JPH0432356A - color separation filter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a color separation filter for a color copying machine.

[Conventional technology]

Conventionally, when constructing an energy-saving color copying machine, it is necessary to improve exposure efficiency and perform low-potential development.

In other words, in order to improve exposure efficiency, it is necessary to minimize the loss in optical members in the optical path, and of the mirrors, lenses, filters, and dustproof glass, excluding the parts related to lighting, the ones that have the greatest effect on loss are: As shown in FIG. 11, it is a filter. When the filter is a colored glass or film filter using a normal coloring material, the peak transmittance is as high as 50 to 60%. On the other hand, if the filter is an interference filter, the peak transmittance will be 90% or more, but the interference filter has the following properties. Interference filters have the property that their transmittance characteristics shift toward shorter wavelengths depending on the angle of incidence of light. Therefore, the color resolution near the center of the filter is different from that near the periphery, causing a difference in color density between the center and the periphery of the image, resulting in problems such as decreased color reproducibility. As a device designed to solve this problem, for example, the device described in Japanese Utility Model Application Laid-open No. 185102/1983 is known. In this filter, the film thickness increases from the center of the filter toward the radial outward direction to suppress changes in the angle of incidence.

On the other hand, when low potential development is performed, the life of the photoreceptor can be extended and ozone generation can be reduced.

[Problems to be Solved by the Invention] However, for the color separation filters of conventional color copying machines that have the above-mentioned incident angle correction function and perform low-potential development, due to the above-mentioned reasons, There was a problem that color spots occurred.

That is, even if the angle of incidence is corrected as described in the above-mentioned publication, it is actually impossible to obtain the characteristics at an angle of incidence of 0 degrees, and the characteristics differ slightly depending on the position. Although this difference is at a level that poses no problem in terms of color separation performance, it causes unevenness in the difference in the amount of light transmitted through the filter.

Furthermore, when low-potential development is performed, the potential per unit amount of light is small, so slight unevenness in the amount of light tends to become potential unevenness.

Therefore, variations in the resolved transmittance characteristics within the filter sheet appear as light intensity and potential unevenness within the filter sheet, which causes color unevenness in the axial direction of the photoreceptor, especially when color-separating halftone gray. .

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a color separation filter that suppresses color spots while saving energy.

[Structure of the Invention] In order to achieve the above object, the color separation filter according to the present invention is used in a color copying machine that transmits image information of an original to a photoreceptor through a lens, and is provided between the lens and the photoreceptor. In the color separation filter, which has a green filter consisting of an interference filter and is capable of correcting spectral transmittance characteristics that shift according to changes in the incident angle of light incident on the green filter, the incidence of light on the green filter is When the angle changes within a predetermined angular range according to the angle of view of the original, the difference in each wavelength on the low-pass side that exhibits 50% transmittance for each incident angle within the angular range is 6 nm or 6 nm.
so that the difference between each wavelength on the high-pass side becomes 6ns+ or smaller than 6nm,
And the difference between each wavelength on the low-pass side showing 50% transmittance and 5
This is characterized in that the spectral transmittance characteristics of the green filter are corrected so that the sum of the width difference of each wavelength showing 0% transmittance is smaller than 7 nm or 7 nm.

Hereinafter, the present invention will be specifically explained based on Examples.

1 to 10 are diagrams showing one embodiment of a color separation filter according to the present invention, and are examples in which the color separation filter is applied to a color copying machine that has a color separation correction function and performs low-potential development.

First, the configuration will be explained.

In FIG. 1, reference numeral 11 denotes a color copying machine. The color copying machine 11 transmits image information of an original (not shown) to a photoreceptor 13 via a lens 12, and forms a latent image on the surface of the photoreceptor 13. A latent image is formed, developed, and transferred onto transfer paper, and since the image forming operation is well known, its explanation will be omitted.

