JP2002135788A - Color/black-and-white switchable camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent hunting motion due to selections in a color/black-and-white switchable camera to take color pictures by insertion of an infrared cutting filter in front of an imaging element when the monitoring objects are in a bright area and to take black-and-white pictures by removing the filter when the objects are in a dark area. SOLUTION: In the camera, the filter is attached at a part of the imaging element, and in switching from taking picture in black-and-white to picture in color, a signal obtained from a pixel of the element which is attached the filter as a reference value of brightness is put to use.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color / monochrome switching camera using an image sensor.

[0002]

2. Description of the Related Art A conventional example will be described below. Most cameras use a CCD as the light receiving element. This C
The sensitivity characteristic of the CD extends over a wavelength region of about 400 nm to 1000 nm, and particularly, the sensitivity in the infrared region (about 700 nm or more) is high. Therefore, if light from an external subject is directly incident on the CCD, the image output from the CCD becomes reddish. Therefore, an infrared cut filter for removing light in an infrared region is inserted between a portion in front of the lens or between the lens and the CCD to remove the redness.

In the daytime, a good color output can be obtained from the CCD due to a large amount of light, but a good color output cannot be obtained in the nighttime due to a small amount of light. Therefore, in order to increase the amount of light input to the CCD as much as possible at night, an infrared cut filter is not used, and light including an infrared region is input to the CCD to obtain a good image. In this case, the output from the CCD is signal-processed to obtain a monochrome image.

In a surveillance camera, taking into account such characteristics of the CCD, switching from color photography to black-and-white photography or switching from black-and-white photography to color photography is required.
The output of the CD is monitored, and when the output level of the CCD is high (the amount of daylight is large), an infrared cut filter is inserted between the lens and the CCD to perform color photographing.
Japanese Patent Application Laid-Open No. 11-239356 discloses a black-and-white / color switching camera that switches an infrared cut filter and automatically inserts a dummy glass when the D output level is small (the amount of night light is small).

The operation of the conventional black-and-white / color switching camera will be briefly described. FIG. 8 is a diagram showing the overall configuration of a conventional color / monochrome switching camera, and is a block diagram when the camera is viewed from above. As shown in FIG.
The camera lens 1, infrared cut filter 2, dummy glass 3, slide mechanism 4, CCD 5, signal processing circuit 6, detection circuit 7, state sensor 8, microcomputer 9
, A motor 10, and a changeover switch 11.

The infrared cut filter 2 removes a wavelength component (about 700 nm or more) in an infrared region from light incident through the lens 1. The dummy glass 3 is made of transparent glass and has an optical path length equal to that of the infrared cut filter 2. The slide mechanism 4 is driven by a motor 10 to lens one of the infrared cut filter 2 or the dummy glass 3
It is inserted between 1 and CCD5, and the other is extracted from between lens 1 and CCD5. CCD5 is infrared cut filter 2
Alternatively, the light irradiated to the light receiving unit through the dummy glass 3 is converted into an electric signal. The signal processing circuit 6 receives the electric signal from the CCD 5 and generates a color signal (composite video signal) Cout and a monochrome signal (luminance signal) Yout. The detection circuit 7 integrates the value of the black and white signal Yout generated by the signal processing circuit 6 and outputs the integrated value Vout. The state sensor 8 outputs an L (logic low) level state signal S when the infrared cut filter 2 is inserted between the lens 1 and the CCD 5, and the dummy glass 3 is placed between the lens 1 and the CCD 5. When it is inserted, it outputs a state signal S of H (logic high) level. The microcomputer 9
When the vertical synchronization signal VD is input from the signal processing circuit 6,
The value of the state signal S from the state sensor 8 and the value of the integrated value Vout from the detection circuit 7 are fetched, and a predetermined threshold V
0 and the integrated value Vout, and when the integrated value Vout is larger than the threshold value V0, the integrated value V0 of the H level is set.
Is smaller than the threshold value Vout, an L-level filter switching signal FC and a monochrome / color switching signal YC are output. The motor 10 outputs an H level filter switching signal FC.
When the lens 1 is received, the slide mechanism 4 is driven to move the lens 1 and C
The dummy glass 3 is taken out from between the CD 5 and the infrared cut filter 2 is inserted between the lens 1 and the CCD 5. When the L-level filter switching signal FC is received, the slide mechanism 4 is driven to connect the lens 1 to the lens 1. The infrared cut filter 2 is removed from between the CCD 5 and the dummy glass 3 is inserted between the lens 1 and the CCD 5. When receiving the H-level monochrome / color switching signal YC, the switch 11 outputs the color signal Cout generated by the signal processing circuit 6 from the output terminal OUT of the camera, and outputs the L-level monochrome / color switching signal YC. Upon receiving the signal, the monochrome signal Yout generated by the signal processing circuit 6 is output from the output terminal OUT of the camera.

