JPH09118040A - Led array head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove ghost light largely and to improve the quality of output image. SOLUTION: A light shielding plate 1 in which the surface has chopping wave shaped unevenness in the cross section is installed between the lens elements 22 of a lens array 23. Among beams emitted from the LED element 20 of a LED array chip 21, beams 3 reflected by the uneven surface of the light shielding plate 1 are reflected in the direction not to be incident on the lens array to remove a ghost.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a digital copying machine,
The present invention relates to an LED array head used in optical writing systems such as printers and facsimiles.

[0002]

2. Description of the Related Art A conventional LED array head shown in FIG. 9 includes an LED array chip 2 in which a plurality of LED elements 20 are arranged in a row and lens elements 22 corresponding to the respective LED elements 20. A lens array 23 arranged in a row, and a light shielding plate 24 arranged between each lens element 22,
It is composed of 24. The surface of the light shielding plate 24 is flat,
Light emitted from the LED element 20 is mixed into an adjacent lens element, so-called "light flux crosstalk" is reduced.

That is, as shown in FIG. 9, a light beam emitted from a point a on the light emitting surface 25 of one LED element 20 forms an image at a point a'on the image surface 26 after passing through the lens array 19. Is done. The points b and c of the other LED elements 20
The light flux emitted from the device is mixed so as not to form an image on the point a '.

[0004]

However, in this conventional structure, a part of the luminous fluxes 28 and 29 which do not pass through the optical axis 27 are reflected by the surface of the light shielding plate 24, and each of them is point b on the light emitting surface 25.
Also, there is a problem that ghost light that causes the point c to be an imaginary point or an imaginary emission point is generated, and images are formed at the points b ′ and c ′ on the image plane 26, that is, so-called ghost light is likely to occur. . This ghost light is a factor that significantly deteriorates the quality of the output image.

It is an object of the present invention to provide an LED array head capable of significantly eliminating ghost light and further improving the quality of an output image.

[0006]

The LED array head according to claim 1 of the present invention comprises an LED array chip having a plurality of light emitting diode elements arranged therein and a plurality of lens elements. L consisting of a lens array
In the ED array head, a light shielding plate is provided between the lens elements, and unevenness is provided on the surface of the light shielding plate to prevent light reflected on the surface of the light shielding plate from entering the lens element. It is characterized by

A second aspect of the LED array head according to the present invention is characterized in that the light shielding plate has a triangular wave-shaped cross section and the irregularities are formed.

A third aspect of the LED array head according to the present invention is characterized in that the light shielding plate has a comb-shaped cross section to form the irregularities.

A fourth aspect of the LED array head according to the present invention is characterized in that the light shielding plate is formed in a corrugated shape in cross section to form the irregularities.

A fifth aspect of the LED array head according to the present invention is characterized in that the light shielding plate has a saw-toothed cross section to form the irregularities.

A sixth aspect of the LED array head according to the present invention is characterized in that the pitch of the saw-toothed cross section is made finer as it is farther from the LED array chip.

A LED array head according to a seventh aspect of the present invention is characterized in that the groove depth of the saw-toothed cross-section is deeper as it is farther from the LED array chip.

The LED array head according to claim 8 of the present invention is characterized in that a matte black paint is applied to the surface of the light shielding plate.

A ninth aspect of the LED array head according to the present invention is characterized in that the light shielding plate and the lens array are integrally molded of the same plastic material.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an LED array head according to the present invention will be described below with reference to the drawings. In the following, description will be made by assigning common reference numerals to parts common to the related art.

FIG. 1 shows L according to the first embodiment of the present invention.
It is sectional drawing which shows an ED array head. In this embodiment,
Although it is structurally almost the same as the conventional example shown in FIG. 9, it is different in that the cross-sectional shape of the light shielding plate 1 is a triangular wave shape.

That is, among the luminous fluxes emitted from the point a on the light emitting surface 25 of the LED element 20, the luminous fluxes 2 ... Which are directly incident on the lens array 23 are imaged at the point a'on the image plane 10. However, among the light beams emitted from the point a, the light beam 3 reflected by the light shielding plate 1 is diffusely reflected by the groove surface of the surface of the light shielding plate 1 having a triangular wave cross section, and is coupled to the lens array 23, that is, the lens. Without hitting the array 23,
Therefore, it does not become ghost light that forms an extra image on the image plane 26.

FIG. 2 is a sectional view showing a light shielding plate according to the second embodiment of the present invention. The cross section of the light shielding plate 4 of this example has a comb shape of the width w of the protruding portion 5, the width w of the groove portion 6, and the depth d of both portions 5, 6. Therefore, of the light beams emitted from the point a on the light emitting surface, the light beam 7 incident on the light shielding plate 4 is not coupled to the lens array 23.

