JPH10253911A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely correct the light quantity of laser light from a laser unit. SOLUTION: A cylindrical lens 13 linearly converging the laser light Lc from a collimate lens 20 of the laser unit 12 and a light quantity correcting photodetector 22 used for correcting the light quantity of the laser light Lc are arranged on a reference base 11a of an optical box 11 with the photodiode 22 under. A glass boundary 13a reflecting the laser light Lc toward the light receiving surface 22a of the photodiode 22 is provided on the cylindrical lens 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device used in a laser printer, a digital copying machine, or the like, deflects a laser beam from a laser unit and forms an image on a photosensitive medium.

[0002]

2. Description of the Related Art In a conventional scanning optical apparatus of this type, laser light emitted from a laser unit as collimated light is condensed linearly by a cylindrical lens.
The light is deflected by the deflector, formed into a spot image on the photosensitive drum by the scanning lens, and is narrowed down optimally within the width of the photosensitive drum for scanning.

As shown in FIG. 6, in a laser unit, an edge emitting semiconductor laser chip 1 is attached to a holder 2.
The laser drive circuit 3 is held at the rear of the holder 2. A collimating lens 4 for collimating laser light L carrying information is arranged on the front side of the laser chip 1, and a photodiode for detecting laser light L ′ from the laser chip 1 on the back side of the laser chip 1. And the like are disposed. The laser chip 1 and the collimating lens 4 are fixed in a state where the optical axis and the focus are adjusted, and the light detecting element 5 is incorporated in the package.

In the laser unit configured as described above, the laser light L on the front side of the laser chip 1 becomes diffused light, exits from the window 6, and becomes the laser light Lc collimated by the collimating lens 4. On the other hand, the laser light L ′ on the back side of the laser chip 1 is detected by the light detecting element 5 and is used for an operation for maintaining a predetermined amount of light emitted from the laser chip 1, a so-called APC operation.
In this APC operation, the fact that the laser light L and the laser light L ′ change almost equivalently with respect to the laser drive current is used. Usually, the light amount is reduced immediately before the start of scanning or during the passage between pages. Adjusted.

[0005]

However, in the above-mentioned conventional example, since the light detecting element 5 is built in the laser unit or disposed on the back side of the laser chip 1, when the ambient temperature changes, A slight difference occurs in the rate of change in the amount of light between the front side laser light L and the back side laser light L ′. For this reason, there is a problem that the light amount of the laser beam L on the front side becomes uneven, and finally the spot image formed on the photosensitive medium becomes uneven in the light amount.

An object of the present invention is to solve the above-mentioned problems and to provide a scanning optical device capable of accurately adjusting the light amount from a laser unit.

[0007]

According to the present invention, there is provided a scanning optical apparatus, comprising: a laser unit for emitting laser light; and a cylindrical lens for condensing the laser light from the laser unit into a linear shape. And a deflector that deflects the laser light from the cylindrical lens, and a scanning lens that forms and scans the laser light from the deflector in an optical box. A light amount correcting light detecting element used for correcting the light amount is provided near the cylindrical lens.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a perspective view of an embodiment,
FIG. 2 is an enlarged sectional view of a main part. At a predetermined position of the optical box 11, a laser unit 12 for collimating and emitting the laser light Lc is attached. Laser unit 1
In the traveling direction of the laser light Lc emitted from the laser unit 2, a cylindrical lens 13 for condensing the laser light Lc from the laser unit 12 in a linear manner, and a polygon mirror 14 for deflecting the laser light Lc from the cylindrical lens 13
And are sequentially arranged. The polygon mirror 14 is held by a drive motor 15 and is driven to rotate at high speed.

In the traveling direction of most of the laser light Lc deflected by the polygon mirror 14, the polygon mirror 14
A scanning lens 16 for imaging and scanning a laser beam Lc from the scanning lens 16 on a photosensitive drum (not shown) and a folding mirror 17 for folding the laser beam Lc from the scanning lens 16 toward the photosensitive drum are arranged in this order. A light detection mirror 18 for detecting the laser light Lc is disposed in the traveling direction of a part of the laser light Lc deflected by the polygon mirror 14 in order to correct the deviation of the scanning start position of the laser light Lc. Laser light Lc reflected by detection mirror 18
A light detection sensor 19 is arranged in the traveling direction of the camera. These constituent members 12 to 19 are fixed to the optical box 11 within a dimensional tolerance by a reference pin or the like (not shown).

