Color picture reproduction using balanced phosphors

Color picture reproduction in which a monochromatic CRT having emissions in the blue, green and red regions successively displays blue, green and red picture signals. The separate color displays are filtered by blue, green and red filters before being imaged on a color print material. The phosphors of the CRT are selected to reduce the blue emissions below the green and red emissions.

BACKGROUND OF THE INVENTION 
1. Related Application 
This application is related to Japanese Patent Application No. 148,192/85, 
upon which is based on U.S. patent application Ser. No. 883,401, filed 
July 8, 1986. 
2. Field of the Invention 
The present invention relates to a color picture reproducing method. More 
particularly, the invention relates to a color picture reproducing method 
in which a color photosensitive material is successively exposed to light 
form tricolor-decomposed pictures displayed on a high-luminance 
monochromatic cathode-ray tube (CRT) for one scene. 
3. Background Art 
It has been recent practice to record pictures on magnetic recording media 
such as a magnetic disk by using electronic cameras (for still pictures). 
Alternatively, pictures are photographed once on color photographic films 
by using ordinary cameras, and are then recorded on magnetic recording 
media such as a magnetic disk, so that the pictures recorded on the 
magnetic media can be reproduced or displayed on CRTs for viewing. With 
the advance of such recording techniques, it has been suggested that color 
pictures recorded on magnetic disks be printed onto color photosensitive 
materials as color prints to be handed to customers. 
As one conventional method for reproducing such color prints, that is, 
color pictures, a method shown in FIG. 1 has been used in practice. 
As shown in the drawing, the conventional method is carried out such that a 
high-luminance monochromatic CRT 1, whose monochromatic output nontheless 
has luminance in the blue (B), the green (G) and the red (R) regions, is 
caused to emit light successively on the basis of its blue, green and red 
picture signals obtained by decomposing a picture into its three color 
components. A color photosensitive material 4 is exposed successively to 
the emitted light on the basis of the respective blue, green and red 
picture signals for each scene through a lens system 2 and respective 
blue, green and red filters 3 (the blue, green and red filters are each 
successively used for the exposure for the pictures corresponding to the 
blue, green and red pictures signal), and then the color photosensitive 
material 4 is developed to obtain a color print. In the above-mentioned 
printing method, however, it is impossible to avoid color mixing owing to 
the fact that not only a blue (B) photosensitive layer but a green (G) 
photosensitive layer and/or a red (R) photosensitive layer are sensitized 
in the blue exposure for the blue (B) photosensitive layer. This results 
in a problem of reduction in saturation, particularly in the blue area. 
Although it is desirable that the above-mentioned printing method is 
carried out in as short time as possible, balance in the sensitivity of 
the color photosensitive material does not match the output of an ordinary 
monochromatic CRT. Accordingly, to obtain a color picture with good color 
balance, the exposure times required for the successive exposures of a 
scene for different color components must be changed from each other. 
Particularly, the exposure time for a blue picture must be significantly 
shorter than the exposure time for a red picture. As a result, handling of 
exposure becomes complex, and this complexity becomes an important factor 
that inhibits speeding up of the whole printing process. 
SUMMARY OF THE INVENTION 
An object of the present invention is, therefore, a method of reproducing a 
color picture including the steps of causing a monochromatic CRT to emit 
light including blue, green and red components on the basis of separate 
and successively applied blue, green and red signals for each scene to 
thus successively obtain a blue picture, a green picture, and a red 
picture, and of exposing a color photosensitive material successively to 
blue, green and red signal pictures through respective blue, green and red 
filters without color mixing. 
A further object of the invention is to perform such color printing with 
equal exposure times for the three color components. 
According to the invention, a fluorescent substance used in the CRT used 
has such a luminance distribution characteristic that a peak in the blue 
luminance region of B is lowered.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will be described more in detail with reference to 
the drawings. 
In FIG. 1, picture signals of the separated blue, green and red components 
of a scene are displayed on a high-luminance CRT 1 for exposure. The CRT 1 
has luminance in the blue, green and red regions, these picture signals 
are, for example, transmitted from a magnetic disk (floppy disk), or the 
like, on which are recorded separate blue, green and red pictures of the 
same color scene. For example, the CRT 1 is caused to successively emit 
light for each scene in such an order that, after the completion of a 
necessary amount of exposure with blue light, exposure to green light and 
exposure to red light are successively made. A color photosensitive 
material 4 is exposed to each of the three colored pictures of light 
emitted from the CRT 1 through a lens 2 and a selectively engaged filter 
3. The exposure can be made on an equisized scale, an enlarged scale or a 
reduced scale. 
