JPS60254018A - Optical device - Google Patents

Abstract

PURPOSE:To obtain an economical synchronism movement type optical image forming device which is easily manufactured, assembled, and adjusted by using a plate type prism lens array. CONSTITUTION:A synchronism movement type electrophotographic copying machine has an exposure lamp 83, reflection mirror 84, and prims lens array 85 arranged under an original platen 82. The surface of photosensitive paper 86 which moves in synchronism with original platen glass 82 is charged electrostatically by a charger 92 and a light image of an original 81 is projected successively through the optical system including the array 85 to form an electrostatic latent image, which is developed by a developing device 92. The prism lens array 85 uses a plastic material, etc., and is constituted by molding the lens array 21 and prism array 22 in one body simultaneously or assembling independently molded arrays while aligning their optical axes to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical device, and particularly to an optical device used in an image information processing device such as an electrophotographic copying machine.

For example, various imaging systems are employed in the exposure optical system of an electrophotographic copying machine. In the synchronous movement type, the lens is stationary,
The original and photoconductor move in synchronization.

In the mirror scanning type, the document and lens are stationary, the first mirror and photoreceptor move at the same speed, and the second mirror moves at half the speed. In the lens box scanning type, the document and photoreceptor remain stationary, and the lens box moves. Each of these has advantages and disadvantages.

By the way, among the requirements for copying machines in recent years,
There is a problem with the 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. A focusing light transmitter is a rod-shaped transparent body with a diameter of about 1 mm whose refractive index changes parabolically from the center to the radial direction, and by appropriately determining its length, it is possible to form an erect, life-size real image with a single rod. can be done. When used as an exposure optical system, elements having the same length, refractive index, and diameter are arranged in a row and used as a play. On the other hand, a microlens array is a array of microlenses with the same curvature, refractive index, and diameter, and is a type of spherical lens. At least three microlenses (array) superimposed on each other are required. Convergent light transmitters have disadvantages in that they are not easy to manufacture and are expensive because each element is treated by ion exchange or the like in order to change the refractive index, and the play is manufactured by assembling each element. In addition, the microlens array also uses a large number of microlenses, aligns their optical axes, and shields light between adjacent microlenses, which has the drawback of not being easy to manufacture and increasing costs.

These imaging elements are characterized by an extremely short focal length, which allows for miniaturization of the device. Therefore, they are not suitable for application to mirror-scanning optical systems that require a long focal length. This is because if you try to obtain a long focal length, the advantage of miniaturization will be lost. An in-prism lens is an imaging element that can achieve a long focal length without losing the advantage of miniaturization. this is,
A triangular prism is placed behind a spherical lens, and even if the focal length of the lens is long, the distance between the lens and prism can be made extremely short, so even if it is configured as an array, the overall size is small. can be maintained. However, since the conventionally known in-prism lens array uses individual lenses and prisms assembled together, manufacturing, assembly, and adjustment are troublesome and time-consuming, resulting in high costs. be.

According to the present invention, a synchronous movement type optical device using a plate-shaped prism lens array is provided.

The plate-shaped prism lens array used in the imaging device according to the present invention is easy and economical to manufacture, assemble, and adjust, and is small and lightweight, so it can provide similar effects to the imaging device in which it is the main part. You can also have 1.

Therefore, an object of the present invention is to provide a synchronous movement type optical imaging device using a plate-shaped prism lens array.

FIG. 1A and FIG. 1B show an imaging system using a prism lens. The prism lens 10 is.

A triangular prism 12 is arranged behind a spherical lens 11, and FIG. 1A shows the imaging optical path viewed from above, and FIG. 1B shows the imaging optical path viewed from the side. As is clear from the figure, the image of the object 13 is formed as an erect, equal-size image in the horizontal direction, and as an inverted, equal-size image 14 in the vertical direction. For example, the letter F is imaged on b. Prism lenses can provide a long focal length without increasing the size of the device. The reason is that the distance L(
This is because even if Lz is made longer, the distance Lz from the lens 11 to the prism 12 can be maintained at an extremely small value. Therefore, if such a prism lens is used for a long focal length, it can also be applied to a mirror scanning type optical system. In order to downsize the entire device, a plurality of small prism lenses can be arranged in a row and used as an array.

The characteristics of the prism lens array used in the optical device according to the present invention are that the lens array and the prism array are
It is formed integrally into a plate shape using a plastic material or the like. This allows mass production, simplifies manufacturing, assembly, and adjustment, and significantly reduces costs. FIG. 2A shows a prism lens array in which the lens array 21 and prism array 22 are integrally molded at the same time, and FIG. 2B shows a prism lens array in which the lens array 21 and prism array 22 are integrally molded separately. Various prism lens arrays are shown assembled with their optical axes aligned. These are the above
This is the content of the meaning of ``integral''. The shape of each lens in the lens array 21 when viewed from the front may be circular, but it is preferable to make it rectangular to match the prism. Also,
The array does not necessarily have to be integral over its entire length; multiple arrays may be arranged side by side to form a complete array. Therefore, this is also the content of ``integral''.

Due to the nature of the prism lens array, in order to put it into practical use, the angle of view in the vertical direction shown in Figure 1B must be made as large as possible. This results in the overlap of one peripheral imaging portion increasing too much in the column direction of the array.

