JPH1132175A - Scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive scanning device for plane-scanning a medium of a large width in which the scanning line width is 40 cm or more, with high accuracy and a high resolution. SOLUTION: This scanning device 10 is provided with plural optical system scanning units 12 for cooperatively scanning the scanning line of the medium along respective scanning paths by a scanning beam based on video signals inputted from the outside, a driving part 14 for relatively moving the respective scanning units to the medium and a control part 16 for controlling the operation of the respective scanning units. The respective scanning units are respectively operated while being synchronized by common synchronizing signals and the scanning paths of the respective scanning units are successively arrayed along the scanning line of the medium and continued while constituting an overlap path by overlapping the end part of the scanning path with the end part of the scanning path of the scanning unit adjacent with each other. The control part 16 decides a scanning in-charge area within the overlap path of the scanning units adjacent with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning device for scanning a medium along a scanning path by a scanning beam, and more particularly, to a scanning device optimal for scanning a wide medium with a printing machine such as a CTP. It is about.

[0002]

2. Description of the Related Art Scanning devices for scanning a medium along a scanning path by a scanning beam such as a laser beam include office printers, facsimile printers, printing printers (Image Setter), and CTP (Computer To Printer).
) Is widely used as a laser beam printer in the field of printing plate making.

In a scanning apparatus using a laser beam, it is necessary to control the beam diameter and the beam speed of the laser beam in a fixed relationship. Usually, a lens for converging the laser beam and a rotating polygon mirror (polygon mirror) are used. Scanning using. Here, a conventional scanning device using laser light will be described with reference to FIG. FIG. 10 is a schematic view showing the structure of a general scanning device using a conventional laser beam. The scanning device 50 determines that the beam deflection angle is proportional to the scanning position by f
A scanning device of a pre-objective scanning system that uses a θ lens and makes a locus of focus linear as a condenser lens. As shown in FIG. 10, a semiconductor laser 52 that emits a laser beam, and a laser beam that is emitted A parallel optical system 54 for turning the light into parallel rays, and a rotating polygonal mirror (polygon having a mirror surface on the side surface of the polygonal prism and rotating around the center line of the polygonal prism by a motor to deflect the laser beam at a deflection angle θ. mirror)
And a condensing lens (fθ lens) 58 having a focal length f for scanning a scanning surface, for example, a PS plate film. Light emission / stop of the semiconductor laser 52 is controlled by a video signal input from the outside.

The scanning method includes a plane scanning method in which a medium or an optical system is moved in parallel with each other and a medium is linearly scanned with a laser beam by a polygon mirror and a condenser lens, and a medium on a cylindrical surface is scanned. Cylindrical surface scanning method. The cylindrical surface scanning method is an outer surface scanning method in which a medium is wound around an outer surface of a rotating drum or the like and rotated, and a light source is moved in the direction of the rotation axis to perform scanning while the medium is wound around the inner surface of the cylinder. There is an inner surface scanning method in which scanning is performed while moving a scanning unit while rotating and scanning.

[0005] By the way, since the flat scanning system can perform continuous scanning by moving the medium, high-speed scanning is possible and the size of the scanning device can be reduced as compared with the cylindrical surface scanning system. Despite the advantages, the conventional planar scanning system limits the scanning line width per scanning device. For example, 2400 dpi (dot /
In many scanning units having a resolution of about inches, the scanning line width is limited to 40 cm or less. In order to make the scanning line width 40 cm or more, the accuracy of the optical system of the scanning device, the angular accuracy of each surface of the polygon mirror used for scanning the laser beam, the bearing accuracy, and the like are increasingly severe as the scanning line width increases. A value is required. As a result, the manufacturing costs of the scanning device are greatly increased, and thus the product price is increased, and it is not economically feasible.

