CN106534663A - Imaging apparatus - Google Patents

Abstract

The present invention provides an imaging device capable of suppressing erroneous operations in the case of automatically correcting the blur of a captured image through simple processing. The imaging device (1) of the present invention comprises: an imaging unit (10), which forms an image of light from a target area on an imaging element (14); an image processing unit (21), which processes a signal output from the imaging element (14) and output video information; and a storage unit (22) storing a reference value of a parameter indicating sharpness of a captured image. The image processing unit (21) acquires the actual measurement value of the parameter based on the signal input from the imaging element (14), stores the actual measurement value acquired at a specific time point as a reference value in the storage unit (22), and then The difference between the obtained measured value and the reference value stored in the storage unit (22) is used to perform sharpening processing on the captured image.

Description

camera device

technical field

The present invention relates to an imaging device for photographing a target area, in particular, an imaging device suitable for photographing scenery whose clarity may be reduced due to rain or fog.

Background technique

Camera devices are known which take pictures of streets or intersections with surveillance cameras. Such an imaging device uses captured images for identification of traffic accidents, for example. In the identification, it is possible to check the conditions of vehicles and pedestrians, the lighting conditions of traffic lights, and the like. In other words, it is possible to confirm whether the traffic lights are lit in red, blue, or yellow at the time of an accident.

However, in places such as streets and intersections, the contrast of the subject may be lowered due to rain or fog. For example, if the intersection is covered with fog, there is a concern that the conditions of vehicles and pedestrians, the lighting conditions of traffic lights, etc. cannot be clearly captured. As a result, authentication using captured images cannot be performed smoothly.

Patent Document 1 below describes a monitoring camera system including a monitoring camera device and a control device. In this monitoring camera system, fog or haze is detected by a control device based on an image captured by the monitoring camera device. The occurrence of fog or haze is detected by comparing a pre-taken image with the current image, and detecting whether or not whitening occurs as a result. In addition, the intensity of fog or haze is judged based on whether or not the level (black peak level) of the portion where the brightness of the image becomes the lowest among the digital video signal components exceeds a specific threshold. Fog or haze is detected in this way, and further, when the intensity of fog or haze is determined, an alarm corresponding to the intensity of fog or haze is output from the control device to an external device. In addition, haze correction corresponding to the determined intensity of fog or haze is performed.

[Background Art Document]

[Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-192762

Contents of the invention

[Problem to be Solved by the Invention]

As described above, in the method of Patent Document 1, in order to correct the image, it is necessary to perform two-step processing of detecting fog or haze and determining the intensity of fog or haze. The intensity of fog or haze is judged based on whether the black peak level exceeds a specific threshold. Therefore, for example, when shooting a scene with a high black peak level in the original video signal, correction may be made. Fear of misoperation.

In view of this problem, an object of the present invention is to provide an imaging device capable of suppressing malfunctions when automatically correcting blur in a captured image through simple processing.

[Technical means to solve the problem]

A main aspect of the present invention relates to an imaging device. The imaging device of this aspect includes: an imaging unit that forms an image of light from a target area on an imaging element; an image processing unit that processes a signal output from the imaging element and outputs image information; and a storage unit that stores a data representing a captured image. Benchmark values for specific parameters of sharpness. Here, the image processing unit acquires the actual measurement value of the parameter based on the signal input from the imaging element, and stores the actual measurement value acquired at a specific time point as the reference value in the storage unit. The difference between the actual measured value obtained thereafter and the reference value stored in the storage unit is used to perform sharpening processing on the captured image.

According to the imaging device of this aspect, since the reference value of the parameter indicating the sharpness of the captured image is set based on the signal input from the imaging element, the set reference value corresponds to the scene to be photographed. For example, when an imaging device is installed to photograph an intersection, the reference value corresponds to the scenery (layout of structures, etc.) of the target area such as the scale of the intersection or the installation status of traffic lights. In addition, since the sharpening process of the captured image is performed based on the difference between the reference value set in this way and the actual measurement value obtained at the time of subsequent imaging, it is possible to appropriately recognize how blurred the target area of the subject is, In addition, it is possible to suppress malfunction of the sharpening process. In this way, according to the imaging device of this aspect, it is possible to suppress malfunctions when automatically correcting the blur of a captured image.

