JP3701043B2 - Auto white balance apparatus and video camera manufacturing method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a video camera having a negative film image capturing function, and more particularly to color temperature detection and color temperature control for white balance control.
[0002]
[Prior art]
In normal video camera white balance control, the detection range and control range are adjusted to suit the shooting of subjects under sunlight, light bulbs, and fluorescent lights. A reference illumination light similar to a lamp is used.
[0003]
However, when the negative film image is captured by the video camera, the detection value and the control value are significantly different from the white balance control of the normal video camera due to special circumstances (1) to (3) below, and There are many variations.
{Circle around (1)} The film itself has an orange base coloring, and the color varies greatly depending on the type of film.
(2) There are many types of light sources for capturing negative film images with a video camera.
(3) The color temperature when shooting with a silver salt camera is unknown.
[0004]
Therefore, when a negative film image is captured by a video camera and white balance control is performed, it is necessary to specially set a detection range and a control range separately from white balance control of a normal video camera.
[0005]
Further, at the time of adjustment for setting the detection range and the control range, it is necessary to use a light source dedicated to a negative film image separately from the reference illumination light for adjustment of a normal video camera.
[0006]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide an auto white balance device and a video camera manufacturing method capable of adjusting a detection range and a control range suitable for capturing a negative film image using the same reference illumination light as a normal video camera. It is to provide.
[0007]
[Means for Solving the Problems]
The configuration of the auto white balance device according to the first aspect of the present invention that solves the above-described problem is a first configuration that stores values of a plurality of color temperature detection signals obtained by imaging a plurality of reference illumination lights having different color temperatures. storage means, second storage means for storing a shift amount of the color temperature detection signal in the case of photographing a negative film with a color temperature detection signal and a predetermined light source for shooting said reference illumination light, the first A color temperature detection axis is obtained based on the values of the plurality of color temperature detection signals stored in one storage means , and the color temperature detection axis is shifted by the shift amount stored in the second storage means. Obtaining a negative color temperature detection axis, detecting a color temperature based on the negative color temperature detection axis, a calculation means for calculating a control signal based on the output of the detection means, Based on the output, distributed to the video signal processing system And characterized by a control means for controlling the gain of the white balance adjustment amplifier are.
[0008]
According to a second aspect of the present invention, there is provided a video camera manufacturing method in which a reference illumination light source having a reference color temperature is replaced with a plurality of color temperature conversion filters to obtain a plurality of reference illumination light sources. Photographing illumination light to obtain a plurality of color temperature detection signals, approximating the color temperature detection axis therefrom, and photographing a negative film under a predetermined light source with the video camera to obtain a color temperature detection signal , Obtaining a negative color temperature detection axis from the color temperature detection signal , and performing a process for a plurality of video cameras including calculating a deviation amount between the negative color temperature detection axis and the color temperature detection axis;
Obtaining an average value of the deviation amounts obtained by performing a plurality of video cameras ;
Determining a ratio of the average value to a difference between the maximum value and the minimum value of the approximate color temperature detection axis;
This ratio is set as a shift amount for correcting a shift of the color temperature detection signal between the reference illumination light and the predetermined light source;
It is characterized by.
[0009]
According to a third aspect of the present invention, there is provided an auto white balance apparatus characterized in that the shift amount obtained by the video camera manufacturing method according to the second aspect of the invention is stored in the second storage means. .
[0010]
Next, an automatic white balance device according to a fourth aspect of the invention provides a plurality of control signal values for gain control of a white balance adjustment amplifier obtained by imaging a plurality of reference illumination lights having different color temperatures. first storage means for storing a second storage means for storing the deviation amount of the control signal in the case of photographing a negative film by a control signal and a predetermined light source in the case of photographing the reference illumination light, the first A color temperature control axis is obtained based on the values of the plurality of control signals stored in one storage means , and the color temperature control axis is shifted by the shift amount stored in the second storage means to make a negative. Obtaining the color temperature control axis for shooting, calculating means for calculating the control signal based on the color temperature control axis for negative shooting, and white balance adjustment arranged in the video signal processing system based on the output of the calculating means Amplifier gain Characterized by comprising a Gosuru control means.