The laser unit 12 comprises a semiconductor laser chip (not shown) for diverging the laser light Lc, a collimator lens 20 for collimating the laser light Lc from the laser chip, a laser drive circuit (not shown) for driving the laser chip, and the like. . The cylindrical lens 13 is used to prevent the laser beam Lc on the photosensitive drum from being displaced in the vertical direction, that is, in the sub-scanning direction, due to a tilt error of the reflection surface of the polygon mirror 14.
The laser light Lc from 2 is compressed in the sub-scanning direction to form a linear image on the reflection surface of the polygon mirror 14. The reflection surface of the polygon mirror 14 and the surface of the photosensitive drum are conjugate in the sub-scanning direction. The scanning lens 16 narrows the laser beam Lc optimally within the width of the photosensitive drum, and scans the photosensitive drum as a spot image at a constant speed.

Here, the cylindrical lens 13 is fixed on a reference base 11 a of the optical box 11 via a photodiode 22. Inside the cylindrical lens 13, there is provided a glass interface 13 a that reflects a part of the laser light Lc from the collimating lens 20 toward the light receiving surface 22 a of the photodiode 22 at a low reflectance. The light receiving surface 22a of the photodiode 22 is an actual laser beam.
It is a portion that receives Lc, and is connected to a drive circuit for APC operation (not shown).

Glass interface 1 of cylindrical lens 13
3a is formed by laminating two glasses having different refractive indices, or forming a deposition surface on one of two glasses having the same refractive index, and then laminating these glasses. Can be formed. Further, since the outer material of the photodiode 22 is often ceramic or the like, the cylindrical lens 1
It is preferable that the photodiode 3 and the photodiode 22 are fixed in advance with an ultraviolet curing adhesive.

When assembling the thus formed cylindrical lens 13 into the optical box 11, first, the cylindrical lens 13 is mounted on the reference base 11a of the optical box 11, and the polygonal mirror is moved while moving in the optical axis direction. 14
Is adjusted so that a line image can be formed on the reflecting surface of the above. Then, the cylindrical lens 13 and the diode 22 are fixed to the reference base 11a with an ultraviolet curing adhesive or the like.

In the scanning optical device configured as described above,
The laser beam Lc from the laser unit 12 passes through the cylindrical lens 13 to form a linear image on the reflection surface of the polygon mirror 14 and is deflected by the polygon mirror 14. Most of the laser light Lc deflected by the polygon mirror 14 passes through the scanning lens 16 and is reflected by the turning mirror 17, and then forms a spot image on the surface of the photosensitive drum. A part of the laser light Lc deflected by the polygon mirror 14 is reflected by the light detection mirror 18 and enters the light detection sensor 19, and the signal from the light detection sensor 19 is used to correct the scanning start position. Is done.

A part of the laser light Lc from the laser unit 12 is applied to the glass interface 1 of the cylindrical lens 13.
The light reflected by 3a is incident on the light receiving surface 22a of the photodetector 22, and the output signal of the photodetector 22 is used for correcting the light amount of the laser light Lc by the APC drive circuit.

As described above, in the first embodiment, the photodiode 22 used for correcting the light amount of the laser light Lc from the laser unit 12 is provided on the cylindrical lens 13, so that even if the ambient temperature changes, Fluctuations in the amount of laser light Lc from the unit 12 can be suppressed to an extremely narrow range with a small number of components.

Further, since the laser light Lc incident on the photodiode 22 is compressed by the cylindrical lens 13, it is possible to improve the utilization efficiency of the amount of light incident on the photodiode 22. Furthermore, if the cylindrical lens 13 and the photodiode 22 are fixed integrally in advance, a change in the amount of laser light Lc incident on the photodiode 22 when adjusting and fixing the optical box 11 can be suppressed, and It is possible to make sure adjustment while checking the level of light quantity.

If a regulating wall (not shown) that contacts the side surface of the cylindrical lens 13 is formed in a part of the reference base 11a in parallel with the optical axis, an ultraviolet curing adhesive is applied between the cylindrical lens 13 and the regulating wall. It becomes possible to apply the ultraviolet rays to the adhesive through the cylindrical lens 13 after the application.

FIG. 3 is a perspective view of a main part of the second embodiment.
The cylindrical lens 31 is a reference base 11 a of the optical box 11.
Is placed directly on top of. Cylindrical lens 31
The glass interface 31a is inclined by 45 ° in the horizontal direction with respect to the traveling direction of the laser light Lc, and a part of the laser light Lc is reflected in the horizontal direction. Further, the light receiving surface 32a of the photodiode 32 is arranged in the reflection direction of the laser light Lc.
Is arranged.

The reference stand 11a of the optical box 11 is provided with a regulating wall 11b for regulating the lateral position orthogonal to the optical axis of the cylindrical lens 31.
The photodiode 32 and the photodiode 32 are moved in the optical axis direction along the regulating wall 11b, and are fixed to the optical box after their positions are adjusted.

