JP2009004874A - Imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device capable of preventing the generation of a hunting operation by enabling proper judgement of switching between a color photographing mode and a black-and-white photographing mode. <P>SOLUTION: The imaging device includes a filter unit 2 made of an infrared ray cutting filter 9 and a dummy glass 10 in an optical path between a photographing lens 1 and an imaging element 3. The imaging device has a color photographing mode and a black-and-white photographing mode. Further, the imaging device includes a CPU 6 as a judging means for judging switching between the color photographing mode and the black-and-white mode from a video signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging device that uses a solid-state imaging device, and more particularly to an imaging device that uses both visible light imaging and infrared light imaging.

  The solid-state imaging device has sensitivity in a wavelength region of about 400 nm to 900 nm. For this reason, when an image in the visible light region is captured, an infrared cut filter is used, the infrared light is cut in a wavelength region of about 400 nm to 700 nm, and a color image is used in combination with a color filter. It has gained.

  When such an imaging device is used for a surveillance camera, a good color image can be obtained during daytime when there are many visible light components. I can not get the image.

  As an improvement measure, at night, etc., an infrared cut filter is removed and replaced with a dummy glass instead, and color processing is not performed to obtain a black and white image so that an image with a sufficient luminance level can be obtained. A device has been proposed. That is, a color imaging mode and a monochrome imaging mode are executed by a single imaging device by switching between two types of filters.

  The main configuration of such an imaging apparatus is shown in FIGS.

  FIG. 5 shows a filter unit. The filter unit 2 includes two types of filters for switching between a color photographing mode and a black and white photographing mode. In the figure, an infrared cut filter 9 is disposed on the upper side of the mounting frame 8 and a dummy glass 10 is disposed on the lower side.

  An image pickup apparatus using the filter unit 2 and a filter position at the time of photographing are shown in FIGS.

  The imaging apparatus includes a photographic lens 1, a filter unit 2, an imaging element 3, a signal processing circuit 4, a detection circuit 5, a CPU 6, and a motor 7.

  The filter unit 2 has an infrared cut filter 9 on the upper side and a dummy glass (dummy filter) 10 on the lower side. As the image sensor 3, a CCD or a MOS is usually used. The signal processing circuit 4 creates a luminance signal, a color signal in the case of color photographing, and the like from the signal from the image sensor 3. The detection circuit 5 checks the level of the luminance signal and detects the magnitude relationship with a predetermined threshold. Usually, this detection operation is performed at regular time intervals. From the detection results of the CPU 6 and the detection circuit 5, it is determined whether to perform monochrome photography or color photography. The motor 7 switches the position of the filter unit 2.

  A state of photographing with this imaging apparatus will be described with reference to FIGS.

  Hereinafter, a case where a subject as shown in FIG. 8 is photographed will be described. In the color photographing mode, the infrared cut filter 9 of the filter unit 2 faces the photographing lens 1 and the image sensor 3 as shown in FIG.

  The image at this time is shown in FIG. In FIG. 9, the hatched portion indicates an image taken through the infrared cut filter 9. On the other hand, in the black-and-white photography mode, the dummy glass 10 of the filter unit 2 faces the photographing lens 1 and the image sensor 3 as shown in FIG.

  The image at this time is shown in FIG. In FIG. 9, the vertical line portion indicates an image taken through the dummy glass 10.

  The CPU 6 instructs the motor 7 to switch the filter when the detection circuit 5 detects that the luminance signal level is lower than a predetermined threshold during color photographing. Then, the filter is switched from the infrared cut filter 9 to the dummy glass 10, and the signal processing circuit 4 is instructed to switch from color signal processing to monochrome signal processing.

  Similarly, when the detection circuit 5 detects that the luminance signal level is lower than a predetermined threshold during monochrome imaging, the motor 7 is instructed to switch filters. Then, the filter is switched from the dummy glass 10 to the infrared cut filter 9, and the signal processing circuit 4 is instructed to switch from monochrome signal processing to color signal processing.

  The above operation is shown in the flowchart in FIG. After initialization of the imaging device (step S1), shooting is started in any mode (color signal processing mode, monochrome signal processing mode) (step S2). After a certain period of time has elapsed (step S3), the level of the luminance signal is determined (step S4), and if it is determined that the condition for switching the mode has been reached, the mode is switched and shooting is continued. If it is not a condition for switching modes, shooting is continued in the mode as it is.