Therefore, as an economical scanning device for scanning a medium having a wide scanning line, a scanning device including a plurality of scanning units has been proposed. In the proposed scanning device,
A plurality of scanning units are arranged so that the scanning paths are sequentially continued while the end point of the scanning path of the scanning unit is coincident with the starting point of the scanning path of the next scanning unit, and the continuous scanning paths are linear. Have been placed. By scanning each scanning path with laser light while synchronizing the operation of each scanning unit with a common synchronization signal, 40 cm
The medium having the above scanning line width is scanned by the plane scanning method.

[0007]

However, the above-described conventional scanning apparatus in which a plurality of scanning units are arranged in a line to scan a wide medium has the following problems. That is, the mechanical accuracy and optical accuracy of the scanning unit,
If the accuracy of the video signal input to each scanning unit is the same level of accuracy as the conventional one, the displacement of the scanning beam occurs at the joint of the scanning paths. For this reason, in a printing press using such a scanning device, the stripes resulting from the connection accuracy of the scanning paths are printed on the printing medium in a direction perpendicular to the scanning direction, that is, parallel to the moving direction of the medium or the scanning device. This is a problem that printing quality deteriorates. On the other hand, if the mechanical accuracy and optical accuracy of the scanning unit and the accuracy of the video signal input to each scanning unit are increased so that the positional deviation of the scanning beam does not occur at the joint of the scanning path, the cost increases. Not economically attractive.

SUMMARY OF THE INVENTION An object of the present invention is to provide an economical scanning device which performs wide-area scanning of a wide medium having a scanning line width of 40 cm or more with high accuracy and high resolution, and is economical.

[0009]

In order to achieve the above object, a scanning apparatus according to the present invention uses a scanning beam on a medium based on a video signal input from the outside along a scanning beam along each scanning path. A plurality of optical scanning units for scanning in cooperation with each other, a driving unit for moving each scanning unit relative to the medium, and a control unit for controlling the operation of each scanning unit. Operate in synchronism with a common synchronization signal, and the scanning paths of the scanning units are sequentially arranged along the scanning lines of the medium, and the scanning paths of the scanning units whose end portions are adjacent to each other. The control unit controls the scanning beam of each scanning unit by determining a scanning area in the overlapping path of the scanning units adjacent to each other. It is characterized in that was.

The scanning device of the present invention scans a medium based on an external video signal, for example, a video signal from an image memory. Here, the video signal is a general term for a series of signals required when the scanning device scans a medium, including an image data signal, a synchronization signal, and the like. The image data is two-dimensional data obtained by printing or digitizing image information of an original image. The video signal (video data) reads out the image data in synchronization with the position where the laser beam scans based on the image data, and turns on the laser beam ("1").
Or, it refers to data for turning off ("0"), and is one-dimensional data depending on the time axis in the present invention. As a start of the time axis, a synchronization signal (origin detection) is output before the start of scanning, and correspondence with each pixel is determined based on the time from the synchronization signal. There is no restriction on the medium as long as it can be scanned with the scanning beam,
For example, it is a photosensitive medium such as a PS plate film. The beam used for scanning is not limited as long as it can scan the medium, and includes, for example, infrared, visible, ultraviolet laser light, X-rays, and the like. The drive unit may move each scanning unit with respect to the medium, and may move the medium with respect to each scanning unit.

In the scanning device according to the present invention, since the scanning path of each scanning unit overlaps the scanning path of the adjacent scanning unit, both scanning units can scan the overlapping path. However, it is not necessary to perform overlapping scanning in both scanning units, and one of the scanning units performs scanning. Therefore, the control unit determines and instructs which scanning unit scans which area in the overlapping path of the scanning path. That is, the control unit analyzes the input image data, performs a logical operation on the image data to be scanned in the overlapping path in the scanning path, and scans the scanning unit in the overlapping path in accordance with a predetermined standard based on the obtained result. Is determined, and which scanning unit scans which area in the overlapping path is indicated.

