JP2001315380A - Rod lens array and image forming apparatus using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rod lens array and an image forming apparatus using the same capable of obtaining a high quality image with less density variation even in an intermediate tone and with less fog variation due to a flare light. SOLUTION: A rod lens array 10 comprises a plurality of rod lenses 1 arranged in an array, an opaque material 4 for fixing the rod lenses with which the gaps among the rod lenses are filled and a side plate 5 for urging the side faces of the rod lenses in the arrangement direction. Surfaces of the peripheries of the rod lenses are coated with a material having a characteristic of absorbing near infrared radiation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rod lens array and an image forming apparatus using the same, and more particularly to recording near-infrared light (light source image) emitted from a light emitting means (optical dot array) in accordance with an image signal. This is suitable for an optical printer head and an optical printer using the optical printer head, for example, which form an image on a photosensitive member surface as a medium with high precision.

[0002]

2. Description of the Related Art Conventionally, a gradient index rod lens array is called an erecting equal-magnification imaging element, and has been widely used as a small-sized copying apparatus or image reading apparatus. Here, in the method of manufacturing an erecting unit-magnification imaging element, only the part related to the present invention will be briefly described with reference to FIG.

FIG. 3 is an explanatory view of a part of a method of manufacturing the rod lens array 30. In FIG.
1. A surface 31 around a rod lens 31 which is subjected to ion exchange in the radial direction and has a predetermined refractive index distribution inside.
A coating (acrylic black coating) 32 is performed on a with a black paint containing acrylic for preventing flare light. This is assembled in a dense structure, fixed with side plates 35 provided in the array direction, filled with black resin 34 in the gap, fixed, and then cut out to an optimal length for erecting a 1x image. I do.

In general, this dense structure has two rows of straws or more than one row in addition to one row. For the sake of simplicity, the description will be made with reference to a single row diagram. FIG.
FIG. 2 is a schematic diagram of a main part of an image reading apparatus using a rod lens 31 as an erecting unity imaging element. Next, the effect of the above acrylic black coating will be described with reference to FIG.

The reading surface 38a of the document 38 and the light receiving surface 40a of the image sensor 40 serving as a reading element are configured to have an optically substantially conjugate relationship using the rod lens 31,
The original 38 is illuminated by a lighting system 39 with visible illumination light (visible light). The light flux based on the image information (projection image) of the document 38 illuminated with visible light is diffusely reflected and enters the rod lens 31. The rod surface 31 of this rod lens 31
The light beam V based on the image information of the document 38 out of the light beam incident from a forms an image on the light receiving surface 40a of the image sensor 40, whereby the image information of the document 38 is read.

At this time, in the light beam incident on the rod lens 31, there is a component which reflects on the side surface 31 a of the rod lens 31 and is reflected internally. Based luminous flux (imaging light)
Flare light that does not contribute to imaging other than V is sufficiently shielded. This makes it possible to obtain an image with high contrast. In FIG. 4, the side surface 3 of the rod lens 31 is shown.
The stop of the light beam hitting 1a schematically indicates that the light beam is blocked there.

FIG. 5 is a schematic view of a main part when an optical printer 57 is constructed by using the rod lens 31 as an erecting equal-magnification imaging element.

In FIG. 1, a light beam (light source image) emitted by a light emitting means (light dot array) 46 such as an LED which selectively emits light in accordance with an image signal is used by a rod lens 31 to precharge OPC ( An image is formed on the surface of a photosensitive drum 47 such as an organic photo conductor. Then, a latent image corresponding to the image signal is formed on the surface of the photosensitive drum 47. When the surface of the photosensitive drum 47 on which the latent image is engraved rotates clockwise (in the direction of arrow A) and reaches the location of the developing device 42, toner adheres to the surface and becomes visible on the surface of the photosensitive drum 47.

Next, the toner is transferred to a medium such as the paper 43 conveyed by the transfer unit 44, and the toner is fixed on the paper surface by the fixing unit 45 using heat or pressure, so that the paper can be printed out. I have to.

[0010]

However, usually, the light dot array 46 as the light emitting means used in the optical printer 57 is a high output type AlGaP or AlGaP having a peak wavelength around 740 nm to 780 nm.
This is an As-based LED.

