JPS60242419A - In-prism lens array - Google Patents

Abstract

PURPOSE:To facilitate the manufacture, assembly, and adjustment and to reduce the cost greatly by arranging a multiprism lens array behind a multilens array so that microprisms correspond to microlenses respectively. CONSTITUTION:A lens array and a prism array are molded in a plate shape integrally and assembled to form the in-prism lens array. A shield plate 23 with a rectangular opening part is arraged between a lens 21 and prism 22 and those are arrayed in quantities in a direction (x) of a projection surface 24. Thus, light shield plates 23 are arranged to constitute the in-prism lens which has a small field angle in the column direction (x) of the array and a large field angle in its perpendicular direction (y). The lenses themselves are formed rectangularly and arrayed contiguously to reduce ineffective spaces.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an in-prism lens array used in an exposure optical system of an electrophotographic copying machine.

Various imaging methods are employed in the exposure optical system of an electrophotographic copying machine. The one shown in FIG. 1 is a synchronous movement type, and the one shown in FIG. 2 is a mirror scanning type. In the synchronous movement type, the imaging lens or optical system 11 is stationary, and the original or original table 12 and photoreceptor 13 are moved synchronously.

In the mirror scanning type, an in-mirror lens 15 with a mirror 14 at the rear and the document or document table 12 are stationary, the first mirror 16 and photoreceptor 13 are moved at the same speed, and the second mirror 17 is moved at half the speed. Move with. If the object to be copied is a thick one such as a book, a synchronous movement type in which the original or the document table moves is not appropriate, and a mirror scanning type in which the original or the original stand remains stationary is suitable.

By the way, among the requirements for copying machines in recent years,
There is a problem with the miniaturization of copying machines. Such a demand for miniaturization naturally extends to the exposure optical system of copying machines, and the use of microlens arrays is being considered as a solution to this demand. This microlens array consists of a large number of microlenses with the same curvature, refractive index, and diameter arranged in a row, and is a type of spherical lens, so in order to obtain an erect 1-magnification real image, it must be as shown in Figure 3. In this case, at least three microlenses 18, 19, and 20 are required, and the optical axes of the three microlenses arranged in the optical axis direction are adjusted, and adjacent microlenses are shielded from light.

It has the disadvantage that it is not easy to manufacture and is expensive.

When a microlens array is used as the exposure optical system 11 of a copying machine as shown in Fig. 1, the distance on the object side and the image side as well as the height of the entire lens can be made relatively low. This makes it possible to create a compact copying device.

However, it is practically impossible to use this in a mirror scanning type optical system as shown in FIG. When applied to a mirror scanning type, it is necessary to place two mirrors between the lunches 18 in FIG. 3 and the object and move and scan them, so the distance Q1 between them must be kept It is necessary to make the focal point of the lens 18 long. As a result, H
2 is naturally long, and H3 and H4 are also relatively long, eliminating the advantage of miniaturization. Although it is relatively possible to make the focal length of the second lens 18 and the third lens 20 long by forming an extremely reduced image on the second lens 19, it is possible to achieve a good image of about 1/1o with this type of lens. It is impossible to image.

On the other hand, an in-prism lens is known as a lens system that can be miniaturized. An in-prism lens has a prism placed behind a spherical lens, and FIG. 4 is a diagram of the imaging optical path of this lens viewed from above, and FIG. 5 is a diagram of the imaging optical path of this lens viewed from the front. The image formed by this lens is
As shown in the plan view of the figure, the image is erected at equal size in the horizontal direction and inverted at equal size in the vertical direction. For example, the letter F is imaged as L. In-prism lenses can achieve a long focal length without increasing the size of the device. The reason is Q in Figure 3.
Even if Lt in FIG. 5, which corresponds to + and H2, is lengthened, h
This is because H2, which corresponds to Ω and Ω, can be maintained at an extremely low value. Therefore, if such an in-prism lens is used with a long focal point, it can be applied to a mirror scanning type optical system as shown in FIG. In order to downsize the entire device, a plurality of small in-prism lenses can be arranged in a row and used as an array.

However, since the conventional in-prism lens array uses nine individual lenses and prisms assembled together, manufacturing, assembly, and adjustment are cumbersome and take up to an hour, resulting in high costs. There is.