In addition, according to the imaging device of the present aspect, the sharpening process is appropriately performed based on the difference between the reference value and the actual measurement value, and therefore it is not necessary to separately perform a process of detecting whether the captured image is blurred. Thus, according to the imaging device of this aspect, it is possible to clear a captured image by simple processing.

In addition, the "difference between the actual measurement value and the reference value" refers not only to the value obtained by subtracting the reference value from the actual measurement value, but also refers to the ratio of the actual measurement value to the reference value, etc., as long as the actual measurement value and the reference value The value of the difference can be any value.

In the imaging device of the present aspect, when the image processing unit accepts an input of a setting instruction, it may be configured such that the actual measurement value of the parameter obtained from the signal from the imaging element is used as the set value. The reference value is stored in the storage unit. In this way, it is possible to smoothly avoid obtaining and setting a reference value at a time when the target area is not clear. Therefore, it is possible to more reliably suppress a malfunction in the case of automatically correcting the blur of a captured image.

In the imaging device of the present aspect, the storage unit may store the second reference value in advance separately from the first reference value based on the actually measured value. In this case, the image processing unit may be configured such that, when a mode using the first reference value based on an actual measurement value is set, the image processing unit acquires the first reference value based on an actual measurement value and executes the In the sharpening process, when the mode is not set, the sharpening process is executed based on the second reference value. In this way, for example, when the mode using the first reference value is not set because a clear captured image suitable for the setting of the first reference value cannot be obtained, it is possible to perform sharpening using the second reference value. processing.

In the imaging device of this aspect, it is possible to configure the image processing unit to switch an adjustment value for sharpening a captured image according to a difference between the actual measurement value and the reference value. In this case, the adjustment value may be a value for performing gamma correction on a signal output from the imaging element. In this way, by adjusting the value for gamma correction, the contrast of the captured image can be smoothly adjusted to a state suitable for sharpening through simple processing.

In addition, in the imaging device of this aspect, as the parameter indicating the sharpness of the captured image, for example, the standard deviation of brightness obtained from a signal of one image output from the imaging element can be used. By using the standard deviation of brightness in this way, it is possible to accurately grasp the unsharpness of a captured image.

[Effect of the invention]

As described above, according to the present invention, it is possible to provide an imaging device capable of suppressing malfunctions when automatically correcting blur in a captured image through simple processing.

The effects and significance of the present invention will be clarified by the description of the embodiments shown below. However, the embodiments shown below are merely examples for implementing the present invention, and the present invention is by no means limited by the contents described in the following embodiments.

Description of drawings

FIG. 1 is a block diagram showing the configuration of an imaging device according to an embodiment.

FIG. 2 is a block diagram showing the configuration of an image processing unit according to the embodiment.

3( a ) to ( d ) are diagrams illustrating the relationship between the state of a captured image and the histogram of brightness according to the embodiment.

4( a ) to ( d ) are diagrams illustrating a method of correcting the contrast of a captured image (sharpening process) according to the embodiment.

5( a ) and ( b ) are diagrams showing changes in the histogram of luminance when the gamma value of the embodiment is changed.

6( a ) and ( b ) are diagrams showing configuration examples of target areas in a case where the brightness distribution range of the histogram is narrow although the captured image according to the embodiment is clear.

FIG. 7 is a flowchart showing the sharpening process of the embodiment.

FIG. 8 is a diagram showing an example of gamma characteristics used in sharpening processing according to the embodiment.

9( a ) and ( b ) are diagrams schematically showing the effect of the sharpening process according to the embodiment.

detailed description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, the present invention is applied to a monitoring camera for photographing intersections, streets, and the like.

