JP2017059905A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device capable of suppressing malfunction when automatically correcting an unclear captured image, by a simple processing.SOLUTION: An imaging device 1 includes an imaging section 10 for making the light from a target area to be focused on an image pickup device 14, an image processing section 21 for processing the signals outputted from the image pickup device 14 and outputting video information, and a storage section 22 for storing the reference value of parameters representing the clearness of the captured image. The image processing section 21 acquires the measured values of the parameters based on the signals inputted from the image pickup device 14, stores the measured values acquired at a predetermined timing, as reference values, in the storage section 22, and executes sharpening of the captured image, based on the difference between the measured values acquired later and the reference values stored in the storage section 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image pickup apparatus that picks up a target area, and is particularly suitable for use in picking up a landscape whose sharpness may be reduced due to the occurrence of rain, fog, or the like.

  2. Description of the Related Art An imaging device that captures images of streets and intersections with a monitoring camera is known. In this type of imaging apparatus, the captured image is used, for example, for verification of a traffic accident. In the verification, the status of vehicles and pedestrians, the lighting status of traffic lights, and the like are confirmed. That is, it is confirmed whether the traffic light was lit in red, blue, or yellow at the time of the accident.

  However, on streets, intersections, etc., the contrast of the subject can be reduced due to rain or fog. For example, if the intersection is covered with fog, there is a risk that the situation of the vehicle or the pedestrian, the lighting state of the traffic light, etc. cannot be clearly imaged. If this happens, verification using the captured image cannot be performed smoothly.

  Patent Document 1 below describes a surveillance camera system including a surveillance camera device and a control device. In this surveillance camera system, fog and haze are detected by the control device based on the image captured by the surveillance camera device. The occurrence of fog and haze is detected by comparing a pre-captured image with the current image, and as a result, whether whitening has occurred. Further, the strength of fog or haze is determined based on whether or not the level (black peak level) of the portion of the digital video signal component where the video brightness is minimum exceeds a predetermined threshold. Thus, when fog or haze is detected and the strength of the fog or haze is determined, an alarm corresponding to the strength of the fog or haze is output from the control device to an external device. Further, the haze correction is performed according to the determined fog and haze strength.

JP 2014-192762 A

  As described above, in the method of Patent Document 1, in order to correct an image, a two-step process of detecting fog and haze and determining the strength of fog and haze is necessary. The determination of fog or haze strength is based on whether the black peak level exceeds a predetermined threshold. For example, when a scene in which the black peak level of the video signal is originally high is taken as the imaging target, There was a risk of malfunction in the correction.

  In view of such a problem, an object of the present invention is to provide an imaging apparatus capable of suppressing a malfunction when automatically correcting unclearness of a captured image by simple processing.

  A main aspect of the present invention relates to an imaging apparatus. An imaging apparatus according to 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 video information, and a sharpened captured image And a storage unit for storing a reference value of a predetermined parameter representing the height. Here, the image processing unit acquires an actual measurement value of the parameter based on a signal input from the image sensor, stores the actual measurement value acquired at a predetermined timing in the storage unit as the reference value, and then Based on the difference between the actually measured value acquired in step S3 and the reference value stored in the storage unit, a sharpening process is performed on the captured image.

  According to the imaging apparatus according to this aspect, the reference value of the parameter representing the sharpness of the captured image is set based on the signal input from the image sensor, and thus the set reference value depends on the scene to be imaged. It will be. For example, when the imaging device is installed to capture an intersection, the reference value corresponds to the scenery of the target area (such as the layout of the structure) such as the size of the intersection and the installation status of the traffic light. Since the sharpening process is performed on the captured image based on the difference between the reference value set in this way and the actual measurement value acquired at the time of subsequent imaging, how much the target area of the imaging target has become unclear Can be properly identified, and malfunction of the sharpening process can be suppressed. As described above, according to the imaging apparatus according to this aspect, it is possible to suppress a malfunction when automatically correcting the unclearness of the captured image.