The criterion that is set is a criterion for switching the scanning in the overlapped path at a position where a seam in the scanning result is hard to be seen. Set in advance. Furthermore,
The criterion is to determine the switching position so as to enhance the continuity of the continuity of the scan, that is, the continuity of the scan result at the seam of the scan, in consideration of the connection accuracy of the scan,
The switching is basically performed in a non-image area. The following lists the principles of the standards. (1) When all of the overlapping paths are non-image areas, the scanning unit may be switched at any position in the overlapping path. However, when the non-image area starts from the start position of the overlap pass, the preceding scanning unit scans up to the start position of the overlap pass, and the subsequent scan path scans the overlap path, that is, the non-image area. (2) When all the overlapping paths are image areas, the scanning unit may be switched at any position in the overlapping path. However, when the image area starts from the start position of the overlapping path of the scanning path, the preceding scanning path scans up to the position before the starting position of the overlapping path, and the subsequent scanning unit scans the overlapping path, that is, the image area. . (3) When the overlapping path is configured in the order of the non-image area and then the image area, the preceding scanning unit scans the non-image area, and the subsequent scanning unit scans the image area. (4) When the overlapping path is composed of an image area and a non-image area in that order, the preceding scanning unit scans the image area and the subsequent scanning unit scans the non-image area.

Thus, although the case of (2) is the same as that of the conventional scanning apparatus, in other cases, the switching of the scanning of the overlapping path is performed in the non-image area. Or, the connection accuracy is significantly improved as compared with the related art.

Here, it is assumed that the image is constituted by an aggregate of pixels colored differently from the ground color of the display medium. The image area refers to an aggregated area of colored pixels, and the non-image area refers to an area without an image, that is, an aggregated area of pixels having the same color as the ground color of the display medium.
The area is not printed, and the area is not colored.

[0015]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment Example This embodiment is an example showing an embodiment of a scanning device according to the present invention, and FIG. 1 is a schematic diagram showing a configuration of the scanning device.
FIG. 2 is a schematic diagram showing a configuration of each scanning unit provided in the scanning device. The scanning device 10 according to the present embodiment has a PS
An apparatus for producing a printing lithographic plate applied to a CTP (computer-to-plate) by scanning a medium made of a plate film with a laser beam and exposing the same to a scanning path by the laser beam as shown in FIG. A control unit 14 for controlling the operation of the scanning unit 12 based on a video signal input from an external image memory; Each time the scanning of the line is completed, a moving device 16 for moving the medium in a direction (direction of an arrow) orthogonal to the scanning path of the scanning unit 12 for each scanning line is provided.

The moving device 16 is composed of a flat plate on which the medium is placed on the upper surface, and a driving device (not shown) for moving the flat plate in the horizontal direction of the arrow. As shown in FIG. When the scanning of m-1 is completed, the flat plate, that is, the medium is moved to the position of the current scanning line m.

The PS plate film is a medium used as a lithographic printing plate, for example, a film having a positive type photosensitive compound, for example, a photosensitive recording medium such as a diazo photosensitive agent layer on an aluminum support. Usually 400-45
A photosensitive recording medium is exposed with a laser beam of 0 nm to prepare a printing lithographic plate.

As shown in FIG. 2, each scanning unit 12 has a laser light emitting device 18 for emitting parallel laser light.
A polygon mirror 20 for deflecting the laser light, f
A condensing lens 22 using a θ lens, a mirror 24 for directing the condensed laser light downward, and an electric motor 26 for rotating the polygon mirror 20 are provided. Further, each scanning unit 12 includes, as a mechanism for adjusting the rotation speed of the electric motor 26, an encoder 28 for measuring the rotation angle of the polygon mirror 20, and the electric motor 26 measured by the encoder 28, that is, the rotation angular speed of the polygon mirror 20. It has a phase comparator 30 that outputs a control signal for the electric motor 26 based on a synchronization signal input from the outside, and an amplifier 32 that amplifies the control signal and outputs it to the electric motor 26. Each scanning unit 12 includes an amplifier 34 for inputting and amplifying a video signal, and controls on / off of emission of laser light from the laser light emitting device 18 based on the amplified video signal.

