JPH0879448A - Optical device - Google Patents

Abstract

PURPOSE: To provide an optical device with which no nonuniformity is generated in moving speed even with any magnification and further high-speed reading is enabled by suitably switching the inertia speed of a scanner corresponding to a variable power rate (the moving speed of each scanner). CONSTITUTION: A disk 33 for inertia application provided with fixed weight and outer diameter is integrated with the output shaft of a clutch 31. The disk 33 is constituted to apply proper inertia force to an optical device 1 only when the clutch is turned on by properly setting its weight and outer diameter or the like. When the clutch 31 is turned on, drive power from a motor 15 is transmitted through a gear to the disk 33 so that the increase of inertia can be performed to the optical device 1. Generally, when setting the variable power rate on the enlarged side, it is preferable to turn on the clutch 31 and to increase inertia, but when setting it on the reduced side, it is preferable to turn it off. Especially, by intensively enlarging inertia conditions on the enlarged side, the generation of speed nonuniformity can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an optical device used in an image reading device used in an image forming apparatus such as a copying machine, and more particularly to an improvement in a driving device for a scanner constituting the optical device.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic process such as a copying machine, a printer, a facsimile machine, a document surface fixed on a contact glass is scanned by using an optical device arranged directly under the contact glass. Thus, the reflected light of the original is obtained, and the reflected light of the original is applied to the photoconductor or guided to the reading unit such as CCD. The above optical device has a first scanner having a light source and a mirror, and a first scanner having another mirror for guiding the light emitted from the light source, reflected by an original, and guided by the mirror to the photoconductor or CCD. It is equipped with two scanners and a drive mechanism for driving each scanner. A DC servo motor is often used as a drive source that constitutes the drive mechanism, but this type of motor has uneven rotation loads due to the influence of magnetic force. In particular, since recent image forming apparatuses are required to operate at high speed and have a wide zoom range, it is necessary to increase the motor power. As a result, the magnetic force generated from the motor increases and the above-mentioned rotational load unevenness occurs. It tends to increase more and more. At the time of reading an image by the optical device, each scanner needs to move at a constant speed, and therefore a motor for driving the scanner is required to rotate at a constant speed. The increase in the rotational load unevenness in the motor as described above causes an increase in the speed unevenness of each scanner driven by the motor (an increase in the amount of speed fluctuation), resulting in deterioration of image quality.

The influence of the rotational load unevenness of the motor on the scanner to be driven decreases as the inertia when the scanner moves increases and the driving force of the motor increases. However, when the inertia of the scanner increases, the power of the motor increases. And the time required for the speed of the scanner to rise increases. In other words, as the scaling ratio decreases, the moving speed of the optical member during image formation increases, so the driving force of the motor decreases and it is less affected by the rotational load unevenness of the motor, but the scaling ratio increases. Since the moving speed of the optical member at the time of forming an image becomes smaller, the driving force of the motor becomes smaller, and as a result, the rotational load of the motor becomes more likely to be affected.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and it is possible to change the magnification in accordance with the difference in magnification (moving speed of each scanner).
An object of the present invention is to provide an optical device capable of performing high-speed reading without unevenness in the moving speed at any magnification by appropriately switching the inertial speed of the scanner. In addition, the purpose is to reduce the occurrence of speed unevenness by intentionally increasing the inertial condition, especially on the enlargement side.

[0005]

To achieve the above object, the present invention is a slit exposure type optical device which obtains reflected light from an original by moving the scanner along a fixed original surface, and the moving speed of the scanner. In which the original is magnified by changing the desired magnification, an inertia changing means for changing the inertia of the optical member according to the magnification is provided, and when the magnification is set to the enlargement side, It is characterized in that the inertia of the scanner when the scanner is moved is made larger than that on the reduction side.

The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings. FIG. 1 is a diagram illustrating the overall configuration of an example of an electrophotographic image forming apparatus using the optical device of the present invention, and FIG.
FIG. 3 is a perspective view showing the overall configuration of an embodiment of the optical device of the present invention, and FIG. FIG. 1 is a structural explanatory view of an example of an image forming apparatus to which the optical device of the present invention is applied. The optical device 1 includes a contact glass 2
The image information read by scanning the document on the contact glass 2 by the optical device 1 is imaged on the reading plate 3 composed of a CCD. The image information photoelectrically converted by the CCD is input to the image processing unit after being A / D converted, and is output from the writing device 4 to the photoconductor 5 after being subjected to predetermined processing such as scaling. Photoconductor 5
Since the configuration and operation of the electrophotographic image forming unit centering on (1) are well known, description thereof will be omitted.