FIG. 1 is a diagram showing the configuration of an imaging device 1 .

The imaging device 1 includes an imaging unit 10 , an image processing unit 21 , a storage unit 22 , a filter driving unit 23 , an aperture driving unit 24 , an input unit 25 , and an output unit 26 .

The imaging unit 10 includes a lens 11 , a diaphragm 12 , a filter 13 , and an imaging element 14 .

The lens 11 captures the light from the target area, and forms the image of the target area on the light-receiving surface of the imaging element 14 . The aperture 12 restricts light from the outside so that an appropriate amount of light is incident on the imaging element 14 according to the intensity of light from the target area. The aperture of the diaphragm 12 is adjusted by the diaphragm driving unit 24 .

The filter 13 includes an IR (Infrared) cut filter for cutting out infrared rays and a dummy glass for transmitting infrared rays together with visible light. The filter 13 is positioned on the optical path between the diaphragm 12 and the imaging element 14 by the image processing unit 21 via the filter driving unit 23 . Specifically, when an illuminance higher than a normal level is obtained in the imaging element 14 , an IR cut filter is inserted into the optical path to cut infrared rays. Also, when the illuminance obtained by the imaging element 14 is low, white glass is inserted into the optical path to introduce infrared rays into the imaging element 14 together with visible light, thereby improving sensitivity.

The imaging element 14 is a color CMOS (Complementary Metal Oxide Semiconductor, Complementary Metal Oxide Semiconductor) image sensor. The imaging element 14 may also be a CCD (Charge Coupled Device, Charge Coupled Device) image sensor. The imaging element 14 outputs a signal corresponding to a captured image to the image processing unit 21 under the control of the image processing unit 21 .

The image processing unit 21 includes an arithmetic processing circuit such as a CPU (Central Processing Unit, central processing unit), and executes image processing based on a program stored in the storage unit 22 . The storage unit 22 includes a storage medium such as a ROM (Read Only Memory) or a RAM (Random Access Memory, random access memory), and not only holds a program for image processing, but also stores a program when the image processing unit 21 performs processing. Used as a work area. The storage unit 22 holds a plurality of gamma correction values corresponding to the level of sharpness of captured images. The gamma correction value held in the storage unit 22 will be additionally described with reference to FIG. 8 .

The filter drive unit 23 and the aperture drive unit 24 are drivers for driving the filter 13 and the aperture 12 under control from the image processing unit 21 , respectively. The input unit 25 has input means such as operation buttons, and accepts instructions from the user. The output unit 26 outputs the image information processed by the image processing unit 21 to an external device via an output terminal.

FIG. 3 is a functional block diagram of the image processing unit 21 .

The image processing unit 21 includes a mosaic processing unit 101, a linear matrix processing unit 102, a gamma correction processing unit 103, a Y/C separation processing unit 104, an outline correction processing unit 105, a color difference correction processing unit 106, and noise removal processing units 107 and 108. .

The signal output from the imaging element 14 in FIG. 1 is input to the mosaic processing unit 101 . The mosaic processing unit 101 generates three-color signals of R, G, and B from signals from each pixel. The linear matrix processing unit 102 performs spectral characteristic correction on the signal generated by the mosaic processing unit 101 .

The gamma correction processing unit 103 performs gamma correction on the signal whose spectral characteristics have been corrected. As described above, the storage unit 22 holds a plurality of gamma correction values corresponding to the level of sharpness of captured images. The gamma correction processing unit 103 applies a gamma correction value corresponding to the sharpness of the captured image. The gamma correction processing unit 103 performs gamma correction on the signal from the linear matrix processing unit 102 using the applied gamma correction value.