FIG. 6 is an explanatory diagram showing the spectral transmittance characteristics of a black paint containing acryl. As shown in the figure,
Conventionally, it can be seen that when the imaging element (rod lens) 31 of the erect equal magnification is used under the visible light V, the flare-cutting function is sufficiently performed by the light-shielding treatment with the acrylic black paint.

However, as shown in FIG.
It can be seen that a sufficient flare-cut effect cannot be obtained for the near-infrared light IR used in No. 7 because the transmittance of the black paint containing acrylic has increased.

[0013] Therefore, as shown in FIG.
1 is the flare light IR
F caused fog unevenness, which in recent years resulted in a loss of uniformity in halftones required for high-quality printers.

The flare light IRF actually generated is emitted in a complicated meandering manner inside the rod lens 31.
In FIG. 7, for the sake of simplicity, it is expressed as if it were diffused and emerged.

Further, since the sensitivity characteristic of the photosensitive drum 47 such as an OPC has a non-linearly high sensitivity to a weak light amount, especially in a system in which the photosensitive drum such as an OPC is used in an optical printer, this fogging phenomenon occurs. Was remarkable.

According to the present invention, the surface around the rod lens is coated with a material having a property of absorbing near-infrared light,
An object of the present invention is to provide a rod lens array suitable for, for example, an optical printer and an image forming apparatus using the same, which can obtain a high-quality image with less density unevenness and less fogging due to flare light even in a half tone.

[0017]

According to a first aspect of the present invention, there is provided a rod lens array comprising a plurality of rod lenses arranged in an array and a space between the plurality of rod lenses to fix the plurality of rod lenses. In a rod lens array having an opaque substance and a side plate suppressing side surfaces in the array direction of the plurality of rod lenses, a surface around the rod lenses is coated with a material having a property of absorbing near-infrared light. It is characterized by:

According to a second aspect of the present invention, in the first aspect, the material having the property of absorbing near-infrared light is a black paint containing carbon black.

A third aspect of the present invention is characterized in that, in the first aspect of the present invention, the material having the property of absorbing near-infrared light is a black paint containing a naphthalocyanine compound.

According to a fourth aspect of the present invention, there is provided an image forming apparatus, wherein near-infrared light emitted according to an image signal from a light emitting means having a plurality of light emitting elements arranged in an array is erected on a recording medium surface by a rod lens array. In an image forming apparatus that forms an image on the recording medium surface by forming an image at the same magnification, the rod lens array includes a plurality of rod lenses arranged in an array, and is filled between the plurality of rod lenses. A material having an opaque substance for fixing a plurality of rod lenses, and a side plate having a side plate in which the side faces in the array direction of the plurality of rod lenses are suppressed, and having a characteristic of absorbing near-infrared light on a surface around the rod lenses. It is characterized by being painted in.

According to a fifth aspect of the present invention, in the fourth aspect, the light emitting means is an LED array.

According to a sixth aspect of the present invention, in the fourth aspect, the recording medium is a photosensitive member having sensitivity to near-infrared light.

According to a seventh aspect of the present invention, in the fourth aspect, the photosensitive member is an OPC (organic semiconductor).

According to an eighth aspect of the present invention, in the fourth aspect, the material having the property of absorbing near-infrared light is a black paint containing carbon black.

According to a ninth aspect of the present invention, in the fourth aspect, the material having the property of absorbing near-infrared light is a black paint containing a naphthalocyanine compound.

[0026]

[First Embodiment] FIG. 1 is a sectional view of a main part of a first embodiment when a rod lens array according to the present invention is used in an image forming apparatus such as an optical printer.

In the figure, reference numeral 27 denotes an optical printer.
Reference numeral 16 denotes an optical printer head, which includes a light emitting unit (optical dot array) 6 described later and an erecting equal-magnification rod lens array 10 as an imaging element. The light emitting means 6 is composed of an LED array in which a plurality of light emitting elements (LEDs) are arranged in an array in the main scanning direction (perpendicular to the paper). The LED array 6 according to the present embodiment emits near-infrared light IR having a peak wavelength around 740 nm to 780 nm, for example. In this specification, near-infrared light IR refers to light having a wavelength of, for example, 700 nm to 1000 nm.