  By the way, with such a configuration, many imaging apparatuses have been proposed in which the switching point between the infrared cut filter 9 and the dummy glass 10 is determined when the luminance signal level from the imaging element 3 is detected. .

  However, it is known that when the filter replacement time is determined with this luminance signal level, the determination is difficult particularly under the condition where infrared illumination is used. That is, when performing color photography using an infrared cut filter, if the luminance level decreases, the imaging apparatus determines to switch to monochrome photography.

  Thereafter, when black-and-white photography is performed using a dummy glass, if there is infrared illumination, the luminance signal level becomes high, and the imaging apparatus determines to switch to color photography. However, when the filter is switched to the infrared cut filter, the effect of infrared illumination is lost, the luminance signal level is lowered, and a determination is made to switch to monochrome photography again. Repeatedly, so-called hunting phenomenon is likely to occur.

On the other hand, a technique described in Patent Document 1 is known as a configuration that avoids this hunting phenomenon by devising filter arrangement. In Patent Document 1, an infrared cut filter is attached to a part of the front surface of an image pickup device, and at the time of monochrome photography, a photographing signal level from a dummy glass is compared with a signal level from the attached infrared cut filter. A technique for performing monochrome switching determination is disclosed.
JP 2002-135788 A

  However, in the configuration of Patent Document 1, since an infrared cut filter is attached separately from the infrared cut filter used during color photographing, the number of parts increases, which is disadvantageous in terms of cost. In addition, high accuracy is required at the position where the infrared cut filter is attached, and it is difficult to manufacture.

  In addition, since the position of the infrared cut filter to be added is only outside the display area where the image is captured, it is necessary to guarantee lens aberration, image sensor defects, and the like up to this area, which further increases the cost. there is a possibility. Further, the mounting position of the filter is fixed, and there is a possibility of erroneous determination due to the subject and illumination.

  An object of the present invention is to provide an imaging apparatus that can appropriately determine whether to switch between a color shooting mode and a monochrome shooting mode, and can prevent occurrence of a hunting operation.

  In order to achieve the above object, an image pickup apparatus according to claim 1 includes a filter unit including a first filter and a second filter in an optical path between a photographing lens and an image pickup element, and the first filter is provided. In an imaging apparatus having a first shooting mode to be used and a second shooting mode using the second filter, a video signal that has passed through the first filter and a video signal that has passed through the second filter On the basis of both, a judging means for judging switching between the first photographing mode and the second photographing mode from a video signal is provided.

  According to the image pickup apparatus of the present invention, it is possible to appropriately determine whether to switch between the color shooting mode and the monochrome shooting mode, and to prevent the occurrence of a hunting operation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing filter positions at the time of determining a color shooting mode / monochrome shooting mode in the imaging apparatus according to the embodiment of the present invention.

  The imaging apparatus includes a photographic lens 1, a filter unit 2, an imaging element 3, a signal processing circuit 4, a detection circuit 5, a CPU 6, and a motor 7. The filter unit 2 is provided in the optical path between the photographing lens 1 and the image sensor 3. The function of each unit is as described in FIG.

  In the imaging apparatus of the present embodiment, shooting in the normal color shooting mode (first shooting mode) and shooting operation in the black and white shooting mode (second shooting mode) are the same as in the past.

  In the present embodiment, the movement of the filter unit 2 is first started after a certain time has elapsed. As shown in FIG. 1, during the movement of the infrared cut filter (first filter) 9 and the dummy glass (second filter) 10, the filter unit 2 is in the middle of the optical path between the photographing lens 1 and the image sensor 4. Is temporarily stopped.

  At this time, the image on the image pickup device 3 is an image that has passed through the infrared cut filter 9 in some image regions, and an image that has passed through the dummy glass 10 in another image region.

  This is shown in FIG. In FIG. 2, the upper portion 11 is an image (shaded portion) that has passed through the infrared cut filter 9, and the lower portion 12 is an image that has passed through the dummy glass 10. The intermediate portion 13 is a portion that becomes a shadow of the light beam that has passed through each filter and the boundary of the filter frame (the frame of the filter unit 2).

  The detection circuit 5 sets a first region in the range of the upper part 11 and sets a second region in the range of the lower part 12 of the video signal. Then, the level of the video signal (luminance signal) corresponding to each area is compared with the threshold value set for each area, and the result is transmitted to the CPU 6.