  In addition, according to the imaging apparatus according to this aspect, since the sharpening process is appropriately executed according to the difference between the reference value and the actual measurement value, a process for separately detecting whether the captured image has become unclear is performed. There is no need. Therefore, according to the imaging device according to this aspect, it is possible to sharpen the captured image by a simple process.

  Note that “difference between measured value and reference value” means not only the value obtained by subtracting the reference value from the measured value, but also how much the measured value differs from the reference value, such as the ratio of the measured value to the reference value. Any value may be used as long as it represents a value.

  In the imaging device according to this aspect, when receiving an input of a setting instruction, the image processing unit stores the measured value of the parameter acquired based on a signal from the imaging element as the reference value in the storage unit. Can be configured. In this way, it is possible to smoothly avoid the reference value being acquired and set at a timing when the target area is unclear. For this reason, it is possible to more reliably suppress a malfunction when automatically correcting the unclearness of the captured image.

  In the imaging device according to this aspect, the storage unit may be configured to store the second reference value in advance separately from the first reference value based on the actual measurement value. In this case, when the mode using the first reference value based on the actual measurement value is set, the image processing unit acquires the first reference value based on the actual measurement value and executes the sharpening process. However, when the mode is not set, the sharpening process may be executed based on the second reference value. In this way, for example, even when a mode using the first reference value is not set because a clear captured image suitable for setting the first reference value cannot be obtained, the second reference value is used for clearness. Can be executed.

  In the imaging apparatus according to this aspect, the image processing unit may be configured to switch an adjustment value for sharpening a captured image based on 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 image sensor. In this way, by adjusting the value for performing gamma correction, the contrast of the captured image can be smoothly adjusted to a state suitable for sharpening by simple processing.

  In the imaging apparatus according to this aspect, for example, a standard deviation of luminance acquired from a signal for one image output from the imaging element can be used as the parameter representing the sharpness of the captured image. Thus, by using the standard deviation of the brightness, it is possible to accurately grasp the unclearness of the captured image.

  As described above, according to the present invention, it is possible to provide an imaging apparatus capable of suppressing malfunctions when automatically correcting the unclearness of a captured image by a simple process.

  The effects and significance of the present invention will become more apparent from the following description of embodiments. However, the embodiment described below is merely an example when the present invention is implemented, and the present invention is not limited to what is described in the following embodiment.

FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus according to the embodiment. FIG. 2 is a block diagram illustrating a configuration of the image processing unit according to the embodiment. FIGS. 3A to 3D are diagrams illustrating the relationship between the situation of the captured image and the luminance histogram according to the embodiment. 4A to 4D are views for explaining a method for correcting the contrast of a captured image (a sharpening process) according to the embodiment. FIGS. 5A and 5B are diagrams showing changes in the luminance histogram when the gamma value according to the embodiment is changed. FIGS. 6A and 6B are diagrams illustrating a configuration example of the target region when the luminance distribution range of the histogram is narrow even if the captured image according to the embodiment is clear. FIG. 7 is a flowchart showing a sharpening process according to the embodiment. FIG. 8 is a diagram illustrating an example of a gamma characteristic used for the sharpening process according to the embodiment. FIGS. 9A and 9B are diagrams schematically illustrating the effect of the sharpening process in the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, the present invention is applied to a monitoring camera that images an intersection, a street, and the like.

  FIG. 1 is a diagram illustrating a configuration of the imaging apparatus 1.

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

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

  The lens 11 takes in light from the target area and forms an image of the target area on the light receiving surface of the image sensor 14. The iris 12 limits light from the outside so that an appropriate amount of light enters the image sensor 14 according to the intensity of light from the target area. The iris amount of the iris 12 is adjusted by the iris driving unit 24.

  The filter 13 is made of an IR cut filter for removing infrared rays and a dummy glass that transmits infrared rays together with visible light. In the filter 13, either the IR cut filter or the dummy glass is positioned in the optical path between the iris 12 and the image sensor 14 by the image processing unit 21 via the filter driving unit 23. Specifically, when the illuminance of the normal level or higher is obtained in the image sensor 14, an IR cut filter is inserted into the optical path, and infrared rays are removed. In addition, when the illuminance obtained in the image sensor 14 is low, dummy glass is inserted into the optical path, and infrared light is guided to the image sensor 14 together with visible light, and sensitivity is increased.