For this reason, as shown in FIG. 3, if the arrangement density of the prism lenses in the column direction of the array is minimized to prevent overlapping of the peripheral imaging areas as much as possible, not only will uneven light intensity occur, but Good resolution performance is obtained near each optical axis, but in each peripheral area, the resolution performance decreases in the peripheral areas of each lens itself, overlapping images in areas with a lot of distortion, and positional deviations in the connecting parts. This inevitably causes a performance drop (approximately 20'' in θ), which causes a practical problem of a drop in image quality in the column direction of the array.

The prism lens array used in this invention is:

Arrange each lens and prism as densely as possible,
The effective angle of view of each lens can be set to the minimum necessary size in the column direction of the array and as wide as possible in the direction perpendicular to the column direction of the array.

Specifically, a shielding plate having a rectangular opening that is short in the array column direction and long in the vertical direction is arranged in front of each lens or prism, or the opening of each prism and/or lens itself is This is achieved by forming it into such a rectangular shape. In FIG. 4, 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. A large number of these are arranged as an array in a direction parallel to the X direction of the projection plane 24. By arranging such a shielding plate 23, the column direction of the array
A prism lens with a low angle of view in the vertical direction and a wide angle of view in the vertical direction y can be obtained.

In order to eliminate unevenness in light and quantity, arranging each lens as densely as possible means that the diameter of the lenses in the prism lens array and the pitch P between the lenses, as shown in the partial front view of FIG. It means to make them equal.

If the lens shape is circular, wasted space will occur between adjacent lenses and between rows. Therefore, by making the lenses and prisms themselves into rectangular shapes as shown in FIG. 6 and placing them adjacent to form an array, wasted space can be reduced and the above-described improvement in the angle of view can also be achieved. If the width W is further reduced as shown in FIG. 7, the inter-lens pitch P will also become smaller, and the light amount distribution will become even flatter. Such a rectangular shape can also be a complete rectangle, as shown in FIG. 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 prism lens array used in the optical device according to the invention further includes one or more additional lenses with different curvatures on the front surface of each lens in order to improve the performance of each lens itself, i.e. to correct each aberration. They can be stacked to form a composite lens system. This additional lens is also formed as a plate-shaped lens array. This method of correcting aberrations by increasing the number of curved surfaces is a method used in many lens systems, but it is particularly effective when the lens is constructed from a plastic material with a limited refractive index. be.

Figure 9 shows some examples of prism lens arrays configured in this way, with the left-hand figure being a partial front view, the center figure being a partial top view, and the right-hand figure being a case in which 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.

FIG. 10 is a schematic diagram of a synchronous movement type electrophotographic copying machine which is an embodiment of the present invention. Electrofax paper is used as the photoreceptor. The document 81 is placed on the document table glass 82, and the document table glass 82 moves forward to the right and back to the left. Below the document table 82, an exposure lamp 83, an opposite mirror 84, and a prism lens array 85 are arranged at predetermined positions. The photosensitive paper 86 is transported to the left by transport ports 87, 88, 89, and 90, during which time it is charged by a corona charger 91, exposed to light by the above-mentioned optical system, and subjected to wet development by a developing device 92. .

The angle θ on the front side in the forward movement direction of the document glass formed by the optical axis of the reflected light from the document 81 and the document glass 82, and the photosensitive paper formed by the optical axis of the light emitted from the prism lens array 85 and the photosensitive paper 86. The angles O on the front side in the moving direction are equal to each other.

Since the copying machine in this embodiment is a direct type, an odd number of mirrors are inserted into the optical system, but if a transfer type is used, an even number of mirrors may be used. Original table glass 82
The surface of the photosensitive paper 86 that moves in synchronization with the charger 9
1 to a predetermined polarity, an optical image of the original 81 is sequentially projected thereon through an optical system including an array 85 to form an electrostatic latent image, which is developed by a developing device 92, and the photosensitive paper is dried. The developed image is fixed.

[Brief explanation of the drawing]

FIG. 1A is a diagram of the optical path of an image formed by a prism lens as seen from above, FIG. 1B is a diagram of an optical path of an image formed by a prism lens as seen from the side, and FIG. 2 shows various configurations of the prism lens array used in this invention. A partial plan view, FIG. 3, shows
FIG. 4 is an illuminance distribution diagram when the exposure width is divided into three by using three prism lenses. FIG. 4 is a diagram showing image formation by the prism lens used in this invention. FIGS. FIG. 9 is a partial front view showing various configurations of the prism lens array used in this invention; FIG. FIG. 1 is a schematic diagram of a synchronous movement type electrophotographic copying machine showing an embodiment of the present invention. 21... Lens, 22... Prism, 23...
...Shielding plate, 24...Additional lens, 81...
Manuscript, 85. ...Prism lens array, 86...
...Photoreceptor. Agent Kabayama Agency-9 Rep.

Claims (1)

[Claims] A lens array in which a large number of lenses are arranged in a row and integrally molded into a single thin strip, and a large number of prisms with an isosceles right triangular cross section are arranged in a row with their apexes parallel to each other and are integrally molded. A prism lens array comprising a prism lens array arranged behind the lens array such that each prism corresponds to each lens is placed between a moving document and a photoreceptor. an optical device that is fixedly disposed on and forms an image of the document on the photoreceptor;