JPS5937910B2 - Optical printer scanning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical printer that prints characters and images by scanning a recording material by reflecting a modulated light beam with a reflecting mirror.

Specifically, the difference between the current position of the light beam on the recording material and the position on the recording material to be scanned is detected, and the optical deflector is controlled based on the detected value to scan a predetermined location. . By doing this, it is possible to reduce variations in data processing speed when reading text and image signals from a recording device, and also to compensate for sagging and eccentricity of the reflecting surface of the reflecting mirror, resulting in high speed processing. The present invention also aims to provide an optical printer that enables accurate image processing. In optical printers that use laser light, etc., the light beam is generally first modulated by signals such as characters or images, and then this light beam is scanned in one direction by a reflecting mirror such as a rotating polygon mirror. At the same time, the photosensitive material is moved in a direction perpendicular to the scanning direction (hereinafter referred to as X-direction scanning), or the scanning position is moved using another rotating mirror (hereinafter referred to as Y-direction scanning) to obtain the desired product. I'm trying to get it.

In such optical printers, characters and images are separated into pixels and stored in a storage device, and a desired character signal is read out from this storage device as needed to modulate the light beam. (In order to obtain high-quality characters, it is necessary to increase the number of pixel resolutions, and processing such as reading character pixel data from the storage device may take a lot of time. Therefore, the period of scanning in the X direction (i.e. Y direction scanning speed) to match the worst conditions of these data processing, or
A method must be taken to stop directional scanning. However, if the Y-direction scan is set to the worst data processing condition, the overall processing speed will slow down, and the method of stopping the Y-direction scan after each X-direction scan takes a long time to start and stop when the mass of the moving object is large. As a result, it becomes impossible to improve the printing speed. Furthermore, when a rotating polygon mirror is used as a reflecting mirror, a phenomenon occurs in which the scanning position of the light beam moves in the Y direction due to sagging or eccentricity of the surface. In view of these points, the present invention aims to enable high-speed printing, and also to make it possible to obtain high-quality products by simultaneously correcting the sagging of the mirror surface even when a rotating polyhedral mirror is used. This was done in order to provide an optical printer.

The present invention will be explained in detail below with reference to the drawings. FIG. 1 shows a schematic configuration of an embodiment of an optical printer according to the present invention, in which 1 is a light beam generator such as a laser, 2 is a light beam modulator, 3 is an optical deflector, and 4 is a rotating polyhedron. A mirror 5 is a fixed reflecting mirror; 6 is a recording material bed on which a recording material is placed and is moved by a drive source (not shown); A position detector such as a linear scale for detecting the current position of the bed 6; 9 an optical position detector for detecting the X-direction scanning start position of the light beam;
10 is an arithmetic circuit.

In the optical printer configured as described above, when data processing for reading character signals from a character storage device (not shown) is performed smoothly, the light beam generator 1
The light emitted from the mirror is modulated by a modulation signal input to the optical modulator 2, passes through the optical deflector 3, and reaches the rotating polygon mirror 4.

The light beam is deflected by the rotating polygon mirror 4 as shown in FIG. 1, and reaches the recording material bed 6 by the fixed reflecting mirror 5. At this time, the light beam first passes through the central portion 20 of the optical position detector 9 and then passes through a predetermined scanning position 21 of the recording material bed 6, as shown in FIG. During this time, the recording material bed 6 is moving in one direction, and the position detectors 7 and 8 of the recording material bed 6 continue to send this value to the arithmetic circuit 10. If the moving speed of the recording material bed 6 matches the scanning period of the light beam in the X direction and the time required for data processing is shorter than that, then when the recording material bed 6 moves by a predetermined amount, the next light beam Scanning begins. But the third
As shown in the figure, data processing for reading character signals from a character storage device (not shown) takes time, and the recording material bed 6 moves first, making it difficult to find the next position to scan, for example. A case may also occur where the position is 31 shown by the two-dot chain line. In this case, the arithmetic circuit 10 receives the signal from the position detector 8 of the recording material bed 6, calculates the difference between the reference scanning position 21 and the position 31 to be actually scanned, and further corrects the difference as necessary. The amount of deflection is calculated and sent to the optical deflector 3. This deflection signal is a signal that deflects the light beam upward in the diagram in FIG. 1 when the scanning position on the recording material bed 6 is to the left in the diagram from the normal scanning position 21 as shown in FIG. Depending on the signal, the light beam passes over the optical position detector 9 and then scans a predetermined position 31 on the recording material bed 6. On the other hand, if the product of the X-direction scanning period of the light beam and the moving speed of the recording material bed 6 is smaller than the scanning pitch of the light beam, and the time required for data processing is shorter than the X-direction scanning period, the third Contrary to the case shown in the figure, it may happen that the position that the light beam should originally scan is to the right of the scanning position 21 in the figure.