[0011]
According to a fifth aspect of the present invention, there is provided a method of manufacturing a video camera, wherein a plurality of color temperature conversion filters are replaced with a reference illumination light source having a reference color temperature to obtain a plurality of reference illumination light sources. Photographing the reference illumination light, obtaining a plurality of control signals for gain control of the white balance adjustment amplifier, approximating the color temperature control axis therefrom, and photographing the negative film under a predetermined light source with the video camera Determining a color temperature control axis for negative imaging from the control signal, and calculating a shift amount between the color temperature control axis for negative imaging and the color temperature control axis . What to do with the video camera;
Obtaining an average value of the deviation amounts obtained by performing a plurality of video cameras ;
Determining a ratio of the average value to a difference between the maximum value and the minimum value of the approximate color temperature control axis;
This ratio is set as a shift amount for correcting a shift of the control signal between the reference illumination light and the predetermined light source;
It is characterized by.
[0012]
Further, the auto white balance apparatus according to the invention of claim 6 is characterized in that the shift amount obtained by the method of manufacturing the video camera of claim 5 is stored in the second storage means. .
[0013]
[Action]
In the present invention, a plurality of light sources having different color temperatures are used as the reference illumination light, the values of the color temperature detection signals obtained at that time are stored in advance in the first storage means, and the color temperature detection signals The amount of deviation from each temperature detection signal when a negative film image is captured with the light source is stored in advance in the second storage means.
[0014]
When the negative film image is actually captured, the color temperature is detected by shifting the temperature detection axis based on the contents stored in the first storage means and the second storage means, and based on the detected color temperature. To control the gain of the white balance adjustment amplifier.
[0015]
In the present invention, a plurality of light sources having different color temperatures are used as the reference illumination light, and the values of the control signals for gain control of the white balance adjustment amplifier obtained at that time are stored in advance in the first storage means. In addition, a deviation amount between each of these control signals and a control signal when a negative film image is captured with a predetermined light source is also stored in advance in the second storage unit.
[0016]
When the negative film image is actually captured, the control signal is calculated by shifting the temperature control axis based on the contents stored in the first storage means and the second storage means, and the control signal obtained by this calculation is calculated. The gain of the white balance adjustment amplifier is controlled based on the above.
[0017]
As described above, the deviation amount of the color temperature detection signal or the control signal when a plurality of reference illumination lights and a predetermined light source are used is stored in advance, and this deviation amount is obtained when the negative film image is actually captured. By detecting the color temperature by shifting the color temperature detection area or the color temperature control area, or by obtaining the control signal, the color temperature of each reference illumination light is not specifically limited. It is possible to adjust an auto white balance device of a video camera having a negative film image capturing function using the reference illumination light.
[0018]
In particular, a plurality of light sources having different color temperatures are used as the reference illumination light, and the difference between the maximum value and the minimum value of the signal obtained at that time is set to 100% as a reference, for example. By storing the amount as a ratio with respect to the difference, for example, as a percentage display, the color temperature detection area and the color temperature control area of the auto white balance device of each video camera are corrected with the ratio, thereby detecting variations in the detection system and reference illumination. An error in feedforward control caused by approximation by light can be reduced to a practically sufficient level.
[0019]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
<First embodiment>
1 to 5 show a first embodiment of the present invention. FIG. 1 is a circuit diagram showing an imaging system of a video camera having a negative film image capturing function. In this embodiment, the case of a CCD using a complementary color filter will be described. As shown in the figure, an optical image formed by the lens 1 is formed on the light receiving surface of a CCD 3 with a built-in complementary color filter, and an imaging signal S is output from the CCD 3. The image pickup signal S is subjected to sample hold processing and gain adjustment by the sample hold and AGC circuit 5, and further converted into a digital signal by the A / D converter 7, and then the luminance signal processing circuit 11 and color separation of the signal processing circuit unit 9. The signal is input to the circuit 13 and the color separation circuit 15.