The Y/C separation processing unit 104 separates the gamma-corrected signal into a luminance signal and a color difference signal. The contour correction processing unit 105 extracts the contour of the subject from the mosaic-processed signal, and adds the contour signal to the Y/C separated luminance signal. The color difference correction processing unit 106 performs correction processing such as emphasizing a specific color on the Y/C separated color difference signal. The noise removal processing units 107 and 108 remove noise superimposed on the Y/C-separated luminance signal and color difference signal, respectively. The noise-removed luminance signal and color difference signal are output to the output unit 26 in FIG. 1 . The output unit 26 serially converts the luminance signal and the color difference signal and outputs it to the outside.

Next, the sharpening processing by the image processing unit 21 will be described with reference to FIGS. 3( a ) to 6 ( b ). In addition, here, for the sake of convenience, the scenery other than the intersection or the street is taken as the subject.

3( a ) to ( d ) are diagrams showing an example of the relationship between the state of the captured image and the histogram of brightness in the embodiment. FIG. 3( b ) is a histogram for the captured image of FIG. 3( a ), and FIG. 3( d ) is a histogram for the captured image of FIG. 3( c ). In addition, Fig. 3 (a), (c) is actually a color image. That is, the mosaic tiles and dolls in the image come in various colors. In addition, the captured image in FIG. 3( c ) was captured by inserting a foggy filter into the imaging optical system.

As shown in FIG. 3( b ) and ( d ), even if the subject is the same, the brightness distribution range ( R1 , R2 ) on the histogram changes according to the sharpness of the captured image. Specifically, the distribution range R2 when the captured image is unclear is narrower than the distribution range R1 when the captured image is clear. In this way, the lower the sharpness (contrast) of the captured image is, the narrower the luminance distribution range becomes. Therefore, the sharpness of a captured image can be detected from the distribution range of brightness.

In addition, the information for determining the sharpness of a captured image is not limited to the brightness histogram. For example, the sharpness of the captured image may be determined using statistical data of the auto iris or the like.

4( a ) to ( d ) are diagrams illustrating a method of correcting the contrast of a captured image (sharpening processing). 4( a ), ( c ) are the histograms shown in FIGS. 3( b ) and ( d ), respectively, and correspond to the histograms of the captured images in FIGS. 3( a ) and (c). 4( b ) and ( d ) are graphs schematically showing gamma correction values (gamma characteristics) when the brightness histograms are shown in FIG. 4( a ) and (b), respectively. In FIGS. 4( a ) and ( b ), the horizontal axis represents the signal level of the input signal, and the vertical axis represents the signal level of the output signal after gamma correction.

As shown in FIG. 4( a ), when the luminance distribution range R1 in the histogram is wide, gamma correction is performed using the normal gamma correction value shown in FIG. 4( b ). On the other hand, as shown in FIG. 4( c ), when the brightness distribution range R2 in the histogram is narrow, gamma correction is performed using a gamma correction value for improving the contrast shown in FIG. 4( d ).

In the gamma correction value of FIG. 4( d ), the input signals whose signal level is lower than the range W are uniformly converted to the output signal of the lowest level. In addition, input signals whose signal levels are higher than the range W are uniformly converted into output signals of the highest level. Therefore, gray input signals near black are uniformly converted to black, and gray input signals near white are uniformly converted to white. Thereby, the contrast of an image improves.

5( a ) and ( b ) are diagrams showing changes in the brightness histogram when the gamma value (gamma characteristic) is changed. In Fig. 5(a), the dotted line is the gamma characteristic used in normal gamma correction when the gamma value is 0.45, and the solid line is the gamma applied when the sharpness (contrast) of the captured image is low characteristic. In Fig. 5(a), the vertical and horizontal axes are normalized to 1. In addition, in FIG. 5(b), the dotted line is a histogram when the gamma characteristic of the dotted line with a gamma value of 0.45 in FIG. 5(a) is applied to a specific captured image, and the solid line is a histogram when applying FIG. 5( a ) is a histogram in the case of the gamma characteristic of the solid line for low contrast.

As shown in FIG. 5( b ), when gamma correction is performed using the gamma characteristic for low contrast, the histogram of the captured image after correction has a significantly wider brightness distribution range than before correction. That is, it is possible to improve the sharpness (contrast) of an image by performing gamma correction by applying the gamma characteristic for low contrast of FIG.

