JPH09164721A - Optically writing led array head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a ghost light due to a light shading plate by a method wherein a part of a light from an LED emission layer is reflected to be refracted by a reflection member to a diagonal direction with respect to the emission layer. SOLUTION: Each reflection plate 5 is provided to a front position of an emission end between respective LED emission elements 3 on an LED array chip 6. A cross section of the reflection plate 5 is roughly of a trapezoidal shape and has inclined planes as reflection faces on both sides. The longitudinal direction of the reflection plate is parallel to a back-an-forth direction of each LED emission element 3. Each of the inclined planes reflects to refract a part of the light emitted from an emission layer 4 of each of the LED emission elements 3 in a diagonally upper direction with respect to a face of the emission layer 4. The part of light from the LED emission layer 4 is not incident on a lens by reflecting to refract the part of the light by using the reflection plate 5 so that a ghost light that may occur due to the provision of a light shading plate is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED printer,
The present invention relates to an optical writing LED array head that can be used in a digital copying machine, a facsimile, and the like.

[0002]

2. Description of the Related Art In printers, digital copying machines, facsimiles, etc., an LED array in which a plurality of light emitting sources of LED light emitting elements are arranged in a line is used, and each LED light emitting element constituting the LED array is used as an input signal. There is known an optical writing LED array head configured to form an image corresponding to an input signal on a photosensitive drum or the like by emitting light according to the light.

An optical writing LED array head using such an LED light emitting element has no vibration or noise as compared with a raster scanning method using a semiconductor laser as a light source and a scanning optical system, and therefore reliability against vibration and noise is high. It has high efficiency and is advantageous in miniaturization. On the other hand, there is a problem in that the variation in the amount of light within one line is large and the beam spot shape is likely to be non-uniform among dots.

As a means for solving such a problem, the LED light emitting elements on the LED array are divided into groups so as to match the arrangement period of the lens array, and each LE is arranged.
A method of reducing the crosstalk of the light flux by providing a light shield plate in parallel with the optical axis of the lens between the D light emitting element groups has been considered. This example is shown in FIG.

In FIG. 7, reference numeral 6 indicates an LED array chip. The LED array chip 6 is formed by arranging a plurality of LED light emitting elements as light emitting sources, and the LED array chip 1 is formed by arranging a plurality of LED array chips 6 having such a configuration in a straight line. On the path of the light emitted from the LED light emitting layer of the LED light emitting element of each LED array chip 6, a lens array element 2 formed by arranging a plurality of lenses is arranged in parallel with the LED array element 1. The light emitted from each LED light emitting element,
The image of the LED light emitting element is focused on a position corresponding to the LED light emitting element on the image plane 11 to form an image on the predetermined image surface. An appropriate number of light shield plates 10 are arranged between the LED array element 1 and the lens array element 2 in the lens optical axis direction. LE of LED array element 1
The D light emitting elements are grouped so as to match the arrangement period of the lenses of the lens array element 2. The light shielding plate 10 is provided in the lens of the lens array element 2 in order to reduce the crosstalk of the light flux between the one LED light emitting element group divided into the groups and the LED light emitting element group adjacent thereto. It is arranged so that the intervals match the array period.

[0006]

However, the above method has a problem that the light flux reflected by the light shielding plate 10 is easily imaged as ghost light on the image surface 11 as shown in FIG. That is, in FIG. 7, for example, it is desirable that the light flux emitted from the LED light-emitting element at a specific point a is focused on the point a ′ on the image surface 11 after passing through the lens, which is opposed to the point a. Is reflected on the surfaces S1 and S2 on the light shielding plate 10, and becomes ghost light having imaginary points (imaginary light emitting points) at points b and c different from the above point a, respectively, as shown in FIG. An image is formed at points b ′ and c ′ on the image plane 11. Since such ghost light causes a significant deterioration in the quality of the output image, a means for removing the ghost light is required.

The present invention has been made in view of the above conventional problems, and in the optical writing LED array head in which the light shield plate is provided between the lenses of the lens array element, the light shield plate is provided. It is an object of the present invention to provide an effective means for removing ghost light caused by the above.