[0020]
The luminance signal processing circuit 11 generates and outputs a digital luminance signal DY by signal processing. This luminance signal DY is inverted through the negative inversion circuit 100 and then converted into an analog luminance signal Y by the D / A converter 17. Is converted to output. The color separation circuit 13 generates and outputs three kinds of primary color signals R, G, and B by signal processing. The primary color signals R, G, B are subjected to white balance control (gain adjustment) by the white balance circuit 19 according to the white balance control signals R _cont , B _cont , and the primary color signals R, G, B subjected to white balance control are color signals. The signal is processed by the processing circuit 21 to become a digital color signal DC. The color signal DC is inverted through the negative inversion circuit 200, then converted to an analog color signal C by the D / A converter 23, and output.
[0021]
The color separation circuit 15 performs signal processing and outputs a digital luminance signal Y and color synthesis signals C _r and C _b . An integrator 27 and a microcomputer 29 are connected to the subsequent stage of the color separation circuit 15. The microcomputer 29 includes a calculation unit 31, a calculation unit 33, a color temperature detection region determination unit 35, a control value calculation unit 37, and a storage unit 39.
[0022]
The basic operation of the microcomputer 29 is as shown in FIG. 2, and the calculation unit 31 inputs the integrated values of Y, C _r , and C _b from the integrator 27 to calculate the R, G, and B color signals. Then, the calculation unit 33 calculates R / G and B / G as color temperature detection values, and whether or not these calculation values exist in a predetermined color temperature detection region (including a color temperature detection axis or a color temperature detection point). Is determined based on the color temperature control axis set for the negative light source from the calculated values of R / G and B / G by the calculation unit 37 because the image is taken under the negative light source. The R control value R _cont and the B control value B _cont are calculated, and these control values are given to the white balance circuit 19 to control the gain of the amplifier.
[0023]
In addition to this basic operation, the storage unit 39 stores the R / G shift amount α (%) of the color temperature detection axis and the B / G shift β (%) for capturing a negative film image. The determination unit 35 detects the color temperatures R / G and B / G by shifting the color temperature detection axis using the% display shift amounts α and β, and supplies them to the calculation unit 37.
[0024]
The shift amounts α and β (%) are obtained by experiments using a number of video cameras. FIG. 3 shows a procedure for determining the shift amounts α and β. First, for example, 3200K reference illumination light is imaged for one video camera to obtain R / G and B / G data. For example, R / G and B / G data is taken with a first color temperature conversion filter of 4000K, and further R / G and B / G data is taken with a second color temperature conversion filter of 7500K, for example. A color temperature detection axis 41 as shown in FIG. 5 is approximated from the three points of data. Next, a negative film is imaged under a predetermined light source, R / G and B / G data are taken, and a deviation amount from the color temperature detection axis approximated by the reference illumination light is calculated for each. After performing such data collection on a large number of N video cameras, the averages α and β of N shift amounts are determined, and the average shift amounts α and β are determined as R / G, B of the color temperature detection axis. / G is displayed in%, where the difference between the maximum value and the minimum value is 100%.
[0025]
The shift amounts α and β (%) determined in this way are stored in the storage unit 39 when each video camera is manufactured.
[0026]
An example of negative white balance adjustment for individual video cameras at the time of manufacture is as shown in FIG. 4. First, 3200K reference illumination light is imaged to obtain R / G and B / G data. This is data (a1, b1) at point A in FIG. Next, the first color temperature conversion filter is attached to the reference illumination light and imaged to obtain R / G and B / G data. This is the data (a2, b2) at point B in FIG. Next, an image is taken with the second color temperature conversion filter, and R / G and B / G data are taken. This is the data (a3, b3) at point C in FIG. These data are stored in a storage unit (not shown) of the microcomputer 29. From these stored data, the determination unit 35 approximates the color temperature detection axis 41 of FIG. 5, and further shifts the color temperature detection axis 41 to the shift amounts α1% and α2% stored in the storage unit 39 as shown in FIG. , Β1%, and β2% are used to shift as N1 and N2 to determine the negative color temperature detection axis 43 of the video camera.
