JP2518009B2 - Registration correction circuit in solid-state color imaging device - Google Patents

Description

The present invention relates to a registration correction circuit in a solid-state color image pickup device.

[Conventional technology]

In a color image pickup apparatus including a color separation optical system that separates a subject image into three primary color lights and an image pickup device that converts each of these three primary color lights into an electric signal, the electric signals obtained from the respective image pickup devices are mixed to form a single image signal. Since one image is represented by a video signal, it is necessary to accurately match the spatial positional relationship of each image sensor by registration adjustment.

Conventionally, in a color image pickup apparatus using an image pickup tube as an image pickup element, a combination of an image pickup tube and a coil assembly having uniform graphic distortion characteristics is selected and used. Furthermore, in order to correct the distortion of the deflected beam due to the influence of geomagnetism, digital registration collection (DRC, Digital Re
The distortion correction waveform obtained by a technique such as gistration correction) is superimposed on the deflection waveform to perform registration correction.

On the other hand, in a color image pickup device using a fixed image pickup element as an image pickup element, signal charges from photoelectric conversion elements arranged regularly on a semiconductor substrate are read out regularly with a clock pulse having a constant cycle, and therefore, in principle, graphic distortion does not occur. Does not occur. Also, it is not affected by geomagnetism. Therefore, once the spatial positional relationship of each solid-state image sensor is adjusted, registration correction is essentially unnecessary.

[Problems to be Solved by the Invention]

However, considering the entire image pickup system including the lens and the color separation optical system, a non-negligible registration error occurs in the peripheral portion of the screen even in the color image pickup apparatus using the solid-state image pickup device described above. This is due to the chromatic aberration of magnification of the lens and the thermal distortion of the color division optical system.

The present invention eliminates the above-mentioned conventional drawbacks, and an object of the present invention is to eliminate a vertical error in a registration error of a solid-state color image pickup device due to a chromatic aberration of magnification of a lens and a thermal distortion of a color separation optical system. It is to provide a circuit for correction.

[Means for solving the problem]

According to the present invention, the video signals output from the three solid-state image pickup devices for converting each of the three primary color lights from the color separation optical system for separating the subject image into the three primary color lights are delayed by at least one horizontal scanning period. Solid color comprising delay means for causing the delayed video signal outputted from the delay means and signal mixing means for mixing the delayed video signal and the non-delayed video signal at a predetermined ratio according to the registration error information. A registration correction circuit in the image pickup device can be obtained.

[Action]

When the mixing ratio of the delayed video signal delayed by at least one horizontal scanning period and the delayed video signal is such that the distortion due to the chromatic aberration of magnification of the lens and the thermal distortion of the color separation optical system are directed in the upward direction of the image plane. By increasing the delayed video signal, and by increasing the video signal that is not delayed when these distortions are directed downward in the image plane, the vertical registration error Can be corrected. Further, by appropriately changing the mixing ratio in association with the information of the focal length of the lens, the imaging distance, and the aperture value, a registration error due to a change in magnification chromatic aberration that occurs when the imaging conditions such as zooming and the aperture are changed. Of these, the error in the vertical direction can be corrected.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating an embodiment.

First, an image pickup system to which the present invention is applied will be described with reference to FIG. In the figure, 1 is a lens, 2 is a color separation optical system, and the most general color separation prism is shown here. Further, 3, 4 and 5 are solid-state image pickup devices. In the figure, the subject image 6 incident through the lens 1 is reflected by the blue reflection dichroic film 7 in the color separation prism 2 and is incident on the solid-state image sensor 5 for blue image. Then, only red light is reflected by the red reflection dichroic film 8 in the color separation prism 2 and is incident on the solid-state image pickup device 3 for red image. Further, the green light in the subject image 6 is transmitted through both the dichroic films 7 and 8 and is incident on the solid-state image sensor 4 for the green image. The solid-state image pickup devices 3, 4 and 5 receive the three primary color lights separated by the color separation prism 2 and convert them into electric signals corresponding to the respective light amounts. The electric signals corresponding to the three primary color lights are mixed by means not shown here to form a color video signal. Therefore, in order to obtain a high quality reproduced image, it is necessary to accurately match the spatial positional relationship of the solid-state image pickup devices 3, 4, and 5. In general, the registration chart is imaged, and the mounting positions of the solid-state imaging devices 3, 4, and 5 on the color separation prism 2 are adjusted so that the color shift on the reproduced image is minimized.