FIG. 3 is a sectional view showing a light shielding plate according to the third embodiment of the present invention. The light shielding plate 8 of this example has a curvilinear cross section. Therefore, of the light beams emitted from the point a on the light emitting surface, the light beam 9 incident on the light shielding plate 8 is not coupled to the lens array 23, and the ghost light is reduced.

FIG. 4 is a sectional view showing a light shielding plate according to the fourth embodiment of the present invention. The light shield plate 10 in this example has a saw-tooth cross section. Therefore, among the light fluxes emitted from the point a on the light emitting surface, the light flux 11 that has entered the light shielding plate 10 is
Reflection is repeated between the surfaces S and S ′ of the groove 13 between the saw teeth 12 ... Therefore, the light flux 11 incident on the light shield plate 10 is not coupled to the lens array 23, and the ghost light is reduced.

FIG. 5 is a sectional view showing a light shielding plate according to the fifth embodiment of the present invention. The light shielding plate 14 in this example is the fourth
Similar to the embodiment described above, the cross section has a saw-tooth shape, and the pitch of the saw teeth 12 is made finer as the distance from the LED array chip which is the light emitting source increases. As a result, even a light beam 15 having a small incident angle which is reflected at a position far from the light emitting source is reliably guided so as to be repeatedly reflected toward the inner side of the groove 13 between the saw teeth. Therefore, the light flux 1 that has entered the light shielding plate 14
The ghost light is reduced because the lenses 1 and 15 are not coupled to the lens array 23.

FIG. 6 is a sectional view showing a light shielding plate according to the sixth embodiment of the present invention. The light shielding plate 16 of this example also has a fourth
Similar to the embodiment described above, the cross section has a saw-tooth shape, and the depth of the groove 13 between the saw teeth 12 is deeper as the distance from the light emitting source increases. Thereby, even if the light beam 15 has a small incident angle, the light beam is surely guided so as to be repeatedly reflected toward the inner side of the groove 13 between the saw teeth 12. Therefore, the light beams 11 and 15 that have entered the light shielding plate 15 are not coupled to the lens array 23, and the ghost light is reduced.

FIG. 7 is a sectional view showing a light shielding plate according to the seventh embodiment of the present invention. The light shielding plate 17 of this example also has a fourth
Similar to the embodiment described above, the cross section has a saw tooth shape, and the pitch of the saw teeth 12 is made finer as it is farther from the light emitting source, and the depth of the groove 13 between the saw teeth 12 is made deeper as it is farther from the light emitting source. Accordingly, particularly in a short optical arrangement from the light emitting source to the lens array 23, even if the light beam 15 has a small incident angle, the light beam can be reliably guided so as to be repeatedly reflected toward the inner side of the groove 13 between the saw teeth 12. Like Therefore, the light flux 11 that has entered the light shielding plate 17,
15 is not coupled to the lens array 23, and the ghost light is reduced.

The sawtooth shape described above also includes the sawtooth 12 in which the surfaces S and S'of the groove 13 between the sawtooths 12 are curved as shown in FIG.

According to the above embodiment, since the light flux reflected by the light shield plate is not directly coupled to the lens array 23, the ghost light can be greatly reduced. However, there is a possibility that the light that is reflected again by the surface of another optical component and is directly incident on the lens array 23 causes ghost light although it is weak. Therefore, although not shown in the drawings, the light shielding plate according to the eighth embodiment of the present invention is configured by applying a matte black paint such as carbon black on the surface. In the present embodiment, the matte black paint applied to the surface of the light shield plate significantly reduces the intensity of the light reflected by the light shield plate, which also reduces the ghost light.

Further, as a ninth embodiment of the present invention, the light shielding plate and the lens array of each of the above embodiments are made of the same plastic material and integrally molded. This can reduce the manufacturing cost.

[0027]

As described above, in the LED array head according to claim 1 of the present invention, since the surface of the light shielding plate is provided with irregularities, the light reflected on the surface of the light shielding plate is a lens. There is an effect that the ghost light that does not enter the element and adversely affects the image quality can be removed.

In the LED array head of the second aspect, since the light shielding plate has a triangular wave-shaped cross section to form irregularities, the inclination angle of the triangular wave is set to an appropriate angle corresponding to the divergence angle of the light emitted from the light emitting diode. By doing so, L of claim 1
In addition to the effect common to the ED array head, there is an effect that the light reflected on the surface of the light shielding plate can escape in a desired direction.