[0027]
In FIG. 5, the moving points N1 (a4, b4) and N2 (a5, b5) are expressed as follows.
a4 = a3 + (a1-a3) × (α1 / 100)
b4 = b1 + (b3−b1) × (β1 / 100)
a5 = a3 + (a1-a3) × (α2 / 100)
b5 = b1 + (b3-b1) × (β2 / 100)
However,
α1 = 100 (a4-a3) / (a1-a3)
β1 = 100 (b4-b1) / (b3-b1)
α2 = 100 (a5-a3) / (a1-a3)
β2 = 100 (b5-b1) / (b3-b1)
[0028]
The color temperature detection axis 43 is not limited to a line as shown in FIG. 5, and there are many factors that cause color variations such as the type of negative, the type of light source for negative imaging, and the color temperature at the time of negative imaging. It may have a certain width. Of course, if these conditions can be limited, the color temperature can be detected using the shaft 43 instead of the region 300, so that the performance of white balance control is improved. Further, once the deviation amounts α and β (%) are determined for one model, they may be written as constants in the software of the microcomputer 29 or may be changed by writing them in an EEPROM (Electrical Erasable Programmable Read Only Memory).
[0029]
As described above, the difference between the maximum value and the minimum value of R / G and B / G at points A, B, and C is set to 100%, and the deviation amount with respect to the reference illumination light is previously determined in% display. Even if there is a variation in the complementary color filter of each CCD, the deviation amount displayed in% is almost constant, so by correcting by the deviation amount in% display, it is possible to suppress the influence due to the variation in CCD, etc. Good feedforward type white balance control is possible.
[0030]
<Second embodiment>
6 to 9 show a second embodiment of the present invention. FIG. 6 is a circuit diagram showing an imaging system of a video camera having a negative film image capturing function. Compared to FIG. 1, a storage unit 39A is added to the microcomputer 29, and a new function is added to the calculation unit 37. It is the same except that is added.
[0031]
In the microcomputer 29, in addition to the basic operations shown in FIG. 2, the storage unit 39A stores the R _cont shift amount α (%) of the color temperature control axis and the B _cont shift amount β (%). The calculating unit 37 calculates the control values R _cont and B _cont by shifting the color temperature control axis using these% display shift amounts α and β, and gives them to the white balance circuit 19.
[0032]
The shift amounts α and β (%) are obtained by experiments using a number of video cameras. FIG. 7 shows a procedure for determining the shift amounts α and β. First, for one video camera, for example, 3200K reference illumination light is imaged to obtain Rcont and Bcont data, and then, for example, 4000K first illumination light is obtained. The data of Rcont and Bcont are obtained by attaching one color temperature conversion filter, and further, for example, the data of Rcont and Bcont are obtained by attaching a second color temperature conversion filter of 7500K, and the standard as shown in FIG. 9 is obtained from these three points of data. The color temperature control axis 45 for the illumination light is approximated. Next, the negative film is actually imaged under a negative light source, Rcont and Bcont data are taken, and the deviation between the color temperature approximated by the reference illumination light and the actual color temperature control axis of sunlight is calculated for each. . After such data acquisition is performed for N video cameras, the average α and β of the N shift amounts are determined, and the average shift amounts α and β are set to the maximum for each of the Rcont and Bcont color temperature control axes. The difference between the value and the minimum value is displayed in%.
[0033]
The shift amounts α and β (%) determined in this way are stored in the storage unit 39A when each video camera is manufactured.
