JPH0197917A - Synchronizing signal generator - Google Patents

Abstract

PURPOSE:To improve the light condensing efficiency by providing an optical element which condenses a synchronizing light beam on the diffusion zone of a condensing bar. CONSTITUTION:A concave cylindrical lens 13 is arranged between a grid 11 and a condensing bar 1 having a diffusion zone 2 for the purpose of converging a synchronizing light beam L1, which is focused on the grid 11, on the diffusion zone 2. The synchronizing light beam L1 passing the grid 11 is diverged by the concave cylindrical lens 13 and converged again on the incidence face of the condensing bar 1 and converged on the diffusion zone 2. Since a small converged beam spot is obtained on the diffusion zone 2, the synchronizing beam L1 is all diffused by the diffusion zone 2 and led to a photodetector while repeating total reflection in the condensing bar 1. Thus, the condensing efficiency of the synchronizing light beam is improved to obtain an efficient synchronizing signal.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a synchronization signal generator used in a photodetection device, particularly a light beam scanning device that scans a light beam for reading or recording image information. .

<Prior Art and its Problems> In recent years, light beam scanning devices that read and/or record images using light beams have been actively developed. In a light beam scanning device that reads and/or records such images, a light beam emitted from a light source is generally reflected and deflected by an optical deflector and sent at a constant speed in a direction perpendicular to the direction of deflection. The object to be scanned (sub-scanned) is main-scanned.

In this case, keeping the scanning speed of the light beam constant is an important requirement to obtain good image quality. However, it is difficult to keep this strictly constant due to the mechanism of the device, so normally the position of the optical beam deflected by an optical deflector is detected, a position detection signal is created, and synchronization is performed with this signal. A method of recording or integrating the image signal is used.

FIG. 4 shows a conventional light beam scanning device equipped with a synchronization signal generator for obtaining a synchronization signal.

In a conventional synchronization signal generator, a grid 1 is formed in which bright areas and dark areas are alternately provided on the optical path of a synchronization light beam.
1, a long cylindrical light condensing bar 1 made of acrylic resin or the like provided behind the grid and having a diffusion zone 2 in the longitudinal direction on the side opposite to the grid; A photodetector 4 provided on the end face is used.

A light beam scanning device equipped with such a synchronization signal generator is
A light beam L0 emitted from a laser light source 5 is expanded to a desired beam diameter by a beam expander 6, and is deflected by a rotating polygon mirror 7 as an optical deflector.

The light beam L0 deflected by the optical deflector 7 is used as a scanning light beam L2 for main scanning the object to be scanned, which is sub-scanned and conveyed in the B direction by the half mirror 9, and a synchronization light/beam for generating a synchronization signal. It is branched into L1, and the synchronization light beam L
1 enters the condensing bar 1 through the grid 11,
The light is diffused by the diffusion band 2, and while repeating reflection inside the light collecting bar 1, it reaches one end of the light collecting bar and enters the photodetector 4. The light incident on the photodetector 4 has a periodic change in the amount of light according to the scanning of the grid, and the light incident on the photodetector 4
The change in light intensity is converted into an electrical signal, and a synchronization signal is thereby obtained.

However, since the synchronization light beam L1 is usually focused on the grid 11, the light passing through the grid is spread out, and as shown in FIG. 3a, the beam diameter of the synchronization light beam L1 hitting the diffusion zone 2 is becomes large, and only a part of the synchronizing light beam Ll hits the diffusion band, and the part that does not hit the diffusion band is not diffused and passes through the condensing bar 1, resulting in a loss of light.

Incidentally, even when a long prismatic object is used as the converging bar 1, the same problem occurs because only a part of the synchronizing light beam L hits the diffusion zone 2, as shown in FIG. 3b. Ta.

Moreover, if the width of the diffusion band is too small, the synchronization light beam L1
Due to positional fluctuations in the synchronizing light beam L, the synchronizing light beam L may be displaced from the diffusion zone 2.