  The image sensor 14 is a color CMOS image sensor. The image sensor 14 may be a CCD image sensor. The imaging element 14 outputs a signal corresponding to the 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) and executes image processing according to a program held 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), and stores an image processing program, and is also used as a work area when the image processing unit 21 performs processing. The The storage unit 22 holds a plurality of gamma correction values corresponding to the sharpness level of the captured image. The gamma correction values held in the storage unit 22 will be described later with reference to FIG.

  The filter driving unit 23 and the iris driving unit 24 are drivers for driving the filter 13 and the iris 12 under the control of the image processing unit 21, respectively. The input unit 25 has input means such as operation buttons and receives instructions from the user. The output unit 26 outputs the video 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, a contour correction processing unit 105, a color difference correction processing unit 106, a noise Removal processing units 107 and 108.

  A signal output from the image sensor 14 of FIG. 1 is input to the mosaic processing unit 101. The mosaic processing unit 101 generates signals for three colors 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 subjected to spectral characteristic correction. As described above, the storage unit 22 holds a plurality of gamma correction values corresponding to the sharpness level of the captured image. A gamma correction value corresponding to the sharpness of the captured image is applied to the gamma correction processing unit 103. The gamma correction processing unit 103 performs gamma correction on the signal from the linear matrix processing unit 102 according to the applied gamma correction value.

  The Y / C separation processing unit 104 separates the signal subjected to gamma correction into a luminance signal and a color difference signal. The contour correction processing unit 105 extracts the contour of the subject based on the signal after mosaic processing, and adds the contour signal to the luminance signal after Y / C separation. The color difference correction processing unit 106 performs correction processing such as emphasizing a predetermined color on the color difference signal after Y / C separation. The noise removal processing units 107 and 108 remove noise superimposed on the luminance signal and color difference signal after Y / C separation, respectively. The luminance signal and color difference signal from which noise has been removed are output to the output unit 26 in FIG. The output unit 26 serially converts the luminance signal and the color difference signal and outputs them to the outside.

  Next, the sharpening process in the image processing unit 21 will be described with reference to FIGS. Here, for the sake of convenience, scenery other than intersections and streets is taken as the subject.

  FIGS. 3A to 3D are diagrams illustrating an example of a relationship between the state of a captured image and a luminance histogram according to the embodiment. 3B is a histogram for the captured image of FIG. 3A, and FIG. 3D is a histogram for the captured image of FIG. 3A and 3C are actually color images. That is, the mosaic tile and the doll in the image are colored in various colors. Further, the captured image of FIG. 3C is obtained by inserting a foggy filter into the imaging optical system.

  As shown in FIGS. 3B and 3D, even if the subject is the same, the luminance distribution range (R1, R2) on the histogram changes depending on 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. Thus, the lower the definition (contrast) of the captured image, the narrower the luminance distribution range. Therefore, it is possible to detect the sharpness of the captured image based on the luminance distribution range.

  Note that the information for determining the sharpness of the captured image is not limited to the luminance histogram. For example, the sharpness of a captured image can also be determined using auto iris statistical data or the like.

  4A to 4D are diagrams for explaining a method of correcting the contrast of a captured image (sharpening process). FIGS. 4A and 4C are the histograms shown in FIGS. 3B and 3D, respectively, and correspond to the histograms of the captured images in FIGS. 3A and 3C. FIGS. 4B and 4D are graphs schematically showing gamma correction values (gamma characteristics) when the luminance histograms are FIGS. 4A and 4B, respectively. 4A and 4B, 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.

  When the luminance distribution range R1 in the histogram is wide as shown in FIG. 4A, gamma correction is performed using the normal gamma correction value shown in FIG. On the other hand, when the luminance distribution range R2 in the histogram is narrow as shown in FIG. 4C, gamma correction is performed using the gamma correction value for increasing the contrast shown in FIG.