[0007]

The following problems occur because the switching between black and white shooting and color shooting is determined according to the level of the CCD output. In other words, the amount of light input to the CCD during shooting in color is reduced,
When the output level falls below the threshold, the camera performs an operation of switching from color photography to black-and-white photography. At this time, since the infrared cut filter between the lens and the CCD is removed and the dummy glass is inserted, the light in the infrared region removed by the infrared cut filter is removed by the CC.
D is input. Therefore, CC is better than color shooting
The level of the D output becomes high, and the camera erroneously determines that the area around the subject has become bright, and switches from monochrome photography to color photography. At this time, in contrast to this, in color photography, an infrared cut filter is inserted between the lens and the CCD, so it is judged that it has become dark and the operation to switch to black and white photography takes place. Is repeated, and a hunting operation occurs. As a method for preventing this hunting operation, a hysteresis characteristic is provided for a threshold value for switching from color photography to monochrome photography and a threshold value for switching from monochrome photography to color photography (threshold for switching to color photography). In some cases, a value A is set, and a threshold value B) for switching to black-and-white shooting.

However, setting a threshold value having such a hysteresis characteristic is generally difficult and cumbersome, since a delicate setting is required depending on the subject and shooting conditions.

[0009] For security applications such as surveillance cameras, lighting devices using LEDs or the like, which emit light in the infrared region near 880 nm, which is completely invisible to human eyes, have begun to be used. Such lighting devices are used in combination with black-and-white cameras that have a large light sensitivity in the near-infrared region. Has a great advantage in that it enables monitoring in the night vision state, in which a clear image can be obtained.

[0010] When such an illumination device near 880 nm is used for a black-and-white / color switching camera, the following serious problem occurs. That is, since the image sensor and the infrared cut filter generally have the spectral characteristics as shown in FIG. 9, when the mode is switched to the black and white mode, light in the near infrared region can be used very effectively. Bright and clear images. At this time, since the video signal level for determining whether to switch between black and white and color is considerably higher than the threshold value A set in advance, switching to color is permitted, and an infrared cut filter is inserted. I select a color image.

When the mode is switched to the color mode in this manner, an infrared cut filter is inserted, and light in the near infrared region is not used at all. , And a black-and-white image is selected by removing the infrared cut filter. As described above, when an illumination device that irradiates near-infrared light to a conventional black-and-white / color switching camera is used, a state occurs in which the color / black-and-white switching operation is continuously performed, and the screen is displayed. It is very hard to see and leads to the problem of the reliability of the switching mechanism by continuous operation.

There is a method of adding a new illuminance sensor in order to obtain information on the brightness of the subject. However, the additional illuminance sensor has a problem in terms of cost. , For the subject the camera is shooting,
There is also a problem that it is very difficult to match the detection areas of the illuminance sensors.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a camera capable of switching between black-and-white shooting and color shooting without malfunction.

[0014]

According to the first aspect of the present invention,
When the external brightness is higher than a predetermined brightness, an infrared cut filter is inserted in front of the image sensor to perform color shooting, and when the external brightness is lower than the predetermined brightness, the infrared cut filter is extracted from the front of the image sensor to produce a black and white image. In a color / monochrome switching camera that performs photographing, an infrared cut filter is attached to a part of a light receiving surface of the image sensor in order to determine the predetermined brightness.

According to a second aspect of the present invention, the color / monochrome switching camera has a signal processing means for generating a monochrome signal and a color signal in accordance with a signal from the image sensor, and a decision for switching from monochrome photography to color photography. A reference value, and a black-and-white signal output from a pixel to which the infrared cut filter of the image sensor is attached, and a black-and-white signal output from a pixel to which the infrared cut filter is attached and the determination reference value. This is a configuration for changing to color photography.

According to a third aspect of the present invention, when an external brightness is higher than a predetermined brightness, an infrared cut filter is inserted in front of the imaging device to perform color photographing. In the color / monochrome switching camera for taking out the infrared cut filter from the front and inserting a dummy glass to perform black and white shooting, an infrared cut filter was attached to a part of the dummy glass in order to judge the predetermined brightness. Configuration.