[0034]
The white balance adjustment of each video camera at the time of manufacture is as shown in FIG. 8. First, 3200K reference illumination light is imaged and R _cont and B _cont data are taken. This is the data (a5, b5) at point A in FIG. Next, the first color temperature conversion filter is attached to the reference illumination light and imaged, and data of R _cont and B _cont are taken. This is the data (a6, b6) at point B in FIG. Next, the second color temperature conversion filter is attached to take an image, and R _cont and B _cont data are taken. This is the data (a7, b7) at point C in FIG. These data are stored in a storage unit (not shown) of the microcomputer 29. Based on these stored data, the calculation unit 37 approximates the color temperature control axis 45 of FIG. 9, and further, the color temperature control axis 45 is shifted by α1% and α2% stored in the storage unit 39A as shown in FIG. , Β1%, and β2% are used to shift as N1 and N2 to determine the color temperature control axis 47 for negative photographing of the video camera.
[0035]
In FIG. 9, when the color temperature change axis moves from ABC to N1-N2, the moving points N1 (a8, b8) and N2 (a9, b9) are expressed as follows.
a8 = a5 + (a7−a5) × (α1 / 100)
b8 = b7 + (b5-b7) × (β1 / 100)
a9 = a5 + (a7−a5) × (α2 / 100)
b9 = b7 + (b5−b7) × (β2 / 100)
However,
α1 = 100 (a8−a5) / (a7−a5)
β1 = 100 (b8−b7) / (b5−b7)
α2 = 100 (a9−a5) / (a7−a5)
β2 = 100 (b9−b7) / (b5−b7)
[0036]
The color temperature control axis 47 is not limited to a line as shown in FIG. 9, and there are many factors that cause color variations such as the type of negative, the type of light source for negative imaging, and the color temperature at the time of negative imaging. It may have a certain width. Of course, if these conditions can be specified, the control can be performed using the shaft 47 instead of the region 400, so that the white balance performance is improved. Further, once the deviation amounts α and β (%) are determined for one model, they may be written as constants in the software of the microcomputer 29 or may be changed by writing them in an EEPROM (Electrical Erasable Programmable Read Only Memory). If it can be changed, the white balance is variable for each video camera.
[0037]
As described above, the difference between the maximum value and the minimum value of R _cont and B _cont at points A, B, and C is set to 100%, and the amount of deviation with respect to the reference illumination light is determined in advance in% display. Even if there is a variation in the color filter of the CCD, the amount of deviation displayed in% is almost constant, so correction by the amount of deviation in% display can suppress the influence of variations in CCD, etc. Forward type white balance control is possible.
[0038]
In each of the first and second embodiments, the color signal negative reversal processing (200) is performed after the normal video camera signal processing (21) is completed, but after the color separation (13). You can go anywhere if you want.
[0039]
In the first and second embodiments, the feedforward method is described. However, the same effect can be obtained by using the feedback method.
[0040]
【The invention's effect】
According to the first aspect of the present invention, the color temperature detection axis or area of the white balance control for the negative film image can be set at the time of adjustment using the same light source as that for adjustment of a normal video camera.
[0041]
According to the second and third aspects of the present invention, color that is not affected by variations in characteristics of an image sensor such as a CCD, a color temperature shift between reference illumination light at the time of adjustment and an actual light source for negative photography, etc. White balance control having a temperature detection axis or region is possible.
[0042]
According to the fourth aspect of the present invention, the color temperature control axis or area of the white balance control for the negative film image can be set at the time of adjustment using the same light source as that for adjustment of a normal video camera.
[0043]
Further, according to the inventions of claims 5 and 6, colors that are not affected by variations in characteristics of an image sensor such as a CCD, a color temperature shift between a reference illumination light at the time of adjustment and an actual light source for negative photography, etc. White balance control having a temperature control axis or region is possible.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a video camera according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a basic control operation of the microcomputer.
FIG. 3 is a diagram illustrating a procedure for determining a deviation amount of a color temperature detection axis.
FIG. 4 is a diagram showing a procedure for determining a color temperature detection region.
FIG. 5 is a diagram illustrating a color temperature detection region.
FIG. 6 is a circuit diagram showing a video camera according to a second embodiment of the present invention.
FIG. 7 is a diagram illustrating a procedure for determining a deviation amount of a color temperature control axis.