  In the gamma correction value of FIG. 4D, an input signal whose signal level is lower than the range W is uniformly converted to an output signal of the lowest level. An input signal having a signal level higher than the range W is uniformly converted to an output signal having the highest level. Therefore, the gray input signal near black is uniformly converted to black, and the gray input signal near white is uniformly converted to white. Thereby, the contrast of an image is raised.

  FIGS. 5A and 5B are diagrams illustrating changes in luminance histograms when the gamma value (gamma characteristic) is changed. In FIG. 5A, the broken line is a gamma characteristic used for normal gamma correction when the gamma value is 0.45, and the solid line is a gamma characteristic applied when the sharpness (contrast) of the captured image is low. It is. In FIG. 5A, the vertical axis and the horizontal axis are normalized by 1. In FIG. 5B, the broken line is a histogram when the gamma characteristic of the broken line having the gamma value of 0.45 in FIG. 5A is applied to a predetermined captured image, and the solid line is the same. It is a histogram at the time of applying the solid-line gamma characteristic for low contrast of Fig.5 (a) with respect to a captured image.

  As shown in FIG. 5B, when the gamma correction is performed by applying the low-contrast gamma characteristic, the histogram of the captured image after the correction has a significantly wider luminance distribution range than before the correction. . That is, the image sharpness (contrast) can be improved by performing gamma correction by applying the low-contrast gamma characteristic of FIG. 5A to a low-contrast captured image with low sharpness.

  As described above, the contrast of the captured image can be increased by selecting the gamma correction value to be applied. The image processing unit 21 in FIG. 1 changes the gamma value (gamma characteristic) applied to the gamma correction processing unit 103 in FIG. 2 when the sharpness (contrast) of the captured image is low, thereby changing the contrast of the captured image. Increase.

  More specifically, the storage unit 22 in FIG. 1 stores a normal gamma value (gamma characteristic) when the sharpness is high and a gamma value (gamma characteristic) applied when the sharpness of the captured image is low. ing. When the sharpness (contrast) of the captured image captured by the image sensor 14 is low, the image processing unit 21 selects a gamma value suitable for the sharpness of the captured image from the storage unit 22, and displays the selected gamma value. The second gamma correction processing unit 103 is applied. Thereby, the sharpness of the captured image can be increased.

  Here, whether or not the sharpness of the captured image is low can be determined based on the histogram of the luminance distribution, as shown in FIGS.

  However, depending on the captured image, the brightness distribution range of the histogram may be narrow depending on the subject layout and the like even though the sharpness is not lowered. For example, the histogram of the captured image (actually a color image) shown in FIG. 6A is as shown in FIG. In this histogram, although the captured image is clear, the luminance distribution range R3 is narrow. In such a case, if a low-contrast gamma value is applied, the sharpness of the captured image is decreased.

  Therefore, in the present embodiment, processing is performed to suppress malfunction when automatically correcting a blurred captured image.

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

  In the flowchart of FIG. 7, a standard deviation σ of a luminance histogram (see, for example, FIGS. 3B and 3D) is used as a parameter representing the sharpness of a captured image. In addition to the gamma value G3 applied in the case of normal sharpness, the storage unit 22 in FIG. 1 stores two types of gamma values G1 and G2 applied when the sharpness is low. .

  Further, in the flowchart of FIG. 7, the mode setting of the sharpening process can be performed by the user via the input unit 25 illustrated in FIG. 1 before or after the process is started. Here, a mode in which a standard deviation reference value σRef is set based on a captured image obtained by imaging a target area is referred to as a preset ON mode, and a general-purpose standard deviation σ0 stored in advance in the storage unit 22 is a reference. A mode set to the value σRef is referred to as a preset OFF mode. The standard deviation σ0 is, for example, a standard deviation of a luminance histogram of a captured image obtained by capturing a standard landscape in a clear state.

  Referring to FIG. 7, when the imaging apparatus 1 is turned on and the initialization process is completed, the image processing unit 21 starts an imaging operation. Thus, after starting the imaging operation, the image processing unit 21 determines whether or not it is the output timing of the vertical synchronization signal (Vsync) (S101). When it is the output timing of the vertical synchronization signal (S101: YES), the image processing unit 21 executes auto iris processing (S102) and auto white balance processing (S103). Furthermore, the image processing unit 21 calculates the standard deviation σ of the luminance histogram in the captured image based on the signal output from the image sensor 14 (S104).

