light quantity control unit 40 adjusts the light emission amount of each LED illumination 32 based on the luminance distribution information obtained by the luminance distribution detection processing unit 38. For example, in the example shown in FIG. 3, there is a structure 24 which is largely contained in the image area A _23. Here, the luminance of the image area A ₂₃ is higher than that of the other image areas because the structure 24 is closer to the monitoring device 30 than the walls and floors of the room reflected in the other image areas and the reflectance thereof is higher. Suppose that halation is very high. When the luminance distribution detection processing unit 38 detects that the luminance of the image area A ₂₃ is high, the light quantity control unit 40 illuminates the image area A ₂₃ based on the illumination response relationship stored in the response storage unit 42. but to understand that it is the L _23. The light amount control unit 40 performs control so as to reduce the emission amount of L _23. Thereby, the halation of the image area A ₂₃ can be suppressed, and an image suitable for the image recognition processing in the intruder detection processing unit 36 can be obtained.
[0028]
Next, the automatic lighting control processing of the present apparatus will be described using a flowchart. Note that this automatic lighting control process is preferably performed in a situation where the LED lighting 32 is used, that is, in a state where night lighting or indoor lighting is turned off. FIG. 5 is a flowchart showing a first example of the illumination automatic control process. In this process, the optimum light emission condition is determined for each image area. Image areas for which the optimum condition determination process has not yet been performed are selected one by one (S50), and the determination process is performed. Only the LED illumination 32 corresponding to the image area selected as the determination process target is caused to emit light with the maximum light amount, and the remaining LED illumination 32 is turned off (S52). Specifically, the light quantity control unit 40 searches the illumination response relationship stored in the response storage unit 42, recognizes the LED illumination 32 corresponding to the processing target image area, and causes only the LED illumination 32 to emit light.
[0029]
A characteristic of an image that is inappropriate for visual recognition and image recognition with respect to luminance is a so-called “collapsed” state in which the luminance is too strong to cause halation, or the image is dark due to insufficient light quantity, and has a low contrast. Here, the luminance dispersion value in the image area is used as an index for determining the optimum light emission state, and the light emission condition for realizing good contrast is obtained. Therefore, the luminance distribution detection processing unit 38 calculates the luminance variance value of the image area to be processed based on the image data from the imaging unit 6, and records the value (S54). Process S54 is repeated while reducing the light emission amount by a certain value (S58) until the light emission amount of the target LED illumination 32 becomes the minimum (S56).
[0030]
When the process of changing the light emission amount from the maximum state to the minimum state is completed for the target image area (S56), the luminance dispersion value recorded at each level of the light emission amount is searched to obtain the luminance dispersion value. The maximum emission level is selected. The light emission condition that maximizes the luminance dispersion value is determined as the optimum light emission condition for the image area (S60). When the process for one image area is completed in this way, it is checked whether there is an image area that has not been processed yet (S62), and if there is, the process returns to process S50. On the other hand, when the optimum light emission conditions are determined for all image areas, the automatic illumination control process ends.
[0031]
Incidentally, when the light emission amount is reduced by a certain value in the process S58, the constant value can be set to a value such as 10% of the maximum light amount.
[0032]
In the above-described processing, the luminance dispersion value is used as the determination index for the optimum state. However, the average luminance within the image area can also be used as the determination index. In a portion having an inappropriate luminance such as overexposure or blackening, the image data takes the maximum value, the minimum value, or a value close to the allowable data range. Therefore, even if a detection object such as an intruder appears in the background, such an inappropriate luminance state does not occur. Therefore, the average luminance of the image area constituting the background is, for example, approximately in the center of the data range. Lighting conditions can be determined as follows. Luminance level U _T to its target, for example, when the image obtained from the imaging unit 6 is a digital data having 256 gradations can be set to an intermediate luminance value 128. If the image is an NTSC analog signal, the intermediate value can be set to 0.35V with respect to 0.7Vp-p.
