JPH0220818A - Light beam scanning device - Google Patents

Abstract

PURPOSE:To generate an accurate synchronous signal by surrounding a reference grating plate where plural slits are formed with a cover means for dust sticking prevention and providing this cover means with a light transmissive member which transmits a light beam for synchronization. CONSTITUTION:A U-sectioned cover member 44 which extends in a main scanning direction is arranged above and by both sides of the reference grating plate 40 and a glass plate 38 is mounted on the cover member 44 while covering an opening part 46. Dust suspended in the device is cut off by the cover member 44 and glass plate 38 and never sticks directly on the reference grating plate 40. Consequently, the synchronizing laser light is securely passed through the slits 60 of the reference grating plate 40 to reach a converging rod 62, thereby obtaining a synchronizing signal with high accuracy. Further, even if the dust sticks on the glass plate 38, the accurate synchronizing signal is generated without being affected by the dust by selecting the gap between the reference grating plate 40 and glass plate 38.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a light beam scanning device, and more specifically, a device for scanning a scanned object to generate a synchronization signal to read or record an image, etc. A light-transmitting member is arranged at a predetermined distance from the reference grid plate on the light beam incident side to prevent dust and the like from directly adhering to the reference grid plate, thereby obtaining an accurate synchronization signal. The present invention relates to a light beam scanning device configured to enable the scanning of light beams.

[Background of the Invention] For example, in the field of printing plate-making, there is an image scanning recording and reproducing system that electrically processes image information carried on a manuscript and creates a film master for the purpose of streamlining work processes and improving image quality. Widely used.

This image scanning recording/reproducing system basically consists of an image reading section and an image recording section.

That is, in the image reading section, image information carried on a document that is conveyed in a sub-scanning direction is main-scanned by a photoelectric conversion element and converted into an electrical signal. Next, the image information photoelectrically converted in the image reading section is subjected to arithmetic processing such as gradation correction and edge enhancement according to the plate-making conditions in the image recording section, and then converted to an optical signal such as Radhe light, and then the image information is filmed. Recording and reproduction are performed on a record carrier made of a photosensitive material such as.

In this case, in order to accurately reproduce image information as a visible image using a light beam such as the laser light, a synchronization signal synchronized with the scanning of the light beam is required. Therefore, in order to generate such a synchronization signal, a reference grating plate is usually used. That is, this reference grid plate has a large number of slits formed at equal intervals along the main scanning direction.
A columnar condensing rod is disposed on the back side of the reference grating plate, and photodetectors are attached to both ends of the condensing rod.

In such a configuration, a synchronizing laser beam is output from the synchronizing light source, and this synchronizing laser beam main scans the reference grating plate. After passing through a slit formed in the reference grating plate, the synchronizing laser beam is guided as a pulsed optical signal via a condensing rod to photodetectors attached to both ends of the condensing rod. . The optical signal guided to the photodetector is photoelectrically converted, and a synchronization signal for controlling the recording light source is generated from this signal.

Incidentally, the slits formed in the reference grid plate are selected to be quite narrow, and therefore, dust floating inside the device may adhere to the reference grid plate and partially block the slits. be. However, if you try to obtain a synchronization signal using a reference grid plate with partially blocked slits, the synchronization laser beam will be blocked by dust and will not be irradiated onto the focusing rod, resulting in accurate synchronization. Unable to form a signal. It has been pointed out that this causes an inconvenience, for example, that distortion or the like occurs in an image that is scanned and recorded via the recording light source.

Therefore, we tried to use a cylindrical lens to adjust the cross-sectional shape of the synchronization laser beam to an elongated ellipse in the longitudinal direction of the slit, that is, in the sub-scanning direction, to obtain accurate synchronization signals without being affected by dust. This idea has been devised. However, this type of cylindrical lens is expensive, and therefore has the disadvantage that the manufacturing cost of the entire device incorporating the cylindrical lens increases considerably. Furthermore, the cross-sectional shape of the synchronizing laser beam can only be selected within a certain range, and it is completely impossible to avoid the effects of all dust and the like adhering to the reference grating plate.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages, and includes a cover means that surrounds at least the upper part of the reference grid plate to prevent dust and the like from adhering to the reference grid plate. The cover means is provided with a light-transmissive member that transmits the synchronization light beam, thereby making it possible to reliably converge the synchronization light beam on the reference grid plate without being affected by the dust or the like. An object of the present invention is to provide a light beam scanning device that can generate accurate synchronization signals with a simple structure.

[Means for achieving the object] In order to achieve the above object, the present invention generates a synchronization signal via a pulsed optical signal obtained by scanning a light beam along a reference grating plate, In the light beam scanning device that scans the object to be scanned based on the synchronization signal and reads or records images, etc., a cover means capable of preventing dust etc. from adhering to the reference grating plate is provided, further comprising: The cover means is characterized in that it includes a light-transmissive member having a light beam incident surface at a position spaced a predetermined distance from the reference grating plate upstream in the light beam incident direction.