  Next, the image processing unit 21 determines whether or not the sharpening processing mode set in the imaging apparatus 1 is the preset ON mode (S105). If the sharpening processing mode is not the preset ON mode (S105: NO), the image processing unit 21 sets the general-purpose standard deviation σ0 stored in advance in the storage unit 22 as the standard deviation reference value σRef. (S108).

  On the other hand, when the sharpening processing mode is the preset ON mode (S105: YES), the image processing unit 21 determines whether the sharpening processing mode is the preset OFF mode at the output timing of the previous vertical synchronization signal. That is, it is determined whether or not the sharpening processing mode has been switched from the preset OFF mode to the preset ON mode (S106). Here, when the sharpening processing mode is the preset OFF mode at the output timing of the previous vertical synchronization signal (S106: YES), the image processing unit 21 uses the standard deviation σ calculated in step S104 as a reference value. σRef is set, and the set reference value σRef is stored in the storage unit 22 (S107).

  Further, when the sharpening processing mode is the preset ON mode at the output timing of the previous vertical synchronization signal (S106: NO), that is, when the preset ON mode is continuing from the previous time, the image processing unit 21 skips step S107 and advances the process to step S109. In this case, at least at the output timing of the vertical synchronization signal before the previous time, the standard deviation σ based on the captured image acquired at that timing is set as the reference value σRef, and this reference value is the output timing of the current vertical synchronization signal. Is also effective.

  Next, the image processing unit 21 acquires the reference value by dividing the reference value σRef by the standard deviation σ acquired in step S104 (S109). The reference value calculated in this way increases as the standard deviation σ acquired in step S104 becomes smaller than the reference value σRef. That is, the reference value increases as the luminance distribution range of the luminance histogram for the captured image acquired this time becomes narrower than the luminance distribution range of the luminance histogram corresponding to the reference value σRef. Therefore, it can be evaluated that the sharpness of the captured image acquired this time is lower as the reference value increases.

  After calculating the reference value in this way, the image processing unit 21 compares the threshold values Th1 and Th2 (Th1> Th2) set in advance with the reference value (S110, S112). If the reference value is larger than the threshold value Th1 (S110: YES), the image processing unit 21 uses the gamma value G1 for low definition stored in the storage unit 22 as the gamma correction processing unit 103 in FIG. (S111). When the reference value is equal to or smaller than the threshold Th1 and greater than the threshold Th2 (S110: NO, S112: YES), the image processing unit 21 uses the low-definition gamma value G2 stored in the storage unit 22, This is applied to the gamma correction processing unit 103 in FIG. 2 (S113). If the reference value is equal to or less than the threshold Th2 (S110: NO, S112: NO), the image processing unit 21 uses the normal definition gamma value G3 stored in the storage unit 22 as the gamma value in FIG. This is applied to the correction processing unit 103 (S114). The gamma correction processing unit 103 in FIG. 2 performs gamma correction based on the gamma value applied in this way.

  Thereafter, 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 arrival of the next vertical synchronization signal output timing (S101). Then, when the output timing of the next vertical synchronization signal arrives (S101: YES), the image processing unit 21 executes the processing subsequent to S102 again. This process is repeatedly executed until the power supply of the imaging apparatus 1 is cut off.

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

  As shown in FIG. 8, the gamma value G2 is corrected such that the range W2 on the low level side of the input signal with respect to the gamma value G3 is corrected to a zero level output signal, and the input signal has a higher level than the gamma value G3. The side is set to approach the maximum level sooner. The gamma value G1 is set so that the input side range W1 is expanded compared to the gamma value G2 range W2, and the high level side of the input signal approaches the maximum level sooner than the gamma value G2. ing.