[0033]
Further, both the luminance dispersion value and the average luminance can be used as a determination index. For example, the light emission condition for each image area can be determined so that both the condition that the average luminance is within a predetermined range near the center of the predetermined data range and the condition that the luminance dispersion value is maximized are satisfied. .
[0034]
FIG. 6 is a flowchart showing a second example of the illumination automatic control process. When the process is started, as an initial state, all LED lights 32 emit light with the maximum light amount (S100). The subsequent processes S102 to S108 are repeatedly executed to search for suitable illumination conditions.
[0035]
The luminance distribution detection processing unit 38 calculates the average luminance of each image area 22 based on the image data from the imaging unit 6 (S102). The light quantity control unit 40 compares the target luminance U _T set in advance with the luminance U _ij of each image area, and selects a high luminance area which is an image area having a luminance higher than U _T (S104).
[0036]
The light quantity control unit 40 searches the illumination response relationship stored in the response storage unit 42 and identifies the LED illumination 32 corresponding to each high-luminance area. If any of the identified LED lights 32 does not reach the minimum value (S106), the LED light 32 that does not reach the minimum value is reduced by a predetermined amount (S108). This reduction amount can be set to a constant value regardless of each LED illumination 32. Further, the amount of light emission reduction of each image area A _ij can be determined by α (U _ij −U _T ) using an appropriate proportionality coefficient α (> 0). It should be noted that the amount of light emission is not reduced for the LED illumination 32 that has already been determined to have reached the minimum value in step S106.
[0037]
In this manner, the process returns to step S102 in a state where the light emission amount of the LED illumination 32 corresponding to the high luminance area is reduced. Similarly, by detecting the high luminance area based on the image obtained in this state and repeating the process of reducing the light emission amount of the corresponding LED illumination 32, the luminance of each image area basically approaches the target luminance, The luminance distribution of the entire image is made uniform, that is, the luminance dynamic range is suppressed.
[0038]
If it is determined in step S104 that there is no high-luminance area, it means that the luminance of all the image areas has almost reached the target state. In this case, each LED illumination 32 obtained is obtained. The light emission conditions are saved and the automatic lighting control process is terminated. Thereafter, when performing the monitoring process by causing the LED illumination 32 to emit light at night or the like, each LED illumination 32 emits light under the stored light emission conditions.
[0039]
On the other hand, if there is a high-luminance area in process S106 but the light emission amount of the LED illumination 32 corresponding to the high-luminance area is already the minimum value, the process is terminated because the process cannot be continued. The light emission condition obtained in this case is considered to be a preferable condition that can be obtained in a situation where the apparatus is installed although the adjustment has not been completed. Therefore, in this case, it is optional to notify the monitor that the adjustment has not been completed or to start the monitoring process using the light emission condition.
[0040]
The process described here is a process of starting from the state where the light quantity is maximum and reducing the light emission amount of the LED illumination 32 so that the brightness of the image area approaches the target brightness. However, on the contrary, it is also possible to employ a process of starting from a state where the light quantity is minimum and increasing the light emission amount of the LED illumination 32 toward the target luminance.
[0041]
By performing the illumination automatic control process described above, a background image suitable for intruder detection can be obtained. Therefore, it is desirable to implement the automatic lighting control process at least before installing the monitoring apparatus and starting the monitoring process. However, it is desirable that the automatic lighting control process is appropriately performed so as to be able to cope with a change in the situation such as a layout change of an arrangement object constituting the background even after the operation is started.