The registration error of the solid-state color image pickup device is caused by the lateral chromatic aberration of the lens and the thermal distortion of the color separation prism, in addition to the above-mentioned deviation of the spatial positional relationship between the three solid-state image pickup elements. In the former case, since the solid-state image pickup element does not cause any geometrical distortion in principle, it can be completely corrected by adjusting the mounting position. However, the latter two changes depending on the type and temperature of the lens, and the correction thereof is very troublesome. Here, FIG. 5 is a view for explaining the chromatic aberration of magnification of the lens, in which 9 is a lens and 10 is a color separation prism. As shown in the figure, the chromatic aberration of magnification is an aberration in which the imaging magnification varies depending on the wavelength, and even if the same subject is imaged, red, green, and
The image heights for blue are different in size, as indicated by 11, 12, and 13. In addition, the chromatic aberration of magnification is the focal length of the lens,
It also changes depending on the imaging distance and aperture value. For example, even a short-focus lens for high-definition television, which is said to have a particularly high quality among the lenses currently on the market, produces an aberration of about 10 μm at the periphery under the worst conditions.

In the present invention, the mixing ratio of the delayed video signal delayed by at least one horizontal scanning period and the delayed video signal is adjusted so that the distortion due to the chromatic aberration of magnification of the lens and the thermal distortion of the color separation optical system are in the upward direction of the image plane. If it is oriented, the delayed video signal is mixed more, and if these distortions are oriented in the downward direction of the image plane, the delayed video signal is mixed more, so that the vertical The registration error in the direction is corrected. FIG. 1 shows an overall configuration diagram of a registration correction circuit in a solid-state color image pickup device according to the present invention. In the figure, the same numbers as in FIG. 4 indicate the same components. Further, 14, 15, 16 are solid-state image pickup devices 3, 4,
1H delay line for delaying the video signal output from each of 5 by one horizontal scanning period (1H), 17H, 18 and 19 are 1H delay line 1
A weighting coefficient circuit for multiplying the delayed video signals from 4, 15, 16 by a predetermined weighting coefficient, 20, 21, 22 are weighting coefficient circuits for multiplying the delayed video signal by a predetermined weighting coefficient, and 23 is Weighting coefficient control circuit for controlling the weighting coefficient circuits 17 to 22, 24, 25, 26
Is a video signal addition circuit, 27, 28, 29 are video signal addition circuits 24, 2
A video signal processing circuit for performing gamma correction or the like on the video signals from 5, 26, and a signal mixing circuit 30 for mixing the video signals from the video signal processing circuits 27, 28, 29 to produce a color video signal. It should be noted that components not directly related to the present invention, such as horizontal and vertical clock drivers and synchronization signal generators, are omitted in the overall configuration diagram.

Next, the operation of the registration correction circuit in the solid-state color image pickup device according to the present invention will be described with reference to FIG. An example of vertical distortion due to lateral chromatic aberration of the lens is shown in FIG. Here, 31 is a scanning line corresponding to the delayed video signal, and 32 is a scanning line corresponding to the delayed video signal delayed by 1H. In this example, the green image 33 is not vertically distorted at all, but the red image 34 is distorted upward (plus direction) at the left and right edges of the image plane, and the blue image 35 is opposite to the red image 34. It is assumed that the image is distorted upward (plus direction) near the center of the image plane. In order to correct the distortion in the vertical direction due to the chromatic aberration of magnification of the lens, the registration correction circuit according to the present invention operates as follows.

Information indicating the type of the lens 1, the focal length, the imaging distance, the aperture value, and the information indicating the temperature of the color separation prism 2 are input to the lookup table 40. Lookup table
In 40, based on the information registered in advance, the registration error due to the variation of the chromatic aberration of magnification that occurs when the imaging condition of the lens 1 is changed and the registration error due to the thermal distortion of the color separation prism 2 are corrected. Such data is transmitted to the weight coefficient control circuit 24.

