JPS6165265A - Image exposing method of color electrophotography - Google Patents

Abstract

PURPOSE:To reproduce a low-density and a high-density part as well as a thin- line part without color mixing to a pure-color part on an image by using an auxiliary lens in addition to a lens for color separation exposure and inserting the auxiliary lens into an optical path during green color separation exposure. CONSTITUTION:A filter turret 2, light shield plate 3, lens 4 for color separation exposure, and auxiliary lens 5 for green color separation are arranged on the optical axis 1, and the filter turret 2 consists of a red color transmission filter 6, green c0lor transmission filter 7, and blue color transmission filter 8 and moves on a driving rail 9 while holding filter surfaces vertically to the optical axis 1. The color separation exposure lens 4 is fixed on the optical axis and the auxiliary lens 5 moves on a driving rail 10 while holding the pupil surface vertically to the optical axis 1. A green color transmission type has half-value width <=20 NM and also has large potential contrast on a sensitive material, and the latitude after a developing process increases and color mixing is eliminated, thereby obtaining a bright image and a stable image.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image exposure method for color electrophotography, and more particularly, to a color electrophotography method in which a latent image is formed on a sensitive material. The present invention relates to a color separation image exposure method when forming a color separation image.

(Prior Art and Problems to be Solved by the Invention) Generally, as a color image recording method, a method is known in which a monochromatic electrophotographic method is repeated a necessary number of times. With this method, color images can be obtained more easily and in a shorter time than with printing methods or color photography methods. However, the image quality is due to the printing method, color photography! 'is generally inferior to the law. The cause of this is that the contrast between necessary and unnecessary colors cannot be obtained sufficiently during the latent image formation stage, and
The problem is that color correction called masking, which is widely used in printing and the like to correct this, cannot be performed during OH-.

The conventional color electrophotographic method will be explained below with reference to FIGS. 7 to 9. FIG. 7 shows the image forming process of a conventional color electrophotographic method using a powder development method.

As a photosensitive material, S[ type or CdS type is usually used, and the 114-coated S14 type will be explained below. The photosensitive material is charged with a 4-inch charger, and then the strip becomes 15cm wide.
Next, the color original image is exposed through a color separation filter as shown in FIG. 8 to form a color 4'\fist image. In FIG. 8, numerals 1', 2 and 3 indicate blue, green, and red color separation filters, respectively. next,
This color latent image is developed with a toner of a complementary color to that of the color H/7 filter, and then a toner image on the sensitive material is formed on paper in a transfer process. The above series of →j° cycles are separated into the required number of colors (usually 1? (red) - C (cyan 1
)・toner, C (green) decomposition-M (magenta) toner, L
((ft) decomposition-Y (yellow) toner Q) 3 times, H
(1) (Black toner development may be added) Repeatedly transfer the required amount onto the paper, and then fix the toner on the paper. Although there is a difference in the latent image formation stage from 1 when CdS is used as the material, the overall process can be considered the same.

There are two issues that arise in this case:

For example, considering the case where the printed matter has 311 images, the reflection characteristics of the process ink are shown in FIG. 9. In this FIG. 9, the symbols U, H, ·\, G, C, S, are respectively cyan ink, yellow L1-ink This shows the different characteristics of Zucian ink and yellow ink. In this Figure 9, the reflection characteristics of each two are the necessary color (color to be developed) and unnecessary color (color to be developed) in each color separation.
(colors that must not be developed). During color separation, the three color filters shown in Figure 8 are sequentially exposed to light, so a light star corresponding to the average reflectance of the original image in the transmission range of each filter is irradiated onto the photosensitive material. Decrease the electrical potential on the material. The post-exposure potential on the photosensitive material is determined from the above steps for necessary colors and unnecessary colors, and the potential difference becomes the contrast.

In the first stage of development, the developing bias installed in the developing device is set between the necessary color potential and unnecessary color potential, and the necessary color is
Toner is developed and unnecessary colors are prevented from being developed. At this time, contrast latte J' on the photosensitive material. The z-tooth becomes narrower, and changes in development characteristics due to conversion factors such as temperature and humidity tend to be directly reflected in the image quality.

