JP2659028B2 - Exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus of a direct plate making apparatus for directly writing information from a computer onto a plate without making a film master and making a plate.

[0002]

2. Description of the Related Art Conventionally, in order to produce an original plate for a newspaper or the like, a film original plate produced by a film plotter has been subjected to close contact baking on a PS plate to make a plate.

[0003]

In recent newspaper printing, its speed has been particularly required due to its mission, and computerization has been attempted. Therefore, each process in the plate making process is reviewed, and the speeding up of each process can be said to be the highest order.

Accordingly, an object of the present invention is to shorten the plate making process and improve the accuracy of plate making.

[0005]

According to the present invention, there is provided a polygon scanner driven by a motor, first and second semiconductor lasers, and first and second semiconductor lasers. Each laser beam emitted from the laser is projected on a different reflecting surface of the polygon scanner,
An exposure apparatus comprising two systems of lens and mirror systems for exposing at different positions, wherein a third semiconductor laser and a light amount sensor are provided at predetermined positions, and a laser beam emitted from the third semiconductor laser emits light. a direction in which reflected according to the angle of rotation of the polygon scanner via the reflecting surface of the polygon scanner, the position that can be incident on the light quantity sensor, characterized in construction that a plurality of mirrors are provided And

[0006]

When writing directly with a laser beam, a semiconductor laser and two lens / mirror systems are provided, respectively.
The number of polygon scanners for scanning is one, and each laser beam is incident on its different reflection surface, for example,
The right and left sides of the newspaper can be written at the same time, and the speed can be increased. At the same time, since one polygon scanner is rotated by a motor to scan each surface with laser light, the printing pitch in the sub-scanning direction of each surface becomes the same. Accordingly, there is no deviation in the printing pitch, and the accuracy of plate making is improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the embodiments shown in the accompanying drawings. FIG. 2 shows an exposure apparatus 30 according to the present invention.
The shutter 32S is provided at a predetermined distance from the plate making material 34 facing upward. These shutters 32S are opened only at the time of plate making to prevent unnecessary exposure of the photosensitive material layer of the plate making material. Two shutters 32
Exposure positions PF and PB exposed by laser beams 26F and 26B projected from F and 32B are exposure pitches by the laser beams 26F and 26B from the two semiconductor lasers 1F and 1B shown in FIG. If this pitch L is adjusted to, for example, the inter-page size of a newspaper, two pages can be exposed simultaneously. The arrow A is the feed direction (sub-scanning direction) of the plate-making material 34, and corresponds to the arrow A in FIG.

Referring to FIG. 1, the main part of the exposure apparatus according to the present invention will be described. In FIG. 1, symbols F or B attached after reference numerals such as lenses correspond to the exposure point PF in front of or the exposure point PB in the rear with respect to the direction A in which the plate-making material advances. Is the same. Therefore, the following mainly describes one system denoted by the symbol F.

Laser light 26F emitted from semiconductor laser 1F
Is a collimator lens 2F, a beam switching unit 3F,
The light passes through a cylinder lens 4F and mirrors 5F and 6F and strikes one surface 7a of the polygon scanner 7 and is reflected. The reflected light is further applied to the cover glass 8F, the fθ lens 9F, the mirror 10
The photosensitive material layer is exposed through F, 11F and a cylinder mirror 12F.

At this time, by rotating the polygon scanner 7 in the counterclockwise direction of the arrow, the laser beam 26F is emitted, and an exposure width in the main scanning direction perpendicular to the sub-scanning direction A is obtained. At this time, the laser beam 26F passing through the left end portion of the cylinder mirror 12F is reflected by the mirror 13F, and is printed by a print start sensor (hereinafter referred to as a BDS1 sensor;
Is called BDS2 sensor. ) Detect at 13F and send out BDS signal. On the other hand, the laser beam 26F passing through the right end portion of the cylinder mirror 12F is reflected by the mirror 15F, and the light quantity detection sensor 16F and the print end sensor (hereinafter, referred to as a BDE1 sensor, and the other system 17B is referred to as a BDE2 sensor) 17F. Detect with
Each of them detects the amount of light and transmits a BDE signal.

The laser beam 26B emitted from the other semiconductor laser 1B passes through another lens / mirror system and performs the same scanning as described above.

A detection mark 28 is provided on the back surface of the polygon scanner 7 and is detected by the home position sensors 19F and 19B so that the respective surfaces 7a to 7h of the polygon scanner 7 can be specified. I have.

A third semiconductor laser 20 is disposed at a position as shown in FIG. 1, and a laser beam emitted therefrom passes through a collimator lens 21 and a cover glass 22 at this time in this embodiment. Is reflected by the surface 7g of the polygon scanner 7 and sequentially enters the light quantity sensor 24 via mirrors 23a, 23b, 23c, 23d, 23e and 23f according to the rotation angle of the polygon scanner 7, and the zone pulse ZNS (see FIG. 4). )make. Each of the mirrors 23a to 23f is attached to a position and a direction in which the laser beam reflected by the surface (surface 7g in FIG. 1) facing the semiconductor laser 20 is incident on the light quantity sensor 24 every time the polygon scanner 7 rotates by a predetermined angle. .

