JPH01200218A - Optical plotting device - Google Patents

Abstract

PURPOSE:To correct the distortion of plotting at low cost without using an expensive f.theta lens as an image-formation lens by providing a plotting distortion correction circuit and expanding and contracting the data of plotting so that the variation of scanning speed can be corrected. CONSTITUTION:Image data which is plotted is read in a data processing part 11 from the outside. When the data processing part 11 sequentially transmits the read data to a converter 12 the converter 12 converts the transmitted data into raster data and outputs it to the plotting distortion correction circuit 13. The plotting distortion correction circuit 13 corrects the inputted raster data to be 2wt/tan(2wt) fold one in a main scanning direction and outputs signal data synchronizing with a fundamental frequency to an optical modulator 14. Laser light 20 emitted from a laser oscillator 10 is modulated in the optical modulator 14 is deflected with fine angle in a light deflecting unit 15 in order to correct the surface tilt of a polygonal mirror 16. The laser beam reflected on the polygonal mirror 16 passes through the image-formation lens 17 and is formed into an image on a photosensitive drum 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical drawing device, and particularly to an optical drawing device having means for correcting the scanning speed of light.

[Conventional technology]

As a conventional technique, for example, the magazine "Electronic Materials" 1986
As shown on pages 104 to 108 of the October issue, f
- There is an optical drawing device that has a θ lens system.

A conventional optical drawing device will be described in detail with reference to the drawings.

FIG. 3 is a perspective view showing an example of a conventional optical drawing device.

The light from the light source 1 is modulated by the optical modulator 2, deflected by a small angle by the optical deflector 3 to correct the surface tilt of the rotating polygon mirror 4, main-scanned by the rotation of the rotating polygon mirror 4, and then sent to the imaging lens 5. passes through and forms an image on the photoreceptor drum 6. At this time, the photosensitive drum 6 is rotationally driven by the motor 7 to perform sub-scanning and record on a two-dimensional plane. Generally, when scanning is performed with a rotating polygon mirror, variations in scanning speed occur on the surface to be scanned. In a conventional optical drawing device, a special lens called an f/θ lens is used as an imaging lens to correct fluctuations in scanning speed.

Next, this correction method will be explained with reference to the drawings.

FIG. 4 shows the angle of incidence of light on the rotating polygon mirror 21 and the surface to be scanned 23.
The relationship with the scanning position above is shown in Figure 3. When a general single lens is used as the imaging lens 22, y = f 6tan θ, θ = 2wt where y = scanning position, f = focal point Distance, θ - angle of fire.

W-angular velocity of the rotating polygon mirror, 1=time, V-scanning speed, where the scanning speed V becomes faster at both ends of the main scanning line and the image is distorted.

In FIG. 4, when an f·θ lens is used as the imaging lens, y=f·θ 0 =2wt, and in this case, the scanning speed V is constant regardless of the incident angle, and no drawing distortion occurs.

[Problem that the invention seeks to solve]

The above-described conventional optical drawing apparatus uses a special lens called an f/theta lens as an imaging lens in order to correct scanning speed fluctuations, and is therefore expensive.

In particular, when drawing large areas, it is necessary to increase the size of the f/θ lens in order to widen the main scanning range, but in this case it is extremely difficult to manufacture the f/θ lens, and even if it is possible, it will be extremely difficult to manufacture. The drawback was that it was expensive.

[Means for solving problems]

The optical drawing device of the present invention includes a light source, a main scanning means for scanning a surface to be scanned using a rotating polygon mirror as scanning light using light emitted from the light source, and a surface to be scanned in a direction perpendicular to the main scanning direction. a data processing device that externally reads image data to be drawn on the scanned surface, a converter that inputs the image data output from the data processing device and converts it into raster data, and the converter. A drawing distortion correction circuit corrects actual drawing distortion of the image data due to scanning speed fluctuations on the scanned surface, and the data output from the drawing distortion correction circuit modulates light. and an imaging lens that forms an image of the light scanned by the rotation of the rotating polygon mirror on the scanned surface.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention.

