JPH09267510A - Optical printer head - Google Patents

Abstract

(57) [Abstract] [Object] The intensity and size of a beam irradiated onto a photoconductor varies due to aberration of a lens. SOLUTION: A plurality of light emitting element arrays 2 in which square light emitting elements 2a are arranged in a line are arranged linearly, and a plurality of light emitting element arrays 2 are arranged on each light emitting element array 2 in a one-to-one correspondence with the arrays 2. In an optical printer head having a plurality of lenses, the length L of the light emitting elements 2a located at both end regions of the light emitting element array 2 is longer than that of the light emitting element 2a located in the central region, and the width W is It is shorter than the light emitting element 2 located in the central region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an optical printer head used as an exposure device for an electrophotographic printer or the like.

[0002]

2. Description of the Related Art In recent years, low-cost, high-resolution optical printer heads using aspherical lenses have been proposed.

In such a conventional optical printer head, for example, a light emitting diode element array in which a large number of square light emitting diode elements (hereinafter referred to as LED elements) are arranged at a constant pitch p on a base plate made of glass or the like. A plurality of LED arrays (hereinafter abbreviated as LED arrays) are linearly arranged and mounted, and a plurality of lenses are arranged on the LED array.
Each LED element of the ED array is caused to selectively emit light in response to an external electric signal, and the light (beam) emitted from the LED element is imaged on an external photoconductor through the lens, and a predetermined photoconductor surface is formed. To function as an optical printer head.

As shown in FIG. 5, the LED array has LED elements 12 of the same size and shape inside.
For example, 64 a are linearly arranged, and when applied to an A4 size, 300 dpi optical printer head, 40 LED arrays 12 each correspond to each lens described above in a one-to-one correspondence. And base plate 11
Will be placed on top.

[0005]

However, in such a conventional optical printer head, since the aspherical lens is used for focusing the beam from the LED array 12 on the photosensitive member, the periphery of the lens is used. The contour of the beam radiated on the photoconductor after passing through the region is blurred due to the aberration of the lens, and the intensity and size of the beam radiated on the photoconductor vary. More specifically, the intensity of light from each LED array 12 is weaker from the LED elements 12a located near both ends thereof than from the LED elements 12a located near the center, and the intensity of the light is large. LED elements 12a located near both ends of the LED array 12 are LED elements 12 located near the center.
It has a wider width than that of a and has the drawback that uneven density of the printed image occurs due to these factors.

[0006]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks. A plurality of light emitting element arrays in which square light emitting elements are arranged in a row are arranged linearly and An optical printer head having a plurality of lenses arranged in a one-to-one correspondence with the light emitting element array, wherein the lengths of the light emitting elements located at both end areas of the light emitting element array are located in the central area. The light emitting element is longer than the light emitting element located in the central region and the width is shorter than that of the light emitting element located in the central region.

Further, in the optical printer head of the present invention, each of the light emitting elements forming the quadrangular shape of the light emitting element array has a length gradually increasing from a central region of the array toward both end regions and a width of the central region of the array. It is characterized in that it gradually becomes shorter from the region toward both end regions.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a vertical sectional view showing an embodiment of the optical printer head of the present invention, FIG. 2 is a partially enlarged view of the LED array and the like of the optical printer head of FIG. 2 is an LED array, 2a is an LED element,
3 is a lens.

The base plate 1 is made of an electrically insulating material such as glass epoxy resin, alumina ceramics or glass, and a plurality of LED arrays 2 are linearly arranged on the upper surface of the base plate 1 with a predetermined space therebetween. It is placed.

The base plate 1 functions as a supporting member for supporting the LED array 2. For example, when the base plate 1 is made of glass epoxy resin, sol-like epoxy resin is poured into glass fibers, and then the epoxy resin is thermoset. It is produced by

The plurality of LED arrays 2 arrayed and mounted on the base plate 1 have a plurality of light emitting diode elements 2a each having a quadrangular shape at a constant pitch p.
The light emitting diode elements 2a individually and selectively emit light in response to an external electric signal, and irradiate the emitted light (beam) on the surface of the external photoconductor P. Thus, a latent image for forming an image is formed on the photoconductor P.

