JP2001045512A - Black.white/color switching camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a mode switching operation of a camera stable under any photographing condition by selecting a different threshold value. SOLUTION: An integration circuit 30 integrates a Y signal corresponding to an object image to obtain an integration value YS. Integration circuits 56, 58 integrate R and B signals corresponding to the object image to obtain integration values RS, BS. A microcomputer 18 sets a prescribed value YTH as a 1st threshold Y1 in the case of selecting a color mode for the photographing mode. Furthermore, in the case of selecting a black/white mode for the photographing mode, a 2nd threshold Y2 or a 3rd threshold Y3 is set to the prescribed threshold YTH on the basis of the integration values RS, BS. The 2nd threshold Y2 and the 3rd threshold Y3 are larger than the 1st threshold Y1 and different from each other. The microcomputer 18 compares the prescribed threshold YTH with the integration value YS and selects the color mode or the black/white mode for the photographing mode depending on the result of comparison.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black-and-white / color switching camera, and more particularly to, for example, a surveillance camera, which switches a shooting mode between a color mode and a black-and-white mode in accordance with the brightness of a subject. It relates to a switching camera.

[0002]

2. Description of the Related Art Many color cameras use a CCD imager as an image pickup device. The photosensitive characteristics of this CCD imager are in the wavelength region of about 400 nm to 900 nm, and the sensitivity in the infrared region (700 nm or more) is particularly high. For this reason, if the light image of the subject is directly irradiated on the CCD imager, the reproduced image will be reddish. In consideration of such points, usually CC
An infrared cut filter (IR cut filter) is provided between the light receiving surface of the D imager and the optical lens.

[0003] However, if an IR cut filter is used even when photographing in a situation where a sufficient amount of light cannot be obtained, such as at night, the amount of light applied to the CCD imager becomes further insufficient, which hinders photographing. I will.

For this reason, in a surveillance camera or the like that requires photographing regardless of day and night, conventionally, the luminance component is compared with a predetermined threshold, and if the luminance component is small, the IR cut filter is turned off and a black-and-white video signal is output. Was. That is, the IR cut filter is turned off to secure the brightness of the reproduced image by using the luminance component included in the infrared region,
A black-and-white video signal has been output in consideration of deterioration in color reproducibility when the cut filter is turned off.

That is, in the prior art, in the daytime when a sufficient amount of light can be secured, the color mode in which the IR cut filter is enabled to output a color video signal is selected, and in the nighttime when the amount of light is insufficient, the IR cut filter is disabled. Black and white mode that outputs a black and white video signal.

[0006]

However, in the prior art, the threshold value used for comparison with the luminance component was a fixed value. When shooting under such an incandescent lamp, the operation may be unstable.
That is, when a voltage lower than the rated voltage is applied to the incandescent lamp, as can be seen from FIG. 7, the spectrum of the illumination light shifts to the longer wavelength side, and the light amount in the near infrared region decreases instead of decreasing the light amount in the visible region. Will increase. Then, when the IR cut filter is in the off state, many luminance components are obtained, whereas when the IR cut filter is in the on state, the luminance component is insufficient. As a result, in shooting under an incandescent lamp driven at a low voltage, the shooting mode switching is frequently repeated, and the operation has been unstable.

SUMMARY OF THE INVENTION It is, therefore, a primary object of the present invention to provide a monochrome / color switching camera capable of stabilizing a mode switching operation regardless of photographing conditions.

[0008]

According to the present invention, there is provided an image sensor for photographing a subject image, first detecting means for detecting a luminance component from an output of the image sensor, and a first detecting means for detecting an R component and a B component from an output of the image sensor. 2 detecting means, comparing means for comparing the luminance component with a predetermined threshold, switching means for switching the photographing mode between the color mode and black-and-white mode according to the comparison result of the comparing means, and the first means for switching the photographing mode to the color mode. First setting means for setting a threshold to a predetermined threshold, and when switching the shooting mode to the monochrome mode, one of a second threshold and a third threshold which are larger than the first threshold and different from each other based on the R component and the B component. A black-and-white /
It is a color switching camera.