[Embodiments] Next, preferred embodiments of the light beam scanning device according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a light beam scanning device according to this embodiment. The light beam scanning device 10 includes a recording light source 12 and a synchronization light source 14. In this case, the recording light source 12 is substantially composed of a laser diode 18 that is driven and controlled by a laser diode drive circuit 16 and outputs the recording laser beam L1, and a collimator 20 that converts the recording laser beam into a parallel light beam. Become. On the other hand, the synchronization light source 14 includes a laser diode 24 that is similarly controlled by a laser diode drive circuit 22 and outputs a synchronization laser beam L2, and a collimator 26. Recording light source 1
The recording laser beam outputted from 2 main scans the film F in the direction of the arrow via the galvanometer mirror 28 and the fθ lens 30 which vibrate at high speed. The film F is held between the drum 32 and nip rollers 34a and 34b, and is conveyed in the sub-scanning direction in the direction of arrow B.

On the other hand, the synchronization laser beam L output from the synchronization light source 14
2 is irradiated onto a reflecting mirror 36 via a galvanometer mirror 28 and an fθ lens 30, deflected by approximately 90 degrees by the reflecting mirror 36, and transmitted through a light-transmitting member such as a glass plate 38 onto a reference grating plate 40. is main scanned in the direction of arrow A. In this case, the schematic mounting structure of the glass plate 38 and the reference grid plate 40 is shown in FIGS. 2 and 3.

That is, support plates 42a and 42b are erected at a large distance from each other with respect to the main scanning direction of the synchronizing laser beam L2, and the upper portions of the support plates 42a and 42b have a U-shaped cross section and extend in the main scanning direction. A plate-shaped cover member 44 is placed thereon.

An opening 46 having a predetermined width and elongated in the main scanning direction is defined on the upper surface of the cover member 44.
A glass plate 38 is attached so as to cover the. Therefore, the cover member 44 and the glass plate 38 constitute a cover means 47. The glass plate 38 is held on the upper surface of the cover member 44 by pressing its longitudinal ends and side portions with a plurality of locking members 48 .

Next, below the cover member 44, the reference grid plate 40 is attached to the support plates 42a, 42b via the first holder 50.
is attached to. An opening 52 is formed in the center of the first holder 50 and extends in the main scanning direction.
A reference grid plate 40 having a width larger than the opening 52 is mounted on the upper surface, and this reference grid plate 40 is slidable in the main scanning direction via a plurality of stop plates 54 having a bent cross section. is maintained. Therefore, the first holder 50
Both ends of the support plate 42a,
Adjustment screws 58a and 58b, which are fixed to the reference grid plate 42b and screwed into the respective support plates 42a and 142b, have their tips abutted against both ends of the reference grid plate 40. Therefore, the adjustment screw 58a
, 58b in a predetermined direction, the reference grid plate 4
0 means displacement in the main scanning direction. In this case, a large number of slits 60 are formed in the reference grid plate 40 at regular intervals along the main scanning direction, and the slits 60 are substantially rectangular in shape orthogonal to the main scanning direction. exhibits.

Further, a prismatic condensing rod 62 is disposed below the reference grid plate 40 via a second holder 64 . Both ends of the second holder 64 are fixed to the support plate 42a142b, and the condensing rod 62 inserted into the center of the second holder 64 is fixed to its position via a plurality of set screws 66 that abut on both sides and the bottom thereof. Adjustably configured. The light collecting rod 62 is exposed outward from the support plates 42a and 42b, and photoelectric conversion elements 68a and 68b are attached to both ends thereof. At that time, the photoelectric conversion element 68a,
68. The pulsed optical signal guided to b is introduced into the PLL circuit 70 as an electric pulse signal, that is, a lattice signal, multiplied by the PLL circuit 70, and sent to the output control circuit 72 as a reference signal. Then, the image signal is modulated in the output control circuit 72 based on this reference signal, and introduced into the laser diode drive circuit 16 as a laser diode drive signal.

The light beam scanning device according to this embodiment is basically constructed as described above, and its operation and effects will be explained next.

First, when the laser diode 24 is driven under the action of the laser diode drive circuit 22, the synchronizing laser beam L2 output from the laser diode 24 is directed to the collimator 2.
After being made into a parallel light beam by 6, the light beam enters a galvanometer mirror 28. The galvanometer mirror 28 vibrates at high speed, and the synchronizing laser beam L2 reflected by the galvanometer mirror 28 enters the mirror 36 via the fθ lens 30, and is reflected vertically downward by the mirror 36. It passes through the glass plate 38 and main-scans the reference grid plate 40 in the direction of arrow A.