14 is a color separation filter used in the color copying machine 11, and the color separation filter 14 is connected to the lens 12 and the photoreceptor 1.
It is located between 3. Further, the color separation filter 14 has a green filter 15 made of an interference filter, and has a function of correcting spectral transmittance characteristics that shift according to changes in the incident angle of light incident on the green filter 15. There is. For example, the above-mentioned Utility Model No. 63-18510
As described in Japanese Patent No. 2, the film thickness is increased from the center of the filter toward the radial outward direction to suppress changes in the angle of incidence between the center and the periphery of the filter. That is, the color separation filter 14 has an incident angle correction function. Further, when the incident angle of light to the green filter 15 changes within a predetermined angular range according to the angle of view of the original, the difference between each wavelength on the low-pass side that exhibits 50% transmittance for each incident angle within the angular range is 6nm or smaller than 6nm, and the difference between each wavelength on the high-pass side is 6nn.
m or less than 6 nm, and 50%
The spectral transmittance characteristics of the green filter 15 are corrected so that the sum of the difference between the wavelengths on the low-pass side indicating transmittance and the width difference between the wavelengths indicating 50% transmittance becomes 7 nm or smaller than 7no+.

Note that 16 is a halogen lamp, 17 is a contact glass, 18 is a mirror, and 19 is a dustproof glass.

Here, the reason for the correction as described above will be explained.

First, as described in the prior art, the halogen lamp 16
, the contact glass 17, the mirror 18, the lens 12, the color separation filter 14, and the dustproof glass 19, excluding the halogen lamp 16, the color separation filter 14 has the greatest effect on the loss in the optical path (see (See Figure 11). Therefore, if the performance of the color separation filter 14 is improved, the exposure efficiency can be improved.

Moreover, FIG. 2 is a schematic diagram showing the principal rays passing through each point 1 to 7 on the interference filter, and it is assumed that the optical axis passes through point 4,
The angle of incidence with respect to the optical axis at each point n (=1 to 7) is θn
shall be. In FIG. 2, 21 is a photosensitive drum, 22 is an interference filter, 23 is a lens, and 24 is a document. This corresponds to the decomposition filter 14 and the lens 12.

The thickness of the interference film of the interference filter 22 increases from the center to the periphery, that is, from point 4 to point 1 or from point 4 to point 7, but in reality it deviates from the ideal virtual curve. ,
Since the refractive index is also not uniform, the spectral characteristics vary for each light beam, as shown in FIGS. Particularly in the case of a low-density original, the influence of light intensity unevenness is large and embedding is likely to occur. When the green filter 15 shown in FIG. 1 is used as a color separation filter, the half-width must be approximately 50 nm, so it is difficult to configure it with a narrow bandpass interference filter as shown in FIG. It is necessary to configure the wide bandpass filter shown in FIG. 7(e), which is a combination of the low-pass filter shown in FIG. 7(a) and the high-pass filter shown in FIG. 7(b). Therefore, the characteristics on the low-pass side and the characteristics on the high-pass side vary independently. Since the variation in spectral characteristics can be considered as parallel movement of the inclined portions shown at A and B in FIG. 3, the wavelength of 50% transmission can be taken as a representative value for each point 1 to 7. Therefore, as shown in FIG. 3, the high-pass wavelength of 50% transmission at point n is set to λ1. ．． R, the wavelength on the low-pass side is λ0, W, , -λ, -
λ, each deviation Δλ5 shown in Figure 4.5
, Δλ8, and ΔW represent the degree of inclusion (unevenness in light amount).

FIG. 8 shows the relationship between document density and surface potential, with the solid line graph showing low potential development and the dotted line graph showing normal development.

On the other hand, by calculating and integrating the energy for each wavelength under the development conditions of FIG. 8, that is, the low potential development conditions, and the conditions of FIGS. 3 to 5, the characteristics of Δλ11, Δλ8, ΔW and potential attenuation can be determined. If the variation with respect to the reference wavelength is defined as shown in FIG.
Shown as shown. However, in Figure 9.10, λ is the 50% transmission wavelength on the short wavelength side, λ□ is the 50% transmission wavelength on the long wavelength side, W is the 50% transmission wavelength width (-λ, -λL), and l is the short wavelength side. , h is the change wavelength on the long wavelength side, d is the change wavelength of the 50% transmission wavelength width, +h, +l are on the long wavelength side, -h, = n is on the short wavelength side, +d is wide On the side, -d
indicates a state in which the values are shifted to the narrow side.

