JPS61233715A - Copying device - Google Patents

Abstract

PURPOSE:To decrease the number of parts and to facilitate adjustments by composing a projection optical system of a mirror and bar lenses which are much longer along an optical axis than an effective diameter. CONSTITUTION:So called bar lenses 3 which are much longer along the optical axis than the effective diameter are arrayed linearly in the lengthwise direction of a body. Luminous flux emitted by the body 1 is polarized by a polarizer 9 into linear polarized light by transmitting only a polarized light component equal to the oscillation plane of the polarizer 9. Then, it is transmitted through a polarization beam splitter 2 whose oscillation plane is equal, and then passed through lenses 3 and a l/4 plate 10 to obtain circular polarized light, which is converged on the mirror 4. The light is reflected by the mirror 4 and transmitted through the l/4 plate 10 again to obtain linear polarized light having a plane of oscillation crossing said linear polarized light at right angles, and the light is reflected totally by the polarization beam splitter 2 and converged on an image surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a copying apparatus, and particularly to a copying apparatus in which a mirror image of an original on an object surface is formed on a photoreceptor by a projection optical system, and a copy is obtained through a transfer process.

(Prior Art) A single projection lens system has been used in the projection optical system of a conventional copying apparatus.However, since the conjugate of a single projection lens system is relatively long, it is difficult to perform copying using a single projection lens. The apparatus was relatively large. Therefore, in order to make the overall size of the copying apparatus compact, a plurality of lens systems with relatively short conjugates were arranged, and each of the objects to be projected onto each of these lens systems was Let the uke have the part,
A copying apparatus has been proposed in which each lens forms a projected image of the entire object on a projection surface.

In other words, the 1974 public announcement on February 28, 1972
Patent Application Publication No. 8893 discloses that a strip area of a document to be copied is captured by a plurality of lens systems arranged along the longitudinal direction of the strip area, and each partial image of the strip area is transferred to a photoreceptor by these lens systems. A reproduction device is shown forming above.

By using such a projection optical system, this copying apparatus can be made relatively compact.

Furthermore, in JP-A-53-2689, an array lens system is used to form an image of an object on a mirror surface, and the light from the image of the object is reflected by the mirror surface, and then enters the array lens system again. A device is shown in which light re-emitted from the array lens system is directed to a re-imaging surface by a half mirror placed between the array lens system and the object, and a mirror image of the object is formed on the re-imaging surface.

However, in these conventional copying apparatuses, since the projection optical system has a plurality of lenses in the optical axis direction, adjusting the optical axis of these lenses is complicated.

[Summary of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a copying apparatus which is free from loss of light quantity due to vignetting and has a simple configuration. The above object of the present invention is to provide a copying apparatus including a lens array and a mirror disposed at or near the image plane of the lens array, so that each lens constituting the lens array can prevent vignetting when transmitting a light beam. This is achieved by using a projection optical system that is designed and consists of a rod-shaped lens whose length along the optical axis is significantly longer than the effective diameter of the lens.

(Example) The present invention will be explained below using the accompanying drawings. Figure 1 of Izutsu is an optical arrangement diagram of a copying apparatus of the present invention. 1 in the figure is an object,
The 45-degree polarizing beam splitter 13 is a so-called bar lens whose length along the optical axis is significantly longer than its effective diameter.

A plurality of bar lenses 3 are arranged one-dimensionally along the longitudinal direction of the object. Reference numeral 4 denotes a lens 2- arranged at a position conjugate or almost conjugate with the object 1 with respect to the lens 3. 5 is a projection surface. 9 is a polarizer whose vibration plane coincides with the vibration plane of the polarizing beam splitter 2. 10 is V4
It is a board. Now, assuming that the field of view of one lens 3 is exactly the size of the letter P, the image of the letter P is formed by the lens 3 on or near the mirror 4. The light forming the image of the letter P is reflected by the mirror 4, enters the lens 3 again, and is directed to the projection plane 5 by the polarizing beam splitter 2. Therefore, a mirror image of the letter P is obtained on the projection plane 5.

The transmission situation of the light flux in the above imaging relationship will be described in detail below.

The light flux emitted from the object 1 becomes linearly polarized light in which only the polarized light component equal to the plane of vibration thereof is transmitted by the polarizer 9.

That is, when the light beam emitted from the object 1 is circularly polarized, the amount of light that passes through the polarizer 9 is halved.゛The linearly polarized light that has passed through the polarizer 9 passes through the polarizing beam splitter 2 whose plane of vibration is the same as that of the linearly polarized light, passes through the lens 3, passes through the λ/4 plate IO, becomes circularly polarized light, and is converged onto the mirror 4. do. It is reflected from the mirror 4, passes through the λ/4 plate 10 again, becomes linearly polarized light having a plane of vibration perpendicular to the nil linearly polarized light, and is directed toward the polarizing beam splitter 2, where it is completely reflected at the image plane 5. to be collected.

As is clear from the above description, when the light beam emitted from the object 1 is circularly polarized, 1/2 of the light beam can be transmitted to the image plane 5. This is done without taking polarization into account when using a normal semi-transparent mirror.
This is twice the amount of light that can be transmitted from the object to the image plane.

The plane of vibration of the light beam from the object is the polarizing beam splitter 2.
2 is a ray diagram of the apparatus shown in FIG. 1. In the figure, 6 is an aperture diaphragm, 7 is a field diaphragm, and 8 is an optical axis.