[0009]

When a subject image is captured by the image sensor, the first detecting means detects the luminance component from the output of the image sensor, and the second detecting means detects the R component and the B component from the output of the same image sensor. On the other hand, the first setting means switches the first mode when the shooting mode is switched to the color mode.
The threshold is set to a predetermined threshold. The second setting means sets one of the second threshold and the third threshold to a predetermined threshold based on the R component and the B component when switching the shooting mode to the monochrome mode. The second threshold and the third threshold are the first threshold
It has values that are greater than the threshold and different from each other. The comparing means compares the predetermined threshold value with the luminance component, and the switching means switches the photographing mode between the color mode and the monochrome mode according to the comparison result.

[0010] In one aspect of the present invention, the second setting means operates as follows. First, the comparing means determines whether the R component and the B component
Compare ingredients. If the R component and the B component do not have a predetermined relationship, the second threshold setting means sets the second threshold to a predetermined threshold, and if the R component and the B component have a predetermined relationship, the third threshold is set. The setting means sets the third threshold to a predetermined threshold.

Here, the third threshold is larger than the second threshold, and the predetermined relationship includes a condition that the R component is larger than the B component.

In another aspect of the present invention, the infrared cut filter removes infrared rays from a subject image irradiated on the image sensor. The video signal generating means generates a black-and-white video signal and a color video signal based on the output of the image sensor, and the selecting means selects one of the black-and-white video signal and the color video signal.

The switching means turns on the infrared cut filter and selects a color video signal in the camera mode, and turns off the infrared cut filter and selects a black and white video signal in the black and white mode.

[0014]

According to the present invention, when the photographing mode is switched to the black and white mode, one of the second threshold and the third threshold is set to the predetermined threshold based on the R component and the B component. Here, the second threshold value and the third threshold value are larger than the first threshold value and have different values from each other. Therefore, the photographing mode can be appropriately switched even under photographing under any conditions, and the operation can be stabilized.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the accompanying drawings.

[0016]

Referring to FIG. 1, a video camera 10 of this embodiment includes an optical lens 12. FIG. Optical lens 12 and CC
Between the D imager 24, a glass member 14 formed in a rectangular plate shape is arranged. As shown in FIG. 2, the upper half of the glass member 14 is formed by the IR cut filter 14a, and the lower half is formed by the dummy glass 14b. The glass member 14 is moved in the length direction by a motor 20 controlled by the microcomputer 20. Therefore, between the optical lens 12 and the CCD imager 24 (on the optical axis), one of the IR cut filter 14a and the dummy glass 14b is arranged. When the IR cut filter 14a is arranged on the optical axis, an infrared component (a wavelength component of 700 nm or more) is cut from the light image of the subject. On the other hand, when the dummy glass 14b is arranged on the optical axis, the light image of the subject including the infrared component passes through the glass member 14 as it is.

The position of the glass member 14 is detected by a state sensor 16, and a detection signal is given to a microcomputer 18.

FIG. 3 shows the light receiving surface of the CCD imager 24.
The color filter 22 in which the color elements of Ye, Cy, Mg and G are arranged in a mosaic pattern as shown in FIG. Of these, two color elements in the vertical direction constitute one line. The subject image transmitted through the glass member 14 is irradiated on the light receiving surface of the CCD imager 24 through such a color filter 22. It should be noted that any of the color elements constituting the color filter 22 transmit not only their own color components but also infrared components. For this reason, the infrared component is cut by the IR cut filter 14a.

Pixel signals are read from the CCD imager 14 in a raster scan manner by a timing generator (not shown). As described above, two color elements in the vertical direction correspond to each line. Therefore, in the odd lines, (Mg + Ye), (G + Cy),
The pixel signal is C in the manner of (Mg + Ye), (G + Cy).
It is output from the CD imager 14 and (G
+ Ye), (Mg + Cy), (G + Ye), (Mg + C
The pixel signals are output from the CCD imager 14 in the manner of y). In both the odd-numbered line and the even-numbered line, adjacent two pixels have all the color components Ye, Cy, M
g and G are included. The sum of all such color components (Ye + Cy + Mg + G) can be approximated to a luminance component, that is, a Y component.