Now, according to Figures 8 and 9, the necessary color is cyan and the unnecessary color is red during red separation exposure, and when both red separation exposures are performed (=5
The difference in average reflectance is large (transmission over 70 nm). But 7
, part; 1.7 exposure, blue separation exposure, as shown in Figure 9, the unnecessary absorption of green and lt of the process ink is large, and the transmission band J! of the filter during color separation is large. V, wide (green exposure half value 5ONM, blind exposure half value l/i 1 0
0 NM) Depending on the situation, the required color.

The average reflectance difference between unnecessary colors is small, and contrast cannot be obtained sufficiently.

The above is what I can say about the first part of the original picture, Solino.
Contrast decreases over time in the line image area. Because ♀;i! In the case of an image, due to the resolution of the lens, light from surrounding non-image areas wraps around the line image area, and the amount of light irradiated onto the material is affected. This is because the area becomes larger than the solid area, and the potential on the sensitive material of the required color becomes further lower than that of the solid area.

Therefore, in terms of image quality, there are problems in that color mixing occurs in the green and bone parts of the original image, resulting in loss of color, and low-density warpage, F areas, and fine lines are not reproduced.

In order to deal with this, conventionally, according to the characteristics of the original picture,
An adjustment section is provided to adjust the exposure rate, development rate, ink, etc., and the operator performs picture matching while making certain adjustments to achieve a somewhat satisfactory image quality. However, such a method not only requires a complicated adjustment mechanism, but also requires a dedicated operator for the adjustment.
It is important for customers to be able to easily handle images and obtain satisfactory image quality.

Another disadvantage is that it is difficult to maintain stability in image quality because color correction is performed in the entire adjustment section without contrast between necessary colors and unnecessary colors.

(Object of the Invention) In view of the drawbacks of the prior art described above, the present invention enables image exposure with high contrast, that is, pure color areas on an image.
There is a method that aims to provide electronic copying and 7 methods that can reproduce fine lines and fine line parts without color.

(Structure of the Invention) In order to grasp the color characteristics of the original image, the color characteristics of the process ink applied to various prints were first adjusted. At this time, four people used indicators called alveolar i and color separation efficiency to quantify the effect of the color characteristics of the process ink on contrast. Here, the color separation efficiency is given by the following equation.

D(λ) = −1,0G(R(λ))11
Necessary color density l)-+(λ); Unnecessary color density U (λ); IL reflectance for process ink Here, necessary colors and unnecessary colors are cyan for red separation, yellow and magenta. , magenta for green decomposition, cyan x yellow,
Blue separation o) 1'>', S, l is yellow, magenta and cyan. FIG. 1 shows the color separation efficiencies obtained for four types of processing rings.

In FIG. 1, °C, fi, 5; nu, ru, and o indicate blue, green, and red decomposition efficiencies, respectively.

From this result, the following two points can be made.

■Due to the color characteristics of the printed matter that is the original image, the nI and last values are small when green and blue are separated.

(2) The wavelengths that give the maximum value of color separation efficiency for various printing inks used in printing are almost the same, and at other wavelengths, the color separation efficiency decreases rapidly.

From the above, it can be seen that in color separation work, it is necessary to increase the contrast during partial resolution and blue separation, and an effective means for this is to narrow the transmission band during color separation. . Moreover, in order to reproduce fine lines, it is necessary to improve the resolution performance of the lens when separating green and blue colors, which have low contrast.

Therefore, the present invention uses the following two methods to eliminate the drawbacks of the conventional method.

■ When blue and green are decomposed, the transmission band is 2O at half value l]
A narrow band vapor deposition filter that is NM or less is used.

■ When separating the green color, an auxiliary lens is used in addition to the exposure lens to achromatize the focal length and the image point. Regarding ζ above, a multilayer interference filter such as the one shown in No. 2121 can be used for ζ. li (1'111, i
-2-//The wavelength can be set freely.