The lens 3 will be explained in detail below. According to experiments conducted by the inventors of the present invention, it has been found that good results can be obtained with this lens 3 by configuring the lens thickness along the optical axis to be 2 to 60 times the effective diameter of the lens. Ta.

In addition, the design of Konoshi/Z3 is based on equations (6) to (
10) is desired to be satisfied. This will be discussed below. First, in order to simplify the explanation of the lens, the symbols shown in FIG. 2 will be used.

The radius of curvature of the first surface of the lens 3, that is, the surface on the object side, is r
l sThe radius of curvature of the second surface, that is, the surface on the image field side, is rz(
In the figure, the central thickness of the lens, that is, the thickness between the first and second surfaces along the optical axis, is expressed as td'l, and the principal refractive index of the lens material is expressed as td'l. That is, the refractive index An1' for a typical design wavelength is assumed.

Also, the effective diameter of this lens is represented by φ, the size of the object P is φo1, the size of the intermediate image formed by this lens 3 is φ2, and the first surface of this lens 3 (the amount of charge in the figure), The distance from the second surface of the lens 3 to the intermediate image is expressed as S/. The intermediate image is used as a lever! The lateral magnification for the body P is expressed as p=(=-1-1).

〆・The effective F-number on the object side of this lens 3 will be expressed as Fe.

The effective F-number determined from the illumination conditions, i.e., the lateral magnification β1 of the intermediate image, which is set so that there is no partial-image clanking.
(1β11<1>, the object distance Sl, and the lens back 5/ to the intermediate image are quantities that can be set in advance. Also, the principal refractive index n/! of the material is determined by setting the material. Five setting amounts Fe, 1g,
S 'I*''From Z, radius of curvature of the first surface of lens 3 '!, radius of curvature of second surface 'Snow, lens center thickness d'1,
The effective diameter I211 of the lens and the effective diameter ^ of the cut body are determined by the following conditions using the ideal theory.

First, the relationship between the single magnification and lens configuration data is given by the following equation.

...------(2) Next, the condition that the principal ray of the incident light flux from the object, that is, the ray passing through the center of the first surface, exits parallel to the optical axis after exiting the second surface is 1. The focal length of the second surface (i.e. 1/ψ) is just el/
Since it is equal to and there are many equivalents, it is expressed by the following relationship.

Next, the condition for the light beam entering the lens 3 from the end of the effective object diameter to not be clanked is that the lower ray of light passes along the edge of the lens 3 parallel to the optical axis after passing through the first surface. A linear ′ relational expression can be obtained from .

? ! =-ten, (1+1・----------(4) I11 Finally, the distance from the second surface of lens 3 to the intermediate image position is 8
The following relational expression is required based on the conditions for maintaining 1' at an appropriate value in advance.

a'=βIX((1-9s es')8t-es'
1 =-= (5) The following result is uniquely obtained by simultaneously solving the conditions of equations (1) to (5) above for rl, rz; d1/I〆1:(aK.

rz = (1=n,') xβI St
−・−・・・(7) dl'=nl' Xβt 8
@ °−---= (8) Furthermore, the inventor of the present invention found that the lens 3 is approximately ±10% from the conditional expressions (6) to (10), that is, KIX (1-nt')
-rlt') X/18tKIXn1'X/181≦d
1′≦*Xn! 'X/l s.

However, Kl=0.9, x, = l, 1.

We have actually designed and confirmed that the 8th angle represented by is also acceptable.

Table 1 shows the data of the example.

(Effect of the invention) As explained above, one aspect of the copying apparatus of the present invention is as follows.

Since the projection optical system is composed of a bar lens and a mirror whose length along the optical axis is significantly longer than the effective diameter, the number of parts can be reduced and adjustment can be simplified.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a first embodiment of the copying apparatus of the present invention, and FIG.
The figure is a ray diagram of FIG. l...Object, 2...Polarizing beam splitter-13.
...Lens, 4...Mirror. 5... Projection surface, 6.7... Aperture, 8... Optical axis, 9... Polarizer, lO... λ/4 plate.

Claims (1)

[Claims] (1) In a copying apparatus that forms a mirror image of a document on an object plane onto a photoreceptor using a projection optical system, the projection optical system includes a plurality of lenses arranged along a predetermined direction and an image plane of the lenses or the image plane thereof. the lens forms an intermediate image on or near the mirror, the intermediate image is again re-formed by the lens on the projection plane, and the configuration data and effective diameter of the lens are The following formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ K_1×(1-n'_1)×β_1S_1×≧r_2≧
K_2×(1-n′_1)×β_1S_1 K_1×n′_1×β_1S_1≦d′_1≦K_2×
n'_1×β_1S_1 ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, r_1 is a lens The radius of curvature of the surface on the physical side of , r_2
The radius of curvature of the surface on the image field side of the lens, d'_1 is the lens thickness on the optical axis between the surface on the object world side of the lens and the surface on the image field side of the lens, φ_1 is the effective diameter of the lens, and φ_0 is the size of the object,
n'_1 is the refractive index of the lens medium for the design wavelength, β
_1 is the lateral magnification of the lens, S_1 is the distance along the optical axis to the object plane based on the surface on the object side of the lens, and S'_2 is the light to the intermediate image plane based on the surface on the image field side. Distance along the axis, Fe is the effective F number on the material side, K_1=0.9, K
A copying apparatus characterized in that _2=1.1.