The weight number control circuit 23 applies a predetermined voltage to the weight coefficient circuits 17 to 22 based on the signal from the look-up table to change each weight coefficient. That is, the third
As shown in the figure, a curve 41 shown in FIG. 3 (a) for a green image, a curve 42 shown in FIG. 3 (b) for a red image, and a curve 43 shown in FIG. 3 (c) for a blue image. The represented voltage is output to each weighting coefficient circuit. The weighting coefficient circuit weights the signal from the solid-state image sensor based on the input signal shown in FIG.
That is, the weighting factors of the weighting factor circuits 18 and 21 corresponding to the solid-state image pickup device 4 for the green image are always 0 for the former and 1 for the latter as shown at 36 in FIG. 2B. Is kept at. On the other hand, the weighting factors of the weighting factor circuits 17 and 20 corresponding to the solid-state image sensor 3 for red image are
As indicated by reference numeral 37 in FIG. 7C, the former shifts so as to approach 1 at the beginning and end of one horizontal scanning cycle, and the latter approaches 1 near the center. The two weighting factors described above have a complementary relationship, and the sum of them is always 1. For example, when the weight coefficient of the weight coefficient circuit 17 is 0.7, the weight coefficient circuit 20
Has a weighting factor of 0.3. On the contrary, the weighting coefficients of the weighting coefficient circuits 19 and 22 corresponding to the solid-state image pickup device 5 for blue image are 1 in the vicinity of the center of one horizontal scanning period as shown by 38 in FIG. , And the latter shifts so as to approach 1 at the beginning and end of one horizontal scanning period. 2 here
The two weighting factors have a complementary relationship, and their sum is always 1. Then, the weighted signal is sent to the video signal processing circuit through the adding circuit and processed. According to such an operation, the solid-state image sensor 3,
The reproduction blue image, the reproduction green image, and the reproduction red image output from each of 4 and 5 can be perfectly matched in the vertical output timing, and the vertical registration error is corrected. In addition, the weight coefficient control circuit 23
Type, focal length, imaging distance, aperture value and temperature of the color separation prism 2 are appropriately generated to generate a proper weighting coefficient, and thereby a registration error caused by a variation in magnification chromatic aberration that occurs when imaging conditions are changed, Of the registration errors due to the thermal distortion of the color separation prism 2, vertical errors can also be corrected.

Since the signal processing after the video signal processing circuit is the same as the conventional one, the description is omitted.

〔The invention's effect〕

As described above, according to the present invention, it is possible to correct the error in the vertical direction among the registration errors caused by the chromatic aberration of magnification of the lens and the thermal distortion of the color separation prism. Also,
By appropriately changing the mixing ratio of the delayed video signal delayed by at least one horizontal scanning period and the delayed video signal in association with the information of the lens type, focal length, imaging distance, and aperture value, the imaging condition It is also possible to correct a registration error that accompanies a change in chromatic aberration of magnification that occurs when is changed.
Further, by using not only the 1H delay line but also the 2H delay line, a larger registration error can be corrected. Furthermore, in the above-described embodiment, the case of correcting the low-order registration error is described as an example, but the high-order registration error can be corrected in the same manner.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a registration correction circuit in a solid-state color image pickup device according to the present invention, FIGS. 2 and 3 are diagrams for explaining the operation of the present invention, and FIG. 4 is applied with the present invention. FIG. 5 is a diagram for explaining the imaging system, and FIG. 5 is a diagram for explaining lateral chromatic aberration of the lens. 1 ... Lens, 2 ... Color separation prism, 3,4,5 ... Solid-state image sensor, 14, 15, 16 ... 1H delay line, 17-22 ... Weighting coefficient circuit, 23 ... Weighting coefficient control circuit , 24,25,26 …… Image signal adder circuit, 27,28,29 …… Video signal processing circuit, 30 …… Signal mixing circuit.

Claims (1)

(57) [Claims] 1. A video signal output from three solid-state image pickup devices for converting each of the three primary color lights from a color separation optical system for separating a subject image into three primary color lights is delayed by at least one horizontal scanning period. Solid-state color imaging comprising delay means and signal mixing means for mixing the delayed video signal output from the delay means and the undelayed video signal at a predetermined ratio according to the information on the registration error. Registration correction circuit in the device.