JP2002214554A - Image forming device using thin film optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device such as a laser printer having constitution by which the tolerance value of the positional deviation of an array laser being a light source can be made large. SOLUTION: In this image forming device, an image carrier 5 such as a photoreceptor drum is scanned and irradiated with a plurality of laser beams emitted from an array laser beam source 21 consisting of the array of surface light emitting lasers or end face light emitting lasers by a light deflector 3 such as a polygon mirror. The device is equipped with at least one thin film optical waveguide 100 to guide a plurality of laser beams along the surface in an optical path leading to the image carrier 5 from the light source 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an optical scanning device for scanning a plurality of light beams, a laser printer, and the like, and more particularly to a displacement of a laser beam emitted from a light source when an array laser is used as a light source. And an image forming apparatus such as a laser printer having a small size.

[0002]

2. Description of the Related Art Many laser beam printers using semiconductor lasers have been developed due to their high speed and high resolution. In particular, with the spread of personal computers in recent years, further speed-up and higher resolution of laser beam printers are desired. For this purpose, a laser beam may be scanned at a high speed. As this means, multi-beam scanning in which the rotational speed of the polygon mirror is increased, and a plurality of modulatable laser beams are simultaneously scanned in one scan, has been proposed.

Among them, there is a limit in increasing the rotation speed of the polygon mirror, and expectations for multi-beam scanning have recently been increased. As a proposal example of such a multi-beam scanning, Japanese Patent Application Laid-Open Publication No.
There is one disclosed in JP-A-5-294005. This example is shown in FIG. Semiconductor laser array 21 by current modulation
The light intensity of each laser beam is modulated, and a single polygon mirror 3 scans a plurality of laser beams simultaneously.

[0004]

However, in the multi-beam scanning, the array light source 21, the lenses 2, 4, 7 and
8. There is a problem that it is difficult to prevent the positional relationship between the polygon mirror 3 and the photosensitive drum 5 from being shifted with respect to all the beams as compared with the case where a light source that emits a single laser beam is used. .

An object of the present invention is to provide an image forming apparatus such as a laser printer having a configuration capable of increasing the allowable value of the above-mentioned positional deviation.

[0006]

An image forming apparatus such as a laser printer according to the present invention which achieves the above object comprises a plurality of laser beams emitted from an array laser light source comprising an array of surface emitting lasers and edge emitting lasers. An image forming apparatus that scans an object to be irradiated such as a photosensitive drum by scanning the object with an optical deflector such as a polygon mirror, and applies a plurality of laser beams along an in-plane light path from the light source to the object to be irradiated. And at least one thin film optical waveguide. By inserting a thin-film optical waveguide into the optical path of the laser beam, the distance between the exit surface and the arrival surface of the laser beam can be reduced, and the tolerance for the optical axis deviation of the laser beam increases, facilitating the construction of an image forming apparatus. become.

[0007] Based on the above basic configuration, the following more specific forms are possible. A thin-film optical waveguide that guides laser light along the plane, between the light source and the optical deflector,
It may be provided at at least one position between the light deflector and the irradiation object. Specific examples thereof include the following configuration. A first lens optical system (collimator lens, cylindrical lens, etc.) is provided between the light source and the optical deflector, and a first thin-film optical waveguide is provided between the light source and the first lens optical system. A first thin-film optical waveguide between the first lens optical system and the optical deflector. A second lens optical system (a toroidal lens, a scanning lens, or the like) between the optical deflector and the irradiation target; and a second thin film between the optical deflector and the second lens optical system. An optical waveguide is provided, or a second thin-film optical waveguide is provided between the second lens optical system and the irradiation object. Further, a first thin-film optical waveguide for guiding the laser light emitted from the light source, an optical deflector for scanning the laser light emitted from the first thin-film optical waveguide, and a laser emitted from the optical deflector And a second thin-film optical waveguide for guiding light to the irradiation object. Where and how long the thin-film optical waveguide is provided may be designed according to the case.

[0008] The thin film optical waveguide may be elastically deformable or have a region having a function of condensing or reflecting light therein. The region having the function of condensing or reflecting the light can be formed by having a refractive index distribution in the thin-film optical waveguide. This refractive index distribution is formed by a change in the layer thickness of the thin-film optical waveguide, or by a difference in the material or the composition of the thin-film optical waveguide. Such techniques are well-known, and these well-known techniques may be used as they are in the present invention.