According to a fourth aspect of the present invention, in the color / monochrome switching camera, signal processing means for generating a monochrome signal and a color signal in accordance with a signal from the image pickup device, and a determination for switching from monochrome photography to color photography. A black-and-white signal output from a pixel of the image sensor that has passed through the infrared cut filter attached to the dummy glass and is incident on the image sensor among black-and-white signals output during black-and-white shooting And a change from black-and-white shooting to color shooting based on the comparison result of the above and the determination reference value.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. In this embodiment, the configuration of the camera itself is the same as that of the conventional example shown in FIG. 8, except that an infrared cut filter is attached to the light receiving surface of the CCD 5. FIG. 1 is a view showing the overall configuration of a color / monochrome switching camera according to an embodiment of the present invention, FIG. 2 is a view showing a light receiving surface of a CCD 5, and FIG. FIG. 4 shows the infrared cut filter of FIG.
FIG. 5 is a diagram showing a state in which an infrared cut filter is attached to CD5, and FIG. 5 is a diagram showing a state in which an infrared cut filter is attached to a part of the light receiving surface of CCD5;
FIG. 6 is a diagram showing a state in which a dummy glass 3 and an infrared cut filter 2 used for switching between black and white and color are integrally formed, and a part of the dummy glass 3 is provided with an infrared cut filter. is there.

First, as shown in FIG. 1, the state in which the dummy glass 3 is inserted with few optical signals from the subject and black-and-white shooting is performed will be described.

In this embodiment, an infrared cut filter shown in FIG. 3 is attached to the protection glass of the CCD 5, and FIG.
It is in the state shown in The portion where the infrared cut filter is attached is a portion outside the display screen which hardly affects the creation of the video signal.

An optical signal from the outside passes through the lens 1 and
Light enters the dummy glass 3. The light that has passed through the dummy glass 3 enters the CCD 5. The CCD 5 converts a light signal into an electric signal and outputs the electric signal to the signal processing circuit 6. The signal processing device 6 receives the electric signal and generates a color signal Cout and a monochrome signal Yout. The value of the black-and-white signal Yout fluctuates according to external brightness. The detection circuit 7 converts the monochrome signal Yout for one screen output from the CCD 5 into a monochrome signal output from a pixel to which the infrared cut filter 20 is attached.
Yout and the black-and-white signal Yout output from the pixel without the infrared cut filter 20 are separately integrated. Then, the integral value VoutN obtained by integrating the black-and-white signal Yout output from the pixel to which the infrared cut filter 20 is not attached and the black-and-white signal Yout output from the pixel to which the infrared cut filter 20 is attached are integrated. The obtained integral value VoutC is output to the microcomputer 9. Microcomputer
At 9, the state sensor 8 confirms that the dummy glass 3 is inserted between the lens 1 and the CCD 5, and the integrated value VoutC is equal to the predetermined value V1 (the first reference value for switching between monochrome shooting and color shooting). If it is larger, switch the changeover switch 11 to the color signal Cout and give an instruction to the motor 01 to set the lens
The dummy glass 3 inserted between 1 and the CCD 5 is replaced with the infrared cut filter 2, and the output (OUT) is switched to Cout. In this case, since the operation of switching from black-and-white shooting to color shooting is performed based on the actual amount of light that has passed through the infrared cut filter 20, the hunting operation shown in the conventional example does not occur. If the integrated value VoutC is smaller than the predetermined value V1, the current state is maintained.

Next, let us consider a case in which, for example, infrared light is emitted from a lighting device in a black-and-white shooting state. FIG.
In the conventional color / black-and-white switching camera shown in FIG. 1, when the illumination device is irradiated with infrared light, the light passes through the lens 1, passes through the dummy glass 3 as it is, and
Enter D5. Detection circuit for monochrome signal Yout from signal processor 6
Output to 7. The detection circuit 7 integrates the black-and-white signal Yout for one screen and sends the integrated value Vout to the microcomputer 9. Microcomputer 9
Then, the integral value Vout is compared with a predetermined value. In this case, since the infrared light is irradiated, if the conventional camera has a large integral value Vout, it is determined that the outside has become bright because the integrated value Vout is large, and the microcomputer 9 instructs the motor 10 to move the infrared cut filter 2 to the lens 1. And CCD5. As a result, in the color photographing state, the infrared light is absorbed by the infrared cut filter 2, and the operation of black-and-white photographing is performed, and the operation of black-and-white photographing and color photographing is repeated.