The pixel signal output from the CCD imager 14 is input to the LPF 28 after being subjected to well-known noise removal by the CDS circuit 26. The LPF 28 smoothes the input pixel signal and converts the smoothed signal, that is, the Y signal, into the integration circuit 3.
Give to 0. Integrating circuit 30 integrates the input Y signal, providing an integral value Y _S to the microcomputer 18.

The pixel signal output from the CDS circuit 26 is also subjected to a well-known gain adjustment by an AGC circuit 32, and then is applied to a color separation circuit 38. The color separation circuit 38 separates pixel signals continuous in the horizontal direction one pixel at a time, and supplies the separated pixel signals to the subtractor 40. In the odd lines, (Mg + Ye) is given to the plus side of the subtractor 40, and (G + Cy) is given to the minus side of the subtractor 40. In the even line, (G + Ye) is given to the plus side of the subtractor 40, and (Mg + Cy) is given to the minus side of the subtractor 40. For this reason, the subtractor 40 outputs 2R-G (= M
g + Ye- (G + Cy)) is output, and G-2B (= G + Ye- (Mg + C)
The pixel signal of y)) is output. The primary color components R, G
And B and the complementary color components Ye, Cy and Mg, Equation 1 holds.

[0022]

Ye = R + G Cy = G + B Mg = R + B The output of the subtractor 40 is directly supplied to one input terminal of an adder 44 and the line memories 42a and 42
The signal is supplied to the other input terminal of the adder 44 via 2b. That is, the pixel signal of the current line and the pixel signal of two lines before are input to the adder 44. The pixel signal of 2R-G is input to the adder 44 if the current line and two lines before are odd lines, and the pixel signal of G-2B is input if the current line and two lines before are even lines. The adder 44 adds the input pixel signals to each other and halves the added value.
To That is, the average of the input pixel signals is obtained. And
The average value is provided to one input terminal of the selector 46.

The other input terminal of the selector 46 is supplied with the pixel signal of the previous line output from the line memory 42a. Therefore, when a 2R-G pixel signal is applied to one end, a G-2B pixel signal is applied to the other end, and when a G-2B pixel signal is applied to one end, 2R-G is applied.
Is applied to the other end. Each of the input pixel signals is output from one output terminal and the other output terminal of the selector 46, and the output terminal is switched for each line. As a result, the 2R-G (= C _R ) pixel signal is always output from one output terminal, and the G-2B (= C _B ) pixel signal is always output from the other output terminal.

The C _R and C _B signals output from the selector 46 in this manner are input to a matrix operation circuit 48. The output of the AGC circuit 32, that is, the Y signal is also input to the matrix operation circuit 48. Matrix operation circuit 48, such C _R signal, performs predetermined matrix computation on the C _B signal and Y signal to produce a R, G and B signals. Generated R signal, G signal and B signal
The signal undergoes white balance adjustment by a white balance adjustment circuit 50 and gamma correction by a gamma correction circuit 52,
It is provided to a matrix operation circuit 54.

The matrix operation circuit 54 receives the input R
The color difference signals RY and BY are generated based on the signal, the G signal, and the B signal, and the generated RY signal and BY are generated.
The signal is input to the encoder 36. The Y signal output from the AGC circuit 32 and subjected to smoothing by the LPF 33 and gamma correction by the gamma correction circuit 34 is also input to the encoder 36. The encoder 36 performs a predetermined encoding process on the RY signal, the BY signal, and the Y signal, and outputs a monochrome video signal (monochrome television signal) having a luminance signal component and a synchronization signal component, and a luminance signal component and A color video signal (color television signal) having a color burst signal component and a color signal component in addition to the synchronization signal component is generated. Then, one of the black and white video signal and the color video signal is output via the switch SW1.

The R and B signals output from the gamma correction circuit 52 are also input to integration circuits 56 and 58. Integrating circuits 56 and 58 integrate the supplied R signal and B signal, respectively, to obtain integrated values R _S and B _S. The obtained integral values R _S and B _S are
Is input to

That is, the microcomputer 18 includes the state sensor 1
6 and the integration circuits 30, 56
And 58 are provided with integrated values Y _S , R _S and B _S output from microcomputer 58, and microcomputer 18 controls motor 20 and switch SW1 based on these signals. The microcomputer 18 takes timing in accordance with the vertical synchronizing signal output from the encoder 36, and integrates the integration circuits 30, 56 and 5
8 is reset in response to the same vertical synchronization signal.

