JPS6246113B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color television imaging device using a color stripe filter and a solid-state imaging device. The present invention relates to a color television imaging device.

Recently, research and development of color television cameras using solid-state imaging devices has been actively conducted, and practical application is approaching soon. Solid-state imaging devices include those with integrated MOS field effect transistors, and CCDs.
(Charge Coupled Device) or BBD (Bucket
There are some that use charge transfer devices such as the Brigade Device (Brigade Device), and color television cameras are usually made using multiple of these devices.

However, this method requires a color separation optical system to split the incident light into three color lights and form an image, and it also requires the images obtained from three devices to be accurately superimposed, making the equipment complex. The drawback was that it was expensive. Therefore, we created a color filter with a width that allows each of the three primary colors (red, green, and blue) to pass through.
Attempts have been made to construct a color television camera with a single solid-state imaging device using color stripe filters arranged in a fine array of about 30 μm. However, in this method, one pixel is formed using three colors, red, green, and blue, so there is a problem of insufficient resolution. In the color television system that is currently the standard in Japan, the United States, etc., the horizontal resolution is about 300 TV lines, which requires 400 pixels horizontally and 1 pixel for three colors, and 1200 pixels for a solid-state imaging device. Must be formed horizontally. It is extremely difficult to completely create a solid-state imaging device with such large pixels. In other words, fine defects often occur somewhere in the solid-state imaging device due to dust adhesion during the manufacturing process of uneven semiconductor substrates, and these appear as scratches on the screen of the receiver, significantly degrading the image quality. become. Therefore, it is necessary to obtain high-resolution color images using a solid-state imaging device with as few pixels as possible. A color television camera using an image pickup tube uses a three-color stripe filter in which red, green, and blue parts are sequentially arranged, and the electrodes corresponding to each color are divided to obtain three-color signals independently. There is a three-electrode single-tube color television camera. In this method, for example, 660 red lines in the horizontal direction,
With green and blue as one set, 220 sets of three-color stripe filters are used to obtain a resolution of 300 TV lines. This is because the cut-off frequency of the LPF for the luminance signal is increased by expressing luminance with each color rather than using the three colors red, green, and blue as one pixel. However, this method cannot be applied to color television cameras that use solid-state imaging devices. This is because solid-state imaging devices have very poor blue sensitivity, so the signal in the blue portion becomes extremely small. Therefore, when achromatic light is incident on a solid-state imaging device through an R, G, and B color stripe filter, only the B signal is small among the output signals, so one out of three outputs becomes small, and the output of the color stripe filter becomes smaller. A carrier wave component also occurs at a frequency that is 1/3 of the carrier wave determined by the pitch. In this case, the LPF, which has the cutoff frequency of the original carrier wave, cannot remove the above-mentioned 1/3 frequency carrier wave component and remains in the luminance signal, causing vertical stripe interference to appear on the screen, significantly degrading the image quality.

This invention was made in view of the above, and is a color television that can obtain clear images with high resolution by using a solid-state imaging device with a relatively small number of pixels as described above and combining it with a special color stripe filter. The object of the present invention is to provide an imaging device.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the configuration of a color television imaging apparatus according to the present invention, in which an optical image of a subject 11 is formed on the photosensitive surface of a CCD 14 via an imaging lens 12 and a color stripe filter 13. CCD
14 is driven by a drive pulse generated by a drive circuit 16 based on a signal from a synchronization generation circuit 15.
The signal photoelectrically converted by the CCD 14 is sent to the amplifier circuit 17
After being amplified, it is added to LPF18. On the other hand, the output of the amplifier circuit 17 is transmitted to the first to third detection circuits 19 to 2.
1, and each color signal is detected by a gate signal generated by a gate signal generation circuit 22 based on a signal from a synchronization generation circuit 15. The output of the third detection circuit 21 is then added to a subtraction circuit 23, where it is subtracted from the output signal of the second detection circuit 20 to produce a blue signal.