The laser light is emitted from the laser light emitting device 18 based on the video signal, deflected by the polygon mirror 20, condensed by the condenser lens 22, and
Scanning along the scanning path P according to the rotation of the polygon mirror 20 while changing the optical path to focus on the scanning surface,
Expose the medium. Therefore, the medium is the laser light emitting device 1
When 8 is on, it is exposed to laser light, and when it is off when no laser light is emitted, it is not exposed. Therefore, an exposure surface according to image data of a video signal is formed on the medium.

The scanning unit 12, as shown in FIG.
The end portion of the scanning path P of each scanning unit is overlapped and continuous with the starting end portion of the scanning path P of the adjacent scanning unit, and is arranged in such a relationship that the continuous scanning paths form a straight line along the scanning line of the medium. Have been. Each scanning unit 12
Scans scanning lines divided into P scanning paths while synchronizing with a common synchronization signal. In this specification, an overlapping portion of the scanning path P is called an overlapping path (see FIG. 1).

In this embodiment, all of the video signals 1 to n input from the external image memory to each scanning unit 12 are once input to the control device 14. Control device 14
Functions as a scanning unit switching instruction mechanism for determining the scanning area in the overlapping path of the scanning units adjacent to each other. To this end, the controller 14 analyzes the input video signal, performs a logical operation on the video signal to be scanned in the overlapping path, and determines a switched position in the overlapping path according to a predetermined standard based on the obtained result. Then, the scanning of the adjacent scanning unit 12 is switched at the switching position.

The control device 14 includes a control circuit 40 for controlling the operation of the scanning units 12 for each scanning unit 12. As shown in FIG. 3, the control circuit 40 stores, for each scanning unit 12, a detection circuit 42 for detecting necessary data from a video signal transmitted from an external image memory, and stores data detected by the detection circuit 42. Register circuit 4
4, an arithmetic circuit 46 for reading the stored data from the register circuit 44, and calculating the switching position of the scanning of the overlapping path according to a predetermined standard, a switching position obtained from the arithmetic circuit 46, and a video signal input from the image memory. And a changeover switch circuit 48 for outputting the video signal to the scanning unit 12 as a video signal for scanning.

The configuration of the control circuit 40 will be described in more detail by taking the scanning unit 12.n as an example. Detection circuit 42n
Receives a video signal, analyzes the image data of the overlapping path, and analyzes the starting position coordinate Y of the image area and the starting position coordinate Z of the non-image area along the overlapping path of the current scan line m.
Alternatively, the end position coordinate Z of the image area is detected. The register circuit 44.n has three registers including a switching register as a first register, an ON register as a second register, and an OFF register as a third register.

The switching position register includes the scanning unit 1
2 · n is the scan path P · n of the previous scan line m−1
The switching position coordinate X obtained by switching the scanning in the overlapping path of is stored. The ON register holds the start position coordinate Y of the image area in the overlapping path of the current scanning line m and the scanning path P · n, and sets NULL when there is no image area starting position in the overlapping path. The OFF register holds the start position coordinate Z of the non-image area or the end position coordinate Z of the image area in the overlapping path of the scan path P · n of the current scan line m, and stores the start position of the non-image area and the image area. If there is no end position, NULL is set.

The arithmetic circuit 46.n calculates the switching position of the scanning of the overlapping path in accordance with a preset reference or rule as described below, and the switching circuit 48.n
To enter. The changeover switch circuit 48 · n matches the scan switching position of the overlapping path calculated by the arithmetic circuit 46 with the video signal input from the image memory, and performs scanning from the switching position with the scanning unit 12 · n-1. To the scanning unit 12.n.