  The CPU 6 determines the level of the video signal. That is, if the video signal level of the upper part (infrared cut filter part) 11 is low and the video signal level of the lower part (dummy glass part) 12 is high, it is determined that the black and white photography mode is appropriate. If the video signal level of the infrared cut filter portion is high and the video signal level of the dummy glass portion is low, it is determined that the color photographing mode is appropriate.

  Then, the CPU 6 as a determination unit determines switching between the first shooting mode and the second shooting mode based on both the video signal that has passed through the first filter and the video signal that has passed through the second filter.

  FIG. 3 is a flowchart showing the procedure of the photographing process executed by the imaging apparatus of FIG.

  This process is executed by the CPU 6 in FIG.

  In FIG. 3, after the imaging apparatus is initialized (step S11), shooting is started in any mode (color signal processing mode, monochrome signal processing mode) (step S12). After a predetermined time has elapsed (step S13), the filter unit 2 is moved (step 4), and the infrared cut filter 9 and the dummy glass 10 are stopped at a position facing the image sensor 3 in half.

  In the present embodiment, it is assumed that the filter unit 2 is initially located above, that is, the dummy glass 10 is in a position facing the image sensor 3. From this position, the filter unit 2 is lowered halfway.

  The detection circuit 5 compares the level of the video signal (luminance signal) corresponding to each of the above-described areas with a set threshold value, and transmits the result to the CPU 6. The CPU (determination means) 6 determines the level of the video signal (step S15).

  If the luminance level is low, the filter unit 2 is returned to the original position (step S16). In other words, the dummy glass 10 is raised to face the image sensor 3 and photographed in the monochrome photography mode. If the luminance level is high, the mode is switched (step S17). That is, the filter unit 2 is further lowered, and the infrared cut filter 9 faces the image sensor 3.

  In this way, in this embodiment, the conventional filter configuration is used as it is, and the filter switching is determined using the moving image. That is, the level of the video signal passing through the infrared cut filter and the level of the video signal passing through the dummy glass are simultaneously acquired and compared.

  Thereby, when there is infrared irradiation, it is possible to appropriately determine a difference in video signal level due to a difference in filters. That is, even if the image signal of the dummy glass portion is high due to infrared irradiation, if the image signal level of the infrared cut filter portion is low, it can be determined that there is no need to switch the black and white shooting mode shooting mode (initially the black and white shooting mode). If) Therefore, an unnecessary filter switching operation can be prevented, and the occurrence of hunting, which has conventionally been easy to occur when infrared irradiation is performed, can be suppressed. Furthermore, this embodiment does not require an additional part for this function, and is realized with almost no change in the part configuration of the conventional imaging apparatus.

  Here, the state of the image at this time will be described again. In FIG. 2, the upper part 11 is an infrared cut filter part, the lower part 12 is a dummy glass part, and there is an intermediate part 13 therebetween. Usually, each of the infrared cut filter 9 and the dummy glass (dummy filter) 10 is housed in a mounting frame 8 as shown in FIG.

  Therefore, there is a boundary portion between the filters, and at the position where both filters are applied as in the present embodiment, a shadow of the boundary portion is generated and appears as a black line on the image. This shadow can be reduced by a process such as narrowing the structure of the boundary portion, or forming the infrared cut filter 9 and the dummy glass 10 in close contact.

  Further, as shown in FIG. 4, the filter unit 2 is mounted at a position closer to the imaging lens 1 than the intermediate position between the imaging lens 1 and the imaging element 3 (toward the imaging lens 1 side), thereby reducing shadows. it can. That is, when the filter unit 2 is mounted close to the photographing lens 1, the portion of the light flux from the photographing lens 1 that is blocked by the boundary portion 14 is reduced. As a result, it is possible to prevent the image of the boundary portion (image of the intermediate portion 13) from becoming a complete black image.

  By doing in this way, the entire screen can be shot even on the screen at the time of the shooting mode switching determination. This is an advantageous configuration when this imaging apparatus is applied to a surveillance camera or the like.

  In the present embodiment, the position where the movement of the filter unit 2 is stopped is a position where a video signal sufficient for determination can be obtained from the images from the two filters (infrared cut filter 9 and dummy glass 10). And it is sufficient.