FIGS. 2 and 3 show the spectral sensitivity of color photo-sensitive 
materials (color paper) used in the present invention, respectively. (In 
the drawings, the spectral sensitivity R in the red is shown with the 
sensitivity enlarged 12 times for the clearness of the drawings.) Each 
color photosensitive material has such spectral sensitivity that its blue 
(B) photosensitive layer has greatest sensitivity in the blue wavelength 
region (ranging from about 360 nm to about 480 nm) of the CRT, its green 
(G) photosensitive layer thereof has significant sensitivity in the green 
wavelength region (ranging from about 460 nm to about 555 nm) of the CRT, 
and its red (R) photosensitive layer has some sensitivity in the secondary 
peak area (ranging from about 700 nm to about 710 nm) of the red 
wavelength region of the CRT. However, each of the blue, green and red 
photosensitive layers has a peak of spectral sensitivity at about 410 nm 
on the basis of intrinsic sensitivity of the silver halide. 
On the other hand, a blue filter for transmitting only light in the blue 
wavelength region is used for the exposure of a blue picture. A green 
filter for transmitting only light in the green wavelength region is used 
for the exposure of a green picture. And a red filter for transmitting 
only light in the red wavelength region (including the infrared area) is 
used for the exposure of a red picture. The blue, green and red filters B, 
G and R used as the filters 3 for the purpose described above have the 
spectral characteristics shown in FIG. 4. Furthermore, in the case of a 
blue exposure, a yellow filter 5 (FIG. 1) having a spectral transmittance 
characteristic as shown in FIG. 4 is inserted in the light path to prevent 
color mixing caused by the fact that the green (G) photosensitive layer 
and the red (R) photosensitive layer of the color photosensitive material 
have spectral sensitivity on the basis of intrinsic sensitivity of silver 
halide. Accordingly, in this case, exposure is made in a wavelength region 
free from any wavelength peak in the intrinsic sensitivity of the silver 
halide. 
It is necessary to use a fluorescent substance having luminance over all 
the regions of sensitivity of the decomposed tricolor components of the 
color photosensitive material. As such, a fluorescent substance that is 
used is a mixture of fluorescent materials named as P-45 and P-22. The 
fluorescent material P-45 has a luminance distribution in a wavelength 
region shorter than about 600 nm, while P-22 has a luminance distribution 
in a wavelength region longer than about 600 nm. 
As an experiment, the color photosensitive material having the spectral 
response shown in FIG. 2 was exposed to light having the spectral 
intensity shown in FIG. 3 by utilizing an equivalent weight mixture of 
P-45 and P-22. A projector CRT was used as the CRT, and supplied with a 
high-voltage of 29 kV and a beam current of 200 .mu.A. Filters whose 
spectral transmittances are shown in FIG. 4 were used. As the result, 
balanced sensitivity was shown at the measured exposure times of 2 sec. 
for red, 0.7 sec. for green and 0.5 sec. for blue. 
In another experiment, a fluorescent mixture of P-45 and P-22 in the weight 
proportion 1:4 was used under the same conditions as described above. This 
mixture of P-45 and P-22 produced a spectral intensity shown in FIG. 6. 
Balanced sensitivity was shown at the measured exposure times of 1 sec. 
for red, 1 sec. for green and 1 sec. for blue. That is, sensitivity 
balance was obtained with equal exposure times for the respective colors. 
The fluorescent material having a main luminance distribution in the 
wavelength region shorter than about 600 nm which is used in the present 
invention may be, for example, a fluorescent material named P-45. This 
fluorescent material P-45 is used in a monochromatic high current density 
display and is composed of (Y.Gd)O.sub.2 S:Tb. P-45 emits a white luminous 
color. The other fluorescent material used in this invention has a main 
luminance distribution in a wavelength area longer than about 600 nm. This 
longer wavelength fluorescent material may be, for example, a fluorescent 
material named P-22 which is used in color television sets and is composed 
of Y.sub.2 O.sub.3 :Eu or Y.sub.2 O.sub.2 S:Eu, and emits a red luminous 
color. 
When the mixture proportion of the fluorescent material P-45 to the 
fluorescent material P-22 is established within a range of from 1:3 to 
1:5, the peak of in the blue luminance region can be lowered to thereby 
correspondingly raise the peak of in the red luminance area. Thus, it is 
possible to make the luminance of the CRT match the sensitivity balance of 
the color photosensitive material. 
According to the present invention, in the case where a color print is 
obtained through tricolor successive scene-by-scene exposure by the use of 
a monochromatic CRT, it is possible to obtain a color print excellent in 
sensitivity balance as well as in color balance respectively with respect 
to the blue, green and red pictures.