JPS6033558A - Exposing device for generating mesh plate - Google Patents

Abstract

PURPOSE:To somplify a lens system and improve exposure precision by arraying LEDs which have the same light emission area width at prescribed pitch in a subscanning direction, and using those LED arrays, a light source having different light emission area width, and a condenser lens in combination. CONSTITUTION:Light emitting diode LED arrays A-C are provided on a substrate 5, and connected to a selecting circuit 9 electrically. The longitudinal direction of the light source 3 corresponds to the main scanning direction of a scanner, and the lateral direction corresponds to the subscanning direction. The LED arrays A-C are selected to vary the width of exposure beams and the number of beams, thus varying the number of screen lines scanned on a recording surface 7 easily. Desired beam width is therefore obtained through the single lens 6, and the exposing device is simplified without making an image dark nor using any complex lens system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exposure device used when a halftone plate for printing plate making is created directly from a document using an image scanning recording device.

Conventionally, in a dot generator-type exposure apparatus that directly outputs a scanning signal obtained by photoelectrically scanning a document for mesh formation, an Ar + ion laser,
Le-Cd gas lasers, He-Ne gas lasers, etc. are commonly used. However, since laser light cannot directly modulate the luminous flux at high speed, digital exposure equipment optically splits a single laser beam into multiple exposure beams, allowing each beam to be independently modulated. It is modulated externally. Therefore, it is necessary to provide a light modulator or the like within the exposure apparatus, which inevitably increases the size and complexity of the apparatus itself.

In addition, in conventional exposure equipment, when changing the number of screen lines, the width of the exposure beam is changed using a zoom lens, but it is difficult to maintain a sharp projected image over a wide zoom range. For example, it is necessary to increase the F number of the lens, which not only results in a dark image but also makes the drive structure of the zoom lens complicated.

In view of the above-mentioned circumstances, the present invention solves the problems in the conventional apparatus, simplifies the structure of the exposure apparatus itself, and in particular, makes it possible to easily and reliably change the number of screen lines. The purpose is to provide an exposure device for creating halftone plates with high reliability.The electric signal obtained by photoelectrically scanning a document is subjected to predetermined processing to produce an image signal, and based on the image signal, In an exposure device for creating a halftone plate that records a desired halftone plate, an LED array in which LEs and D having the same light-emitting area width are arranged in rows at a predetermined pitch in the sub-scanning direction is used, each having a different light-emitting head width. The screen also includes a light source device arranged sequentially in the main scanning direction, and at least one condensing lens for condensing the exposure beam from the light source device, and a corresponding LED array according to a desired number of screen lines. The present invention relates to an exposure apparatus for forming a halftone plate, characterized in that the exposure control of the LED array is selectively performed.

Next, an embodiment of the exposure apparatus for creating a halftone plate according to the present invention will be described with reference to the accompanying drawings.

Figure 1 shows an example of the structure of the unit halftone dots of the halftone plate, and shows the distance between the four corner points (B) (C1 (
Halftone dots are formed in D) with a halftone dot area ratio of 50%. In general, the number of screen lines t depends on the size of the screen pattern, that is, the number of light beams used during exposure and the exposure beam width, and the size of a unit halftone dot is Dp (m\the number of beams forming a unit halftone dot is β, The beam width is Bp (crn
), then the relationship is Dp-β·Bp (1). Therefore, when using this screen pattern, the number of screen lines L (line / z) is
t-1/β・B, ... (2) 9 In conventional equipment, in order to change the number of screen lines, a zoom lens is used to change the exposure beam width (Bp
) had been changed.

FIG. 2 is a schematic diagram showing the outline of the case where the exposure device according to the present invention is applied to the recording section of a color scanner. 2).

The exposure device (1) has an exposure light source device (3) inside thereof.
An image signal obtained by photoelectrically scanning an original image and subjecting it to predetermined electrical processing is input to this light source device (3).

The exposure device (1) is slidably mounted on a ball screw (4) and is moved in the sub-scanning direction indicated by the arrow at a predetermined feed pitch.

FIG. 6 shows an example of the light source device (3) shown in FIG.
D arrays (A), (B), and (C) are arranged in a row, and each array is
It is electrically connected to the array selection circuit (9). 6th
In the figure, the vertical direction of the light source device (3) corresponds to the main scanning direction of the color scanner shown in FIG. 2, and the horizontal direction of the light source device (3) corresponds to the sub-scanning direction.

The first LED array (A) is composed of light emitting regions (a1 to 16) each having the same light emitting region width (Pl) and arranged in rows in the sub-scanning direction at a predetermined pitch.

The second L E I) array (13) comprises the first T,
B Consisting of light emitting regions (+) 1 to 1) 8) having the same array length as the D array (A), each having the same light emitting region width (P2), and arranged in rows in the sub-scanning direction at a predetermined pitch. There is.

The sixth L E D array -f (1 is the first and second
The T, E D array (A) (t1) has the same light emitting region width (P3) and is arranged in rows in the sub-scanning direction at a predetermined pitch. ~C1□
).

When changing the number of screen lines, select i, ED array (A), (B) or (C1) corresponding to the desired number of screen lines.
is selected by the array selection circuit (9), and the number of each beam is selected by a multiplexer in a dot generator circuit as shown in Japanese Patent Application No. 58-80659, for example, so that the document is sent to the selected LED array. By inputting the scanning signal from the LED and turning on and off the desired T and ED, the LED beam is passed through the optical lens (6).
1-, the image is projected onto the exposure recording surface (7) and formed as a halftone image.