Next, this operation will be explained. CCD14 is vertical 512
It is a two-dimensional CCD consisting of 320 horizontal pixels, and a color stripe filter 13 as shown in FIG. 2a is formed on the photosensitive surface. That is, a large number of red transparent portions 25, edge transparent portions 26, and blue and green, or cyan, transparent portions 27 are arranged in stripes with a width of 30 μm, and these are provided corresponding to each pixel of the CCD 14. Therefore, CCD1
As shown in FIG. 2B, the output signal from 4 is a form in which three color signals of red, green, and cyan corresponding to the color stripe filter 13 are sequentially changed, and is a so-called dot sequential signal. On the other hand, the gate signal generation circuit 22 is driven by the signal from the synchronization generation circuit 15, and here a counter is formed, and as shown in FIG. signal is obtained. The phase relationship in FIG. 2 is such that c corresponds to a red signal, d corresponds to a green signal, and e corresponds to a cyan signal. Therefore, these signals are applied to the first to third detection circuits 19 to 21, and signals corresponding to each part of the color stripe filter 13 are detected. Here, since the cyan signal includes a green signal, a blue signal is obtained by removing the green component in the subtraction circuit 23, and in this way, three primary color signals of red, green, and blue are obtained. On the other hand, the luminance signal is processed by an LPF with a cutoff frequency of 3MHz.
18. This luminance signal has
Almost no 1MHz carrier wave component is included.
In other words, the wavelength at which maximum sensitivity is obtained for solid-state imaging devices used in ordinary color cameras is 550 nm.
~650nm, in the green to red range. Therefore, the imaging device output signals corresponding to the G and R portions of the color stripe filter are large. On the other hand, the C part of the color stripe filter has a spectral characteristic in which G light is added to the original B light, so the output signal from the other R or G parts has a value almost equal to that of the C part. A signal (more precisely, a signal slightly larger than the signal of the G part) is obtained, and if the subject is black and white or achromatic, a balanced output is obtained. The pitch of the color stripe filter becomes the carrier wave, so in this example of 320 horizontal pixels, the carrier wave is 2.9MHz.
becomes.

When the subject is achromatic, the output of the solid-state imaging device via the R, G, and C color stripe filters is
For example, if we assume that the output of only C is small, the output of one out of three will be small, so in addition to the original 2.9MHz carrier wave,
A carrier wave component occurs at 2.9MHz/3=0.97MHz, that is, about 1MHz. In this case, simply passing the signal through an LPF with a cutoff frequency of 3 MHz cannot completely remove the 1 MHz component, making it impossible to obtain a high-quality luminance signal, resulting in deterioration of image quality.

However, as described above, in this embodiment of the present invention, the output of the solid-state imaging device using the R, G, and C color stripe filters is a balanced output, so the 1 MHz component is hardly generated. LPF1 with cutoff frequency of 3MHz
8, a luminance signal from which the carrier component is almost completely removed is obtained. In the end, the deterioration in image quality as described above hardly occurs.

As explained above, the present invention has a major feature in that it is possible to obtain a clear color image with high resolution using one CCD having a relatively small number of pixels. That is, by using a color stripe having a fourth color light transmitting portion consisting of the first or second color light and the third color light, a fourth color light signal is primarily obtained together with the first and second color light signals. Therefore, even though a solid-state imaging device is used that has lower sensitivity to the third colored light than to the first and second colored lights, it is possible to obtain uniform signals with a relatively small amplitude difference in the output signals. The frequency band of the luminance signal can be widened without vertical stripes caused by differences in vertical sensitivity occurring on the screen, and therefore a color image with high resolution can be obtained.

In addition, the simple configuration of the color stripe filter makes it easy to manufacture, and the three primary color signals can be easily obtained by adding a simple subtraction circuit, making the color separation circuit simple to configure and adjustable. It has the advantage of being easy to remove.

Further, since the same detection circuit can be used for R, G, and C, there is an advantage that color separation is easy and a color image with good color balance can be obtained.

In the above embodiment, the case of R, G, and C is shown in the configuration of the color stripe filter, but magenta (blue, red transparent) M may be used instead of C. In this case, color separation can be easily performed in the same way as described above by subtracting the red signal from the magenta signal to obtain the blue signal.

Moreover, although the case where a two-dimensional CCD is used as a solid-state imaging device has been shown, it goes without saying that the present invention can be similarly applied to charge transfer devices such as BBDs, and solid-state imaging devices such as MOS FETs.

Although the output signal of the amplifier circuit 17 is directly applied to the LPF 18 in order to separate the luminance signal, a detection circuit such as a sample and hold circuit may be provided between the LPFs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the color television imaging device of the present invention, FIG. 2a is a block diagram of a color stripe filter used in the color television imaging device of the present invention, and FIG. It was shown to
The signal waveform diagrams obtained from the CCD, FIGS. 2c to 2e, are gate signal waveform diagrams for color separation added to the detection circuit of FIG. 1. 13...Color stripe filter, 14...
CCD, 15...Synchronization generation circuit, 18...LPF,
19-21...Detection circuit, 22...Gate signal generation circuit, 23...Subtraction circuit.

Claims (1)

[Claims] 1 A part of the subject that transmits the first color light, a part that transmits the second color light, and a part that transmits the fourth color light consisting of the first or second color light and the third color light is sequentially formed into a stripe shape. color stripe filters arranged in a color stripe filter, and an optical image of a subject formed through the color stripe filters having a sensitivity to a third color light lower than sensitivities to the first color light and the second color light, into electrical signals. a solid-state imaging device for converting, a means for passing an output signal of the solid-state imaging device through a low-pass filter to obtain a luminance signal, and separating first, second, and fourth color light signals from the output signal of the solid-state imaging device, respectively. and means for subtracting the first or second color light signal included in the separated fourth color light signal from the separated fourth color light signal.