An erecting equal-magnification rod lens array 10 as an image forming element includes a plurality of rod lenses 1 arranged in an array.
And an opaque substance (filled resin) 4 filled between the plurality of rod lenses 1 to fix the plurality of rod lenses 1
And a side plate 5 in which side surfaces of the plurality of rod lenses 1 in the array direction (main scanning direction) are suppressed.

In this embodiment, the surface 1a (other than the entrance surface 1b and the exit surface 1c) of the rod lens 1 is made of a material having a property of absorbing near-infrared light, for example, a black paint containing carbon black. Painting (near infrared light absorbing coating)
Three. This black paint containing carbon black is the mainstream of the oscillation wavelength of the LED for optical printers.
It has sufficient absorption characteristics for near-infrared light in the vicinity of 00 nm to 800 nm.

Reference numeral 7 denotes a photosensitive member (photosensitive drum) as a recording medium, which is made of an OPC (organic semiconductor) having flexibility in photosensitive characteristics (sensitivity, photosensitive wavelength, etc.) and has sensitivity to near-infrared light IR. ing.

In the present embodiment, a plurality of near-infrared lights (light source images) emitted from the light emitting means 6 in response to an image signal are erected by the rod lens array 10 on the photosensitive drum 7 which is charged in advance. Image at × 2. Then, a latent image corresponding to the image signal is formed on the surface of the photosensitive drum 7. When the surface of the photosensitive drum 7 on which the latent image is engraved rotates clockwise (in the direction of arrow A) and reaches the location of the developing device 12, toner is attached,
The image is visualized on the surface of the photosensitive drum 7.

Next, the toner is transferred to a medium such as the paper 13 that has been conveyed by the transfer unit 14, and the toner is fixed on the paper surface by the fixing unit 15 using heat or pressure, so that printout on paper is possible. I have to.

At this time, in this embodiment, as shown in the figure, the coating material applied to the surface 1a around the rod lens 1 so that the near-infrared light IR hitting the inner surface of the rod lens 1 does not become flare light. (Black paint containing carbon black). As a result, a high quality image with less density unevenness and less fog unevenness due to flare light is obtained even in a half tone.

In the present embodiment, a black paint containing carbon black is used as a material having the property of absorbing near-infrared light as described above. This utilizes the excellent absorption characteristics of carbon black up to infrared light, and as a commercially available product, for example, fastite (manufactured by Ohashi Chemical Industries) is widely known. As shown by the solid line A in FIG. 2, the spectral transmittance characteristics of the black paint containing carbon black have absorption characteristics over the entire wavelength range from the visible light wavelength range to the infrared light wavelength range.

As described above, in the present embodiment, the coating material applied to the surface 1a around the rod lens 1 as described above includes:
By using a black paint containing carbon black having absorption properties for near-infrared light used as a light source, as shown in FIG. This makes it possible to obtain a high-quality image with less density unevenness even in a halftone and less fog unevenness due to flare light.

It is needless to say that the rod lens array of the present embodiment can be applied to the above-described image reading apparatus using visible light as illumination light.

[Second Embodiment] Next, a second embodiment of the present invention will be described.

The present embodiment differs from the first embodiment in that the surface 1a (other than the entrance surface and the exit surface) 1a of the rod lens 1 is coated with a material having a characteristic of absorbing only near-infrared light. It is. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.

That is, in the present embodiment, the surface 1a around the rod lens 1 is coated with a black paint containing a naphthalocyanine compound as a material having a property of absorbing only near-infrared light (near-infrared light absorption). Painted). The spectral transmittance characteristics of the black paint containing the naphthalocyanine compound allow visible light to pass therethrough as shown by a broken line B in FIG. 2, but have sufficient absorption characteristics for near-infrared light IR. . Thus, similar to the first embodiment described above, sufficient measures to shield flare light from near-infrared light IR of the LED can be performed.

