JPH0651223A - Deflection scanning device - Google Patents

Abstract

PURPOSE:To deal with different product specifications of an image forming device by easily changing the amount of a laser beam focused onto a photoreceptor. CONSTITUTION:A laser beam L1 used in deflection scanning by means of a rotating polygon mirror 5 with its scanning speed corrected by an image focusing lens system 6 is reflected at a return mirror 7 and then applied to the photoreceptor of a rotating drum D. The intensity of the laser beam L1 is decreased to a predetermined value by means of reflection at the return mirror 7. The amount of the laser beam applied to the photoreceptor may be varied by using a return mirror of different reflectance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection scanning device used in an image forming apparatus such as a laser beam printer or a laser facsimile.

[0002]

2. Description of the Related Art A deflection scanning device used in an image forming apparatus such as a laser beam printer or a laser facsimile is disclosed in Japanese Patent Publication No. 62-36210 and U.S. Pat. No. 46390.
As disclosed in Japanese Patent Laid-Open No. 72-72, laser light emitted from a light source such as a semiconductor laser is applied to a rotary polygon mirror having a plurality of mirror surfaces through a collimator lens and a cylindrical lens, and the rotary polygon mirror is rotated. The deflected and scanned laser light is imaged on the photoconductor of the rotary drum through an imaging lens system including a spherical lens and a toric lens. The laser light imaged on the photoconductor forms an electrostatic latent image on the photoconductor by main scanning by rotation of the rotary polygon mirror and sub-scanning by rotation of the rotating drum.

On the other hand, an image forming apparatus such as a laser beam printer or a laser facsimile equipped with such a deflection scanning device has specifications (hereinafter referred to as "product specifications") such as a process speed, a writing speed and a sensitivity of a photoconductor. ), The required amount of laser light on the surface of the photoconductor differs, so that the output level can be changed by changing the amount of light on the chip surface of the semiconductor laser that is the light source of the deflection scanning device for each mounted image forming apparatus, or The amount of laser light reaching the photoconductor was adjusted by changing to a semiconductor laser having a different output, or by changing to a collimator lens having a different numerical aperture, thereby changing the coupling efficiency of the laser light. .

[0004]

However, according to the above conventional technique, as described above, when a semiconductor laser having a different output is replaced, the accompanying driver circuit must be changed, and the semiconductor laser is replaced. If the amount of light on the chip surface is changed without doing so, the output becomes unstable and the life of the semiconductor laser is shortened. Further, if a collimator lens having a different numerical aperture is used, the diameter of the point image on the photoconductor changes and the image quality also changes, so it is necessary to take measures to prevent this.

The present invention has been made in view of the above-mentioned unsolved problems of the prior art. The light amount of the laser light imaged on the photoconductor is not changed, without changing the output of the semiconductor laser or the numerical aperture of the collimator lens. It is an object of the present invention to provide a deflection scanning device which can be easily changed to meet different product specifications of image forming apparatuses.

[0006]

In order to achieve the above-mentioned object, a deflection scanning device of the present invention is a rotary polygon mirror having a plurality of mirror surfaces, and an image forming apparatus for a laser beam deflected and scanned by the rotary polygon mirror. Of at least one folding mirror having a reflectance for attenuating to a predetermined intensity based on the product spec., And it is possible to adapt to different product specifications of an image forming apparatus simply by exchanging the folding mirror. .

[0007]

The laser beam deflected and scanned by the rotary polygon mirror is reflected by the folding mirror, and is attenuated to a predetermined intensity by this, and then is irradiated onto the photoconductor. By exchanging only the folding mirror, it is possible to change the light amount of the laser beam applied to the photoconductor according to the product specifications.

[0008]

Embodiments of the present invention will be described with reference to the drawings.

[0009] Figure 1 is an explanatory view for explaining an embodiment of the present invention, the deflection scanning apparatus E includes a semiconductor laser 1 which generates a laser beam L _0, condenses the laser beam L ₀ into parallel light The collimator lens 2, the diaphragm 3 that determines the beam diameter of the condensed laser light L ₀ , and the laser light L ₀ that has passed through the diaphragm 3.
It has a cylindrical lens 4 for linearly focusing the laser beam and a rotary polygon mirror 5 for deflecting and scanning the linearly focused laser beam L ₀ .

The laser beam L ₀ deflected and scanned by the rotary polygonal mirror 5 is reflected by a folding mirror 7 through an imaging lens system 6 and forms an image on a photosensitive member (not shown) of the rotary drum D, and the rotary polygonal mirror. An electrostatic latent image is formed by the main scanning by the rotation of 5 and the sub scanning by the rotation of the rotary drum D. The rotary polygon mirror 5 is rotated at a high speed by a motor 51, and the linear laser light L ₀ emitted from the cylindrical lens 4 toward the rotary polygon mirror 5 is deflected and scanned by each mirror surface 5a to 5f. The imaging lens system 6 is composed of a spherical lens 6a and a toric lens 6b, and corrects the laser beam L ₀ deflected and scanned by the rotary polygon mirror 5 at a constant angular velocity into a laser beam L ₁ for scanning the surface of the photoconductor at a constant velocity.

A part of the laser beam L ₁ deflected and scanned by the rotary polygon mirror 5 and corrected by the imaging lens system 6 is reflected by the detection mirror 8 and is incident on the sensor 9, where the scanning is started. Converted to a signal.