The operation of the microcomputer 18 will be described with reference to FIG. First, the microcomputer 18 selects the color mode in step S1. That is, the IR cut filter 14a is arranged on the optical axis, and the switch SW1 is connected to the terminal S2.
To the side. As a result, a color video signal is output from the switch SW1. The microcomputer 18 then sets a threshold value Y _TH to the first threshold value Y ₁ at step S3. Subsequently, it is determined in step S5 whether a vertical synchronization signal has been input.
If YES, the integrated values Y _S , R _S and B _S are fetched from the integration circuits 30, 56 and 58 in step S7.

In step S9, the integral value Y _{S is set} to a threshold value Y _TH
Compare with If Y _S > Y _TH here, step S1
In step 1, the current shooting mode is determined. If the current shooting mode is the color mode, the process returns to step S5. If the current shooting mode is the monochrome mode, the process returns to step S1.

On the other hand, if Y _S ≤Y _TH , the microcomputer 18
Goes from step S9 to step S13,
As in step 11, the current shooting mode is determined. If the current shooting mode is the monochrome mode, the process returns to step S5. If the current shooting mode is the color mode, the process proceeds to step S15. In step S15, it is determined whether or not B _S «R _S. If “NO” here, the threshold value Y _TH is set to the second threshold value Y ₂ in step S17, but if “YES”, the process proceeds to step S17.
Setting the threshold Y _TH to the third threshold value Y ₃ at 19. Specifically, when the integral value B _S is almost zero and the integral value R _S is sufficiently large, YES is determined in the step S15. Threshold Y
_{When the TH} update processing is completed, the microcomputer 18 selects the monochrome mode in step S21, and returns to step S5. That is, the dummy glass 14b is arranged on the optical axis, the switch SW1 is connected to the terminal S1, and the process returns to step S5.

First threshold value Y₁, The second threshold Y_TwoAnd the third threshold
Y_ThreeIs shown in FIG. The value indicated by each threshold is Y₁, Y
_Two, Y_ThreeIn the order of. Also, the first threshold value Y₁And the second threshold
Value Y _TwoIs larger than the second threshold value Y_TwoAnd the third threshold Y_Three
Is greater than the difference between Threshold Y_THIs the color mode
The first threshold Y with the selection of₁Is set to Color mode
Is selected and the integral Y_SIs the first threshold Y₁While exceeding
, The processes of steps S5 to S11 are repeated. Integral
Value Y_SIs the first threshold Y₁When it has decreased to
S21 is processed, and the threshold Y_THIs the second threshold Y_TwoOr Y_ThreeTo
Is updated and the shooting mode is switched to black and white mode
available.

In the state where the black and white mode is selected, as long as the integral value Y _S does not exceed the threshold value Y _TH (= Y ₂ or Y ₃ ),
The processes in steps S5 to S13 are repeated, and the monochrome mode is maintained. When the integral value Y _S exceeds the threshold value Y _TH rises, the processing in step S11, S1 and S3 are performed. As a result, the shooting mode is switched to the color mode, and the threshold Y _TH is updated to the first threshold Y ₁ .

As shown in FIG. 7, the wavelength characteristic of the incandescent lamp to which a voltage lower than the rated voltage is applied shifts to a longer wavelength side than when the rated voltage is applied. When performing imaging in this situation, the integral value Y _S is increased when the IR cut filter 14a is turned off, the IR cut filter 1
4a is when the ON state occurs a phenomenon that the integral value Y _S decreases. For this reason, if a single value is used as the threshold value Y _{TH which} is a criterion for switching the shooting mode, the mode switching is frequently repeated, and the operation becomes unstable.