Therefore, in the present embodiment, a new determination method for shifting from the black-and-white shooting state to the color shooting is added. In this case, as described above, the black-and-white signal Yout output from the signal processing circuit is output from the pixel to which the infrared cut filter 20 is not attached and the black-and-white signal Yout output from the pixel to which the infrared cut filter 20 is not attached. The integrated value VoutN obtained by integrating the black-and-white signal Yout output from the pixel not provided with the infrared cut filter 20 and the integrated value VoutN obtained by integrating the black-and-white signal Yout output from the pixel provided with the infrared cut filter 20 Integral value VoutC obtained by integrating monochrome signal Yout
Is output to the microcomputer 9. In the microcomputer 9, first, the predetermined value V1
Is compared with the integral value VoutC, and when the integral value VoutN is smaller than the predetermined value V1, the switching operation is not performed as it is, and then the integral value VoutC is changed to the predetermined value V1 (for switching between color shooting and monochrome shooting, If it is larger than the reference value (1), the operation is switched from the dummy glass 3 to the infrared cut filter 2.
Since the integrated value VoutC is cut off the infrared light, it is possible to determine whether the surroundings have actually become brighter or that the black-and-white signal Yout has become larger due to infrared irradiation when taking color images. The hunting operation of switching between color / black and white, which is caused by the irradiation of infrared light by the camera, is eliminated.

In this embodiment, the infrared cut filter is mounted around the light receiving surface of the CCD 5, but may be a part of the light receiving section of the CCD 5 as shown in FIG. Further, as shown in FIG. 6, it may be attached to a part of the dummy glass 3. The shape of the infrared cut filter to be attached is not a limiting factor of the present invention.

In a state in which the infrared cut filter 2 is inserted with a large amount of light signals from the subject and the color photographing is being performed, the black-and-white signal Yout output from the pixel without the infrared cut filter 20 is attached. The integrated value VoutN obtained by the integration is compared with a predetermined value V0. If the integrated value VoutN is smaller than the predetermined value V0, the operation of removing the infrared cut filter 3 and inserting the dummy glass 3 and the output (OUT) are Yout. Switch to

Next, the processing operation of the microcomputer 9 of this embodiment will be described.

FIG. 7 is a flow chart showing a microcomputer operation for switching from black-and-white shooting to color shooting or from color shooting to black-and-white shooting.

First, the dummy glass 2 is inserted,
A description will be given from the state where black-and-white shooting is performed. To determine whether the monitoring target is bright and color shooting is possible,
VoutC obtained from the portion of the CD to which the infrared cut filter is attached is compared with a predetermined value V1 for switching from black-and-white shooting to color shooting. If VoutC is smaller than the predetermined value V1, step 1 is repeated again, and If the value is larger than the predetermined value V1, the process proceeds to step 2 and the dummy glass
The microcomputer outputs FC (H) from 9 to the motor 10 so as to switch from 3 to the infrared cut filter 2.
0 is to operate the slide mechanism 4 to pull out the dummy glass 3 between the lens 1 and the CCD 5, and
Insert Then, the process proceeds to step 3, where the microcomputer 9 outputs YC (H) to the changeover switch 11 to switch the output from Yout to Cout. Then, in step 4, it is confirmed that the slide mechanism 4 has been switched to the infrared cut filter 2. As a result, a color photographing state is set.

Next, this time, it is determined whether or not VoutN has become equal to or less than a predetermined value V0 in step 5 in order to determine whether or not the color of the object to be monitored is dark and color photographing is difficult, and black and white photographing is not performed. If VoutN is larger than the predetermined value V0, the current state is maintained. If VoutN is equal to or smaller than the predetermined value V0, the process proceeds to step 6, where the microcomputer 9 sends the FC
(L), and the motor 10 operates the slide mechanism 4 to operate the infrared cut filter 2 between the lens 1 and the CCD 5.
And insert the dummy glass 3. Proceeding to step 7, the microcomputer 9 switches the changeover switch 11 to the YC
(L) is output to switch the output from Cout to Yout.
Then, in step 8, it is confirmed that the slide mechanism 4 has been switched to the dummy glass 2. As a result, a black-and-white shooting state is set. Then, the process returns to step 1 and the same operation is repeated.

In this embodiment, the infrared cut filter is mounted on a part of the light receiving surface of the CCD. However, when the infrared cut filter is mounted on a part of the dummy glass 3 as shown in FIG. Since the determination can be made only by the value (the value extracted from the pixel of that part), the predetermined value may be only V1, and the determination process is further simplified. That is, CC
When an infrared cut filter is attached to a part of the light receiving surface of D, the infrared cut filter 2 is connected to the lens 1 and the CC.
When it is between D5, the light that passes through the infrared cut filter attached to a part of the light receiving surface of the CCD passes through the infrared cut filter 2 before that, so it passes through the infrared cut filter twice. I have. Therefore, the initial value for judgment cannot be set to one (there is almost no problem even if it is the same), but when it is attached to a part of the dummy glass 3, it passes through the infrared cut filter twice like that Therefore, the predetermined value V0 is unnecessary and can be determined only by the predetermined value V1.