  By setting the gamma values G1 and G2 in this way, as described with reference to FIGS. 5A and 5B, the case of performing gamma correction by applying the gamma value G2 is more normal. The sharpness (contrast) of the captured image is improved as compared with the case where the gamma correction is performed by applying the gamma value G3. In addition, when performing gamma correction by applying the gamma value G1, the sharpness (contrast) of the captured image is further enhanced as compared to performing gamma correction by applying the gamma value G2.

  Therefore, if it is determined in step S110 in FIG. 7 that the reference value is larger than the threshold value Th1, that is, it is determined that the sharpness reduction of the captured image is severe, the gamma value G1 is used as the gamma correction processing unit 103 (see FIG. 2). By applying gamma correction to the image, it is possible to effectively sharpen the captured image. In addition, when it is determined in step S112 in FIG. 7 that the reference value is larger than the threshold value Th2, that is, the sharpness reduction of the captured image is moderate, the gamma value G2 is applied to the gamma correction processing unit 103. By performing gamma correction, it is possible to effectively sharpen the captured image without performing excessive sharpening processing on the captured image.

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

  FIG. 9A shows a state in which the sharpness of the 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 size of the reference value, that is, the level of sharpness reduction of the captured image, and thus the captured image is as illustrated in FIG. The sharpness of the image is improved. Thereby, the user can confirm correctly the condition of the traffic light 2, the intersection 3, the person 4, and the motor vehicle 5 with a captured image.

<Effect of embodiment>
According to this embodiment, the following effects are produced.

  As shown in steps S104 and S107 in FIG. 7, a reference value σRef of a parameter (standard deviation of luminance histogram) representing the sharpness of a captured image is set based on a signal input from the image sensor 14. For this reason, the set reference value σRef is in accordance with the scenery to be imaged. For example, as shown in FIGS. 9A and 9B, when the imaging apparatus 1 is installed to capture an intersection 3, the reference value σRef is a target such as the scale of the intersection 3 or the installation status of the traffic light 2. This corresponds to the scenery of the area (structure layout, etc.). Then, based on the difference (reference value: σRef / σ) between the reference value σRef set in this way and the actually measured value (standard deviation σ) acquired at the time of subsequent imaging, a sharpening process is performed on the captured image. Therefore, it is possible to properly identify how much the target area to be imaged is unclear, and it is possible to suppress the malfunction of the sharpening process. As described above, according to the imaging device 1 according to the present embodiment, it is possible to suppress malfunctions in the case of automatically correcting the unclearness of a captured image.

  Further, according to the imaging apparatus according to the present embodiment, the sharpening process is appropriately executed according to the difference (reference value: σRef / σ) between the reference value σRef and the actual measurement value (standard deviation σ). There is no need to perform processing for detecting whether or not the captured image has become blurred. Therefore, according to the imaging apparatus 1 according to the present embodiment, the captured image can be sharpened by a simple process.

  Moreover, in the imaging device 1 according to the present embodiment, when receiving an input of a preset ON mode setting instruction from the user via the input unit 25 as illustrated in step S105 in FIG. The measured value (standard deviation σ) of the parameter acquired based on the signal from the image sensor 14 is stored in the storage unit 22 as the reference value σRef. For this reason, the user can set the standard deviation σ based on a clear captured image as the reference value σRef by inputting a preset ON mode setting instruction at a timing when the target area is clear. Thereby, it is possible to smoothly avoid the reference value being acquired and set at a timing when the target area is unclear. Therefore, it is possible to more reliably suppress a malfunction when the unclearness of the captured image is automatically corrected.

  In the imaging apparatus 1 according to the present embodiment, the general-purpose reference value σ0 is stored in the storage unit 22 in advance before the reference value σRef based on the actual measurement value (standard deviation σ) is set. Then, as shown in steps S105 to S108 in 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, executes the sharpening process, and performs the presetting. When the ON mode is not set, the sharpening process is executed based on the general-purpose reference value σ0. For this reason, even when the preset ON mode is not set because a clear captured image suitable for the setting of the reference value σRef cannot be obtained, for example, when the imaging apparatus 1 is activated at a cloudy day The sharpening process can be executed using a large reference value σ0.