The optical drawing apparatus shown in FIG. 1 inputs a laser oscillator 10, a laser beam 20 emitted from a laser oscillator 0, a data processing section 11 that reads drawing data, and data output from the data processing section 11. The converter 12 converts into raster data and the data output from the converter 12 is input, and 2wt/tan (2wt
) Drawing distortion correction circuit 1 that corrects the raster data area by twice as much
3, an optical converter B1 unit 14 that adjusts the laser beam by 2 Otv according to the data output from the drawing distortion correction circuit 13, a rotating polygon @ 16 for performing main scanning, and a rotating polygon @ 16 for correcting the surface tilt of the rotating polygon mirror 16. An optical deflector 15, an imaging lens 17 for forming an image of the laser beam main-scanned by the rotating polygonal mirror 16 onto the photoreceptor drum 18, and an F5+ scanning direction for the photoreceptor drum 18 in a direction perpendicular to the main scanning direction. It is configured to include a motor 19 that rotates in the direction.

The data processing unit 11 reads image data to be drawn from outside. The data processing unit 11 sequentially sends the read data to the converter 12. The converter 12 converts the sent data into raster data and outputs it to the drawing distortion correction circuit 13.

In the drawing distortion correction circuit 13, the manually generated raster data is
Correct by t/tan (2wt) times.

The data correction method by the drawing distortion correction circuit 13 is shown in FIG.
) to (d).

FIG. 2(a) shows a basic clock pulse train that determines on/off timing based on raster data.

FIG. 2(b) shows on/off signals based on raster data output from the converter 12. Figure 2 (c) shows that N, m, and n shown in Figure 2 (bl) are each 2 wt/lan.
(2wt) times the signal. Figure 2(d) is shown in Figure 2(d).
c) of the signal ρ1. This shows a signal obtained by truncating one period or less of the fundamental frequency of ml and n4 and synchronizing it with the fundamental frequency.

The drawing distortion correction circuit 13 inputs the data shown in FIG. 2(b), performs correction, and outputs the data shown in FIG. 2(d) to the optical modulator 14.

A laser beam 20 emitted from a laser oscillator 10 is modulated by an optical modulator 14 and deflected by a small angle by an optical deflector 15 to correct the surface tilt of a rotating polygon mirror 16.

The laser beam 20 reflected by the rotating polygon mirror 16 passes through the imaging lens 17 and forms an image on the photoreceptor drum 18 . At this time, the laser beam 20 is main scanned by rotating the rotating polygon ψ16,
The photosensitive drum 18 is driven by the motor 19 to perform sub-scanning.

〔Effect of the invention〕

Instead of correcting scanning speed fluctuations by using an f/θ lens as an imaging lens, the optical drawing device P of the present invention is provided with a writing distortion correction circuit to expand drawing data so as to correct scanning speed fluctuations. By shortening, the cost can be reduced because drawing distortion is corrected.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG. 2 (at
-(d) are the time charts of FIG. 1, FIG. 3 is a perspective view showing a conventional example, and FIG. 4 is an optical path diagram of FIG. 3. 1.10... Laser oscillator, 2.14...
...Light modulator, 3.15...Light deflector, 4.1
6... Rotating polygon mirror, 5°17... Imaging lens, 6.18... Photosensitive drum, 7.19
... Motor, 11 ... Data processing device, 12 ... Converter, 13 ... Drawing distortion correction circuit. Representative Patent Attorney Uchihara Volume 17 1 : ; : (i)

Claims (1)

[Claims] a light source, a main scanning means for scanning a surface to be scanned using a rotating polygon mirror as scanning light emitted from the light source, and a sub-scanning means for driving the surface to be scanned in a direction perpendicular to the main scanning direction; a data processing device that externally reads image data to be drawn on the scanned surface; a converter that inputs the image data output from the data processing device and converts it into raster data; and inputs the raster data output from the converter. a drawing distortion correction circuit that corrects actual drawing distortion of image data due to scanning speed fluctuations on the scanned surface; a light modulation element that modulates light according to data output from the drawing distortion correction circuit; An optical drawing device comprising: an imaging lens that forms an image of light scanned by rotation of a polygon mirror on the surface to be scanned.