[0031]

When the infrared cut filter is attached to a part of the light receiving surface of the CCD or the infrared cut filter is attached to a part of the dummy glass, the object to be monitored is dark and the lens and the CCD are not connected. Even when a dummy glass is inserted between the lens and the CCD, it is possible to measure the amount of light to the CCD when an infrared cut filter is inserted between the lens and the CCD in that state. The hunting operation accompanying the switching of the shooting is eliminated. In particular, the hunting operation as in the related art does not occur in photographing in the case of infrared irradiation.

In addition, there is no need to provide a hysteresis characteristic to the threshold value for switching from black-and-white shooting to color shooting, and the camera can be easily installed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a color / monochrome switching camera according to an embodiment of the present invention.

FIG. 2 is a diagram showing a light receiving surface of a CCD 5;

FIG. 3 is an infrared cut filter to be attached to a light receiving surface of a CCD 5;

FIG. 4 is a view showing a state in which an infrared cut filter is attached to the CCD 5.

FIG. 5 is a diagram showing a state in which an infrared cut filter is attached to a part of the light receiving surface of the CCD 5.

FIG. 6 shows an example in which a dummy glass 3 and an infrared cut filter 2 used for switching between black and white and color are integrally formed.

FIG. 7 is a flowchart illustrating a microcomputer operation for switching from monochrome photography to color photography or from color photography to monochrome photography.

FIG. 8 is a diagram showing an overall configuration of a conventional color / monochrome switching camera.

FIG. 9 is a diagram showing spectral characteristics of a color CCD.

[Explanation of symbols]

2: Infrared cut filter, 3: Dummy glass, 4:
Slide mechanism, 5: imaging device (CCD), 6: signal processing circuit, 9: microcomputer, 10: motor, 11: changeover switch

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) G03B 15/00 G03B 15/00 Z 5C065 H04N 5/225 H04N 5/225 CD 5/33 5/33 5 / 335 5/335 V 7/18 7/18 EF term (reference) 2H002 DB02 DB06 DB15 DB17 DB19 DB25 GA26 GA33 JA08 JA11 2H083 AA04 AA20 AA27 AA36 AA53 AA54 5C022 AA01 AB03 AB13 AC42 AC55 5C024 AX01 AX06 BX04 DX01 EX04 5C054 AA05 CA04 CA05 CC05 CG03 CH01 FB01 FB04 HA18 5C065 AA02 BB08 CC01 CC08 CC10 DD02 EE16 GG22 GG24

Claims (4)

[Claims] When the external brightness is brighter than a predetermined brightness, an infrared cut filter is inserted in front of the image sensor to perform color photographing. When the brightness is darker than a predetermined brightness, the infrared cut filter is inserted from the front of the image sensor. A color / monochrome switching camera for taking out a filter and photographing in black and white, wherein an infrared cut filter is attached to a part of a light receiving surface of the image sensor in order to determine the predetermined brightness. camera. 2. The color / monochrome switching camera includes signal processing means for generating a monochrome signal and a color signal in accordance with a signal from the image sensor, and a criterion value for switching from monochrome photography to color photography. The black and white signal output from the pixel of the image sensor to which the infrared cut filter of the image sensor is attached among the black and white signals output at the time of black and white shooting is compared with the determination reference value. 2. The color / black-and-white switching camera according to claim 1, wherein the camera is changed. 3. When the external brightness is brighter than a predetermined brightness, an infrared cut filter is inserted in front of the image sensor to perform color photographing. When the brightness is lower than a predetermined brightness, the infrared cut filter is inserted from the front of the image sensor. A color / monochrome switching camera for taking out a filter and inserting a dummy glass to perform black-and-white shooting, wherein an infrared cut filter is attached to a part of the dummy glass to determine the predetermined brightness. / Black and white switching camera. 4. The color / monochrome switching camera includes signal processing means for generating a monochrome signal and a color signal according to a signal from the image sensor, and a criterion value for switching from monochrome photography to color photography. A black-and-white signal output from a pixel of the image sensor that has passed through the infrared cut filter attached to the dummy glass and is incident on the image sensor among black-and-white signals output during black-and-white shooting, and the determination reference value. 4. The color / monochrome switching camera according to claim 3, wherein a change is made from black-and-white shooting to color shooting based on the result of comparing.