As described above, it is possible to improve the contrast of a captured image by selecting the gamma correction value to be applied. The image processing unit 21 of FIG. 1 improves the contrast of the captured image by changing the gamma value (gamma characteristic) applied by the gamma correction processing unit 103 of FIG. 2 when the sharpness (contrast) of the captured image is low.

More specifically, the storage unit 22 in FIG. 1 stores the gamma value (gamma characteristic) applied when the resolution of the captured image is low and the normal gamma value (gamma characteristic) when the resolution is high. storage. The image processing unit 21 selects a gamma value suitable for the sharpness of the captured image from the storage unit 22 when the resolution (contrast) of the captured image captured by the imaging element 14 is low, and sets the selected gamma value to The value is applied to the gamma correction processing unit 103 in FIG. 2 . Thereby, the sharpness of a captured image can be improved.

Here, whether or not the sharpness of the captured image is low can be determined from the histograms of the luminance distribution as shown in FIGS. 3( a ) to ( d ).

However, depending on the captured image, there are cases where the brightness distribution range of the histogram is narrowed due to the layout of the subject, etc., although the sharpness does not decrease. For example, the histogram of the captured image (actually a color image) shown in Fig. 6(a) is shown in Fig. 6(b). In this histogram, although the captured image is clear, the luminance distribution range R3 is narrow. In this case, if the gamma value for low contrast is applied, the sharpness of the captured image will be reduced instead.

Therefore, in the present embodiment, processing for suppressing malfunctions in the case of automatically correcting an unclear captured image is performed.

FIG. 7 is a flowchart showing sharpening processing performed by the image processing unit 21 .

In the flowchart of FIG. 7 , the standard deviation σ of a brightness histogram (for example, see FIGS. 3( b ), ( d ) ) is used as a parameter indicating the sharpness of a captured image. In addition, the storage unit 22 in FIG. 1 stores two gamma values G1, G1, G2.

Furthermore, in the flowchart of FIG. 7 , the mode setting of the sharpening process can be performed by the user via the input unit 25 shown in FIG. 1 before or after the process starts. Here, the mode in which the reference value σRef of the standard deviation is set based on the photographed image obtained by photographing the target area is referred to as the preset ON mode, and the general-purpose standard deviation σ0 held in advance in the storage unit 22 is set as the reference value σRef. mode is called preset disconnect mode. The standard deviation σ0 is, for example, the standard deviation of the brightness histogram of a captured image obtained by capturing a standard landscape in a clear state.

Referring to FIG. 7 , when the imaging device 1 is powered on and the initialization process is completed, the image processing unit 21 starts the imaging operation. In this way, after the imaging operation is started, the image processing unit 21 determines whether or not it is the output timing of the vertical synchronization signal (Vsync) ( S101 ). When the vertical synchronization signal is output (S101: YES), the image processing unit 21 executes automatic iris processing (S102) and automatic white balance processing (S103). Furthermore, the image processing unit 21 calculates the standard deviation σ of the luminance histogram of the captured image based on the signal output from the imaging element 14 ( S104 ).

Subsequently, the image processing section 21 determines whether or not the mode of the sharpening process set in the imaging device 1 is the preset ON mode (S105). Here, when the mode of the sharpening process is not the preset ON mode (S105: NO), the image processing unit 21 sets the common standard deviation σ0 previously stored in the storage unit 22 as the reference of the standard deviation. Value σRef (S108).

On the other hand, when the mode of the sharpening processing is the preset ON mode (S105: YES), the image processing unit 21 determines whether the mode of the sharpening processing is the preset OFF mode at the output timing of the previous vertical synchronizing signal. On mode, that is, whether the mode of the clearing processing is switched from the preset off mode to the preset on mode (S106). Here, when the mode of the sharpening process at the previous output timing of the vertical synchronizing signal is the preset off mode (S106: YES), the image processing unit 21 sets the standard deviation σ calculated in step S104 to The reference value σRef is set, and the set reference value σRef is stored in the storage unit 22 (S107).