Therefore, the peak wavelength is set to the wavelength (445 NM, 515 NM) that J'j exceeds the maximum value of the color separation efficiency shown in FIG. Furthermore, regarding the above item (2), this is a measure taken in relation to the chromatic aberration of the lens. Traditionally, chromatic aberration is caused by the wavelength dependence of the refractive index of glass, which is the lens material.
It is expressed by the Atsbe number V.

+16-t V = -1-------- ny nc n; refractive index nr; refractive index nc for 4861 people; f; refractive index n for 563 people,...; refraction for 5876 people・← , the relationship between the focal length correction Δr and the wavelength is expressed by the following equation.

Δr-f/V l'i Focal length For this reason, a low-dispersion glass with a large Abbe number is selected as the lens material. In addition, an achromatic lens is also known in which several lenses with different numbers (A, 2, and 1) are closely combined to form Δ[=0. In this way, the movement of the focal length and image point between the two wavelengths can be corrected, but for light at an intermediate wavelength (green region), achromatization still does not occur, and this phenomenon is considered to be a secondary spectrum. being called.

In the present invention, we focused on this phenomenon and first used a lens material with no chromatic aberration in the blue and red regions, which has a large degree of affluence in the exposure lens, and achieved resolution performance for wavelength light in the blue and red regions. After sufficiently increasing the angle, an auxiliary lens was further inserted into the optical path in the edge region in order to eliminate focal point and image point movement due to the secondary spectrum. By adopting this configuration, it is possible to obtain high resolution performance for the three wavelengths of blue, green, and red light, and it is possible to obtain good fine line reproducibility even in blue and edge areas with low contrast. This is the result obtained.

(Example) FIG. 3 shows an example of the present invention. On the optical axis 1 are a filter turret 2, a light shielding plate 3, and a color segment? + for exposure lens 4,
and a green color separation auxiliary lens 5 are located. The filter surface 2 consists of three filters, namely a red transmission filter 6, a green transmission filter 7, and a blue transmission filter 8, and is mounted on the drive rail 9 while keeping the filter surface perpendicular to the optical axis 1. can be moved.

The color separation exposure lens 4 is fixedly arranged on the optical axis, and the auxiliary lens 5 is movable on a nine-movement rail 10 with the pupil plane kept perpendicular to the optical axis 1. There is.

In addition, the light shielding plate 3 is provided with an aperture (13a) corresponding to the lens power and the light beam located on the optical axis 1, and if there is no auxiliary lens 5 on the optical axis, the auxiliary lens (2) is provided. The luminous flux is cut. The auxiliary lens 5 and filter turret 2 configured as shown in FIG. by.

Hereinafter, the operation of the tree will be explained with reference to FIG. First, for red exposure n1, the filter turret 2 is returned to the 71st position, and the red transmission filter 6 is located on the optical axis, and the 1m auxiliary lens 5 is located off the optical axis. After red exposure, the filter turret 2 and auxiliary lens 5 are moved in the positive direction (arrow a in Fig. 3) by the drive motor.
The green transmission filter 7 and the auxiliary lens 5 are positioned on the optical axis 1. Next, after green exposure, the filter turret 2 moves in the positive direction, and the auxiliary lens 5 moves in the negative direction.
The blue transmission filter 8 is positioned on the optical axis 1, and the auxiliary lens 5 is moved off the optical axis. After the blue exposure, the filter turret 2 is moved in the negative direction and returns to the horn 1,1 position.

Next, the filter lens used in the above embodiment of the present invention will be explained below. Three filters are used: a red transmitting type, a blue transmitting type, and a green transmitting type.The red method TD type 2C filter uses a colored glass filter, and the N color transmitting type and the green iJ passing filter use a multilayer evaporation, 11 type filter. Filter, I'm here. 1 when it passes through! Blue transmission type Center wavelength 445NM Half value [[1≦2ONM Pan'd pass filter Green transmission type Center wavelength 515NM Half value 111! +Width≦2ONM Bandpass filter Red transmission type CUT leaf 11 wavelengths 59ONM Sharp cut filter Each filter can be manufactured by various optical component manufacturers, and commercially available products, such as Toshiba Chemical Industries Kl and series filters, are also equivalent. It also has the performance of Nippon Vacuum Optical Co., Ltd.
Types can also be used. At this time, the center wavelength of the blue-passing and green-transmitting filters is as shown in Fig.
! The wavelength is set at which the color separation efficiency of the process ink of the printed matter 'i' is maximized.

