JPS6058450B2 - In-prism lens array - Google Patents

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 original or original platen 12 are stationary, the first mirror 16 and the photoreceptor 13 move at the same speed, and the second mirror 17 moves at half the speed. move at a speed of 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. Incidentally, among the requirements for copying machines in recent years is the issue of miniaturization of copying machines. Such demands for miniaturization naturally apply to the exposure optical systems of copying machines, and as a response to this demand, the use of converging light transmitter arrays or microlens arrays in place of conventional lenses is being considered. There is. The converging light transmitter has a diameter of 1w and the refractive index changes parabolically from the center to the radial direction.
By appropriately determining the length of a rod-shaped transparent body of about 1n, it is possible to form an erect, life-size real image with a single rod-shaped transparent body. When used as an exposure optical system, elements having the same length, refractive index, and diameter are arranged in rows and used as an array. On the other hand, a microlens array is a row of microlenses with the same curvature, refractive index, and diameter.
Since it is a type of spherical lens, at least three microlenses (array) 18, 19, and 20 are required as shown in FIG. 3 in order to obtain an erect, equal-magnification real image. Convergent light transmitters are difficult to manufacture and expensive because each element is treated by ion exchange or other methods to change the refractive index, and the arrays are assembled by assembling each element, whereas microlenses Arrays also use a large number of microlenses, adjust the optical axes of three microlenses in the optical axis direction, and shield adjacent microlenses from light, so they are not easy to manufacture and are expensive. There is. 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. Ru.

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 insert two mirrors between the first lens 18 in FIG. 3 and the object and move and scan them. The distance 11 between them must be long, and the first lens 18 must have a long focal point. As a result, 1. naturally becomes longer, and 13 and 14 also become proportionally longer, eliminating the advantage of miniaturization. It is relatively possible to make the first lens 18 and the third lens 20 have long focal lengths by forming an extremely reduced image on the second lens 19, but this kind of lens has a good It is impossible to form an 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. As shown in the plan view of FIG. 4, the image formed by this lens is erect at equal magnification in the horizontal direction and inverted at equal magnification in the vertical direction. For example, the letter F is imaged as E. The in-prism lens allows a long focal length without making the device large. The reason for this is that even if L1 in FIG. 5, which corresponds to 11 and 12 in FIG. 3, is lengthened, L2, which corresponds to 13 and 14, can be maintained at an extremely small 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, conventionally known in-prism lens arrays use individual lenses and prisms assembled together, making manufacturing, assembly, and adjustment cumbersome and time-consuming, resulting in high costs. It was hot.

Furthermore, due to the nature of this in-prism lens, in order to put it into practical use, the vertical angle of view shown in Figure 5 must be as large as possible. A large value results in the overlap of the peripheral imaging portions increasing too much in the column direction of the array. For this reason, as shown in FIG. 6, the arrangement density of in-prism lenses in the column direction of the array is minimized,
If you try to prevent the overlap of the peripheral imaging areas as much as possible, it will not only cause unevenness in the amount of light, but also provide good resolution near each optical axis. Deterioration in resolution performance due to image duplication in areas with a lot of distortion, and further performance deterioration due to positional deviation in the connecting part (approximately 20 θ characters)
This inevitably occurs, resulting in a practical problem of deterioration of image quality in the column direction of the array. Accordingly, it is an object of the present invention to provide an improved in-prism lens array.

A further object of the present invention is to provide an in-prism lens array that uses an in-prism lens array with a wide angle of view and prevents overlapping of peripheral image areas in the array column direction as much as possible. The first feature of the in-prism lens array according to the present 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 second feature of the in-prism lens array according to the present invention is that it is a plate-shaped in-prism lens array in which each lens and prism are arranged as densely as possible, and the effective angle of view of each lens is The size is set to the minimum necessary size, and it is 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 This is achieved by molding it into a rectangular shape. In FIG. 7, 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 lens 21 and the prism 22. In the direction parallel to the X direction of the projection plane 24,
A large number of these are arranged in an array. By arranging such a shielding plate 23, an in-prism lens having 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 lens diameter D and the inter-lens pitch P equal, as shown in FIG. If the lens shape is circular, wasted space will occur between adjacent lenses and between rows.

Therefore, by making the lenses themselves rectangular as shown in FIG. 9 and making them adjacent to form an array, wasted space can be reduced and the object of the invention can also be achieved. If the width W is made even smaller as shown in FIG. 10, the pitch P between the lenses becomes even smaller, and the light quantity distribution becomes even flatter. Also,
Since more lenses can be squeezed into the same length, 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 third 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. In this way, the method of correcting aberrations by increasing the number of curved surfaces is a method used in many lens systems, but when the lens is constructed from a plastic member with a limited refractive index, , is particularly effective. FIG. 11 shows some embodiments of the invention, the left-hand diagram being a partial side view;
The center figure is a partial plan view, and the right figure is an equivalent plan view when no prism is used. Reference numeral 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 the optical dimension when the in-prism lens array according to the present invention is used in the exposure optical system of a mirror scanning type electrophotographic copying machine is as follows.