In addition, when the mode of the sharpening process at the output timing of the previous vertical synchronizing signal is also the preset ON mode (S106: NO), that is, when the preset ON mode is in continuation from the previous time , the image processing unit 21 skips step S107, and proceeds to step S109. In this case, at least at the previous output timing of the vertical synchronization signal, a standard deviation σ based on the captured image obtained at that timing is set to the reference value σRef, and the reference value is set at the output timing of the current vertical synchronization signal. The output timing of is also valid.

Next, the image processing unit 21 divides the reference value σRef by the standard deviation σ obtained in step S104 to obtain a reference value (S109). The reference value thus calculated becomes larger as the standard deviation σ acquired in step S104 is smaller than the reference value σRef. That is, the narrower the luminance distribution range of the luminance histogram obtained this time for the captured image is compared with the luminance distribution range of the luminance histogram corresponding to the reference value σRef, the larger the reference value. Therefore, the larger the reference value, the lower the sharpness of the captured image obtained this time can be estimated.

After the reference value is calculated in this way, the image processing unit 21 compares the preset thresholds Th1 and Th2 (Th1>Th2) with the reference value (S110, S112). Here, if the reference value is larger than the threshold Th1 (S110: YES), the image processing unit 21 applies the gamma value G1 for low-resolution stored in the storage unit 22 to the gamma correction processing unit 103 of FIG. 2 (S111). . Also, if the reference value is equal to or less than the threshold Th1 and greater than the threshold Th2 (S110: NO, S112: YES), the image processing unit 21 applies the low-resolution gamma value G2 stored in the storage unit 22 to the The gamma correction processing unit 103 (S113). Also, when the reference value is equal to or less than the threshold Th2 (S110: NO, S112: NO), the image processing unit 21 applies the normal sharpness gamma value G3 stored in the storage unit 22 to the gamma value G3 in FIG. 2 . The MA correction processing unit 103 (S114). The gamma correction processing section 103 of FIG. 2 performs gamma correction based on the thus applied gamma value.

Then, the image processing unit 21 determines whether or not the output timing of the vertical synchronization signal has ended (S115). When the output timing of the vertical synchronization signal ends (S115: YES), the image processing unit 21 returns the process to step S101, and waits for the next output timing of the vertical synchronization signal to arrive (S101). Then, when the next output timing of the vertical synchronization signal comes (S101: YES), the image processing unit 21 executes the processing after S102 again. This process is repeatedly executed until the power of the imaging device 1 is turned off.

FIG. 8 is a diagram schematically showing gamma characteristics of gamma values G1 , G2 , and G3 .

As shown in FIG. 8, the gamma value G2 is set so as to correct the range W2 on the low-level side of the input signal to a zero-level output signal with respect to the gamma value G3, and compared with the gamma value G3, The high side of the input signal approaches the maximum level more quickly. In addition, the gamma value G1 is set so that the range W1 on the input side is wider than the range W2 of the gamma value G2, and the high-level side of the input signal approaches the maximum voltage faster than the gamma value G2. flat.

By setting the gamma values G1 and G2 in this way, as described with reference to FIGS. Compared with the case where gamma correction is performed, the sharpness (contrast) of the captured image is improved. In addition, when the gamma correction is performed using the gamma value G1, the sharpness (contrast) of the captured image is further improved compared to the case where the gamma correction is performed using the gamma value G2.

Therefore, in step S110 of FIG. 7 , when it is determined that the reference value is greater than the threshold Th1, that is, the sharpness of the captured image decreases sharply, the gamma correction processing unit 103 (see FIG. 2 ) To perform gamma correction, it can effectively clear the captured image. In addition, in step S112 of FIG. 7 , when it is determined that the reference value is greater than the threshold Th2, that is, the sharpness of the captured image is reduced to a moderate degree, gamma is performed by applying the gamma value G2 to the gamma correction processing unit 103. MA correction can effectively sharpen the captured image without excessive sharpening processing on the captured image.