Here, in order to gradate the development potential of 300■ in 6 steps, 300 V/6 = 50 V, and in order to suppress the inclusion within one step, the unevenness at the potential must be less than 1/2 of 50 V. There is. Other factors that cause inclusion include light intensity unevenness of the lighting unit, sensitivity unevenness of the photoreceptor, and charge ring of the charger, so the unevenness caused by the filter is 50V/2 = 25V.
Must be less than or equal to Therefore, the potential decay is approximately 2
It is necessary to set Δλ18, Δλ8, and ΔW so that the voltage is 0V or less. As shown in Figure 10, the potential attenuation is ±
20V and the curve is Δλ8+ΔW=7nm, so Δ
If λ8+ΔW≦7 nge and ΔλL≦6 nm, Δλ8≦6n−, the potential difference will be about 20 V or less, and the inclusion can be brought to a level where it does not become a problem.

That is, according to this example, Δλ, ≦6 nm.

and Δλ9≦6 nm, and Δλ8+ΔW≦7 nm
Since the correction is made so that

In addition, it has an incident angle correction function, which improves color reproducibility.Furthermore, since it uses an interference filter with a large peak transmittance, it can improve exposure efficiency and further reduce Energy saving can be realized by potential development.

Note that this embodiment can also be applied to a color image scanner or the like.

〔effect〕

According to the present invention, the difference between the wavelengths on the low-pass side showing 50% transmittance is 6 nm or smaller than 6nlIl, and the difference between the wavelengths on the high-pass side is 6 nm or 6 nm.
green so that the sum of the difference between the wavelengths on the low-pass side that shows 50% transmittance and the difference in the width of each wavelength that shows 50% transmittance is 7 nm or smaller than 7 nm. Since the spectral transmittance characteristics of the filter are corrected, the occurrence of inclusion can be suppressed while saving energy.

[Brief explanation of drawings]

1 to 10 are diagrams showing one embodiment of the color separation filter according to the present invention, FIG. 1 is a sectional view of a color copying machine using the filter, FIG. 2 is an explanatory diagram of its operation, and FIG. The figure is a graph showing the relationship between transmittance and wavelength at each angle of incidence, Figure 4 is a graph showing the amount of wavelength shift at each point on the filter, and Figure 5 is a graph showing the variation in wavelength width at each point on the filter. Graphs showing the amounts, Figures 6 and 7 (a
), (b), and (C) are graphs showing the transmission characteristics of each filter, FIG. 8 is a graph showing the relationship between the surface potential and document density, and FIG. 9 is a graph showing the transmission characteristics with respect to the reference wavelength. FIG. 10 is a graph showing the potential attenuation characteristics thereof, and FIG. 11 is a graph showing the characteristics of each component of the conventional color copying machine. 11...Color copying machine, 12...Lens, 13...Photoreceptor, 14...Color separation filter, 15...Green filter . Figure 1 No. 11

Claims (1)

[Claims] It is used in a color copying machine that transmits image information of an original to a photoreceptor through a lens, and has a green filter consisting of an interference filter, which is installed between the lens and the photoreceptor, and is used to prevent light from entering the green filter. In a color separation filter capable of correcting spectral transmittance characteristics that shift according to changes in angle, when the incident angle of light to the green filter changes within a predetermined angular range according to the angle of view of the original, the angle The difference between each wavelength on the low-pass side showing 50% transmission for each incident angle within the range is 6 nm or 6 nm.
and so that the difference between each wavelength on the high-pass side is 6 nm or smaller than 6 nm, and
The sum of the difference between each wavelength on the low-pass side that shows 50% transmittance and the difference in the width of each wavelength that shows 50% transmittance is 7nm or 7n
A color separation filter characterized in that the spectral transmittance characteristic of a green filter is corrected so that it becomes smaller than m.