For example, since the exposure recording surface (7) of the drum (2) is rotated in synchronization with the original image drum (not shown) by the halftone rotation shaft (8), the imaged beam from the LED array is The exposure recording surface (the sumo wrestler can be scanned to obtain the desired halftone image).

FIG. 4 shows an example different from the light source device shown in FIG. 6, in which the light emitting areas of each LED array are staggered in the sub-scanning direction with a predetermined gap in the main-scanning direction. They are arranged in a row.

In this example, each light emitting region is spaced apart from each other at a constant interval in the main scanning direction to ensure electrical and optical insulation and separation between adjacent light emitting regions.

Therefore, in this example, since the adjacent light-emitting areas move up and down in the sub-scanning direction, the image signal input to the light source device (3) is This will cause a delay.

In order to keep this delay time constant, the vertical spacing between adjacent light emitting regions is the same for each LED array.

By configuring the light source device in this manner, it is possible to obtain a halftone image of excellent image quality with no gaps between the beams.

As is clear from what has been described above, the 1N/]D array used as a light source device uses individually separated L
It may be a hybrid type in which EDs are bonded in a non-bridled manner, or a monolithic type in which an array is formed on a single crystal substrate.

In the above embodiment, six types of LED arrays were arranged on the substrate (51J-), but the types may be set as necessary. It goes without saying that this is not limited to the above-mentioned embodiment, and can be set arbitrarily.

Since the exposure apparatus for producing a mesh plate according to the present invention has the above-described configuration, it exhibits extremely advantageous effects in practical use as described below.

First, in forming a halftone image, depending on the desired number of screen lines, L
By selecting an HD array, the exposure beam width and the number of exposure beams can be changed, and the recording surface (the number of screen lines scanned by the sumo wrestlers) can be changed very easily.

Second, when changing the screen line number, the exposure apparatus according to the present invention can obtain a desired beam width of the beam from the selected LED array using only a single lens. Thus, the structure of the exposure apparatus can be simplified and the apparatus itself can be made smaller without causing problems such as a dark image or a complicated lens system.

Sixth, since each LED array arranged in a row in the light source device has the same array length, the feed pitch in the sub-scanning direction of the exposure device is constant no matter what type of array is selected. Therefore, the driving mechanism of the exposure apparatus can be simplified. However, if the number of light emitting areas is constant for each array and the array length is different for each array, the desired feed pitch in the sub-scanning direction can be set according to the array length of the selected LED array. It goes without saying that it is possible to obtain a halftone version of the number of lines of the screen, and such a case is also within the scope of the present invention.

Further, an LED array is used as a light source of the exposure apparatus according to the present invention.1. Therefore, it is not possible to directly modulate the LED, and an external modulator, which is required in conventional laser beams, is no longer required.Therefore, the exposure equipment itself can be made smaller. However, the structure can be simplified.

As is clear from the above description, the present invention provides an extremely advantageous mesh plate that not only eliminates various drawbacks of conventional devices, but also improves exposure accuracy and operability, although it is extremely simple and compact. This enabled us to provide an exposure device for production.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a unit halftone dot structure of a halftone plate, FIG. 2 is a schematic plan view showing an embodiment in which the present invention is applied to a recording section of a color scanner, and FIG. 3 is a schematic diagram of a light source device. FIG. 4 is a schematic front view showing an outline of the light source device, and FIG. 4 is a schematic front view showing another embodiment of the light source device shown in FIG. (1)...Exposure device (3)f3')・Light source device (6
) - Focused light 7 (AXBIIClcA'KrrXdl
-r, B D71/ -fp)・Light emitting area width +r,
i Array length Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] (1) Exposure for creating a halftone plate in which an electric signal obtained by photoelectrically scanning a document is subjected to predetermined processing to produce an image signal, and a desired halftone plate is recorded based on the image signal. In the device, a light source is provided in which an LED array in which r and EDs having the same light emitting area width are arranged in rows at a predetermined pitch in the sub-scanning direction is sequentially arranged in the main scanning direction with each light emitting region width being different from each other. and at least one condensing lens that condenses the exposure beam from the light source device, and selects a corresponding LED array according to a desired number of screen lines and controls exposure of the LED array. An exposure device for making a halftone plate, characterized by: (2) Claim (1) characterized in that the array length of the LED array is the same for each array.
Exposure device for creating halftone plates as described in . f3) A patent characterized in that the number of light emitting areas of the LED array is the same for each array, and the movement of the exposure device in the sub-scanning direction is controlled according to the width of the light emitting area of each LED array. An exposure apparatus for creating a halftone plate according to claim (1). (4) The LED arrays are arranged in one row in the sub-scanning direction.
3) The exposure device for creating a halftone plate according to any one of items 3). (5) The mesh plate according to any one of claims (1) to (3), characterized in that each LED array is arranged in a row with a phase shift at a predetermined interval in the main scanning direction. Exposure device for creation. (6) The exposure apparatus for forming a halftone plate according to any one of claims (1) to (5), wherein the LED array is formed by a hybrid type LED. (The exposure apparatus for forming a halftone plate according to any one of claims (1) to (5), characterized in that the 7+ LED array is formed of monolithic LEDs.)