As described above, the reference grating plate 40 has a plurality of slits 60 formed therein, and the synchronizing laser beam L2 that has passed through the slits 60 is incident on the focusing rod 62 as a pulsed optical signal. Next, the optical signal incident on the condensing rod 62 is transmitted to photoelectric conversion elements 68a attached to both ends.
, 68b, converted into a lattice signal, and sent to the PLL circuit 7.
0 is introduced. The grid signal is multiplied by this PLL circuit 70 and sent to an output control circuit 72 as a reference signal. The output control circuit 72 modulates the image signal based on the reference signal and introduces it to the laser diode drive circuit 16 as a laser diode drive signal. This controls the laser diode 18, and the laser diode 18 outputs a recording laser beam L1 modulated according to image information.

The recording laser beam is made into a parallel beam by a collimator 20, and then enters a galvanometer mirror 28 which is vibrating at high speed. Then, the recording laser beam L1 reflected by the galvanometer mirror 28 is transmitted to the fθ lens 3.
0 onto the film F. At this time, the film F is conveyed in the sub-scanning direction in the direction of arrow B while being held between the drum 32 and the nip rollers 34a and 34b, and the recording radar light is emitted onto the film F.

An image is formed two-dimensionally.

In this case, according to the present embodiment, the upper part of the reference grid plate 40 is surrounded by the cover member 44, and the cover member 4
Since the optically transparent glass plate 38 is disposed at the reference grid plate 40, it is possible to prevent dust and the like from adhering to the reference grid plate 40 and to generate accurate synchronization signals.

That is, as shown in FIGS. 2 and 3, a cover member 44 having a U-shaped cross section and extending in the main scanning direction is disposed above and on both sides of the reference grid plate 40. A glass plate 38 is placed on the cover member 44 so as to cover the opening 46 . Therefore, dust floating inside the device 10 is blocked by the cover member 44 and the glass plate 38 and does not directly adhere to the reference grid plate 40. Therefore, the synchronization laser beam L2 reliably passes through the plurality of slits 60 of the reference grating plate 40 and reaches the condensing rod 62, making it possible to obtain a highly accurate synchronization signal.

Furthermore, by selecting the distance between the reference grid plate 40 and the glass plate 38, even if dust adheres to the glass plate 38, it will not be affected by the dust (accurate synchronization signals can be generated; that is, it is possible to As shown in FIG.
Assuming that the distance between the reference grid plate 40 and the glass plate 38 is S, the distance S is set so that the relationship of equation (1) holds.

As a result, even if dust 80 is attached to the glass plate 38, the synchronizing laser beam L2 reliably passes through the slit 60 formed in the reference grid plate 40 and enters the condensing rod 62, allowing photoelectric conversion. It becomes possible to obtain an accurate synchronization signal via elements 68a, 68b. Therefore, a highly accurate image is formed on the film F under the driving action of the recording light source 12 based on the synchronization signal.

In addition, in this embodiment, the glass plate 3 is used as the light-transmitting member.
8 is used, but a plate made of synthetic resin or the like may be used as long as it transmits the synchronization laser beam L2.Also, a light transmitting member having a thickness S may be used. may be configured by superimposing them on the reference grid plate 40.

[Effects of the Invention] As described above, according to the present invention, a reference grid plate in which a plurality of slits are formed to generate a synchronization signal is surrounded by a cover means for preventing dust adhesion, and a synchronization light is provided in this cover means. A light-transmitting member that transmits the beam is provided. This prevents dust from directly adhering to the reference grid plate and clogging the slits, making it possible to generate accurate synchronization signals. Furthermore, by separating the reference grid plate and the light-transmitting member by a predetermined distance, even if dust adheres to the light-transmitting member, the synchronization light beam is not affected by the dust, and the synchronization light beam is directed to each of the reference grid plates. It can pass through the slit reliably. This has the effect that distortion or the like does not occur in the read image or recorded image, making it possible to obtain an image with excellent quality. Furthermore, this device has the advantage that it is essentially only necessary to use a light-transmitting member and a cover member, and that an accurate synchronization signal can be obtained with an extremely simple configuration, and that the device itself can be manufactured economically. becomes apparent.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a schematic configuration of a light beam scanning device according to the present invention, FIG. 2 is a cross-sectional perspective explanatory diagram showing the main parts of the light beam scanning device, and FIG. 3 is a vertical cross-section of the main parts shown in FIG. 2. The side view and FIG. 4 are explanatory diagrams for setting the distance between the reference grating plate and the glass plate constituting the light beam scanning device. 10... Light beam scanning device 12... Recording light source 14... Synchronization light source 18.24... Laser diode 38... Glass plate 44... Cover member 47... Cover means 60 ...slit 6
2... Focusing rod

Claims (1)

[Claims] (1) Generate a synchronization signal through a pulsed optical signal obtained by scanning a light beam along a reference grating plate, scan the object to be scanned based on the synchronization signal, and read or record images, etc. In a light beam scanning device that performs A light beam scanning device comprising a light-transmissive member having a light beam incident surface at a position spaced apart by a predetermined distance.