As such a light emitting diode element 2a, a GaAsP type or GaAlAs type light emitting diode is used. For example, in the case of a GaAsP type light emitting diode, first, a GaAs substrate is heated to a high temperature in a furnace and AsH ₃ (Arsine) and PH ₃ (Phoshin) and Ga
A gas containing an appropriate amount of (gallium) is brought into contact with the surface of the substrate to grow a single crystal of n-type semiconductor GaAsP (gallium-arsenic-phosphorus), and then Si ₃ H is deposited on the surface of the GaAsP single crystal.
A windowed film of ₄ (silicon nitride) is deposited, and Zn (zinc) gas is exposed to the window to form an n-type semiconductor GaAsP.
Zn is diffused into a part of the single crystal to form a p-type semiconductor,
It is formed by providing a pn junction.

The light emitting diode element 2a is made of A4
In the case of an optical printer head of a size, 2560 (300 per inch) are linearly arranged. For example, in order to obtain an image of 300 dpi, LE of 508 dpi is used.
When the D array 2 is used, 64 light emitting diode elements 2a are arranged at a constant interval p and the length L is about 3.15 mm.
By arranging 40 ED arrays 2 linearly at intervals of 5.414 mm, 2560 light emitting diode elements 2a are arranged on the base plate 1. Further, in each of the LED arrays 2, all the LED elements 2a have substantially the same area, and the shape thereof is as shown in FIG.
The length L of the LED elements 2a located at both ends of each LED array 2 (the length in the direction orthogonal to the arrangement of the LED elements 2a)
Is longer than the LED element 2a located in the central region, and
The width W (length in the direction parallel to the arrangement of the LED elements 2a) of the LED elements 2a located in both end areas of the LED array 2 is shorter than that of the LED elements 2a located in the central area.

For example, the shape of each LED element 2a is LE
When the length L of the LED element 2a located in the center of the D array 2 is 50 μm and the width W is 50 μm, the length L is increased by 2 to 5 μm from the center toward both ends, and the LED is located at both ends. The length L of the element 2a is set to 100 μm, and the width W is shortened by 0.5 to 1 μm from the center toward both ends to set the width W of the LED elements 2a located at both ends to 27.5 μm. .

As described above, since the LED elements 2a located in the both end areas of each LED array 2 have the length L longer than that of the LED elements 2a located in the central area, the LED elements 2a are located in the both end areas of the LED array 2. The emission intensity of the LED element 2a located is larger than that of the LED element 2a in the central region, and the intensity of all the beams irradiated onto the photoconductor P via the lens 3 can be made substantially equal.

Moreover, in the LED array 2, the width W of the LED elements 2a located in both end regions is in the central region.
Since it is shorter than the element 2a, the beam from the LED elements 2a located at the both end areas of the array 2 has a central area.
The beam width is sharper than that of the above, and the widths of all beams irradiated onto the photoconductor P through the lens 3 can be made substantially equal.

As described above, since the intensity and size of all the beams radiated on the photoconductor P through the lens 3 can be made substantially equal to each other, uneven density can be effectively prevented from occurring and a good image can be printed. Can be formed.

The length L and the width W of the LED element 2a are appropriately set according to the aberration of the lens 3 described later.

On the base plate 1 on which the LED array 2 is placed, a plurality of lenses 3 supported by a lens plate 4 are provided, and the lenses 3 and the LED array 2 correspond to each other in a one-to-one correspondence. It is fixed in the same way.

The lens 3 is a light emitting diode element 2a.
Is used to irradiate and image the light emitted from the photoconductor P. For example, when the LED array 2 of 508 DPI is used to obtain an image of 300 DPI, an aspheric lens that magnifies 1.692 times is used and the focal length is Set to 23.28 mm. The lenses 3 are generally made of a transparent resin such as acrylic resin or polycarbonate resin or a translucent inorganic material such as glass, and each of them has a predetermined aberration.