Figure 6 shows the lens resolution performance. In FIG. 6, when green color is separated, the performance is the sum of the exposure lens 4 and the auxiliary lens 5. (, 1") The optical lens 4 is designed using a low-dispersion glass with a large Abbe number, and moreover, the resolution performance is more focused on the internal color component h/7 o'clock than when red color separation. As a result,
As shown in FIG. 6, when blue color is separated,
7o%r1L 14 1p/sm, 55 at red resolution
A lens with %at141ρ/dragon was obtained. this is,
As shown in FIG. 1, this is done in consideration of the fact that the contrast during blue separation is lower than the contrast during red separation, so that the contrast balance on the photosensitive material through the lens can be maintained. Also, when the green color is decomposed,
A thin auxiliary lens is used to correct the secondary spectrum (image point movement, focus movement) generated by the exposure lens. , as a method of correcting the influence of the secondary spectrum, it is possible to move either the exposure lens or the original surface of the photosensitive material by a small distance, but the drive mechanism must be designed with high precision, and technology is required. 14: l ′T, iiC
(ru). Therefore, in the present invention, the method described in 6.: Installation and installation of the G-light Rennes was adopted.

In the embodiments of the present invention as described above, the electron 4Y'/1 contrast obtained on the sensitive material was compared with that obtained by the conventional method.
+1. -1. In this case, the 1111th part lE position is 900
V, the white part potential is set to 103 V, and the original color is 6+1 using the color bar and Ite for the original document.

As a result, when green'+j11'r, the conventional 1. S<X
, 1. during blue decomposition. ．． You can see that the 1x-1 contrast has increased by 1 knob. As you can see, the potential contrast on the photosensitive material has been greatly improved compared to the conventional one, so it is possible to improve the image quality during development, which has the drawbacks of the conventional image quality mentioned above. can be removed.

(Effect of the invention) Compared to the conventional method, as mentioned in section 2, the potential contrast on the photosensitive material can be increased, which increases the radiation after the development process, which reduces unnecessary areas in terms of image quality. Color mixing is eliminated and colorful images are obtained, and also,
The advantage of making it easier to obtain stable images is 1°4.
°ru

Furthermore, this eliminates the need to use a complicated adjustment mechanism to perform the merging from t as in the conventional method, and a copying style that is easy for the customer to handle can be obtained.

4. During the drawing song, 7. (Explanation Figure 1 is a graph showing the color separation efficiency calculated from the color characteristics of process dunk. Figure 2 is a graph showing the color separation efficiency that can be used in the present invention.
Example: Fig. 3 is a schematic diagram of a soi embodiment of the present invention, Fig. 4 is a sequence diagram showing the operation in the embodiment of the present invention, and Fig. 5 is a color separation used in the embodiment of the present invention. A graph showing the spectral characteristics of the filter, Fig. 6 is a graph showing the lens resolution performance used in the examples of the present invention, Fig. 7 is a process diagram of the conventional electrophotographic method, and Fig. 8 is FIG. 9, which is a graph showing an example of a color separation filter used in conventional color electrophotography, is a graph showing the color characteristics of a typical printing process ink.

■...Optical axis, 2...Filter turret, 4...
Exposure lens, 5...auxiliary lens.

Figure 1 Wave Awe (N-) Figure 2 Wave length (NM) Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] An image exposure method for color electrophotography using a blue separation filter and a green separation filter which is a narrow band vapor deposited filter with a half width of 20 NM or less, the method comprising: using at least one auxiliary lens in the lens for color separation exposure; An image exposure method for color electrophotography, characterized in that the auxiliary lens is inserted into an optical path during green color separation exposure.