  For example, when determining the mode shift in the color photographing mode, the image of the dummy glass portion (the image of the lower part 12 in FIG. 2) is suppressed to about several lines of the video signal. That is, it is limited to a small area in the entire image that does not affect the main part of the subject. In this way, it is possible to determine the mode switching with little influence on the main part of the currently captured color image.

  When the processing capability of the detection circuit 5 and the CPU 6 is sufficiently high, it is possible to acquire the image shown in the present embodiment using one moving image without stopping the filter unit 2. is there.

  That is, it is possible to determine switching between the color photographing mode and the black and white photographing mode as follows while the infrared cut filter 9 and the dummy glass 10 are moving. That is, a part of the image on the image pickup device 3 is an image that has passed through the infrared cut filter 9, and another region is a video signal that is an image that has passed through the dummy glass 10. It is possible to determine whether to switch between black and white photography modes.

  However, it is necessary to consider the processing capability of the detection circuit 5 and the CPU 6, and the filter position detection accuracy at the time of image acquisition. For this reason, whether or not to stop is selected depending on the capability and cost of the device.

  Further, during normal shooting, control for appropriately acquiring a video signal such as AE and AWB is performed. When acquiring the moving image of the filter unit 2 shown in the present embodiment, it is desirable to keep the function of changing the video signal level in a state before starting the movement.

  In the present embodiment, the filter is arranged up and down, the infrared cut filter 9 is arranged on the upper side, and the dummy glass 10 is arranged on the lower side. This is for the sake of brevity, and the present invention is arranged and moved in the filter. The method is not limited.

  As described above, according to the present invention, it is possible to appropriately determine whether to switch between the color shooting mode and the black and white shooting mode with almost the same component configuration of the device, and to prevent the occurrence of a hunting operation. it can.

It is a figure which shows the filter position at the time of color imaging mode / monochrome imaging mode determination in the imaging device which concerns on embodiment of invention. It is a figure which shows the image at the time of imaging | photography mode determination by the imaging device of FIG. 3 is a flowchart illustrating a procedure of imaging processing executed by the imaging apparatus of FIG. 1. It is a figure which shows the positional relationship of the imaging lens in the imaging device of FIG. 1, a filter unit, and an image pick-up element. It is a block diagram of a filter. It is a figure which shows the filter position at the time of color imaging mode. It is a figure which shows the filter position at the time of black-and-white photography mode. It is a figure which shows the imaging | photography condition by an imaging device. It is a figure which shows the example of an image at the time of color imaging mode. It is a figure which shows the example of an image at the time of black-and-white photography mode. It is a flowchart which shows the procedure of the imaging | photography process performed with the conventional imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shooting lens 2 Filter unit 3 Image pick-up element 4 Signal processing circuit 5 Detection circuit 6 CPU
7 Motor 9 Infrared cut filter 10 Dummy glass

Claims (8)

A filter unit including a first filter and a second filter is provided in an optical path between the photographing lens and the image sensor, and a first photographing mode using the first filter and a second filter using the second filter. In an imaging device having two shooting modes,
And determining means for determining switching between the first shooting mode and the second shooting mode based on both the video signal that has passed through the first filter and the video signal that has passed through the second filter. An imaging device that is characterized.   The video signal is a video signal from an image that has passed through the first filter in a partial area of the image sensor and an image that has passed through the second filter in a different area. The imaging device according to claim 1.   The video signal is a video signal from an image in a state where movement of the first filter and the second filter with respect to the image sensor is temporarily stopped during movement of the first filter and the second filter. Imaging device.   2. The image pickup apparatus according to claim 1, wherein the first filter and the second filter are located at an attachment position where a width of a boundary portion between the filters is smaller than a light flux from the photographing lens.   Either the image area that has passed through the first filter or the image area that has passed through the second filter is an image area that does not affect the main part of the subject in the entire image. The imaging apparatus according to claim 1, wherein the imaging apparatus is provided.   The image pickup apparatus according to claim 1, wherein during movement of the first filter and the second filter, control for the video signal is made constant in a state before the movement is started.   The imaging apparatus according to claim 1, wherein the first filter is an infrared cut filter, and the second filter is a dummy glass.   The imaging apparatus according to claim 1, wherein the first shooting mode is a color shooting mode, and the second shooting mode is a monochrome shooting mode.

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