In this case, as described above, the difference between the position on the recording material where the light beam should originally scan and the current position of the light beam is calculated, and this difference signal is sent to the deflector 3 as a deflection signal. The position that should originally be scanned can be scanned.
The above explanation was due to the difference between the position where the light beam should originally scan and the position where the light beam actually occurs, but the scanning position on the recording material bed is the same as the reference position. Even though the current position of the light beam is shifted from the position 20 of the optical position detector 9, in other words, the rotating polygon mirror is eccentric or the mirror surface is tilted. Even if there is, it can be processed in the same way.

As described above, the scanning method of the optical printer according to the present invention, when the position to be scanned on the recording material bed and the current position of the light beam are different, detects the difference and uses it as a deflection signal.
The scanning position of the light beam is made to match the scanning position on the recording material. As a result, even if the original position to be scanned is advanced due to data processing delay or vibration, or if the rotating polygon mirror is eccentric or the mirror surface is tilted, it can be corrected. If this is possible and data processing is proceeding smoothly, advance printing can be performed against the moving speed of the recording material bed 6 within the allowable deflection angle of the optical deflector 3. . Therefore, high-speed, high-quality printing is possible without taking measures such as slowing down the movement of the recording material bed (Y-direction scanning) unnecessarily or stopping it after each X-direction scanning as in the past. . In the above explanation, the case where the recording material bed 6 is moved as scanning in the Y direction has been explained.
It is only necessary that the light beam and the recording material move relative to each other, and the idea of the present invention can be applied as is even if, for example, the recording material bed 6 is fixed and the reflecting mirror 5 is rotated instead.

In this case, it is sufficient to detect the scanning position of the recording material bed with the optical position detector 9 provided in the Y direction. Furthermore, the rotating polyhedron theory 4 may be a swinging mirror such as a galvanometer, and the fixed reflecting mirror 5 is not necessarily required. Furthermore, if this fixed reflecting mirror is constructed of a galvanometer or the like, similar processing can be performed by transmitting the deflection signal to the galvanometer. Furthermore, in the present invention, the deflection angle of the deflector is fixed before scanning, but by providing a beam for beam position detection and a wide range optical position detector, the beam can be controlled at all times. is clear.
Many other embodiments can be obtained without exceeding the scope of the present invention.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the outline of an embodiment of an optical printer according to the present invention, and FIGS. 2 and 3 are diagrams for explaining the scanning position of a light beam. DESCRIPTION OF SYMBOLS 1... Light beam generator, 2... Light modulator, 3... Light deflector, 4... Rotating polyhedral mirror, 5... ...Fixed reflector, 6...
・Recording material bed, 7... Linear scale, 8.
...Position detector, 9...Optical position detector,
10... Arithmetic circuit.

Claims (1)

[Claims] 1. In an optical printer, a light beam from a light beam generator is directed to a reflecting mirror through a sub-scanning direction optical deflector, and the recording material is scanned in the main scanning direction by the movement of the reflecting mirror. An optical printer that detects a difference between a current position in the sub-scanning direction on the recording material and a position in the sub-scanning direction to be scanned on the recording material, and controls the sub-scanning direction optical deflector based on the detected value to scan a predetermined sub-scanning position. scanning method.