In order to eliminate such instability of the operation, the threshold value when switching from the color mode to the monochrome mode and the threshold value when switching from the monochrome mode to the color mode may be made different. That is, the threshold for switching the first threshold value Y ₁ shown in FIG. 5 to the monochrome mode,
The third threshold value Y ₃ may be the threshold of the color mode. However, this difference between the first threshold value Y ₁ and the third threshold value Y ₃ is too large, although the operation in an incandescent lamp of low voltage driving is stabilized, in other situations for example incandescent lamp rated voltage driving, fluorescent Mode switching does not work well when shooting under light or daylight. In other words, a phenomenon occurs in which switching is not performed even in a situation where the photographing mode is desired to be switched.

[0035] Therefore, in this embodiment, the integrated value B _S when switching from the color mode to the monochrome mode as compared with the integrated value R _S, in accordance with the comparison result, the second threshold value Y ₂ and the third threshold value Y _{3 Is} set to the threshold _YTH . This solves the problem that the photographing mode is frequently switched when photographing is performed under an incandescent lamp driven by a low voltage. Further, when shooting is performed in another situation, the shooting mode is switched at an appropriate timing.
That is, it is possible to stabilize the operation of switching the shooting mode under any conditions.

In this embodiment, the output of the CDS circuit 26 is supplied to the integration circuit 30 through the LPF 28, but the output of the AGC circuit 32 may be supplied to the integration circuit 30. In this embodiment, the R signal and the B signal output from the gamma correction circuit 52 are supplied to the integration circuits 56 and 58. However, the R signal and the B signal output from the matrix operation circuit 48 or the white balance adjustment 50 are provided. The B signal may be provided to the integration circuits 56 and 58.

Further, in this embodiment, the color filter 22
, A primary color filter in which R, G, and B color elements are arranged on a mosaic may be used. In this embodiment, the pixel signal is subjected to analog processing. However, the present invention can be applied to a camera that performs digital processing on the pixel signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is an illustrative view showing one example of a glass member;

FIG. 3 is an illustrative view showing one example of a complementary color filter;

FIG. 4 is a flowchart showing a part of the operation of the embodiment in FIG. 1;

FIG. 5 is an illustrative view showing one portion of an operation of the embodiment in FIG. 1;

FIG. 6 is a graph showing output characteristics of a CCD imager when an IR cut filter is used and when it is not used.

FIG. 7 is a graph showing wavelength characteristics of daylight, an incandescent lamp, and a fluorescent lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Black-and-white / color switching camera 14a ... IR cut filter 14b ... Dummy glass 16 ... State sensor 18 ... Microcomputer 20 ... Motor 30, 56, 58 ... Integrating circuit 36 ... Encoder

Claims (5)

[Claims] An image sensor for photographing a subject image; a first sensor for detecting a luminance component from an output of the image sensor;
Detecting means; second detecting means for detecting an R component and a B component from the output of the image sensor; comparing means for comparing the luminance component with a predetermined threshold value; Switching means for switching between modes; first setting means for setting a first threshold to the predetermined threshold when switching the shooting mode to the color mode;
And when the shooting mode is switched to the black and white mode, the first mode is set based on the R component and the B component.
A second threshold and a third that are greater than the threshold and different from each other
A monochrome / color switching camera, comprising: a second setting unit that sets one of the thresholds to the predetermined threshold. A second setting means for comparing the R component and the B component; setting the second threshold value to the predetermined threshold value when the R component and the B component do not have a predetermined relationship; 2. The monochrome / black / white / black / white / black / white / black / white / black-and-white printer according to claim 1, further comprising: a second threshold value setting unit for setting, and a third threshold value setting unit for setting the third threshold value to the predetermined threshold value when the R component and the B component have a predetermined relationship. Color switching camera. 3. The monochrome / color switching camera according to claim 2, wherein said third threshold value is larger than said second threshold value, and said predetermined relationship includes a condition that said R component is larger than said B component. An infrared cut filter for removing infrared rays from a subject image irradiated on the image sensor; a video signal generating means for generating a black and white video signal and a color video signal based on an output of the image sensor;
4. The black-and-white / color switching camera according to claim 1, further comprising a selection unit that selects one of the black-and-white video signal and the color video signal. 5. The switching means turns on the infrared cut filter and selects the color video signal in the camera mode, and turns off the infrared cut filter and selects the black and white video signal in the black and white mode. 5. A monochrome / color switching camera according to claim 4.