Focal length f=150T! UfL Lens diameter D=15Tfr! n Inter-lens pitch P = 15Trn Lens F value F: 10 Object side distance = Image side distance = 300Tn! n Lens maximum half angle of view θ = 83~100 Column direction effective half angle of view θ1 = 5~~60 Composite F number F: 5 equivalent prism aperture shape 15 x 8 W$L When considering application to mirror scanning type, f = around 200 T is required, but with an in-prism lens array, the exposure width in the scanning direction is relatively small and the overall size is compact, so f = 150 T! r! About n is sufficient.

In addition, the F value of each lens is F:10, but by setting the degree of overlap of images on the image plane to about 4, the F value becomes a composite F value, which is equivalent to the in-mirror lens currently used. It is estimated that Figures 12 and 13 are
1 is a schematic diagram of a mirror scanning type electrophotographic copying machine using an in-prism lens array according to the present invention; FIG.

31 is a document, 32 is a document table, 33 is an exposure lamp, 3
4 is a first scanning mirror, 35 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. . In the apparatus shown in FIG. 16, in the optical path between the in-prism lens array 36 and the photosensitive drum 37,
Furthermore, fixed mirrors 42 and 43 are arranged. The in-prism lens array 36 forms an array in the axial direction of the photoreceptor drum 37. The exposure lamp 33 and the first scanning mirror move together in the direction of the arrow at a speed of
2 is scanned. The second scanning mirror 35 moves in the same direction at a speed of V/2, and the photosensitive drum 37 moves at a peripheral speed of
to rotate in the opposite direction. 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 photosensitive drum 37 is
First, the charger 38 uniformly charges the original 31, and an optical image of the original 31 scanned by the exposure optical system including the in-prism lens array 36 is irradiated thereon, and the charged charges are changed depending on the brightness of the optical image. It dissipates, forming an electrostatic latent image of the charge pattern thereon. This electrostatic latent image is made visible by adsorbing colored fine particles called toner in the developer supplied from the developing device 39, and the visible image is transferred to the transfer paper 41 by the transfer charger 40. transcribed. 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]

Figure 1 shows a synchronous movement type exposure optical system, Figure 2 shows a mirror scanning type exposure optical system, and Figure 3 shows a case where a spherical lens is used to obtain a 1-magnification erect image. imaging optical path diagram,
Figure 4 is an imaging optical path diagram seen from above using an in-prism lens, Figure 5 is an imaging optical path diagram seen from the front using an in-prism lens, and Figure 6 is an exposure width diagram using three in-prism lenses. FIG. 7 is a diagram showing image formation by the in-prism lens of the present invention, and FIGS. 8 to 10 are diagrams showing examples of lens arrangement states in the present invention. FIG. 11 is a diagram showing an example of a combination of a lens and a prism according to the present invention, and FIG.
13 and 13 are diagrams showing an example of an electrophotographic apparatus in which an in-prism lens according to the present invention is applied to an exposure optical system. 21...Luns, 22...Prism, 2
3... Light shielding plate, 24... Additional lens.

Claims (1)

[Claims] 1. A multi-lens array in which a large number of small lenses are arranged in a row and integrally molded into a plate shape, and a multi-prism array in which a large number of small prisms are arranged in a row and integrally molded into a plate shape. an in-prism lens array comprising a multi-prism array arranged behind the lens array such that each of the small prisms corresponds to each of the small lenses;
In order to make each of the small lenses have a low angle of view in the column direction and a wide angle of view in the direction perpendicular to the column direction, the aperture of each of the small lenses or small prisms is short in the column direction and wide in the vertical direction. In-prism lens array with a long rectangular shape. 2. The in-prism lens array according to claim 1, wherein the rectangular shape is obtained by a shielding plate having apertures of a similar shape. 3 A multi-lens array in which a large number of small lenses are arranged in a row and formed into a plate shape, and a multi-prism array in which a large number of small prisms are arranged in a row and formed in a plate shape, and each of the small prisms is An in-prism lens array comprising a multi-prism lens array arranged behind the lens array so as to correspond to each of the small lenses, wherein each of the small lenses has a low angle of view in the column direction, and In order to obtain a wide angle of view in the vertical direction, the opening of each of the small lenses or small prisms is formed into a rectangular shape that is short in the column direction and long in the vertical direction, and the front surface of the multi-lens array has a different curvature. In-prism lens array with an additional multi-lens array consisting of a large number of small lenses with . 4. The in-prism lens array according to claim 3, wherein the rectangular shape is obtained by a shielding plate having apertures of a similar shape.