FIG. 9 is a diagram schematically showing captured images when the imaging device 1 is installed at an intersection.

FIG. 9( a ) shows a state in which the sharpness of a captured image is lowered due to the influence of rain, fog, or the like. In the present embodiment, as described above, an appropriate gamma value is applied according to the magnitude of the reference value, that is, the level at which the sharpness of the captured image is lowered. Therefore, as shown in FIG. 9( b ), the sharpness of the captured image can be improved. Thereby, the user can accurately confirm the conditions of the traffic signal 2 , the intersection 3 , the person 4 , and the vehicle 5 from the captured image.

<Effects of the implementation>

According to this embodiment, the following effects can be exhibited.

As shown in steps S104 and S107 of FIG. 7 , a reference value σRef of a parameter (standard deviation of the luminance histogram) indicating the sharpness of a captured image is set based on a signal input from the imaging element 14 . Therefore, the set reference value σRef is a value corresponding to the scenery to be photographed. For example, as shown in FIGS. 9( a ) and ( b ), when an imaging device 1 is installed to photograph an intersection 3 , the reference value σRef becomes the target area corresponding to the scale of the intersection 3 or the installation status of traffic lights 2 . The value corresponding to the scenery (the layout of the structure, etc.). Then, the sharpening process of the captured image is performed based on the difference (reference value: σRef/σ) between the reference value σRef set in this way and the actual measurement value (standard deviation σ) acquired at the time of subsequent imaging, so that it is possible to accurately It is possible to suppress the erroneous operation of the sharpening process by recognizing the degree of blurring of the target area of the subject. In this manner, according to the imaging device 1 of the present embodiment, it is possible to suppress malfunctions when automatically correcting blurring of captured images.

In addition, according to the imaging device of this embodiment, the sharpening process is appropriately performed based on the difference between the reference value σRef and the actual measurement value (standard deviation σ) (reference value: σRef/σ), so it is not necessary to separately perform detection of whether the captured image has become blurred or not. Unclear processing. Thus, according to the imaging device 1 of the present embodiment, it is possible to clear a captured image by simple processing.

In addition, the imaging device 1 of the present embodiment is configured so that, as shown in step S105 of FIG. The unit 21 stores the actually measured value (standard deviation σ) of the parameter obtained from the signal from the imaging element 14 as a reference value σRef in the storage unit 22 . Therefore, the user can set the standard deviation σ based on a clear captured image as the reference value σRef by inputting an instruction to set the preset on mode when the target area is clear. Accordingly, it is possible to smoothly avoid obtaining and setting a reference value at a time when the target area is unclear. Thereby, it is possible to more reliably suppress malfunctions in the case of automatically correcting the blur of the captured image.

In addition, in the imaging device 1 of the present embodiment, before setting the reference value σRef based on the actual measurement value (standard deviation σ), the common reference value σ0 is stored in the storage unit 22 in advance. Next, as shown in steps S105 to S108 of FIG. 7 , when the preset ON mode is set, the image processing unit 21 acquires the reference value σRef based on the actual measurement value and performs sharpening processing. In the ON mode, clearing processing is performed based on a common reference value σ0. Therefore, for example, when the image pickup device 1 is started on a cloudy day, etc., and a clear captured image suitable for the setting of the reference value σRef cannot be obtained and the preset on-mode is not set, the general-purpose switch can also be used. The base value σ0 of σ is used to perform the sharpening process.

In addition, in the imaging device 1 of the present embodiment, as shown in steps S110 to S114 of FIG. Therefore, the contrast of the captured image can be smoothly adjusted to a state suitable for sharpening by simple processing.

In addition, in the imaging device 1 of the present embodiment, as a parameter indicating the sharpness of the captured image, the brightness standard deviation σ obtained from the signal of one image output from the imaging element 14 is used. As described in (b), the blurriness of the captured image can be accurately grasped.