In order to avoid the above problem, the width of the diffusion zone 2 in the direction perpendicular to the longitudinal direction of the condensing bar 1 can be increased, but the width of the diffusion zone 2 should be narrower in order to increase the condensing efficiency Preferably, when the width of the diffusion band 2 is widened, the light that enters the light collection bar 1 and is diffused by the diffusion f2 is reflected again inside the light collection bar until it reaches the photodetector 4. There is a problem in that the amount of light that is diffused in the diffusion band and finally reaches the photodetector 4 is reduced, resulting in a low light collection efficiency.

<Objective of the Invention> The present invention aims to solve the problems associated with the prior art as described above, and it is an object of the present invention to solve the problems associated with the prior art as described above. It is an object of the present invention to provide a synchronization signal generating device that can improve the condensing efficiency of a synchronizing light beam even when the diffusion band of the condensing bar 1 is interposed.

<Detailed Description of the Invention> According to the present invention, an object to be scanned is scanned with a scanning light beam deflected by an optical deflector, and a synchronization light beam deflected by the optical deflector is placed on its optical path. The scanning direction of the scanning light beam on the object to be scanned is determined by making the light incident on a grid provided and detecting the light that has passed through the grid using a condensing bar having a diffusion band provided in a longitudinal direction. A synchronizing signal generator for detecting the position of a synchronizing signal generator, further comprising: an optical element that is capable of converging the synchronizing light beam onto a diffusion band of the condensing bar, between the grid and the condensing bar. A synchronization signal generation device is provided.

In the present invention, the optical element is preferably provided on the condensing bar, or the optical element is preferably a cylindrical lens.

Further, it is preferable that the grid is formed on the optical element.

<Specific Configuration of the Invention> Next, the synchronization signal generating device of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a perspective view conceptually showing an embodiment of a light beam scanning device to which a synchronization signal generating device of the present invention is applied.

This light beam scanning device basically consists of a laser light source 5 that generates a laser light beam Lo, a beam expander 6 that makes the light beam a desired diameter, and a rotating polygon mirror 7 that serves as an optical deflector that deflects the light beam 5. , a scanning lens 8 such as an fφ lens provided on the optical path, a half mirror 9 provided extending in the main scanning direction on the optical path, and a sub-scanning conveyance means (not shown) for sub-scanning the object 10 to be scanned in the B direction. is provided.

The half mirror 9 reflects an amount of light beam necessary for scanning out of the incident light beam 2 as a scanning light beam L2, and transmits the remaining light beam as a synchronization light beam L1. The scanning light beam L2 reflected by the half mirror 9 is focused on the object to be scanned 10 placed on the optical path, and is conveyed (sub-scanned) in the direction of arrow B over the object to be scanned 10 in the direction of arrow C. Main scan repeatedly.

Synchronization light beam L1 divided by half mirror 9
A grid 11 is provided on the optical path extending in the main scanning direction.

The grid 11 is formed of bright and dark areas at a pitch corresponding to the pixels on the object to be scanned 10, and the synchronizing light beam L1 that has passed through this grid 11 is directed to the grid 1.
The light is condensed by a condensing bar 1 provided behind 1.

The grating of the grid 11 is provided so as to correspond to the pixels on the object to be scanned by the light beam, and the amount of light incident on the condensing bar 1 is converted into an electrical signal by the photodetector 4, and then
Since it can be multiplied and used as a synchronization signal, it is not necessarily necessary to have a one-to-one relationship with the pixels.

The grid 11 may periodically change the reflection state of the synchronization light beam, and in that case, the condensing bar 1 may condense the light reflected by the grid.

The light collecting bar 1 is a long cylindrical rod made of a transparent material such as acrylic resin or glass, and is a strip or the like coated with a light-scattering paint in the longitudinal direction of the side opposite to the grid 11. A certain diffusion zone 2 is provided.

Note that the condensing bar 1 is not limited to an elongated cylindrical shape, but may be an elongated prismatic shape.

The synchronizing light beam L1 incident on the condensing bar 1 passes through the diffusion zone 2
The light is diffused by the light beam, and while repeating total reflection on the surface of the light condensing bar 1, it reaches the photodetector 4 provided on the end face of the light condensing bar 1 and is detected.

The amount of light detected by the photodetector 4 is determined by the grid 11
The lattice changes periodically with the main scanning of the scanning light beam L2.

