JPS6030722Y2 - color stripe filter - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement of a color stripe filter in a phase separation system or a three-electrode division system of a single tube type or luminance separation type two-tube color television camera.
The purpose is to measure the improvement of sensitivity, white balance, and color reproducibility.

As an example of the electronic index phase separation method,
The device shown in Publication No. 1609 has color stripe filters arranged sequentially in red, blue, and green at right angles to the horizontal scanning direction of the beam, and overlapping this, a transparent electrode is divided into two with equal period and comb shape. By applying a horizontally moving alternating potential of 172 cycles between these two electrodes, the back surface potential of the photoconductive film is changed every horizontal cycle, and the signal optically modulated by the color stripe filter is simultaneously transmitted. By reading, a composite signal of the color carrier component and the index component having a phase difference of 180 degrees for each horizontal scan is obtained, and the color carrier signal and the index signal are separated by the correlation of the signal of one horizontal period, and this index signal is obtained. Thus, a color difference signal is obtained by detecting a color carrier signal.

The most important condition in the phase separation method is that when the subject is colorless, that is, white, under illumination with a light source of a certain color temperature, the output from the image pickup tube through the red, blue, and green striped filters must be approximately equal. .

Generally, light sources with a color temperature around 3000 degrees are often used for lighting in studios, etc., but when using a light source with such a low color temperature, a general image pickup tube, such as a videocon tube using antimony trisulfide, is used. In such cases, the sensitivity of blue is lower than that of other colors.

If the transmittance of the red and green filters is determined by adjusting the sensitivity to blue, the overall sensitivity will decrease.

This relationship is shown in FIG.

In Figure 1, A is the spectral sensitivity characteristic of a videcon tube using antimony trisulfide as the photoconductive film, and B is the color temperature of the lighting at 300.
0' K spectral characteristics, C is the spectral transmission characteristics of the infrared removal filter, D solid lines are the spectral transmission characteristics of each color of the color stripe filter, E solid lines are the overall spectral sensitivity characteristics, and this spectral sensitivity characteristic is called the blue sensitivity. When adjusted to , the characteristics of red and green become as shown by the dotted lines, and the spectral transmission characteristics of the color filters in this case must be reduced in transmittance of the red and green color filters as shown by the dotted lines in D.

This is not preferable because the overall sensitivity decreases.

In order to eliminate this drawback, it has been proposed to use a cyan color instead of a blue filter, as shown in Japanese Patent Publication No. 50-19207.

In FIG. 2, A represents the spectral transmission characteristics of the cyan, green, and red color filters, and the overall spectral characteristics in this case are as shown in B, where C:G:R are approximately equal.

If cyan, green, and red color stripe filters are arranged at equal intervals, the axes of each color in the hue diagram will become as shown in FIG. 3.

In Figure 3A, R, G, and C become signals with different phases by 120°, and if these are replaced with R, G, and B, the third
As shown in Figure B, the G axis is shifted by about 1200 degrees and the B axis is shifted by about 120 degrees with respect to the R axis.

On the other hand, the NTSC signal is EN, c=0.3OR+0.59G
+0.11B 10.632RCO3Wt 10, 593GCO3 (WC+222') +Q, 44
7BCO3 (Wt+115°), so the NTS
As the brightness signal approaches the C signal, the luminance signal also approaches the NTSC signal.

However, the spectral characteristics of red, blue, and green for obtaining an ideal NTSC signal have low energy near 5001 m, as shown in FIG.

Therefore, in a color imaging device using red, green, and cyan color filters, the cyan color around 500 nm is sensitive to the image pickup tube as a blue signal, which has the disadvantage that the color error of the cyan color becomes large.

In order to eliminate this drawback, the cyan filter characteristics should be attenuated near 5001 m, but in reality it is difficult to obtain such a filter, and generally the cyan filter characteristics are attenuated at around 5001 m.
It is conceivable to insert a cyan correction trimming filter with attenuated transmittance near 01 m throughout the optical path.

However, it is difficult to obtain an ideal trimming filter with this trimming filter, and the width of the attenuated wavelength becomes wider than necessary, which greatly affects the green color filter characteristics.

In order to eliminate the above-mentioned drawbacks, in the present invention, a trimming filter for cyan correction is inserted into only a portion of the cyan color filter.

An example of implementing the present invention will be described below based on the drawings.

First, 1 is a multilayer film (having a characteristic of increasing the attenuation of the transmission characteristic at wavelengths around 500 nm) formed by vacuum evaporation as a stripe-shaped cyan correction trimming filter using a method such as a lift-off method on a glass substrate 2. This is a dichroic filter, and cyan, red, and green absorption type dye filters 3.4.5 are sequentially provided on the glass substrate 2 by a transfer dyeing method or a method of dyeing a gelatin support in stripes.

In this case, what is important is to arrange the cyan filter 3 above the cyan correction trimming filter [dichroic filter 1].

That is, as shown in FIG. 5, a cyan filter 3 is placed on top of a dichroic filter 1, and red and green filters 4 and 5 are placed on a glass substrate 2 at different positions.

Its spectral characteristics are shown in FIG.

Figure 6A shows the spectral pass characteristics of the trimming filter for cyan correction, and Figure 6B shows the overall spectral characteristics of Figure 6A and Figure 2A.
It can be seen that the characteristics are almost similar to that of .

The phase separation method has been described above, but considering the dynamic range or stability in the three-electrode split method, it is desirable that the output signals from the three electrodes be equal when photographing an achromatic subject, so this method also applies. The same can be said for a two-tube system that performs luminance separation.

As explained above, according to the present invention, the photographing characteristics of the camera can be brought close to the ideal photographing characteristics of NTSC, so that color reproducibility is improved.

In addition, since only a specific color (cyan color) is corrected, color errors do not occur due to effects on other color filters.

Furthermore, even if the wavelength width of the correction filter becomes somewhat wider, it does not affect color reproducibility much.

In addition, the trimming filter allows brightness characteristics to be brought closer to ideal values, and the sensitivity of the camera does not decrease.

[Brief explanation of drawings]

In Figure 1, A is the spectral sensitivity characteristic diagram of the videcon tube, B is the spectral characteristic diagram of the light source at 3000°, C is the spectral transmission characteristic diagram of the infrared removal filter, and D is the spectral transmission characteristic diagram of the red, green, and blue color stripe filters. In Figure 2, A is a spectral transmission characteristic diagram of each color stripe filter of red, green, and cyan, and B is an overall spectral sensitivity characteristic diagram of each color using red, green, and cyan. In Figure 3, A is a vector diagram of a red, green, and cyan color stripe filter, B is a vector diagram of a red, green, and blue color stripe filter, Figure 4 is an NTSC ideal filter characteristic diagram, and Figure 5 is a vector diagram of a red, green, and cyan color stripe filter. A sectional view showing an example of implementation of the present invention, A in FIG.
is a spectral transmission characteristic diagram of the trimming filter for cyan correction, B is the red color through the trimming filter for cyan correction,
FIG. 3 is a spectral transmission characteristic diagram of green and cyan. 1... Guicroic filter 2...
・Glass substrate, 3゜4゜5...Cyan, red, green filters.

Claims (1)

[Scope of utility model registration request] A color stripe filter constituted by repeating red, green, and cyan absorptive color filter elements is provided on a glass substrate, and only the filter element having cyan color has 50
A color stripe filter in which trimming filter elements made of a multilayer film having a characteristic of increasing the attenuation of the transmission characteristic of wavelengths around 0.1 m are superimposed.