FIG. 8 is a diagram illustrating a procedure for determining a color temperature control axis.
FIG. 9 is a diagram illustrating a color temperature control axis.
[Explanation of symbols]
3 CCD
16 color separation circuit 19 white balance circuit 29 microcomputer 31 R, G, B operation unit 33 R / G, B / G operation unit 35 color temperature detection area determination unit 37 control operation unit 39, 39A storage unit 100, 200 for negative Inversion circuit

Claims (6)

First storage means, a color temperature detection signal in the case of photographing the reference illumination light with a predetermined storing the value of the plurality of color temperature detection signal obtained by the imaging of a plurality of reference illumination light color temperature is different the second storage means for storing a shift amount of the color temperature detection signal in the case of photographing a negative film with a light source, based on the value of the first of said plurality of color temperature detection signal stored in the storage means A color temperature detection axis is obtained, and the color temperature detection axis is shifted by the shift amount stored in the second storage means to obtain a negative color temperature detection axis. Based on the negative color temperature detection axis, A detecting means for detecting a color temperature, a calculating means for calculating a control signal based on the output of the detecting means, and a white balance adjusting amplifier arranged in the video signal processing system based on the output of the calculating means and control means for controlling the gain Auto white balance and wherein the door. A reference illumination light source having a reference color temperature is replaced with a plurality of color temperature conversion filters to obtain a plurality of reference illumination light sources, and a plurality of reference illumination lights are photographed by a video camera to obtain a plurality of color temperature detection signals. Approximating the color temperature detection axis from these, and taking a negative film under a predetermined light source with the video camera to obtain a color temperature detection signal, obtaining the color temperature detection axis for the negative from this color temperature detection signal, Performing a process including calculating a deviation amount between the color temperature detection axis for negative and the color temperature detection axis for a plurality of video cameras;
Obtaining an average value of the deviation amounts obtained by performing a plurality of video cameras ;
Determining a ratio of the average value to a difference between the maximum value and the minimum value of the approximate color temperature detection axis;
This ratio is set as a shift amount for correcting a shift of the color temperature detection signal between the reference illumination light and the predetermined light source;
A method of manufacturing a video camera characterized by the above.   3. The auto white balance apparatus according to claim 1, wherein the shift amount obtained by the video camera manufacturing method according to claim 2 is stored in the second storage means. First storage means for storing the values of the plurality of control signals for the gain control of the white balance adjustment amplifier obtained by imaging a plurality of reference illumination light color temperature are different, taken the reference illumination light second storage means for storing the deviation amount of the control signal and the control signal for shooting the negative film at a predetermined light source when the value of said first of said plurality of control signals stored in the storage means A color temperature control axis is obtained based on the color temperature control axis, and the color temperature control axis is shifted by the shift amount stored in the second storage means to obtain a color temperature control axis for negative photography. features and calculating means for calculating a control signal based on the axis, based on the output of the arithmetic means, to a control means for controlling the gain of the white balance adjustment amplifier are arranged in a video signal processing system auto white to Balancing device. A reference light source having a reference color temperature is replaced with a plurality of color temperature conversion filters to obtain a plurality of reference illumination light sources, and a plurality of reference illumination lights are photographed with a video camera for gain control of a white balance adjustment amplifier. A control signal is obtained by photographing a negative film under a predetermined light source with the video camera, and a color temperature for negative photography is obtained from the control signal. Obtaining a control axis and performing a process for a plurality of video cameras including calculating a deviation amount between the color temperature control axis for negative photography and the color temperature control axis ;
Obtaining an average value of the deviation amounts obtained by performing a plurality of video cameras ;
Determining a ratio of the average value to a difference between the maximum value and the minimum value of the approximate color temperature control axis;
This ratio is set as a shift amount for correcting a shift of the control signal between the reference illumination light and the predetermined light source;
A method of manufacturing a video camera characterized by the above.   6. The auto white balance apparatus according to claim 4, wherein the shift amount obtained by the video camera manufacturing method according to claim 5 is stored in the second storage means.

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