[0042]
The illumination response relationship used in the above-described configuration is that the image area 22 and the LED illumination 32 have a one-to-one correspondence relationship. However, depending on the setting method of the image area and the configuration of the LED illumination 32, each light from the adjacent LED illumination 32 may irradiate a common image area. In such a case, the illumination response relationship can be defined as a many-to-one correspondence relationship between the image area 22 and the LED illumination 32, or a one-to-many correspondence relationship. These relationships will be specifically described using the above-described image area array A _ij and LED array L _ij . First, the many-to-one relationship is, for example, that light emitted from L ₂₂ is not only A ₂₂ but also A ₁₁ , A ₁₂ , A ₁₃ , A ₂₃ , A ₃₃ , A ₃₂ , A ₃₁ , A _{21 around} it. It also represents reaching. Therefore, a plurality of A _ij is associated with one L _ij . At this time, the degree of influence of L _{ij on} each of the plurality of A _ijs , that is, weighting information, can be included in the illumination response relationship. For example, the influence of the light emitted from L ₂₂ is 0.3 in the upper, lower, left, and right image areas A ₁₂ , A ₂₃ , A ₃₂ , and A ₂₁ with A ₂₂ as the reference value 1, and the image area A located on the diagonal line ₁₁ , A ₁₃ , A ₃₃ , and A ₃₁ can be defined such that the illumination response relationship is 0.1.
[0043]
The one-to-many relationship is also the same as the many-to-one relationship. However, if it is described using an example just in case, for example, the illumination that affects A ₂₂ is not only L ₂₂ but also the surrounding L ₁₁ , L ₁₂ , L ₁₃ , L ₂₃ , L ₃₃ , L ₃₂ , L ₃₁ , and L ₂₁ also indicate that the area A ₂₂ is affected. Therefore, a plurality of L _ij is associated with one A _ij . At this time, the weighting information can be defined by including it in the illumination response relationship. For example, the influence exerted on A ₂₂ is 0.3 from the illumination L ₁₂ , L ₂₃ , L ₃₂ , and L _{21 of the} upper, lower, left and right illuminations L, and the illumination L located on the diagonal line with the influence from L ₂₂ as the reference value 1. Illumination response relationships such as ₁₁ , L ₁₃ , L ₃₃ , and L ₃₁ to 0.1 can be defined.
[0044]
【The invention's effect】
According to the imaging apparatus of the present invention, the fluctuation range of the luminance in the image due to the difference in the structure or the like existing in the imaging region is suppressed, and an image suitable for image recognition processing in human visual recognition and automatic monitoring is obtained. There is an effect.
[Brief description of the drawings]
FIG. 1 is a schematic top view of a camera substrate constituting the apparatus.
FIG. 2 is a schematic cross-sectional view of a camera substrate including a lens array.
FIG. 3 is a schematic diagram of an image obtained by the apparatus.
FIG. 4 is a schematic block diagram of a monitoring apparatus to which an imaging apparatus according to the present invention is applied.
FIG. 5 is a flowchart showing a first example of illumination automatic control processing.
FIG. 6 is a flowchart showing a second example of the illumination automatic control process.
[Explanation of symbols]
2 camera substrate, 4 camera lens, 6 imaging unit, 8 LED, 10 lens array, 30 monitoring device, 32 LED illumination, 34 image processing unit, 36 intruder detection processing unit, 38 luminance distribution detection processing unit, 40 light quantity control unit 42 Response storage unit.

Claims (2)

A plurality of illumination means which are light sources for illuminating the imaging region and capable of individually controlling the light emission amount;
A light amount control means for controlling light emission with an individual light emission amount for each of the illumination means;
Imaging means for acquiring an image of the imaging area;
Response storage means for storing each of the illumination means and information of an image area affected by the illumination means in association with each other;
When the light emission control of the illumination unit corresponding to the image area of interest is controlled by the light amount control unit, a process for obtaining a luminance dispersion value of the image area of interest is performed a plurality of times while changing the amount of light emission. an image processing means for storing prior crisp Suponsu storage means the relationship between the light emission amount of the illumination means corresponding to the luminance variance value obtained image area of the focus when asked for it,
Including
The light amount control means refers to the response storage means, determines a light emission amount that maximizes the luminance dispersion value for the illumination means, and corresponds to the image area of interest by the determined light emission amount. An image pickup apparatus that performs light emission control of an illumination unit. The imaging device according to claim 1,
The light amount control unit performs light emission control with a plurality of light emission amounts including a maximum light amount and a minimum light amount of the illumination unit corresponding to the image area of interest in a process of obtaining a luminance dispersion value of the image area of interest. ,
An imaging apparatus characterized by the above.

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