Due to the nature of in-prism lenses, when it comes to practical use,
The vertical angle of view shown in Figure 5 must be made as large as possible, so by increasing the angle of view of each in-prism lens in the array, the overlap of the peripheral imaging areas increases in the column direction of the array. The result is too much. For this reason, as shown in Fig. 6, if the arrangement density of the in-prism lenses in the direction of the play columns is minimized to prevent overlapping of the peripheral imaging areas as much as possible, it will not only cause unevenness in the amount of light; , good resolution performance is obtained near each optical axis, but in each peripheral area, the resolution performance decreases in the peripheral area of each lens itself, image overlap in areas with a lot of distortion, and the position of the connecting part Deterioration of performance due to misalignment (θ: around 20') inevitably occurs, leading to a practical problem of deterioration of image quality in the column direction of the array, but this problem can be solved by selecting the shape of the lens. This can be resolved by

It is an object of this invention to provide an improved in-prism lens array.

The feature of this invention is that the lens array and the prism array are each molded into a plate shape by integral molding using a mold, and then assembled to form an in-prism lens array. This allows mass production, simplifies manufacturing, assembly, and adjustment, and significantly reduces costs.

The in-prism lens array according to the present invention is a plate-shaped in-prism lens array in which lenses and prisms are arranged as densely as possible if necessary, and the effective angle of view of each lens is set to the minimum required in the column direction of the array. It can be made as wide as possible in the direction perpendicular to the column direction of the array. Specifically, in front of each lens or prism, a shielding plate having a rectangular aperture that is short in the column direction of the array and long in the vertical direction is placed, or the aperture of each prism or lens itself is Shape into a rectangular shape. FIG. 7 shows the lens 21 and prism 22.
A case is shown in which a shielding plate 23 having a rectangular opening consisting of a horizontal side smaller than the diameter of the lens 21 and a vertical side equal to the diameter of the lens 21 is arranged between the projection surface 24 and the projection surface 24. A large number of these are arranged in an array in a direction parallel to the X direction. Such a shielding plate 2
3, an in-prism lens with a low angle of view in the column direction X of the array and a wide angle of view in the vertical direction y can be obtained.

In order to eliminate unevenness in the amount of light, arranging the lenses as densely as possible means making the diameter of the lenses equal to the pitch P between the lenses, as shown in FIG.

If the lens shape is circular, wasted space will occur between adjacent lenses and between rows. Therefore, the lens itself was
By forming rectangular shapes as shown in the figure and arranging them adjacent to each other to form an array, wasted space can be reduced. If the width W is further reduced as shown in FIG. 10, the inter-lens pitch P will also be further reduced.
The light intensity distribution also becomes flatter. Furthermore, since more lenses can be squeezed into the same length range, a sufficient amount of light can be obtained. Furthermore, since the adverse effects caused by the overlap of peripheral image areas are corrected by the high-quality images near the optical axis, it is possible to obtain a uniform and good image as a whole.

The second feature of the in-prism lens array according to the present invention is that one or more additional lenses with different curvatures are superimposed on the front surface of each lens in order to improve the performance of each lens itself, that is, to correct each aberration. This is because it is a synthetic lens system. This additional lens is also formed as a plate-shaped lens array. Although this method of correcting aberrations by increasing the number of curved surfaces is used in many lens systems, it is particularly effective when the lens is constructed from a plastic material with a limited refractive index. It is.

Several embodiments of the invention are shown in FIG. 11, with the left-hand figure being a partial side view, the center figure being a partial plan view, and the right-hand figure being an isometric plan view when no prism is used. , 21 is a lens array, 22 is a prism array,
23 is a shielding plate, and 24 is an additional lens array.

A design example regarding optical dimensions when the in-prism lens array according to the present invention is used in an exposure optical system of a mirror scanning type electrophotographic copying machine is as follows.

Focal length f = 150mm Lens diameter D = 15mm Lens pitch P = 15mm Lens F value F: 10 Object side distance = Image side distance = 300mm Lens maximum half angle of view θ = 8° to 10° Column direction effective half angle of view θ1 -5° ~ 6° Composite F value F = 5 equivalent prism aperture shape 15 x 8 mm When considering application to mirror scanning type, f = 200 m
Although approximately m is required, in the in-prism lens array, the exposure width in the scanning direction is relatively small and the overall size is compact, so f = 150+n+++ may be sufficient. Also, the F value of each lens is F:10.

