JP3583952B2 - Black and white / color switching camera - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a black-and-white / color switching camera, and more particularly to a black-and-white / color switching camera which is applied to, for example, a surveillance camera and switches a shooting mode between a color mode and a black-and-white mode in accordance with the brightness of a subject.
[0002]
[Prior art]
Many color cameras use a CCD imager as an image sensor. The photosensitive characteristics of the CCD imager are in a 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 becomes reddish. In consideration of such points, usually, an infrared cut filter (IR cut filter) is provided between the light receiving surface of the CCD imager and the optical lens.
[0003]
However, if an IR cut filter is used even when shooting 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 will be further insufficient, which will hinder shooting.
[0004]
For this reason, in a surveillance camera or the like that requires shooting 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. . In other words, the IR cut filter is turned off in order to secure the brightness of the reproduced image using the luminance component included in the infrared region, and the black and white video is considered in consideration of the deterioration in color reproducibility when the IR cut filter is turned off. Signal was output.
[0005]
That is, in the prior art, in the daytime when a sufficient amount of light can be secured, a color mode in which the IR cut filter is enabled and a color video signal is output is selected. The black and white mode that outputs a signal was selected.
[0006]
[Problems to be solved by the invention]
However, in the related art, the threshold value used for comparison with the luminance component is a fixed value. Operation could result in unstable operation. 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 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, a phenomenon occurs in which 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.
[0007]
SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a black-and-white / color switching camera capable of stabilizing a mode switching operation regardless of shooting conditions.
[0008]
[Means for Solving the Problems]
A black-and-white / color switching camera according to the present invention includes an image sensor for photographing a subject image, first detection means for detecting a luminance component from an output of the image sensor, and second detection means for detecting an R component and a B component from an output of the image sensor. Comparing means for comparing a luminance component with a predetermined threshold value, switching means for switching a photographing mode between a color mode and a black-and-white mode according to a comparison result of the comparing means, and setting a first threshold value to a predetermined threshold value when switching the photographing mode to the color mode And a second setting means for setting one of the second threshold and the third threshold to a predetermined threshold when the shooting mode is switched to the monochrome mode , wherein both the second threshold and the third threshold are set. The third threshold value is greater than the first threshold value, and the third threshold value is greater than the second threshold value. When the R component and the B component do not satisfy the predetermined condition, the second threshold value is set. A second threshold setting means for setting a predetermined threshold; and a third threshold setting means for setting a third threshold to a predetermined threshold when the R component and the B component satisfy a predetermined condition, wherein the R component has a higher value than the B component. Including the condition of being large .
[0009]
[Action]
When a subject image is photographed by the image sensor, the first detecting means detects a luminance component from the output of the image sensor, and the second detecting means detects an R component and a B component from the output of the same image sensor. On the other hand, the first setting means sets the first threshold to a predetermined threshold when switching the shooting mode to the color mode. 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 value and the third threshold value are larger than the first threshold value and have different values from each other. The comparing means compares such a 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 compares the R component and the B component. 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.
[0011]
Here, the third threshold is larger than the second threshold, and the predetermined relation includes a condition that the R component is larger than the B component.
[0012]
In another aspect of the present invention, the infrared cut filter removes infrared rays from the subject image irradiated on the image sensor. Further, 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.
[0013]
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]
【The invention's effect】
According to the present invention, when the shooting mode is switched to the monochrome 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 shooting mode can be appropriately switched even under shooting under any conditions, and the operation can be stabilized.
[0015]
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 drawings.
[0016]
【Example】
Referring to FIG. 1, a video camera 10 according to this embodiment includes an optical lens 12. A glass member 14 formed in a rectangular plate shape is arranged between the optical lens 12 and the CCD imager 24. As shown in FIG. 2, the upper half of the glass member 14 is formed by an IR cut filter 14a, and the lower half is formed by a 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.
[0017]
The position of the glass member 14 is detected by the state sensor 16, and a detection signal is given to the microcomputer 18.
[0018]
As shown in FIG. 3, a color filter 22 in which Ye, Cy, Mg, and G color elements are arranged in a mosaic pattern is mounted on the light receiving surface of the CCD imager 24. 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. In addition, any of the color elements constituting the color filter 22 transmits not only its own color component but also an infrared component. For this reason, the infrared component is cut by the IR cut filter 14a.
[0019]
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. For this reason, pixel signals are output from the CCD imager 14 in the manner of (Mg + Ye), (G + Cy), (Mg + Ye), (G + Cy)... , (Mg + Cy)... Are output from the CCD imager 14. In each of the odd-numbered line and the even-numbered line, adjacent two pixels include all color components Ye, Cy, Mg, and G. The sum (Ye + Cy + Mg + G) of all such color components can be approximated to a luminance component, that is, a Y component.
[0020]
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 supplies a smoothed signal, that is, a Y signal to the integration circuit 30. Integrating circuit 30 integrates the input Y signal, providing an integral value Y _S to the microcomputer 18.
[0021]
The pixel signal output from the CDS circuit 26 is also subjected to a well-known gain adjustment by the AGC circuit 32, and is thereafter provided to the color separation circuit 38. The color separation circuit 38 separates pixel signals that are continuous in the horizontal direction one pixel at a time, and supplies the separated pixel signals to a 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. On 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 a pixel signal of 2R-G (= Mg + Ye- (G + Cy)) on an odd line and a pixel signal of G-2B (= G + Ye- (Mg + Cy)) on an even line. You. Equation 1 holds between the primary color components R, G, and B and the complementary color components Ye, Cy, and Mg.
[0022]
(Equation 1)
Ye = R + G
Cy = G + B
Mg = R + B
The output of the subtracter 40 is supplied to one input terminal of the adder 44 as it is and to the other input terminal of the adder 44 via the line memories 42a and 42b. 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. That is, the average of the input pixel signals is obtained. Then, the average value is given to one input terminal of the selector 46.
[0023]
The other input terminal of the selector 46 is supplied with the pixel signal of the previous line output from the line memory 42a. For this reason, 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, a 2R-G pixel signal is applied. A pixel signal is provided 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 pixel signals of 2R-G (= _{C R)} are output at all times from the other hand the output terminal, the pixel signals of the G-2B (= _{C B)} is always outputted from the other output terminal.
[0024]
Thus C _R signal and C _B signal outputted from the selector 46 in the is input to the 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. The generated R signal, G signal, and B signal are provided to a matrix operation circuit 54 through white balance adjustment by a white balance adjustment circuit 50 and gamma correction by a gamma correction circuit 52.
[0025]
The matrix operation circuit 54 generates color difference signals RY and BY based on the input R signal, G signal and B signal, and inputs the generated RY signal and BY signal 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.
[0026]
The R and B signals output from the gamma correction circuit 52 are also input to integration circuits 56 and 58. Integrating circuit 56 and 58 are given R signals and B signals each integrated to obtain the integrated value _{R S} and _{B S.} The obtained integral values R _S and B _S are input to the microcomputer 18.
[0027]
That is, the microcomputer 18, the integration value outputted from the detection signal and the integrator circuit 30,56 and 58 output from the state sensor 16 _Y S, given _{R S} and _{B S,} the microcomputer 18 based on these signals To control the motor 20 and the switch SW1. The microcomputer 18 takes a timing according to the vertical synchronization signal output from the encoder 36, and the integration circuits 30, 56 and 58 are reset in response to the same vertical synchronization signal.
[0028]
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. 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, whether the vertical synchronizing signal is input is determined at step S5, if YES, the capture integral value _Y S, the _{R S} and _{B S} from the integrator 30,56 and 58 in step S7.
[0029]
In step S9, it compares the integral value _{Y S} with the threshold _{Y TH.} Here, if a _{Y S> Y TH,} determines the current shooting mode in step S11. 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.
[0030]
On the other hand, if Y _S ≦ Y _TH , the microcomputer 18 proceeds from step S9 to step S13, and determines the current shooting mode as in step S11. If the current shooting mode is the monochrome mode, the process returns to step S5, and 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. Here it is to set the threshold value _{Y TH} at step S17 if NO in the second threshold value _{Y 2,} set if YES in step S19 the threshold _{Y TH} to the third threshold value _{Y 3.} Specifically, when the integral value _BS is almost zero and the integral value _RS is sufficiently large, YES is determined in the step S15. When the update process of the threshold Y _TH 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.
[0031]
The first threshold value _{Y 1,} the relationship between the second threshold value _{Y 2} and the third threshold value _{Y 3,} shown in FIG. The value indicated by each threshold increases in the order of Y ₁ , Y ₂ , and Y ₃ . Further, towards the difference between the first threshold value Y ₁ and the second threshold value Y ₂ is greater than the difference between the second threshold value Y ₂ and the third threshold value Y _3. The threshold Y _TH is set to the first threshold Y ₁ together with the selection of the color mode. Color mode is selected and the integral value _{Y S} is while above the first threshold value _{Y 1,} the process of step S5~S11 is repeated. When the integral value _{Y S} decreases to the first threshold value _{Y 1,} step S13~S21 are processed, together with the threshold value _{Y TH} is updated to the second threshold value _{Y 2} or _{Y 3,} shooting mode is switched to the monochrome mode.
[0032]
In a state where the monochrome 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 processing in step S5~S13 are repeated, 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 .
[0033]
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, IR cut filter 14a is integral value Y _S is increased when the OFF state, IR cut filter 14a is in the on state phenomenon occurs 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.
[0034]
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 first threshold value Y ₁ shown in FIG. 5 as a threshold value for switching 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, either the second threshold value Y ₂ and the third threshold value Y ₃ One is set to the threshold Y _TH . 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.
[0036]
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.
[0037]
Further, in this embodiment, a complementary color filter is used as the color filter 22, but 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]
Reference Signs List 10 black-and-white / color switching camera 14a IR cut filter 14b dummy glass 16 state sensor 18 microcomputer 20 motor 30, 56, 58 integration circuit 36 encoder