[0009]

The principle of operation of the gist of the present invention will be described. Figure 5
FIG. 2 is a diagram showing a semiconductor laser array 21 and arrival points A and B of laser beams emitted from one semiconductor laser in the array. Let L be the distance between the semiconductor laser array 21 and the plane containing points A and B. When trying to propagate a laser beam from the semiconductor laser to point A, FIG.
It is assumed that the optical axes are shifted by the angles θ and φ as shown in FIG. In this case, the deviation between point A and point B is Δy = Lθ in the y direction and Δz in the z direction.
= Lφ. Then, y of the semiconductor laser array 21
Assuming that the size in the direction and the size in the z direction are Ly and Lz, respectively, the surface that the laser beam reaches
It must have a size of Ly + Δy, Lz + Δz or more in each of the z directions. This is common to all cases where functions such as light collection, reflection, and light reception are realized on a laser beam arrival surface. On the other hand, the size of the arrival surface is restricted by the size of the lens, the size of the polygon mirror, the size of the light receiving surface, and the like. Therefore, when the chip interval in the array 21 is constant, the Ly, As Lz increases, the tolerances for the displacements Δy and Δz decrease.

As described above, the positional deviations Δy, Δz (Δy =
(Lθ, Δz = Lφ) is proportional to L, so that by reducing L, the tolerance for the angle deviation θ, φ can be increased. For this purpose, a light source, lens, polygon mirror,
Although it is conceivable to reduce the distance between the light receiving surfaces and the like, there is a limit in reducing the distance due to the size of each component. Therefore, the positional relationship of the existing parts is left as it is (or the existing parts are unnecessary),
Consider a way to reduce L. The point is that the distance between the emission surface of the laser beam and the arrival surface may be reduced. Therefore, by using the thin-film optical waveguide, L becomes the distance between the thin-film optical waveguide and the light source or the distance between the thin-film optical waveguide and the polygon mirror, so that L can be easily reduced. Once the laser light is coupled into the thin-film optical waveguide, the light propagates in a state confined in the thin-film optical waveguide, so care must be taken only on the coupling between the light incident and exit surfaces of the thin-film optical waveguide and the existing components. I just need. The size of the laser array can be made sufficiently smaller than the thickness of the thin-film optical waveguide, and the thin-film optical waveguide is sufficient for the slab type (that is, there is no need to use a channel type that confine light three-dimensionally). This light coupling is easy.

Furthermore, if the thin-film optical waveguide is elastically deformable, the thin-film optical waveguide can be bent so that light can be coupled using the thin-film optical waveguide even in a place where there is not enough space, and the space is effectively utilized. You.

In addition, since the thin-film optical waveguide has a region having a function of condensing light therein, it is possible not only to efficiently couple light emitted from the thin-film optical waveguide to existing parts, This eliminates the need for existing lenses, and is expected to save space and reduce costs. Such a region having the function of condensing light can be realized by providing a refractive index distribution in the thin-film optical waveguide. For example, by changing the layer thickness in the thin film optical waveguide, the equivalent refractive index has a distribution. Further, since the refractive index depends on the material constituting the thin-film optical waveguide, the refractive index distribution is formed by changing the material or changing the composition depending on the position.

[0013]

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

FIG. 1 shows a first embodiment of the present invention.
3 is a drawing that best represents the features of the embodiment of FIG. In the figure, 2 is a collimator lens, 3 is a rotating polygon mirror (polygon mirror), 4 is a scanning lens, 5 is an image carrier (irradiated object), 6 is a spot, 7 is a cylindrical lens, 8
Is a toroidal lens, 9 is a scanning line, 11 is a reflection mirror,
12 is a photodetector, 21 is a semiconductor laser array, 100
Is a thin film optical waveguide. The same functional elements are denoted by the same reference numerals in the drawings of the embodiment of the present invention as in FIG. 6 of the conventional example.

The thin-film optical waveguide includes a simple sheet-shaped waveguide formed of a transparent resin, a substrate formed of a transparent resin on a substrate, and a substrate formed of a core layer sandwiched between clad layers on a substrate.

In the above configuration, the light source 2 × 2 (2 × 2
The laser beam emitted from the semiconductor laser array 21 may be incident on the first thin-film optical waveguide 100 having a film thickness of 100 μm (in FIG. Although the pitch is drawn large with respect to the film thickness, this pitch is sufficiently smaller than the film thickness of the thin-film optical waveguide 100). At this time, the distance between the end faces of the semiconductor laser array 21 and the first thin-film optical waveguide 100 is 1 μm, and the optical coupling loss is 3 dB. Next, the laser beam emitted from the first thin-film optical waveguide 100 is collimated by a collimator lens 2 and a cylindrical lens 7 (this is a beam that is linearly incident on the rotary polygon mirror 3, and is scanned by a scanning lens 4, a toroidal (Which constitutes a so-called surface tilt correction system together with the lens 8), and then enters the second thin-film optical waveguide 100. Then, the four laser beams that have propagated through the second thin-film optical waveguide 100 enter the rotary polygon mirror 3. These four laser beams are scanned by the rotary polygon mirror 3 at a time.