The following is an example of a rule for switching the scanning of the overlapping path applied in this embodiment. Note that the following rule is that, when switching is performed within an overlapping path that is a non-image area or an image area, the scanning unit that scanned the overlapping path of the previous scanning line m-1 is preferentially selected, and The scanning unit is caused to scan the overlapping path of the current scanning line m. In the following equation, for example, “switch position register <ON register” means that the coordinate Y held by the ON register is larger than the coordinate X held by the switch register. The inequality sign and the equal sign in other formulas have the same meaning. Rule 1: When the switching position register <ON register and the switching position register <OFF register, the scanning switching position is determined by the ON register and the OF register.
The smaller coordinate of the F register is used.

Referring to FIG. 4, the meaning of rule 1 will be described in detail. FIG. 4A shows a set of pixels indicated by n-1 over scan lines m-3 to m-1, and m to m.
There are two image areas of the set of pixels indicated by n along the +2 scan line, and the other areas are non-image areas. n-1 means that the scanning is performed by the scanning unit 12.n-1, and n means that the scanning is performed by the scanning unit 12.n. Also, in FIG. 4, it is assumed that the coordinate values increase from left to right. This is illustrated in FIGS. 5 to 9 below.
But the same is true. Scanning path P · n of scanning unit n-1
-1 is a line II from the left side of the line II to the right over the line II.
-II. The scanning path P · n of the scanning unit n extends from the line II to the right over the line II-II to the right side of the line II-II. Therefore, the scanning path from the line II to the line II-II is an overlapping path. Since the previous scan on the scan line m-1 is switched at the position of the coordinate X, the switching position register holds the coordinate X. The ON register holds the start position coordinates Y of the current scan line m image area, and the OFF register holds the end position coordinates Z of the current scan line m image area.

In the case of the image area / non-image area configuration in the overlapping path as shown in FIG. 4A, the switching position register <ON register and the switching position register <OFF register
Can be displayed as a register. In this case, the current switching position is the smaller coordinate of the ON register and the OFF register, that is, the coordinate Z of the OFF register, and the scanning unit 12.n-1 scans the non-image area in the overlapping path. The units 12.n scan the image areas respectively.

Also, in the case of an image area as shown in FIG. 4B, the switching position register <ON register, and
Switching position register <OFF register can be displayed.
In this case, the current switching position is the smaller coordinate of the ON register and the OFF register, that is, the coordinate Y of the ON register, and the scanning unit 12.n-1 scans to the coordinate Z in the overlapping path, The scanning unit 12.n scans from the coordinates Z of the overlapping path. Rules 2 to 6 below are:
Although the explanation is omitted, the rule 2 corresponds to FIGS. 5 (a) and 5 (b).
6A and 6B, Rule 4 can be explained based on FIG. 7, Rule 6 can be explained based on FIG. 8, and Rule 7 can be explained based on FIG. 9, respectively. It is to be noted that the rule 5 is self-evident on the basis of the principle without being illustrated, so that the illustration is omitted.

Rule 2: When the switching position register> ON register and the switching position register> OFF register, the scanning switching position is set to ON register and OFF register.
The larger coordinate of the register. Rule 3: When the switching position register ≦ ON register and the switching position register ≧ OFF register, the scanning switching position is O and the scanning switching position is O.
Set the coordinates in the N register. However, when the switching position register = ON register, the scanning switching position is set to the coordinates of the ON register + 1.

Rule 4: When the switching position register> ON register and the switching position register <OFF register, the scanning switching position is set to the OFF register.
Rule 5: When ON register = NULL and OFF register = NULL, an arbitrary position in the overlapping path is set as a scan switching position.

Rule 6: When ON register = NULL and OFF register = NULL, the scan switching position is set to the coordinates of the OFF register. Rule 7: When OFF register = NULL and ON register = NULL, the scan switching position is set to the coordinates of the ON register.