Claims (3)

An image sensor that captures the image of the subject,
First detecting means for detecting a luminance component from the output of the image sensor,
Second detection 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,
Switching means for switching a shooting mode between a color mode and a black and white mode in accordance with a comparison result of the comparing means,
First setting means for setting a first threshold value to the predetermined threshold value when the shooting mode is switched to the color mode; and setting one of the second threshold value and the third threshold value when the shooting mode is switched to the monochrome mode to the predetermined value. A second setting means for setting a threshold value ;
Both the second threshold and the third threshold are larger than the first threshold,
The third threshold is greater than the second threshold,
A second threshold setting unit that sets the second threshold to the predetermined threshold when the R component and the B component do not satisfy a predetermined condition; and a second threshold setting unit that sets the R component and the B component to the predetermined condition. A third threshold setting unit that sets the third threshold to the predetermined threshold when
The monochrome / color switching camera, wherein the predetermined condition includes a condition that the R component is larger than the B component . An infrared cut filter that removes infrared rays from a subject image irradiated on the image sensor,
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, and further comprising a selection means for selecting one of the black and white video signal and the color video signal, No placement claim 1 Symbol Black and white / color switching camera. Said switching means selects said color video signal as well as on the infrared cut filter in the camera mode, selects the monochrome video signal turns off the infrared cut filter in the monochrome mode, according to claim 2, wherein Black and white / color switching camera.

Images