＜Modification example＞

In the above-described embodiment, the sharpening of the captured image is performed by adjusting the gamma value applied by the gamma correction processing unit 103 , but the sharpening process of the captured image is not limited to this. For example, in an imaging device equipped with a sharpening engine for sharpening, it is also possible to sharpen captured images by adjusting parameter values set in the sharpening engine.

In addition, in the above-described embodiment, two gamma values G1 and G2 are prepared for correction of a low-resolution captured image, but the types of gamma values used for sharpening processing are not limited thereto. For example, in the flowchart of FIG. 7 , three or more threshold values for comparison with the reference value may be set, and three or more gamma values for sharpening processing may be set. In this way, more accurate sharpening processing can be realized. Alternatively, it is also possible to set one threshold value and one gamma value.

In addition, in the above-mentioned embodiment, the reference value is set as the ratio of the reference value σRef to the actual measurement value (standard deviation σ), but the reference value is not limited to this, as long as it is a value indicating how much the actual measurement value differs from the reference value, it can be used. Can be any value. For example, a value obtained by subtracting an actual measurement value (standard deviation σ) from a reference value σRef may be used as a reference value.

In addition, in the above-described embodiment, the variance of the luminance histogram is used as the parameter indicating the sharpness of the captured image, but the parameter indicating the sharpness of the captured image is not limited to this. In addition, the parameter indicating the sharpness of the captured image is not necessarily limited to one type, and two or more parameters may be combined to determine the sharpness of the captured image.

In addition, in the above-described embodiment, the update of the value (gamma value) used for the sharpening process is performed in synchronization with the vertical synchronization signal, but the timing of performing this update is not limited to this. For example, the update of the value used for the sharpening process may be performed every specific time (for example, several seconds to several tens of seconds), or may be performed when a weather change is detected based on date and illuminance.

In addition, the block configuration of the imaging device 1 is not limited to the configuration shown in FIG. 1 , and various changes can be made. In addition, the image processing unit 21 may be constituted by hardware (circuit), or may be constituted by software. In addition, the imaging device 1 can be used for various purposes other than a monitoring camera for photographing a street or an intersection.

In addition, the embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims.

Explanation of symbols

1 Camera

10 camera department

21 Image Processing Department

22 Storage

Claims (6)

1. A camera, characterized in that: The imaging unit is used to image the light from the target area on the imaging element; an image processing unit that processes a signal output from the imaging element and outputs image information; and a storage unit storing a reference value of a specific parameter indicating the sharpness of the captured image; The image processing unit acquires the actual measurement value of the parameter based on the signal input from the imaging element, and stores the actual measurement value acquired at a specific point of time as the reference value in the storage unit, and then obtains the parameter based on The difference between the actual measured value and the reference value stored in the storage unit is used to perform sharpening processing on the captured image. 2. The imaging device according to claim 1, characterized in that: The image processing unit stores, as the reference value, an actually measured value of the parameter obtained from a signal from the imaging element in the storage unit when receiving an input of a setting instruction. 3. The imaging device according to claim 1 or 2, characterized in that: The storage unit previously stores a second reference value separately from a first reference value based on an actual measurement value, The image processing unit acquires the first reference value based on an actual measurement value and executes the sharpening process when a mode using the first reference value based on an actual measurement value is set, and when the first reference value based on an actual measurement value is not set. In the case of the above mode, the sharpening process is executed based on the second reference value. 4. The imaging device according to any one of claims 1 to 3, characterized in that: The image processing unit switches an adjustment value for sharpening a captured image according to a difference between the actual measurement value and the reference value. 5. The imaging device according to claim 4, characterized in that: The adjustment value is a value for performing gamma correction on a signal output from the imaging element. 6. The imaging device according to any one of claims 1 to 5, characterized in that: The parameter representing the sharpness of a captured image is a standard deviation of brightness obtained from a signal of an image output from the imaging element.