JPH02277018A - Light beam scanner - Google Patents

Abstract

PURPOSE:To eliminate the loss of the quantity of light which is made incident on a photodetector and to improve the photodetection efficiency by using a bundle of optical fibers, which have one-end parts arrayed and arranged along a reference grating plate and other-end parts bundled opposite to the detection surface of a photodetector, as a light converging means. CONSTITUTION:Laser light L1 for recording which is outputted by a laser diode 2 is made into parallel light, which is guided onto a film F through a galvanometer mirror 8 and an ftheta lens 10 to record an image. Laser light L2 for synchronization which is outputted by a laser diode 4, on the other hand, is made into parallel light, which is passed through the galvanometer mirror 8 and ftheta lens 10 to make a main scan on the reference grating plate 18 as shown by an arrow A. Many slits 20 are formed in the reference grating plate 18 and the laser light L2 for synchronization which is passed through the slits 20 is converged by the optical fiber bundle 30 as the light converging means and enters an optical waveguide rod 23 from the other-end parts and the light is reflected repeatedly in its internal surface to enter the photodetector 34 without being diverged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a light beam scanning device, in particular, scanning a light beam along a reference grating plate to obtain a pulsed light signal; Relating to a light beam scanning device that guides this optical signal to a photodetector via an optical fiber and an optical waveguide member to generate a synchronization signal, scans a scanned object based on the synchronization signal, and reads or records an image, etc. .

[Background of the Invention] For example, in the field of printing plate-making, there are image scanning recording and reproducing systems that electrically process image information carried on a manuscript and create 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-scan direction is main-scanned by a photoelectric conversion element and converted into an electrical signal. Next, the image information photoelectrically converted by the image reading unit is subjected to arithmetic processing such as gradation correction and edge enhancement according to the plate-making conditions in the image recording unit, and then converted to an optical signal such as a laser beam. Recording and reproduction are performed on a record carrier made of a photosensitive material such as film.

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. FIG. 1 shows a conventional technology related to a light beam scanning device equipped with a mechanism for generating such a synchronization signal.

This light beam scanning device has a laser diode 2 that outputs a recording laser beam L1, and a laser diode 4 that outputs a synchronization laser beam L2. The recording laser beam output from the laser diode 2 is converted into a parallel beam by a collimator 6, and is main-scanned over the film F in the direction of arrow A via a galvanometer mirror 8 and an fθ lens 10 that vibrate at high speed. In this case, film F is on drum 1.
2 and nip rollers 14a and 14b, and is conveyed in the sub-scanning direction in the direction of arrow B. Therefore, an image is two-dimensionally formed on the film F by the recording laser beam modulated according to the image information.

On the other hand, the synchronizing laser beam L2 outputted from the laser diode 4 is made into a parallel beam by the collimator 16, and main-scans on the reference grating plate 18 in the six directions of arrows via the galvanometer mirror 8 and the fθ lens IO. In this case, a large number of slits 20 are formed in the reference grating vi]8 at equal intervals along the main scanning direction. Therefore, the synchronizing laser beam L2 that has passed through the slit 20 is guided as a pulsed optical signal to photodetectors 24a and 24b via a cylindrical condensing rod 22 arranged on the back side of the reference grating plate 18. . The optical signals guided to the photodetectors 24a and 24b are photoelectrically converted, and a synchronization signal for controlling the laser diode 2 is generated from this signal.

By the way, the synchronizing laser beam L2 that has passed through the slit 20 of the reference grating plate 18 is repeatedly reflected by the inner surface of the transparent condensing rod 22, and then is reflected by the photodetectors 24a and 24b disposed at both ends thereof. reach. In this case, the synchronizing laser beam L2 that enters both ends of the condensing rod 22 via the reference grating plate 18 has a large incident angle with respect to the condensing rod 22, and is therefore reflected by the inner surface of the condensing rod 22. The synchronizing laser beam L2 is relatively efficiently transmitted to the photodetector 24a.
, 24b.

However, since the angle of incidence of the synchronizing laser beam L2 that enters near the center of the condensing rod 22 is small, a considerable portion of the synchronizing laser beam L2 is inconveniently scattered to the outside of the condensing rod 22. .

As a result, the photodetector 2 is
There is a possibility that the amount of light of the optical signal reaching 4a and 24b decreases, making it impossible to generate an accurate synchronization signal.

Therefore, in order to suppress the dissipation of the synchronizing laser beam L2 from the focusing rod 22, the present applicant has proposed a focusing rod 26 having the shape shown in FIG. 2, for example.
142589). The condensing rod 26 is formed in a shape that gradually becomes thicker from the center of the reference grid plate 18 toward both ends.