[0008]

According to the first aspect of the present invention,
Optical writing LE including an LED array element having a plurality of light emitting sources and a lens array element having a plurality of lenses
In the D array head, a light shield plate provided in the lens optical axis direction between the lenses of the lens array element, and the LE
It is provided between the individual LED light-emitting elements of the D array element, at a position in front of the light-emitting end, and has a reflection member that reflects and bends a part of the light from the LED light-emitting layer in an oblique direction with respect to the light-emitting layer surface. And Part of the light from the LED light emitting layer which is reflected and bent obliquely with respect to the light emitting layer surface by the reflecting member does not enter the lens, and ghost light is not generated.

According to a second aspect of the present invention, the reflecting member may be formed of a part of a substantially convex spherical surface. The reflecting member formed of a part of the substantially convex spherical surface reflects a part of the light from the LED light emitting layer at a large angle and bends it, so that it is more difficult to enter the lens.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an optical writing LED array head according to the present invention will be described below with reference to the drawings. The same components as those in the example shown in FIG. 7 are designated by common reference numerals. A first embodiment is shown in FIGS. 1, 2 and 3. 1, 2, and 3, the LED array element 1 includes an LED array chip 6 and LEs as a plurality of light emitting sources arranged on the LED array chip 6.
And a D light emitting element 3. Further, on the LED array chip 6, at the front position of the light emitting end between the individual LED light emitting elements 3, the reflecting member 5 having a substantially trapezoidal cross-sectional shape and inclined planes as reflecting surfaces on both sides is arranged in the longitudinal direction. The LED light emitting element 3 is provided in parallel with the front-back direction. Each of the reflecting members 5 has a part of the light emitted from the light emitting layer 4 of the individual LED light emitting element 3 due to its inclined plane.
It is reflected and bent obliquely upward with respect to the surface. In FIG. 1, reference numeral 8 indicates an electrode provided for each LED light emitting element 3 in order to supply a drive current to each LED light emitting element 3.

As shown in FIG. 2, a plurality of LED array chips 6 formed by arranging a plurality of LED light emitting elements 3 are arranged in a straight line to form an LED array element 1. LE
A lens array element 2 having a plurality of lenses 7 is arranged in parallel with the LED array element 1 in front of the D array element 1, that is, on the path of the light flux emitted from each of the LED light emitting elements 3. An appropriate number of light shield plates 10 are arranged between the LED array element 1 and the lens array element 2 in the lens optical axis direction. The LED light emitting elements 3 of the LED array element 1 are grouped so as to match the arrangement period of the lenses of the lens array element 2. In the example shown,
Each LED array chip 6 is divided into groups. The light shield plate 10 reduces the crosstalk of restraint between one LED light emitting element group divided into the groups and the LED light emitting element group adjacent thereto.
The lens array elements 2 are arranged at the same intervals as the arrangement period of the lenses.

Among the luminous fluxes emitted from the individual LED light emitting elements 3, the luminous flux Rs not directly coupled to the lens 7 is
The reflecting surface of the reflecting member 5 is reflected obliquely upward and bent with respect to the surface of the light emitting layer 4. In other words, the light emitting layer 4
In the direction (Z direction in FIGS. 1, 2 and 3) orthogonal to the surface (the surface parallel to the paper surface in FIG. 3), the emission angle in the same direction becomes larger.

As a result, the light shield plate 1 for the light flux Rs is formed.
The incident angle β to 0 (see FIGS. 2 and 3) becomes large, and the light flux Rs reflected by the light shield plate 10 can be removed from the optical path incident on the lens array 2, and the ghost light on the image plane Image formation can be reduced. Therefore, the quality of the output image can be improved.

FIGS. 4, 5, and 6 show a second embodiment. FIG. 5 shows a part of the second embodiment in accordance with FIG. 3 in order to compare the operation with the first embodiment.
The difference between the second embodiment and the first embodiment is that the reflecting member arranged at the front position of the light emitting end between the individual LED light emitting elements 3 is a part of a substantially convex spherical surface, more specifically Specifically, the point is that the reflecting member 9 is composed of a convex spherical surface that is ½ of a sphere or smaller. This reflective member 9
Is fixed on the LED array chip 6 with its convex spherical surface protruding from the upper surface of the LED array chip 6. In addition, the maximum height of the reflecting member 9 is determined by the individual LED light emitting elements 3
Is sufficiently higher than the height position of the light emitting layer 4. The rest of the configuration is the same as that of the first embodiment, so description of the configuration is omitted.