The polygon scanner 7 is rotated by a spindle motor (not shown). Generally, the rotation speed of the polygon scanner fluctuates due to uneven rotation of the motor. Therefore, rotate the spindle motor in advance,
Average value T1, T of each pulse interval between mirrors 23a to 23f
2, T3, T4, and T5 are determined. Thereafter, if the pulse interval measured during the actual exposure is T1 + α instead of T1, as shown in FIG. 4, for example, the exposure recording timing is corrected by α in the next T2 section ( that is, the exposure recording timing is corrected).
(T2-α ) to perform a correction control of a shift of the exposure recording position (so-called servo control) . By performing the correction control one after another, the exposure length 1 in the main scanning direction scanned by one surface becomes constant without being substantially affected by the fluctuation of the rotation speed of the spindle motor, and the printing accuracy is improved.

On the other hand, as shown in FIG. 5, the set length l of exposure in the main scanning direction by each surface 7a to 7f of the polygon scanner 7 actually varies for each surface. Therefore, the BDS1 sensor 14F to the BDE1 sensor 17F or the BDS2 sensor
The scanning time between the 14B-BDE2 sensor 17B is measured, and these are averaged to determine one ideal time. The exposure length corresponding to the ideal time is 1 shown in FIG. 5, and if no correction is made, the exposure lengths of the surfaces 7a to 7f are slightly shifted. Therefore, at the time of actual exposure, the surface to be exposed can be specified by the operation of the home position sensors 19F and 19B. Therefore, the deviation of the exposure length between the surfaces is generated by correcting the deviation amount peculiar to the ideal exposure length l. And printing accuracy is improved.

FIG. 3 is a front view of a beam switching unit 3F for switching a beam diameter. For example, in a newspaper,
The printing dot density differs between the text section and the advertising section.
Therefore, for example, three types of apertures 40, 42, and 44 for 909 dpi, 681 dpi, and 454 dpi are prepared, and the disks 39 arranged at regular intervals of 120 degrees are connected to the stepping motor 48 and the sensor.
The laser beam 26F can be passed through a desired aperture by being appropriately rotated by the control with the laser beam 46F.

[0017]

As is apparent from the above description, according to the present invention, two laser beams are scanned by different systems using one polygon scanner, so that two surfaces can be simultaneously exposed. As a result, the plate making speed is doubled and the printing pitch is not shifted in the sub-scanning direction in each of the simultaneously exposed surfaces, so that the printing quality is improved. In addition, the direct exposure method using a laser beam eliminates the need for a conventional step of preparing a film master in the plate making step.

[Brief description of the drawings]

FIG. 1 is a plan view of an exposure apparatus according to the present invention, and is a cross-sectional view taken along line II shown in FIG.

FIG. 2 is an external side view of the exposure apparatus according to the present invention.

FIG. 3 is a front view of a beam switching unit.

FIG. 4 is a diagram illustrating control of an exposure length by one surface of a polygon scanner.

FIG. 5 is a diagram illustrating a difference in exposure length between surfaces of a polygon scanner.

[Explanation of symbols]

 1F: Semiconductor laser 3F: Beam switching unit 7: Polygon scanner 9F: fθ lens 13F: BDS1 sensor 15F: BDE1 sensor 20: Semiconductor laser 24: Light intensity sensor

Claims (4)

(57) [Claims] 1. A polygon scanner (7) rotated by a motor, first and second semiconductor lasers (1F, 1B), and respective laser beams emitted from the first and second semiconductor lasers. (26F, 26B) are projected onto different reflecting surfaces (7a, 7b) of the polygon scanner (7) and exposed at different positions (PF, PB) by two lens mirror systems (5F, 6F, 2B). 9F, 12F; 5B, 6B, 9B, 12B),
An exposure apparatus comprising: a third semiconductor laser (20) and a light amount sensor (24) provided at predetermined positions; and a laser beam emitted by the third semiconductor laser (20) is a direction in which reflected in accordance with the rotation angle of the reflecting surface (the polygon scanner via a 7 g) (7) 7), to a position that may be incident on the light amount sensor, a plurality of mirrors (. 23A to 23f ) Is provided. Wherein the optical path of at least one system of the lens mirror system of the two systems, this beam switching unit capable of switching the beam diameter of the laser beam are provided
The exposure apparatus according to claim 1, wherein the door. 3. An origin position check sensor capable of specifying each reflection surface of the polygon scanner is provided .
Exposure apparatus according to claim 1 or 2 wherein. 4. The method according to claim 1, further comprising the steps of:
Openable and closable shutters (32F,
32B) is provided.
The exposure apparatus according to claim 1.