In this case, since the synchronizing laser beam L2 incident near the center of the reference grating plate 18 is incident on the tapered surfaces 28a and 28b at a relatively large incident angle, the laser beam L2 is detected with a small number of reflection apertures. It reaches the containers 24a and 24b. Therefore, there is little attenuation due to reflection, and the high-energy synchronizing laser beam L2 reaches both ends of the condensing rod 26.

However, if the condensing rod 26 is configured in this way, there is a risk that the area of both end faces will be expanded, and in order to condense the synchronizing laser beam L2 at the end face without leaking, a large light receiving surface is required. A detector is required. In this case, a photodetector with a large light-receiving surface generally has low responsiveness in photoelectric conversion, which causes a problem that high-speed processing of the laser beam L2 is impossible. It has also been pointed out that the SN ratio of the signal photoelectrically converted by the photodetector decreases, making it impossible to generate accurate synchronization signals. Furthermore, a photodetector with a large light-receiving surface and excellent characteristics is extremely expensive.

Therefore, in order to eliminate the above-mentioned disadvantages, it is conceivable to use an optical fiber instead of the condensing rod 22 or 26 as a condensing means. That is, one end portion of a large number of optical fibers is aligned along a reference grating plate, and the other end portions are bundled to face the light receiving surface of the photodetector to constitute a condensing means. However, with this configuration, if it becomes necessary to increase the amount of grating data by increasing the size of the reference grating plate, for example, the length of the reference grating plate increases and the optical scanning distance increases, so the number of optical fibers increases. This increases the area of the end of the optical fibers bundled facing the detector.In this case, the optical fibers have the characteristic of emitting light in a diverging manner. Therefore, a correspondingly large photodetector is also required.

[Object of the Invention] The present invention has been made in order to overcome the above-mentioned disadvantages, and the present invention has been made in order to overcome the above-mentioned disadvantages. In a light beam scanning device that guides an optical fiber bundle to a photodetector to generate a synchronization signal, and scans a scanned object based on the synchronization signal to read or record an image, one end of the optical fiber bundle is guided along the reference grating plate. A loss in the amount of light incident on the photodetector can be reduced by arranging them in alignment, with the other end facing the photodetector, and by interposing an optical waveguide member between the other end and the photodetector. It is an object of the present invention to provide a light beam scanning device that can prevent the above problems and improve the photodetection efficiency.

[Means for Achieving the Object] In order to achieve the above object, the present invention detects a pulsed optical signal obtained by scanning a light beam along a reference grating plate through a focusing means. In the light beam scanning device, the light beam scanning device generates a synchronization signal by guiding the light beam to a device, and scans the object to be scanned based on the synchronization signal to read or record an image. a bundle of optical fibers arranged in alignment and bundled with the other end facing the detection surface of the photodetector, and between the other end of the optical fiber bundle and the detection surface of the photodetector. It is characterized by intervening an optical waveguide member.

[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.

FIG. 3 is a diagram showing the configuration of a light beam scanning device according to the present invention. In this case, the recording laser L1 and the synchronization laser L2 are connected to the recording body (film F) and the reference grating plate 1, respectively.
The configuration of the optical system for irradiating light onto the light beam 8 is similar to that of the conventional light beam scanning device shown in FIG. 1, and detailed explanation thereof will be omitted.

In Fig. 3, the synchronizing laser beam L2 has a large number of slabs)
The reference grid plate 18 on which the reference grid plate 20 is provided is scanned in the main scanning direction (the direction indicated by the arrow). The synchronizing laser beam L2 that has passed through the reference grating plate 18 is focused by an optical fiber east 30, which is a focusing means, and detected by a photodetector 34. The detection output of the photodetector 34 is sent to a synchronization signal generator (not shown),
A synchronization signal necessary for image recording, etc. is generated.

The optical fiber east 30 is composed of a large number of optical fibers whose one end is aligned along the reference grating plate 18.
The other ends of the plurality of optical fibers, that is, the side facing the photodetector 34, are bundled, and the end face thereof is coupled to one end of the transparent optical waveguide rod 32. Further, a photodetector 34 is provided at the other end of the optical waveguide rod 32. Note that the leading wave rod 32 is made of a cylindrical transparent material such as acrylic resin.

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 4 is driven, the synchronizing laser beam L2 output from the laser diode 4 is made into a parallel beam by the collimator 16, and then enters the galvanometer mirror 8. The galvanometer mirror 8 is vibrating at high speed, and the synchronizing laser beam L2 reflected by the galvanometer mirror 8 main-scans the reference grating plate 18 in the direction of the arrow via the fθ lens l□. In this case, a large number of slits 20 are formed in the reference grating plate 18, and the synchronization laser beam L passing through the slits 20
2 enters one end of the optical fiber east 30 as a pulsed optical signal. Next, the optical signal incident on the optical fiber east 30 is repeatedly reflected by its inner surface, and then passes through the optical waveguide rod 32 attached to the other end to the photodetector 34.
guided by.