In the second embodiment shown in FIG. 4, FIG. 5 and FIG. 6, the LED array chip 6 constituting the LED array element 1 is provided at a light emitting end front position between the individual LED light emitting elements 3 substantially at the light emitting end. Since the convex spherical reflecting member 9 is provided, among the luminous fluxes emitted from the LED light-emitting element 3, the luminous flux Rs that is not directly coupled to the lens 7 is reflected by the substantially convex spherical reflecting surface of the reflecting member 1 to emit light. It is kicked up in the direction (Z direction in FIGS. 4 and 5) orthogonal to the layer 4 surface. At the same time, as shown in FIG. 5 in accordance with FIG. 3, in the present embodiment, the first convex surface of the reflecting member 9 is reflected, so that the first
In comparison with the case where the reflection member 5 having a trapezoidal transverse cross section is reflected by the inclined plane in the embodiment of the present invention, the X perpendicular to the Z axis is crossed.
The opening angle α in the −Y plane becomes large. As a result, as in the first embodiment, the angle α with respect to the lens 7 is increased with respect to the lens 7 in the first embodiment while keeping the incident angle β to the light shield plate 10 large. It can be larger than the angle α.

Therefore, as shown in FIG. 6, the ghost light Rs2 in this embodiment strikes the light shield plate 10 at a position farther from the lens 7 than the ghost light Rs1 in the first embodiment. Since it is reflected and bent, the ghost light Rs2 can be largely deviated from the optical path incident on the lens 7, and the image formation due to the ghost light can be further reduced as compared with the first embodiment, and the quality is higher. An output image can be obtained.

In place of the reflecting member 5 having a trapezoidal cross section in the first embodiment, a partial arcuate cross section,
That is, a cylindrical reflecting member may be used as a whole.
In addition, the convex spherical reflecting member 9 according to the second embodiment
Instead of this, it is possible to use a reflecting member having a shape in which a reflecting surface made of a flat surface is combined into a partial spherical surface as a whole, in other words, a large number of flat cut surfaces are formed on the partial spherical surface. In addition, the shape of the reflecting member is arbitrary as long as the object of the present invention can be achieved.

[0018]

According to the invention described in claim 1, between the light shield plate provided in the lens optical axis direction between the lenses of the lens array element and the individual LED light emitting elements of the LED array element, the front of the light emitting end. Since a reflecting member that is provided at a position and reflects and bends a part of the light from the LED light emitting layer in an oblique direction with respect to the light emitting layer surface is provided, the light emitted from each LED light emitting element is directly coupled to the lens. The non-ring luminous flux is reflected by the reflecting surface of the reflecting member in an oblique direction with respect to the surface of the LED light emitting layer and is bent, so that it is possible to easily reduce the ghost light that adversely affects the image quality.

According to the second aspect of the present invention, since the reflecting member is formed of a part of the substantially convex spherical surface, the light emitted from each LED light emitting element that is not directly coupled to the lens is converted into the lens. It can be applied to the light shield plate at a position farther from, further reducing the influence of ghost light,
It is possible to obtain a higher quality output image.

[Brief description of the drawings]

FIG. 1 is a perspective view of a portion of an LED array element showing an embodiment of an optical writing LED array head according to the present invention.

FIG. 2 is a perspective view of the above embodiment.

FIG. 3 is a plan view showing the operation of the reflection member of the above embodiment.

FIG. 4 is a perspective view of an LED array element portion showing another embodiment of the optical writing LED array head according to the present invention.

FIG. 5 is a plan view showing the operation of the reflection member of the above embodiment.

FIG. 6 is a perspective view of the above embodiment.

FIG. 7 is a plan view showing an example of a conventional optical writing LED array head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 LED array element 2 Lens array element 3 LED light emitting element as a light emitting source 4 LED light emitting layer 5 Reflecting member 7 Lens 9 Reflecting member 10 Light shielding plate

Claims (2)

[Claims] 1. An optical writing LED comprising a light emitting diode (hereinafter referred to as "LED") array element having a plurality of light emitting sources and a lens array element having a plurality of lenses.
In the array head, a light shield plate provided in the lens optical axis direction between the lenses of the lens array element and the LED light emitting element of each of the LED array elements is provided at a light emitting end front position, An optical writing LED array head, comprising: a reflecting member that reflects a part of light in a direction oblique to a light emitting layer surface and bends the light. 2. The optical writing LED array head according to claim 1, wherein the reflecting member is formed of a part of a substantially convex spherical surface.