  Further, in the imaging apparatus 1 according to the present embodiment, as shown in steps S110 to S114 in FIG. 7, adjustment values (gamma values G1 to G3) for sharpening the captured image based on the size of the reference value. Therefore, the contrast of the captured image can be smoothly adjusted to a state suitable for sharpening by simple processing.

  In the imaging apparatus 1 according to the present embodiment, the luminance standard deviation σ acquired from the signal for one image output from the imaging element 14 is used as a parameter representing the sharpness of the captured image. As described with reference to (b) and (b), it is possible to accurately grasp the unclearness of the captured image.

<Example of change>
In the above-described embodiment, the captured image is sharpened by adjusting the gamma value applied to the gamma correction processing unit 103, but the captured image sharpening process is not limited to this. For example, in an imaging apparatus equipped with a sharpening processing engine for sharpening, a captured image may be sharpened by adjusting a parameter value set in the sharpening processing engine.

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

  In the above embodiment, the reference value is the ratio between the standard value σRef and the actual measurement value (standard deviation σ). However, the reference value is not limited to this, and how much the actual measurement value differs from the standard value. Any value may be used as long as it represents a value. For example, a value obtained by subtracting an actual measurement value (standard deviation σ) from the standard value σRef may be used as the reference value.

  In the above embodiment, the variance of the luminance histogram is used as a parameter representing the sharpness of the captured image, but the parameter representing the sharpness of the captured image is not limited to this. Further, the parameter representing the sharpness of the captured image is not necessarily limited to one type, and the sharpness of the captured image may be determined by combining two or more types of parameters.

  In the above embodiment, the value (gamma value) used for the sharpening process is updated in synchronization with the vertical synchronization signal. However, the timing at which the update is performed is not limited to this. For example, the value used for the sharpening process may be updated every predetermined time (for example, several seconds to several tens of seconds), or such update is performed at the timing when a change in weather is detected from the date and time and illuminance. May be.

  In addition, the block configuration of the imaging apparatus 1 is not limited to the configuration illustrated in FIG. 1, and various changes can be made. Further, the image processing unit 21 may be configured by hardware (circuit) or may be configured by software. Moreover, the imaging device 1 can be used for various purposes in addition to a monitoring camera that images streets and intersections.

  In addition, the embodiment of the present invention can be variously modified as appropriate within the scope of the technical idea shown in the claims.

DESCRIPTION OF SYMBOLS 1 ... Imaging device 10 ... Imaging part 21 ... Image processing part 22 ... Memory | storage part

Claims (6)

An imaging unit that focuses light from the target region on the imaging device;
An image processing unit that processes video signals output from the image sensor and outputs video information;
A storage unit that stores a reference value of a predetermined parameter that represents the sharpness of the captured image,
The image processing unit acquires an actual measurement value of the parameter based on a signal input from the image sensor, stores the actual measurement value acquired at a predetermined timing in the storage unit as the reference value, and then acquired An image pickup apparatus that executes a sharpening process on a picked-up image based on a difference between an actual measurement value and a reference value stored in the storage unit. The imaging device according to claim 1,
The image processing unit, when receiving an input of a setting instruction, stores the measured value of the parameter acquired based on a signal from the image sensor as the reference value in the storage unit. apparatus. The imaging device according to claim 1 or 2,
The storage unit stores a second reference value in advance separately from the first reference value based on the actual measurement value,
When the mode using the first reference value based on the actual measurement value is set, the image processing unit acquires the first reference value based on the actual measurement value and executes the sharpening process, An image pickup apparatus, wherein when the mode is not set, the sharpening process is executed based on the second reference value. In the imaging device according to any one of claims 1 to 3,
The image processing unit switches an adjustment value for sharpening a captured image based on a difference between the actual measurement value and the reference value. The imaging apparatus according to claim 4,
The image pickup apparatus, wherein the adjustment value is a value for performing gamma correction on a signal output from the image pickup device. In the imaging device according to any one of claims 1 to 5,
The imaging device, wherein the parameter representing the sharpness of a captured image is a standard deviation of luminance acquired from a signal for one image output from the imaging device.