The folding mirror 7 attenuates the intensity of the laser light L ₁ by reflecting it. Therefore, by using a folding mirror with different reflectance according to the product specifications,
It is possible to change the amount of laser light with which the photoconductor is irradiated. That is, the amount of laser light required on the surface of the photoconductor is calculated based on the product specifications such as the process speed, the writing density and the sensitivity of the photoconductor of the laser beam printer or the laser facsimile equipped with the deflection scanning device E, and The reflectance of the folding mirror is calculated from the ratio to the light amount of the laser light that reaches the photoconductor without being reflected by the folding mirror, and the folding mirror 7 having the calculated reflectance is created and assembled in the deflection scanning device. wear. This deflection scanning device is common except for the mirror 7 even if the product specifications change.

Therefore, the light quantity of the laser light imaged on the photosensitive member can be easily changed only by exchanging the folding mirror according to the specifications of the apparatus equipped with the deflection scanning apparatus E. By exchanging only the folding mirror in this way, it is possible to deal with image forming apparatuses having different product specifications with a single deflection scanning apparatus without exchanging the rest of the semiconductor laser, the imaging lens system and the like. Especially when changing the light quantity of the laser light by a factor of 1.5 or more, compared with the method of changing the output of the semiconductor laser, exchanging the different output with the semiconductor laser, or changing the numerical aperture of the imaging lens system. Can be adjusted much more easily and with high precision.

If a single folding mirror having a predetermined reflectance cannot be manufactured, a plurality of folding mirrors may be used in combination.

A specific example will be described below.

Concrete Example 1 Two laser beam printers P1 and P having specifications shown in Table 1
2 is equipped with a deflection scanning device manufactured in the same manner except for the folding mirror. Both laser beam printers P1 and P
Although the writing density of 2 and the sensitivity of the photoconductor are the same, the required amount of laser light on the surface of the photoconductor is a ratio of 1: 2 because the process speeds are different. Therefore, the reflection surface of the folding mirror of the deflection scanning device mounted on the laser beam printer P1 is made of a chromium-based multilayer film, and the reflection surface of the folding mirror of the deflection scanning device mounted on the laser beam printer P2 is a copper-based multilayer film. The reflectance of both folding mirrors is 49% and 9 respectively.
8%. This allows both laser beam printers P
The light quantity ratio of the laser light on the surface of the photoconductors 1 and P2 can be set to 1: 2.

[0017]

[Table 1] Concrete Example 2 Two laser beam printers P3, P having the specifications shown in Table 2
4 is also equipped with a deflection scanning device manufactured in the same manner except for the folding mirror. The deflection scanning device of this example uses two folding mirrors. Both laser beam printers P3 and P4 have the same process speed and the same sensitivity of the photoconductor, but since the writing densities are different, the required amount of laser light on the photoconductor surface is a ratio of 1: 0.5. . Therefore, the reflectances of the first folding mirror of each deflection scanning device are 98% and 49%, respectively.
%, The light quantity ratio of the laser light on the surface of the photoconductor of both laser beam printers P3 and P4 is set to 1: 0.5.

[0018]

[Table 2] Concrete Example 3 Three laser beam printers P5, P having the specifications shown in Table 3
6 and P7 are equipped with deflection scanning devices manufactured in the same manner except for the folding mirror. The deflection scanning device of this example uses two folding mirrors. First,
Although the two laser beam printers P5 and P6 have the same process speed and the same sensitivity of the photoconductor, the required light amount of the laser beam on the surface of the photoconductor is 1: 0.5 because the writing density is different. Becomes Therefore,
By using the first folding mirrors of the respective deflection scanning devices whose reflectances are 98% and 49%, respectively, the light quantity ratio of the laser light on the surface of the photoconductors of both laser beam printers P5 and P6 is 1: 0. Set to 5.

Next, two laser beam printers P5 and
Comparing P7, the photosensitivity of the photoconductor is the same, but the process speed and writing density are different, so the required amount of laser light on the surface of the photoconductor is 1:
The ratio is 0.25. Therefore, the first of each deflection scanning device
The reflectivity of the folding mirror is 98% and 49, respectively.
%, The reflectance of the second folding mirror is 98%, respectively.
%, 49% are used. As a result, the light quantity ratio of the laser light on the surfaces of the photoconductors of the two laser beam printers P5 and P7 can be set to 1: 0.25.

[0020]

[Table 3] The optical efficiencies shown in Tables 1 to 3 represent the proportions of the laser light emitted from the semiconductor laser that reaches the photoconductor without being reflected by the folding mirror.

[0021]

Since the present invention is configured as described above, it has the following effects.

The light quantity of the laser light imaged on the photosensitive member can be easily changed only by using folding mirrors having different reflectances without changing the output of the semiconductor laser or the numerical aperture of the collimator lens. Therefore, it is possible to easily manufacture the deflection scanning device which can freely correspond to the product specifications of different image forming apparatuses.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating an example.

[Explanation of symbols]

E Deflection / scanning device L ₀ , L ₁ Laser light D Rotating drum 1 Semiconductor laser 2 Collimator lens 3 Aperture 4 Cylindrical lens 5 Rotating polygon mirror 6 Imaging lens system 7 Folding mirror

Claims (1)

[Claims] 1. A rotary polygonal mirror having a plurality of mirror surfaces, and at least one having a reflectance for attenuating a laser beam deflected and scanned by the rotary polygonal mirror to a predetermined intensity based on the product specifications of an image forming apparatus. A deflection scanning device comprising a folding mirror, which can be adapted to different product specifications of an image forming apparatus simply by exchanging the folding mirror.