Here, in the light beam scanning device according to this embodiment, the condensing means is configured as shown in FIG. That is, the synchronizing laser beam L2 transmitted through the reference grating plate 18 is focused by the optical fiber east 30, which is a focusing means. The optical fiber east 30 is composed of a large number of optical fibers arranged along the reference grating plate 18 at one end, and the other end of the large number of optical fibers, that is, the end facing the photodetector 34. are bundled, and a transparent optical waveguide rod 3 is attached to the end face.
2 are combined. Therefore, the transmitted light collected by the optical fiber east 30 is repeatedly reflected on the inner surface of the leading wave rod 32, and then enters the photodetector 34 without being completely destroyed. Next, the detection output of the photodetector 34 is sent to a synchronization signal generation section (not shown), and a synchronization signal necessary for image recording and the like is generated.

Note that the leading wave rod 32 is made of a cylindrical transparent material such as acrylic resin, for example, in order to make it easier for transmitted light guided through the optical fiber east 30 to cause diffuse reflection within the optical wave guide rod 32. If the inner wall of the leading wave rod 32 is made into a diffuse reflection surface, one end of the leading wave rod 32 will be guided in a substantially --like manner with respect to the other end, and the photodetector 34 will be more efficient. Transmitted light can be detected.

FIG. 5 shows an optical waveguide rod 36 having another structure. In this case, the optical waveguide rod 36 is formed into a conical shape whose diameter gradually decreases from one end coupled to the optical fiber east 30 to the other end where the photodetector 34 is provided.

By making the optical waveguide rod 36 into such a shape,
The transmitted light collected by the optical fiber east 30 does not leak to the outside of the optical waveguide rod 36, and is guided while being gradually narrowed down to enter the photodetector 34. Therefore, most of the transmitted light incident on the optical waveguide rod 36 is guided to the photodetector 34, which makes it possible to generate an extremely good synchronization signal and further The element can have a small light-receiving surface, which allows the use of an inexpensive element with good characteristics.

[Effects of the Invention] As described above, according to the present invention, a pulsed optical signal obtained by scanning a light beam along a reference grating plate is guided to a photodetector via a focusing means and synchronized. In a light beam scanning device that generates a signal and scans a scanned object based on the synchronization signal to read or record an image, one end is aligned along the reference grating plate and the other end is aligned. Optical signals are generated using a plurality of optical fibers bundled facing the photodetector and a leading wave rod interposed between the other end side of the optical fiber bundle and the photodetector. It is configured to lead to a photodetector. In this case, even if the area of the end of the optical fiber bundle becomes large, it is possible to efficiently guide the optical signal to the photodetector, thereby generating an extremely good synchronization signal. I can do it. Also,
It becomes possible to use a light extractor with a small light receiving surface,
Another advantage is that it is possible to use a photodetector that is inexpensive and has good characteristics.

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 drawings]

FIG. 1 is a schematic diagram of a light beam scanning device according to the prior art; FIG. 2 is a diagram of a condensing means according to the prior art; FIG. 3 is a schematic diagram of a light beam scanning device according to the present invention; FIG. 4 is a structural explanatory diagram of the condensing means in the light beam scanning device according to the present invention, and FIG. 5 is a constitutional diagram showing another embodiment of the condensing means in the light beam scanning device according to the present invention. 18... Reference grid plate 20... Slit 30
...Optical fiber east 32...Optical waveguide rod 34
... Photodetector 36 ... Optical waveguide rod L1
...Recording laser light L2...Synchronization laser light FI
G.2

Claims (2)

[Claims] (1) A pulsed optical signal obtained by scanning a light beam along a reference grating plate is guided to a photodetector via a focusing means to generate a synchronization signal, and the scanned object is scanned based on the synchronization signal. In a light beam scanning device that scans a body and reads or records images, etc., one end of the light focusing means is aligned along the reference grid plate, and the other end faces the detection surface of the photodetector. What is claimed is: 1. A light beam scanning device comprising a bundle of optical fibers bundled together, wherein an optical waveguide member is interposed between the other end of the bundle of optical fibers and a detection surface of the photodetector. (2) In the device according to claim 1, the optical waveguide member is formed in a conical shape whose diameter gradually becomes narrower toward the light receiving surface of the photodetector from the other end of the optical fiber bundle. A light beam scanning device.