The laser beam scanned by the rotating polygon mirror 3 passes through the toroidal lens 8 and the scanning lens 4 (a thin film optical waveguide 100 may be further inserted between the rotating polygon mirror 3 and the toroidal lens 8). Third thin film optical waveguide 1
The laser beam incident on the laser beam 00 and emitted from the third thin-film optical waveguide 100 forms a spot 6 on the image carrier 5 placed on the surface to be scanned. At this time, the distance between the third thin-film optical waveguide 100 and the surface to be scanned is 10 μm.

The portion irradiated with the laser beam on the surface to be scanned loses its surface charge, and is developed by selectively electrostatically attaching toner thereto. After that, the toner is electrostatically transferred to a transfer material such as paper or an OHP sheet, and finally is fused and fixed to the transfer material by applying pressure with a roller or the like.

The reflecting mirror 11 is located at a position within the deflection range of the laser beam and not involved in scanning the surface to be scanned.
Is provided. The laser beam reflected by the reflection mirror 11 enters the photodetector 12. Then, the semiconductor laser array 21 is modulated according to data using the horizontal synchronization signal output from the photodetector 12.

The thin-film optical waveguide 100 and the lens 2,
7, 4 and the distance from the rotary polygon mirror 3 were all 1 mm.
If there is no thin film optical waveguide, the distance between the light source, the lens and the rotating polygon mirror is on the order of cm. From this,
As described in the above description, in this configuration, the length L is
As a result, the allowable value of the displacement is 50 or less.
If it is μm, the allowable value of the angle shift becomes 10 times or more. To allow a larger angle shift, the thin film optical waveguide 1
The thickness of 00 may be increased. It is possible up to the order of mm.

The thin-film optical waveguide 100 may be made of any material having a function of transmitting a laser beam, such as quartz or transparent resin.

(Second Embodiment) FIG. 2 is a drawing showing the characteristics of the second embodiment of the present invention best.
The difference is that the thin-film optical waveguide 101 is flexible.

The configuration shown in FIG. 2 is characterized in that the thin-film optical waveguide 101 between the scanning lens 4 and the image carrier 5 is bent. Thereby, the distance between the scanning lens 4 and the image carrier 5 can be shortened, and further downsizing of the laser printer is realized. Also, even if the thin film optical waveguide 1
Even if 01 is bent, the laser beam can propagate through the thin-film optical waveguide 101 with a small radiation loss at the bent portion. However, since the distance between the scanning lens 4 and the image carrier 5 is on the order of cm, the thin film optical waveguide 101
Without it, it does not contribute to the reduction of the displacement. Moreover, since the thin-film optical waveguide 101 is bent, the same-sized thin-film optical waveguide 101 is used for optical connection between various spaces.

As the material of the thin-film optical waveguide 101, any material can be used as long as it is a material having a function of transmitting a laser beam, such as a transparent resin, and has a bendable property.

(Third Embodiment) FIG. 3 is a drawing that best illustrates the features of a third embodiment of the present invention. In FIG. 3, reference numeral 102 denotes a thin-film optical waveguide including a lens portion.

The configuration of FIG. 3 differs from that of the first embodiment in that the thin-film optical waveguide 102 has a lens function. The semiconductor laser array 21 as a light source is 2 × 2
Arrangement. For this reason, the thin-film optical waveguide 102 has a laminated structure, and four beams are transmitted using one thin-film optical waveguide 102 having two layers.

Of course, it goes without saying that two thin film optical waveguides 102 may be prepared and stacked one above the other.

The lens function here is based on the thin-film optical waveguide 10.
Except for the lens area 2 (indicated by a black-painted pattern in FIG. 3), the lens areas 1, 4,
8 (reflection mirror 1
The region 1 may be set to be a light absorption region). The method of forming the layer thickness distribution in the thin-film optical waveguide 102 is not limited to etching, but may be any method such as pressure bonding and pressing.

This not only eliminates the need for a conventional lens, but also saves space previously occupied by the lens. As a result, the cost and size of the laser printer can be further reduced.

The lens region has a refractive index difference in the optical waveguide,
The dents and bulges are formed and formed. There are a geodesic lens that propagates light along the grating, and a grating lens that converges by diffracting light at a grating line.

(Fourth Embodiment) FIG. 4 is a drawing that best illustrates the features of a fourth embodiment of the present invention. In FIG. 4, reference numeral 103 denotes a thin-film optical waveguide including a lens portion.