The photodetector 4 detects periodic changes in this synchronizing light beam L1, and this change in light amount is converted into an electrical pulse signal.
A synchronization signal indicating the position of the scanning light beam L2 in the main scanning direction is obtained.

A synchronizing light beam L1 focused on the grid 11 between the grid 11 and the condenser bar 1 with a diffusion zone 2
A concave cylindrical lens 13 is arranged to converge the light onto the diffusion zone 2 (see FIG. 2a).

That is, if the concave cylindrical lens 13 is not present, as shown in FIG. The synchronizing light beam L1 that has passed through the synchronization lens 11 is diverged by a concave cylindrical lens 13 so that it can be focused on the diffusion zone 2.

<Specific Effects of the Invention> The effects of the above-mentioned light beam scanning device to which the synchronization signal generating device 3 of the present invention is applied will be described below with reference to FIG.

After the light beam LO emitted from the laser light source 5 passes through a beam expander 6 and reaches a desired beam diameter, it enters a rotating polygon mirror 7 rotating in the direction of arrow A, where it is reflected and deflected. Ru.

As an optical deflector for deflecting the light beam 5, in addition to the rotating polygon mirror 7, a galvanometer mirror, a hologram scanner, an AOD (acousto-optic optical deflector), or the like can be used.

The light beam 5 reflected and deflected by the rotating polygon mirror 7 passes through a scanning lens 8 such as an fθ lens provided on the optical path, and then passes through a half mirror provided on the optical path extending in the main scanning direction.
9.

Of the incident light beams 5, this half mirror 9 reflects an amount of light beam necessary for scanning as a scanning light beam j2, and transmits the remaining light beam as a synchronization light beam L1. The scanning light beam L2 reflected by the half mirror 9 converges on the object to be scanned 10 placed on the optical path,
Scanned object 10 transported (sub-scanned) in the direction of arrow B
Main scanning is performed repeatedly in the direction of arrow C.

On the other hand, the synchronization light beam L transmitted through the half mirror 9
1 is incident on a grid 11 arranged at a conjugate position with respect to the object to be scanned 10 and the half mirror 9.

Since the grid 11 is formed in a lattice shape with a pitch corresponding to the pixels on the object to be scanned 10, the amount of light of the synchronizing light beam L1 that has passed through the grid 11 varies with the main scanning of the scanning light beam L2. It changes periodically.

The synchronization light beam L1 that has passed through the grid 11 is
As shown in the figure, it is diverged by the concave cylindrical lens 13 and converged again at the incident surface of the condensing bar 1 to form a diffusion band 2.
converge on top.

Conventionally, in a synchronization signal generator without an optical element, the third
As shown in Figure a, the synchronization light beam L1 that passed through the grid 11 did not converge on the diffusion zone 2, and the beam diameter increased at the diffusion surface, resulting in a loss of light.

In the synchronization signal generator of the present invention, since a small beam spot converged on the diffusion band 2 can be obtained, the synchronization beam L
1 is almost all diffused by the diffusion zone 2, and the light condensing bar 1
The light undergoes total internal reflection repeatedly and is guided to the photodetector 4.

Also, since the width of the diffusion band 2 can be narrowed according to the spot of the converged synchronization beam Ll, as in the case where the width of the diffusion band 2 is wide, the light incident on the condensing bar 1 is diffused by the diffusion band 2. While the light is repeatedly reflected inside the condensing bar 1 and reaches the photodetector 4, it is diffused and absorbed again in the diffusion zone 2, so that the amount of light that finally reaches the photodetector 4 does not decrease. , the light collection efficiency of the synchronization signal is improved.

The light conveyed in the longitudinal direction by the condensing bar 1 enters the photodetector 4, which detects periodic changes in the synchronizing light beam L1, and this change in light amount is detected by the synchronizing signal generating means. (not shown) is converted into an electrical pulse signal, and a synchronization signal indicating the position of the scanning light beam L2 in the main scanning direction is obtained.

Note that the present invention is not limited to the above embodiments,
Other embodiments of the present invention will be described below.

In the embodiment shown in FIG. 2b, if the condensing bar 1 is a square bar, the condensing position of the synchronizing light beam L1 will spread on the diffusion zone 2 (see FIG. 3b), so the convex cylindrical lens 1
This is an example of condensing light using 2.