The lens plate 4 for supporting these lenses 3 has a plurality of lenses 3 on the base plate 1 on which the LED array 2 is mounted so that each lens 3 corresponds to the LED array 2 in a one-to-one correspondence. , Each lens 3 and each L
It is made of polycarbonate, liquid crystal polymer, or the like, and has a function of fixing it side by side so that the distance from the ED array 2 is constant.

Further, a shielding member 5 is arranged between the lenses 3 supported by the lens plate 4 so as to form a wall in a direction orthogonal to the arrangement direction of the LED array 2.

The shielding member 5 is for making the beam incident on each lens 3 only the beam from the LED array 2 corresponding to the lens 3, so that the beam from the adjacent LED array 2 is a lens. It is designed to prevent the image formation on the photoconductor P via the image forming device 3. The shielding member 6 is formed into a predetermined shape by using, for example, polycarbonate or liquid crystal polymer.

Thus, in the above-mentioned optical printer head, each light emitting diode element 2a of each LED array 2 is caused to individually and selectively emit light in response to an external electric signal, and
The light (beam) emitted from the light emitting diode element 2a is focused on the external photoconductor P via the lens 3 to form a predetermined latent image on the photoconductor P, thereby functioning as an optical printer head.

The present invention is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the scope of the present invention. For example, in the above-described embodiments, the light emitting element array is used. 2, the length L of each light emitting element 2a is sequentially increased from the central region of the array 2 toward both end regions,
The length L and the width W of each light emitting element 2a may be finely set so as to correspond to the aberration of the lens 3 with high accuracy by, for example, sequentially shortening the width from the central region of the array 2 toward both end regions,
By doing so, the print quality can be further improved.

Further, as shown in FIG. 4A, the LED element 2
LED element 2a by forming individual electrodes 6 and the like on a
Is divided into two, or as shown in FIG.
The LED element 2a may be divided into four light emitting regions by the individual electrodes 6 and the slits. By doing so, the contour of the beam irradiated on the photoconductor is emphasized to make it clearer. You can

Further, in the above embodiment, the optical printer head using the LED element as the light emitting element has been described, but it is also applicable to an optical printer head such as an EL head, a plasma dot head, a liquid crystal shutter head, a fluorescent head, and a PLZT. Is.

[0029]

According to the optical printer head of the present invention, it is possible to make the intensity and size of all the beams irradiated onto the external photoconductor through the aspherical lens substantially equal to each other, thereby causing the uneven density. It is possible to effectively prevent the above phenomenon and form a good print.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of an optical printer head of the present invention.

FIG. 2 is a partially enlarged view of the LED array of the optical printer head of FIG. 1 as seen from above.

FIG. 3 is a diagram schematically showing the shape of an LED element.

FIG. 4 is a partially enlarged view showing a modification of the present invention.

FIG. 5 is a partially enlarged view of an LED array in a conventional optical printer head.

[Explanation of symbols]

 1 ... Base plate 2 ... LED array 2a ... Light emitting diode element 3 ... Lens 4 ... Lens plate

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Claims (2)

[Claims] 1. A plurality of light emitting element arrays in which square light emitting elements are arranged in a row are arranged linearly, and
An optical printer head in which a plurality of lenses corresponding to each of the light emitting element arrays are arranged on a one-to-one basis, wherein the length of the light emitting elements located at both end areas of the light emitting element array is set to a central area. An optical printer head, characterized in that it is longer than the light emitting element located and is shorter in width than the light emitting element located in the central region. 2. The light emitting elements forming the quadrangular shape of the light emitting element array have their lengths gradually increasing from the central region to both end regions of the array, and their widths from the central region to both end regions of the array. 2. The length is gradually shortened.
The optical printer head described in 1.