The glass interface 31a of the cylindrical lens 31 can be formed in the same manner as in the first embodiment.
It is preferable to fix them in advance.

In the second embodiment, the same effects as those of the first embodiment can be obtained.
2 can be prevented from being affected by the thickness of the photodiode 32.

FIG. 4 is a perspective view of a main part of the third embodiment.
The cylindrical lens 33 is disposed directly on the reference base 11a, and a thin glass 34 is disposed on the rear side of the cylindrical lens 33 at an angle of 45 ° in the horizontal direction with respect to the traveling direction of the laser light Lc. Further, the light receiving surface 35 of the photodiode 35 is arranged in the reflection direction of the thin glass 34.
a is arranged.

At this time, it is preferable to fix one end of the thin glass 34 to the cylindrical lens 33. If a vapor deposition film or the like is provided on the incident surface of the thin glass 34 where the laser beam Lc is incident, a desired reflectance can be obtained. . The third embodiment can provide the same effects as the second embodiment.

FIG. 5 is a perspective view of a main part of the fourth embodiment.
The cylindrical lens 36 is disposed directly on the reference base 11a, and a diffraction grating 37 is provided on, for example, the back of the cylindrical lens 36. The light receiving surface 38a of the photodiode 38 is arranged in the traveling direction of the laser light Lc 'split by the diffraction grating 37. Note that the diffraction grating 37 is attached to the cylindrical lens 36 as a sheet-shaped separate body, or a photosensitive material such as a photoresist is applied to the surface of the cylindrical lens 36, and then becomes the diffraction grating 37 by another light irradiation device. In this manner, the photosensitive material is exposed, and the photosensitive material is partially peeled off.

In the fourth embodiment, the laser light Lc incident on the cylindrical lens 36
The light is transmitted as the next-order diffracted light, that is, so-called non-diffracted light, and travels in the direction calculated by the prescribed formula as the first-order or higher-order diffracted light Lc ′ and enters the photodiode 38. In the fourth embodiment, the same effect as in the second embodiment can be obtained.

Although the photodiode 22 is disposed below the cylindrical lens 13 in the first embodiment, it can be disposed above the cylindrical lens 13, and the thin glass 34 is used above the third embodiment as in the third embodiment. Alternatively, the diffraction grating 37 can be used as in the fourth embodiment.

In the first to fourth embodiments, the photodiodes 22, 32, 35, and 38 are first moved to the
a, etc., and then the cylindrical lenses 13, 3
Positions of 1, 33, 36 are photodiodes 22, 32,
Adjustment by 35 and 38 is also possible.

[0029]

As described above, in the scanning optical device according to the present invention, the light amount correcting light detecting element used for correcting the light amount of the laser light from the laser unit is provided near the cylindrical lens. Even if the environmental temperature changes, the rate of change of the light amount can be kept the same, and the light amount from the laser unit can be adjusted accurately.

[Brief description of the drawings]

FIG. 1 is a perspective view of a first embodiment.

FIG. 2 is a sectional view of a main part.

FIG. 3 is a perspective view of a main part of a second embodiment.

FIG. 4 is a perspective view of a main part of a third embodiment.

FIG. 5 is a perspective view of a main part of a fourth embodiment.

FIG. 6 is a configuration diagram of a conventional laser unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Optical box 11a Reference stand 12 Laser unit 13, 31, 33, 36 Cylindrical lens 13a, 31a Glass interface 14 Polygon mirror 16 Scanning lens 22, 32, 35, 38 Photodiode 34 Thin glass 37 Diffraction grating

Claims (7)

[Claims] 1. A laser unit for emitting laser light, a cylindrical lens for linearly condensing laser light from the laser unit, a deflector for deflecting laser light from the cylindrical lens, and A scanning lens that forms and scans the laser light in an optical box, wherein a light amount correcting light detecting element used to correct the light amount of the laser light from the laser unit is provided near the cylindrical lens. A scanning optical device, wherein the scanning optical device is provided. 2. The scanning optical device according to claim 1, wherein said light detecting element is integrated with said cylindrical lens. 3. The scanning optical device according to claim 1, further comprising a reflecting portion near the cylindrical lens for reflecting a part of the laser light toward the photodetector. 4. The scanning optical device according to claim 3, wherein the reflection section is a glass interface provided inside the cylindrical lens. 5. The scanning optical device according to claim 3, wherein the reflecting portion is a thin glass provided outside the cylindrical lens. 6. The scanning optical device according to claim 4, wherein the reflection section is a deposition surface. 7. The scanning optical device according to claim 3, wherein the reflection section is a diffraction grating provided on a side surface of the cylindrical lens.