FIG. 2c shows an embodiment in which an optical element is provided on the condensing bar 1. The synchronizing light beam L1 that has spread through the grid 11 is focused onto the diffusion zone 2 by a convex cylindrical lens 14 provided on the incident side surface of the condensing bar 1. With this configuration, the optical element and the condensing bar can be provided as the same member.

FIG. 2d shows an embodiment in which the grid 11 is formed on the optical element 1, and on the side surface of the incident side of the concave cylindrical lens 15.
A grid 11 is formed by applying paint or the like to form a grid consisting of bright areas and dark areas corresponding to the pixels on the object to be scanned by the light beam.

With such a configuration, there is no need to provide the grid 11 as a separate member.

In the embodiment described above, the light beam Lo emitted from the laser light source 5 is deflected by the rotating polygon mirror 7, passes through the scanning lens 8, and then is separated into the scanning light beam L2 and the synchronization light beam L1 by the half mirror 9. However, the light beam Lo may be split before entering the rotating polygon mirror 7, and each light beam may be incident on separate reflecting surfaces of the rotating polygon mirror 7. Furthermore, it is also possible to provide separate light sources for the scanning light beam and the synchronization light beam. In this case, if the scanning light beam and the synchronization light beam have different wavelengths, a dichroic mirror or the like can be used. It is also possible to combine them into the same optical path using , and then split them again.

In either embodiment, the synchronization signal generating device of the present invention can be used to improve the focusing efficiency of the synchronization light beam and obtain an efficient synchronization signal.

<Effects of the Invention> According to the device of the present invention, since an optical element capable of focusing the synchronization light beam is provided on the diffusion band of the condenser bar, almost all of the synchronization light beam L+ is diffused by the diffusion band. Moreover, the width of the diffusion zone can be narrowed, light loss can be reduced, and light collection efficiency can be increased. 7 If the above optical element is provided on a condensing bar or a grid is formed on the optical element, the device can be made compact and minute positional adjustments between each element are not required. .

[Brief explanation of the drawing]

FIG. 1 is a perspective view conceptually showing an embodiment of a light beam scanning device to which a synchronization signal generating device of the present invention is applied. Figure 2a is a schematic diagram illustrating an embodiment of the invention;
Figures 2b, 2c and 2d are schematic illustrations of other embodiments of the invention. FIGS. 3a and 3i are schematic diagrams illustrating a conventional example. FIG. 4 is a perspective view conceptually showing a conventional light beam scanning device. Explanation of the symbols 1... Focusing bar, 2... Diffusion band, 3... Synchronization signal generator, 4... Photodetector, 5... Laser light source, 6... Beam expander , 7... Rotating polygon mirror, 8... Scanning lens, 9... Half mirror-1 10... Scanned object, 11... Grid, 12... Convex cylindrical lens, 13... Concave Cylindrical lens, 14... Convex cylindrical lens, 15... Concave cylindrical lens, LO... Light beam, Ll... Light beam for synchronization, L2... Light beam for scanning Patent applicant Fuji Photo Film Co., Ltd. Representative Attorney: Patent Attorney Nobuto Watanabe Patent Attorney: Yo Ishii FIG, 1 FIG, 2a FIG, 2b FIG
, 4 Δ

Claims (4)

[Claims] (1) Scan the object to be scanned with a scanning light beam deflected by an optical deflector, and make the synchronization light beam deflected by the optical deflector enter a grid provided on the optical path to create a grid. In a synchronization signal generating device that detects the position of the scanning light beam on the object to be scanned in the scanning direction by detecting the passed light using a condensing bar having a diffusion band provided in a longitudinal direction. . A synchronization signal generating device, characterized in that an optical element is provided between the grid and the condenser bar, the optical element capable of converging the synchronization light beam onto a diffusion band of the condenser bar. (2) The synchronization signal generating device according to claim 1, wherein the optical element is provided on the condensing bar. (3) The synchronization signal generating device according to claim 1, wherein the optical element is a cylindrical lens. (4) The synchronization signal generating device according to any one of claims 1 to 3, wherein the grid is formed on the optical element.