In the LED array head of the third aspect, since the light shielding plate has a comb-shaped cross section to form irregularities, by setting the depth and width of the comb to appropriate dimensions, the LED array of the first aspect. In addition to the effect common to the head, there is an effect that the light reflected on the surface of the light shielding plate can escape in a desired direction.

In the LED array head of claim 4, since the light shielding plate has a curved wave-shaped cross section to form irregularities, the curvature radius is set to an appropriate value.
In addition to the effect common to the ED array head, there is an effect that the light reflected on the surface of the light shielding plate can escape in a desired direction.

In the LED array head of the fifth aspect, since the light shielding plate has a saw-toothed cross-sectional shape to form irregularities, in addition to the effect common to the LED array head of the first aspect, the light shielding plate is reflected by the surface of the light shielding plate. There is an effect that light can be emitted in a desired direction.

According to a sixth aspect of the present invention, in the LED array head, the pitch of the sawtooth cross section of the light shielding plate is made finer as it is farther from the LED array chip which is the light source.
In addition to the effect common to the LED array head of, the light flux is guided so that it repeats reflection toward the inner part of the groove between the sawtooths even for light fluxes with a small incident angle (those that reflect at a location far from the light emitting source) There is an effect that harmful light can be attenuated.

In the LED array head of claim 7, the groove depth of the saw-toothed cross-section of the light shielding plate is made deeper as it goes farther from the LED array chip which is the light source. Therefore, the LED array head of claim 5 or 6 In addition to the effect common to the above, in particular, even in a short optical arrangement from the light source to the lens, the luminous flux is guided so as to repeat reflection toward the inner part of the groove between the sawtooths according to the incident angle, and attenuates harmful light. There is an effect that can be.

In the LED array head of claim 8, since the matte black paint is applied to the surface of the light shielding plate, the reflectance of the light shielding plate is reduced and the surface of the light shielding plate is reduced in addition to the common effects described above. The intensity of the reflected light can be reduced, and it is possible to prevent the reflected light from being reflected by another optical component to generate ghost light.

In the LED array head of the ninth aspect, since the light shield plate and the lens array are integrally molded from the same plastic material, the number of parts is reduced and the parts cost and the assembly cost are reduced in addition to the above-mentioned common effects. There is an effect that can be done.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an LED array head according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a light shield plate of an LED array head according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a light shield plate of an LED array head according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a light shield plate of an LED array head according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view showing a light shield plate of an LED array head according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view showing a light shield plate of an LED array head according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view showing a light shield plate of an LED array head according to a seventh embodiment of the present invention.

FIG. 8 is an LED according to fourth to seventh embodiments of the present invention.
It is sectional drawing which shows the modification of the sawtooth shape of the light-shielding plate of an array head.

FIG. 9 is a sectional view showing a conventional LED array head.

[Explanation of symbols]

 1, 4, 8, 10, 14, 16, 17, 24 Light shielding plate 2, 3, 7, 9, 11, 15, 28, 29 Light flux 12 ... 12-n, 12-n + 1 Sawtooth 13 Between sawtooths Groove 20 LED element 21 LED array chip 22 Lens element 23 Lens array 25 Light emitting surface 26 Image plane 27 Optical axis S, S ′ Surface of groove between saw teeth

Claims (9)

[Claims] 1. An LED array head comprising an LED array chip having a plurality of light emitting diode elements arranged therein and a lens array having a plurality of lens elements arranged therein, wherein a light shielding plate is provided between the respective lens elements. An LED array head, wherein the LED array head is provided with unevenness for preventing light reflected by the surface of the light shield plate from entering the lens element. 2. The LED array head according to claim 1, wherein the light shielding plate has a triangular cross-section and the irregularities are formed. 3. The LED array head according to claim 1, wherein the light-shielding plate has a comb-shaped cross section to form the irregularities. 4. The LED array head according to claim 1, wherein the light shielding plate has a curvilinear cross-sectional shape to form the irregularities. 5. The L according to claim 1, wherein the light shielding plate has a saw-toothed cross section to form the unevenness.
ED array head. 6. The pitch of the sawtooth cross-sectional shape is set to the LE.
6. The LED array head according to claim 5, wherein the farther from the D array chip, the finer the size. 7. The groove depth of the sawtooth cross section is set to the LE.
7. The LED array head according to claim 5, wherein the farther from the D array chip, the deeper the LED array head. 8. The LED array head according to claim 1, wherein a matte black paint is applied on the surface of the light shielding plate. 9. The LED array head according to claim 1, wherein the light shielding plate and the lens array are integrally molded of the same plastic material.