JPS6067920A - Beam diameter controller for laser beam printer - Google Patents

Abstract

PURPOSE:To stabilize picture quality without any increase in cost by moving a plastic lens in a predtermined direction by a specific value, and calculating the proper amount of displacement of the plastic lens from the variation in beam diameter about the movement point. CONSTITUTION:A laser beam 3 before being modulated with a video signal X is incident to a CCD9 near a no-image area on a photosensitive body 8 and the CCD9 outputs a beam diameter signal D1 corresponding to the beam diameter of the laser beam 3 perpendicular to a deflection direction. Then, a collimator lens 5 is moved along an optical axis toward a rotary polygon mirror 6 by the specificl value, and when the CCD9 is irradiated with the next laser beam 3, a beam diameter signal D2 corresponding to the beam diameter is detected and a control part 11 performs arithmetic D1-D2. The control part 11 compares the arithmetic result with a beam diameter signal DC corresponding to a specific beam diameter and a moving device 10 moves the collimator lens 5 to correct the laser beam diameter to the specific beam diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a beam diameter control device for a laser beam printer, which has a simple configuration and stabilizes image quality without leading to cost storage and maintenance.

[Prior art]

Compared to glass lenses, plastic and cremmet lenses have advantages such as ease of manufacturing aspherical surfaces and low cost, but on the other hand, when environmental changes (changes in temperature and humidity) occur, the shape changes and the refractive index changes. Because of these characteristics, when Plasti and Kurenme are used in laser beam printers,
The laser beam diameter changes due to environmental changes, and as a result,
The disadvantage is that the image quality deteriorates.

Therefore, when applying plasti and cremme to a laser beam printer, it is possible to provide a means to detect the beam diameter and move the lens along the optical axis according to the result, but it is possible to simply detect the beam diameter. It is not possible to determine the direction in which the knife/zu should be moved. Therefore, in order to detect the beam diameter and determine the direction of movement of the lens, conventional methods were as shown in Figure 1 (A).
As shown in (b), a combination of a cylinder lens l and a light reception detection section 2 having four divided light amount detection elements 2a to 2d is used, and a laser beam 3 is transmitted to the light amount detection section 2 through the cylinder lens 1. There is a device that detects the output from each of the light amount detection elements 26 to 2d when the light is incident on the light, calculates the shift in the focal position from the detected value, and moves the lens according to the result. In this device, it is possible to determine not only the amount of movement of the lens but also the direction of movement by the above calculation.

However, with conventional beam diameter control devices, it is necessary to provide a cylinder lens in front of the light amount detection section, which complicates the device configuration and increases costs. As shown in FIG. 1 (b), it is necessary to set the beam diameter signal values of the major axis and minor axis U' of the laser beam in advance, which has the disadvantage that initial setting is difficult.

[Objective and Structure of the Invention] The present invention has been made in view of the above, and in order to stabilize the image quality with a simple structure and without leading to an increase in cost, the present invention has been made in order to stabilize the image quality without increasing the cost. based on the change in beam diameter before and after the movement,
The present invention provides a beam diameter control device for a laser beam printer that calculates an appropriate amount of displacement of a sharpening.

〔Example〕

Hereinafter, a beam diameter control device for a laser beam printer according to the present invention will be explained in detail.

FIG. 2 shows an embodiment of the present invention, which includes a semiconductor laser 4 as a laser beam generator, a collimator lens 5 that makes the laser beam 3 generated from the semiconductor laser 4 into a parallel beam,
Rotating polygon mirror 6 rotating clockwise to deflect a parallel beam
, Fθ that corrects the scanning speed of the deflected laser beam 3
A lens 7, a photoconductor 8 that forms an electrostatic latent image based on the laser beam 3, and an fcCO disposed in a non-image area near the photoconductor 8.
D9, and a moving device 10 that moves the position of the collimator lens along the optical axis, and the movement of the moving device 10 is controlled by a control unit (e.g., microcomputer) 11 via a drive circuit 12f. controlled by Note that the collimator lens 3 and Fθ lens 7 described above are made of plastic.

In the above configuration, the operation will be explained as follows using the flowchart shown in FIG.

Laser beam 3 turned on and off by video signal X
is generated by the semiconductor laser 4, made parallel to the collimator lens 5, and then reflected by the rotating polygon mirror 6.
An image is formed on the photoreceptor 8 via the Fθ lens 7f. On the other hand, before the laser beam 3 is modulated by the video signal
It is placed near the non-image area of the photoreceptor 8 and enters the 90OD 9, which outputs a beam diameter signal (DI) corresponding to the beam diameter in the direction perpendicular to the deflection direction of the laser beam 3.