By setting the degree of image overlap on the image plane to about 4, the F
It is estimated that the combined F value is comparable to that of the in-mirror lens used for development.

FIGS. 12 and 13 are schematic diagrams of a mirror scanning type electrophotographic copying machine that uses an in-prism lens array according to the present invention. 31 is a document, 32 is a document table, 33 is an exposure lamp, 34 is a first scanning mirror, 3
5 is a second scanning mirror, 36 is an in-prism lens array, 37 is a photosensitive drum, 38 is a charger, 39 is a developing device, 40 is a transfer charger, and 41 is a transfer paper.

The apparatus shown in FIG. 13 includes an in-prism lens array 3
Further, fixed mirrors 42 and 43 are arranged in the optical path between the photoreceptor drum 37 and the photoreceptor drum 37 . The in-prism lens array 36 forms an array in the axial direction of the photoreceptor drum 37. The speed of the exposure lamp 33 and the first scanning mirror is ■
The document 31 on the document table 32 is moved integrally in the direction of the arrow.
scan.

The second scanning mirror 35 moves in the opposite direction at a speed of V/2, and the photosensitive drum 37 rotates in the opposite direction at a peripheral speed of . In the case of an in-prism lens, due to its inherent imaging method, the direction of movement of the scanning mirror and the direction of movement of the photoreceptor are opposite. The surface of the photoreceptor drum 37 is first uniformly charged by a charger 38, and is irradiated with a light image of the original 31 scanned by an exposure optical system including an in-prism lens array 36, and is charged depending on the brightness of the light image. The charged charges are dissipated, and an electrostatic latent image is formed there by the charge pattern. This electrostatic latent image is
Colored fine particles called toner in the developer supplied from the developing device 39 are adsorbed to form a visible image, and the visible image is transferred onto a transfer paper 41 by a transfer charger 40 .

This electrophotographic copying machine is also provided with a fixing device, a static eliminator, a cleaning device, etc., which operate according to known methods.

Although the present invention has been described above mainly in the case where it is applied to an exposure optical system of an electrophotographic copying machine, it goes without saying that the in-prism lens array according to the present invention can be applied to other optical devices.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a synchronous movement type exposure optical system, and FIG. 2 is a diagram showing a mirror scanning type exposure optical system. Figure 3 is an imaging optical path diagram when obtaining a 1:1 magnification standing image using a single spherical lens, Figure 4 is an imaging optical path diagram seen from above using an in-prism lens, and Figure 5 is an imaging optical path diagram when using an in-prism lens. An imaging optical path diagram seen from the front, Figure 6 is an illuminance distribution diagram when three in-prism lenses are used and the exposure width is divided into three parts, and Figure 7 shows image formation by the in-prism lens of this invention. 8 to 10 are diagrams showing an example of a lens arrangement state in this invention, FIG. 11 is a diagram showing an example of a lens and prism combination state in this invention, and FIGS. FIG. 13 is a diagram showing an example of an electrophotographic apparatus in which the in-prism lens according to the present invention is applied to an exposure optical system. 21... Lens, 22... Prism, 23...
...Shielding plate, 24...Additional lens. U7K y 420,? 7 Egen,'? I

Claims (1)

[Claims] ■ A multi-lens array in which a large number of small lenses are arranged in a row and integrally formed into a thin strip, and a large number of small prisms each having an isosceles right triangular cross section, with their apexes mutually arranged. A multi-prism lens array arranged in parallel in a row and integrally molded, the multi-prism lens array being arranged at the rear of the multi-lens array so that each small prism corresponds to each of the small lenses. An in-prism lens array. 2. A multi-lens array in which a large number of small lenses are arranged in a row and integrally molded into a thin strip, and a large number of small prisms with an isosceles right triangular cross section are arranged in a row with their apexes parallel to each other. an in-prism lens array comprising a multi-prism lens array integrally molded with a multi-prism lens array arranged behind the multi-lens array so that each small prism corresponds to each of the small lenses; An in-prism lens array, wherein an additional multi-lens array consisting of a large number of small lenses having different curvatures is arranged in front of the multi-lens array.