The characteristics of the above naphthalocyanine compound are as follows:
For example, it is disclosed in JP-A-09-263658. In this publication, a near infrared absorbing resin composition is prepared by containing a naphthalocyanine compound in a base resin.

As described above, in the present embodiment, since the surface 1a around the rod lens 1 has a sufficient absorption characteristic only for near-infrared light as described above, the LED as shown in FIG. As a result, it is possible to obtain a high-quality image with less density unevenness and less fog unevenness due to flare light even in a half tone.

In the present invention, the surface around the rod lens is painted using the above-mentioned black paint containing carbon black or black paint containing a naphthalocyanine compound, but the coating material is not limited to this. Never
70 which is the main range of oscillation wavelength of LED for optical printer
Any type may be used as long as it has sufficient absorption characteristics for near-infrared light in the range of 0 nm to 800 nm.

In the case where an AlGaAs LED array is used as the light emitting means, for example, a material capable of absorbing light up to a wavelength region near 900 nm is more preferable because there is a case where there is an auxiliary light emission having a bandwidth of the GaAs substrate. desirable.

[0044]

According to the present invention, as described above, the surface around the rod lens is coated with a material having a characteristic of absorbing near-infrared light, so that density unevenness is small even in a half tone and fog unevenness due to flare light. For example, it is possible to obtain a rod lens array suitable for an optical printer and an image forming apparatus using the same, which can obtain a high-quality image with less image quality.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the spectral transmittance of the coating material of the present invention.

FIG. 3 is an explanatory view of a part of a method for manufacturing a rod lens array.

FIG. 4 is a schematic diagram of a main part of a conventional image reading apparatus.

FIG. 5 is a schematic diagram of a main part of a conventional optical printer.

FIG. 6 is an explanatory diagram showing a spectral transmittance of a black paint containing acrylic;

FIG. 7 is a schematic diagram of a main part of an image reading apparatus showing a conventional problem.

[Explanation of symbols]

 1, 31 rod lens 3 near-infrared light absorbing coating 4, 34 opaque substance (filled resin) 5, 35 side plate 6 light emitting means 7 recording medium (photoreceptor) 10 , 30 rod lens array 16, 46 optical printer head 27, 47 optical printer 32 acrylic black coating 38 original 39 illumination system 40 image sensor 12, 42 developing unit 13 , 43 ... paper 14, 44 ... transfer unit 15, 45 ... fixing unit

Claims (9)

[Claims] 1. A plurality of rod lenses arranged in an array, an opaque substance filled between the plurality of rod lenses to fix the plurality of rod lenses, and a side surface of the plurality of rod lenses in an array direction A rod lens array comprising: a side plate in which the surface of the rod lens is suppressed; and a surface around the rod lens is coated with a material having a property of absorbing near-infrared light. 2. The rod lens array according to claim 1, wherein the material having the property of absorbing near-infrared light is a black paint containing carbon black. 3. The rod lens array according to claim 1, wherein the material having the property of absorbing near-infrared light is a black paint containing a naphthalocyanine compound. 4. A near-infrared light emitted from a light emitting means in which a plurality of light emitting elements are arranged in an array in accordance with an image signal is imaged on a recording medium surface at an equal magnification by a rod lens array, and the recording is performed. In an image forming apparatus for forming an image on a medium surface, the rod lens array includes a plurality of rod lenses arranged in an array, and an opaque member that is filled between the plurality of rod lenses to fix the plurality of rod lenses. An image, comprising: a substance; and a side plate in which side surfaces in the array direction of the plurality of rod lenses are suppressed, and a surface around the rod lenses is coated with a material having a property of absorbing near-infrared light. Forming equipment. 5. The image forming apparatus according to claim 4, wherein said light emitting means is an LED array. 6. The image forming apparatus according to claim 4, wherein said recording medium is a photosensitive member having sensitivity to near-infrared light. 7. The image forming apparatus according to claim 6, wherein the photoconductor is an OPC (organic semiconductor). 8. The image forming apparatus according to claim 4, wherein the material having the property of absorbing near-infrared light is a black paint containing carbon black. 9. The image forming apparatus according to claim 4, wherein the material having the property of absorbing near-infrared light is a black paint containing a naphthalocyanine compound.