In the configuration shown in FIG. 4, the difference from the third embodiment is a method of realizing the lens function of the thin-film optical waveguide 103. Here, a lens function was realized by using a glass substrate as a base of the thin-film optical waveguide 103 and forming a refractive index distribution by ion exchange, ion implantation, diffusion, or the like. The base material of the thin-film optical waveguide 103 is not limited to a glass substrate, but may be any material that can provide a refractive index distribution. It is also preferable that the material is flexible.

[0033]

As described above, according to the invention of the present application, in an image forming apparatus such as a laser printer using a light source composed of an array laser, an allowable value of the above-described angle shift using a thin film optical waveguide is used. Can be increased. As a result, the optical axis adjustment becomes easy. Further, the space can be effectively used, and reduction in size and cost of an image forming apparatus such as a laser printer can be expected.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an optical system according to a first embodiment of the present invention.

FIG. 2 is a perspective view illustrating an optical system according to a second embodiment of the present invention.

FIG. 3 is a perspective view illustrating an optical system according to a third embodiment of the present invention.

FIG. 4 is a perspective view illustrating an optical system according to a fourth embodiment of the present invention.

FIG. 5 is a diagram illustrating the principle of the gist of the present invention.

FIG. 6 is a perspective view illustrating a conventional example.

[Explanation of symbols]

 1: Lens 2: Collimator lens 3: Rotating polygon mirror (polygon mirror) 4: Scanning lens 5: Image carrier (irradiated object) 6: Spot 7: Cylindrical lens 8: Toroidal lens 9: Scanning line 11: Reflection mirror 12: Photodetector 21: Semiconductor laser array 100: Thin-film optical waveguide 101: Flexible thin-film optical waveguide 102, 103: Thin-film optical waveguide including a lens region

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/113 H04N 1/04 104A F-term (Reference) 2C362 AA07 AA13 AA14 AA43 AA45 AA48 BA58 BA60 BA61 BA81 DA03 2H045 AA01 BA02 BA23 BA32 CA02 CA33 CA62 2H047 LA05 LA09 NA10 RA04 5C072 AA03 CA06 DA02 HA02 HA06 HA13 XA01 XA05

Claims (16)

[Claims] An image forming apparatus for irradiating an object to be irradiated by scanning a plurality of laser beams emitted from a light source comprising an array laser with an optical deflector. An image forming apparatus comprising at least one thin-film optical waveguide for guiding the laser light along the plane. 2. The image forming apparatus according to claim 1, further comprising at least one first thin-film optical waveguide for guiding laser light along a plane between the light source and the optical deflector. 3. The apparatus according to claim 1, further comprising at least one second thin-film optical waveguide for guiding a laser beam along a plane between the light deflector and the irradiation object. Image forming device. 4. A light source comprising: a first lens optical system between the light source and the optical deflector; and the first thin film optical waveguide between the light source and the first lens optical system. The image forming apparatus according to claim 2, wherein: 5. A system according to claim 1, further comprising a first lens optical system between said light source and said optical deflector, and said first thin-film optical waveguide being provided between said first lens optical system and said optical deflector. 5. The image forming apparatus according to claim 2, wherein: 6. A second lens optical system is provided between the optical deflector and the irradiation object, and the second thin-film optical waveguide is provided between the optical deflector and the second lens optical system. An image forming apparatus according to claim 3, 4 or 5, wherein: 7. A second lens optical system is provided between the optical deflector and the irradiation object, and the second thin-film optical waveguide is provided between the second lens optical system and the irradiation object. The image forming apparatus according to claim 3, 4, 5, or 6, wherein 8. A first thin-film optical waveguide for guiding laser light emitted from the light source, an optical deflector for scanning the laser light emitted from the first thin-film optical waveguide, and an emission light from the optical deflector. The image forming apparatus according to claim 1, further comprising at least a second thin-film optical waveguide for guiding the laser light to the irradiation target. 9. An image forming apparatus according to claim 1, wherein at least one of said thin film optical waveguides is elastically deformable. 10. The image forming apparatus according to claim 1, wherein at least one of said thin film optical waveguides has a region having a function of condensing or reflecting light therein. 11. The image forming apparatus according to claim 10, wherein the region having a function of condensing or reflecting the light is formed by having a refractive index distribution in the thin-film optical waveguide. 12. An image forming apparatus according to claim 11, wherein said refractive index distribution is formed by changing a layer thickness in said thin film optical waveguide. 13. An image forming apparatus according to claim 11, wherein said refractive index distribution is formed by a difference in material or a change in composition of said thin film optical waveguide. 14. An image forming apparatus according to claim 1, wherein said array laser is an array of surface emitting lasers. 15. An image forming apparatus according to claim 1, wherein said light deflector is a polygon mirror. 16. The image forming apparatus according to claim 1, wherein the irradiation target is a photosensitive drum.