FIG. 2 is a perspective view of a slit exposure type optical apparatus 1. The optical apparatus 1 is supported by a guide 10 on the main body of the image forming apparatus so that the first scanner 11 can be moved forward and backward in the scanning direction indicated by the arrow. And a second scanner 12, each of which is connected to a wire (or belt) 14 supported by a pulley 13, respectively.
The wire 14 is wound around a drive pulley 16 whose shaft center is fixed to an output shaft 15a of a motor 15 such as a DC servo motor fixed at a predetermined position, so that the drive pulley 16
Drive power of both scanners 11 and 12 to speeds V and V, respectively.
Press / 2 to move back and forth in the direction of the arrow.

The first scanner 11 has a light source 20 and a first mirror 21, and the second scanner 12 has second and third mirrors 22 and 23. The light emitted from the light source 20 to the original on the contact glass is input to the reading plate 3 via the mirrors 21, 22, and 23. The first scanner 11 is fixed to a proper position 14A of the wire 14, and the second scanner 12 is wrapped around the pulley 13A with the wire 14 folded back. Therefore, the first scanner 11 moves by the amount of the wire fed out, and the second scanner 11 moves by half the distance.

The belt 14 moves the first scanner 11 at a speed V
And the second scanner 12 is moved in the same direction at the speed V / 2 in the same direction, and the rotation with the motor 15 realizes the movement having the above speed difference. By changing the moving speed of the optical device 1, a predetermined scaling factor can be obtained. That is, when the linear velocity of the photosensitive drum 5 during rotation is V ₀ and the scaling factor is M, M = V ₀ /
V, and it becomes possible to continuously set the scaling factor by continuously changing the speed V of the first scanner.

In FIG. 2, the output shaft 15a of the motor 15
The drive pulley 16 has its shaft center fixed, while the output shaft 15a has a gear 30 further shaft fixed. The gear 30 meshes with a clutch-side input gear 32 whose shaft center is fixed to an input shaft of an adjacently disposed clutch 31, and the output shaft of the clutch 31 has a constant weight.
An inertia imparting disk 33 having an outer diameter is integrated. The driving force from the motor is not transmitted to the disk 33 when the clutch is turned off, but is transmitted when the clutch is turned on. The disc 33 is configured to give a proper inertial force to the optical device 1 only when the clutch is turned on by appropriately setting its weight, outer diameter and the like. The gear 30, the gear 32, the clutch 31, and the disc 33 constitute inertia changing means.

In the above structure, the clutch 31 is turned off.
When set to, the driving force of the motor is transmitted only to the driving pulley, the gear 32 idles, the disk 33 does not rotate, and inertia is not applied to the optical device 1 (scanners 11 and 12). On the other hand, when the clutch 31 is turned on, the driving force from the motor 15 is applied to the gears 30, 3
Since it is transmitted to the disk 33 via 2, the inertia is increased for the optical device. In general, it is preferable to turn on the clutch to increase the inertia when setting the scaling factor to the enlargement side, and to turn off the clutch when setting the scaling factor to the reduction side. Although FIG. 1 shows an image forming apparatus of the type that guides the reflected light of the original to the CCD, the optical device of the present invention is not limited to the analog type in which the reflected light of the original is directly projected onto the photosensitive member, but also the image forming unit. It can also be applied to a simple image reading device that does not have it.

[0012]

By properly switching the inertial speed of the scanner according to the difference in magnification (moving speed of each scanner), there is no unevenness in moving speed at any magnification, and high-speed reading is possible. The occurrence of speed unevenness can be reduced by intentionally increasing the inertial condition, especially on the enlargement side.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of an example of an image forming apparatus to which an optical device of the present invention is applied.

FIG. 2 is a diagram illustrating the overall configuration of an embodiment of the optical device of the present invention.

FIG. 3 is an explanatory diagram of a main part configuration of FIG. 3;

[Explanation of symbols]

1 optical device, 2 contact glass, 3 reading plate,
4 writing device, 5 photoconductor, 10 guide, 11 first scanner, 12 second scanner, 13 pulley, 14
Wire, 15 motor, 15a output shaft, 16 drive pulley, 20 light source, 21 first mirror, 22, 23
Second and third mirrors, 30 gears, 31 clutches, 32
Gears, 33 discs,

Claims (2)

[Claims] 1. A slit exposure type optical device that obtains reflected light from a document by moving the scanner along a fixed surface of the document, and changing the moving speed of the scanner to change the document as desired. What is claimed is: 1. An optical device which is variable in magnification and which includes an inertia changing means for changing the inertia of an optical member according to the variable magnification. 2. When the magnification is set to the enlargement side,
The optical device according to claim 1, wherein the inertia of the scanner when the scanner is moved is made larger than that on the reduction side.