In this embodiment, the switching position of the scanning in the overlapping path is determined based on the content of the image data to be output, thereby preventing the output image from being deteriorated due to the scanning deviation due to the positional deviation at the switching position. The scanning result is realized. More specifically, the scanning unit 12 in the preceding stage
The scanning unit 12 is arranged so that the overlapping path can be scanned by either the n-1 scanning unit 12n or the subsequent scanning unit 12.n, and the preceding scanning unit 12n at any position of the overlapping path.
The control unit 14 determines whether to switch the scanning from the -1 to the subsequent scanning unit 12.n according to the setting standard. The setting criterion is to switch the scanning at a position where the mechanical, optical and electrical errors of the scanning unit are inconspicuous or the influence of the errors is small based on the content of the image data to be output. Is to increase.
By using a plurality of scanning units having mechanical, optical and electrical precisions of ordinary levels, a wide plane scan which was conventionally difficult in terms of economy can be achieved with high precision and economically. can do.

[0034]

According to the structure of the present invention, a plurality of scanning units which operate by a common synchronization signal are provided, the scanning paths of each scanning unit are sequentially arranged along the scanning lines of the medium, and The end portion is overlapped with the end portion of the scanning path of the scanning unit adjacent to each other so as to be continuous, and the control unit determines which of the scanning units adjacent to each other scans the overlapping path of the scanning path. Improve the quality of the scanning result at the connection between the path and the scanning path,
As a result, a large and economical scanning device capable of scanning a wide medium having a long scanning line is realized. By using the scanning device according to the present invention, it is possible to scan a wide medium which has been conventionally difficult technically and economically with high accuracy and economically.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an embodiment of a scanning device according to the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of a scanning unit according to the embodiment.

FIG. 3 is a block diagram illustrating a control circuit of the control device 14.

FIGS. 4A and 4B respectively show rules 1
FIG.

FIGS. 5A and 5B respectively show rules 2
FIG.

FIGS. 6A and 6B show rules 3
FIG.

FIG. 7 is a diagram for explaining rule 4;

FIG. 8 is a diagram for explaining rule 6;

FIG. 9 is a diagram for explaining rule 7;

FIG. 10 is a diagram showing a configuration of a conventional scanning device using laser light.

[Explanation of symbols]

 Reference Signs List 10 scanning device embodiment 12 scanning unit 14 control device 16 moving device 18 laser light emitting device 20 polygon mirror 22 focusing lens 24 mirror 26 electric motor 28 encoder 30 phase comparator 32 amplifier 34 amplifier 40 control circuit 42 detection circuit 44 register Circuit 46 Arithmetic circuit 48 Switch circuit 50 Conventional scanning device 52 Semiconductor laser 54 Parallel optical system 56 Polygon mirror 58 Condensing lens (fθ lens)

Claims (3)

[Claims] A plurality of optical scanning units for cooperatively scanning a scanning line of a medium along a respective scanning path with a scanning beam based on an externally input video signal; A driving unit that relatively moves each scanning unit; and a control unit that controls the operation of each scanning unit. Each scanning unit operates while being synchronized by a common synchronization signal, and scans each scanning unit. The paths are sequentially arranged along the scan lines of the medium, and an end portion of the scan path overlaps with an end portion of the scan path of the adjacent scanning unit to form an overlapped path. A scanning apparatus wherein a scanning area in an overlapping path of matching scanning units is determined, and a scanning beam of each scanning unit is controlled. 2. A control unit analyzes an input video signal, performs a logical operation on image data to be scanned by an overlapping path in a scanning path, and, based on the obtained result, scans adjacent to each other in accordance with a setting criterion. The scanning device according to claim 1, wherein a position at which scanning is switched in the unit overlapping path is determined. 3. The scanning device according to claim 2, wherein the control unit divides the overlapping path into an image area and a non-image area, and determines a switching position according to the following criteria. (1) When all of the overlapping paths are non-image areas or image areas, the scanning units adjacent to each other before and after the preceding and subsequent stages may be switched at any position in the overlapping path. (2) When the overlapping path is configured in the order of the non-image area and then the image area, the preceding scanning unit replaces the non-image area by
The subsequent scanning unit scans the image area. (3) When the overlapping path is configured in the order of the image area and then the non-image area, the preceding scanning unit scans the image area, and the subsequent scanning unit scans the non-image area.