Next, the collimating lens 5 is moved i'++ along the optical axis in the direction of the rotating polygon mirror 6 by a specified value, and when the next laser beam 3 is irradiated with OOD 9''Ir, a beam diameter signal ( Ds ) is detected and the control unit 11 calculates Shiver-D!.The control unit 11 generates a beam diameter signal (
Do), the drive circuit 12 is set so that C=1)c.
The laser beam diameter is corrected to the specified beam diameter by using the moving device 10 to move the 5ft collimator lens along the optical axis to correct the laser beam diameter to the specified beam diameter. .

The start button of the laser beam printer is turned on, and the print operation f is started. Block 13 then detects the beam diameter signal (Dt)' corresponding to the beam diameter (Pro 14). Next, the collimator lens 5 is moved along the optical axis by a specified value in the direction of the plate mirror 6 (block 15).
, beam diameter signal (Di)m corresponding to the beam diameter at that time
( )' y116 ), DI-D2 is calculated (block 17). If the operation result is greater than zero, then Dllll
: Compare with the specified beam diameter signal DC (block 18), and if the value is positive, move the collimator lens 5 in the direction of the rotating polygon mirror 6 so that DI=D. For example, the collimator lens 5 is moved in the direction of the semiconductor laser 4 so that DI=DC (block 2
0). Also, if the calculation result of %DI-Dl is less than zero, D2 is similarly compared with the specified beam diameter signal DC and block 2
1) If the value is positive, move the collimator lens 5 in the direction of the semiconductor laser 4 so that DI = Dc. 22) If the value is negative, move the collimator lens 5 so that DI = DC. The collimator lens 5t moves in the direction of the rotating polygon mirror 6 (Pro 23). Of course, if the diameter is the same as the specified beam diameter signal DC, the collimator lens is not moved.

In addition, in the 70-chart in Figure 3, the 8-include calculation is performed first, but the comparison between Crow and DC may be performed before the calculation of DI + D2, and the comparison between D2 and DC may be performed instead. Shi, Ha and DC
You can also compare.

Furthermore, since the movement of the collimator lens 5 is performed in a non-image area, it does not adversely affect the image quality.

In the above embodiment, the laser beam diameter was controlled by moving the collimator lens 5, but the same effect can be obtained by moving the Fθ lens 7 instead of the collimator lens 50 or together with the collimator lens.

〔Effect of the invention〕

As described above, according to the beam diameter control device for a laser beam printer according to the present invention, the plastic lens is moved by a specified amount in a predetermined direction, and the appropriate displacement amount of the plastic lens is determined based on the change in the beam diameter before and after the movement. is calculated, the configuration is simple and image quality can be stabilized without increasing costs.

[Brief explanation of the drawing]

FIG. 1 shows the entire conventional beam diameter detection device in a laser beam printer, (A) is a schematic explanatory diagram thereof, and (←) is a front view of a light amount detection element. FIG. 2 is a schematic configuration diagram of a beam diameter control device for a laser beam printer showing an embodiment of the present invention, and a block diagram of its control system. FIG. 3 is a flowchart showing the processing operation of the beam diameter control device for the laser beam printer of the present invention. Explanation of symbols 1... Cylinder lens, 2... Light amount detection element, 3...
...Laser beam, 4...Semiconductor laser, 5...Collimator lens, 6...Rotating polygon mirror, 7...Fθ lens, 8...Photoconductor, 9...00D110...Movement Device, 11...control unit, 12...drive circuit,
X...Video signal. Figure 1 (A) (Rono

Claims (1)

[Claims] A beam diameter control device for a laser beam printer that forms an electrostatic latent image on a photoreceptor through an optical system having a plastic lens based on a laser beam, and obtains an image by visualizing the latent image. , a detection means disposed in a non-image area near the photoconductor and outputting a beam diameter signal according to a diameter of the laser beam based on a change in shape of the plastic lens; and at least one of the plastic lenses. control means for moving the lens by a specified amount in a predetermined direction and calculating an appropriate displacement amount of the plastic lens based on a change in beam diameter before and after the movement; A beam diameter control device for a laser beam printer, characterized in that it includes a moving means for moving a lens.