JPH0921969A - Multibeam detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the passing of each light beam with high precision by making light beam for data writing to be smaller than the inner side pitch of each light beam which simultaneously scans the width of the sensor surface of the light detecting elements that receive the light beam. SOLUTION: The laser light beams from a point light source 1 are converted into parallel beams by a collimating lens 2. The beam radius is determined by an aperture diaphragm 3. The beams pass a cylindrical lens 4 and are converged on a polygon mirror 5 in a line form. The light beams, which are deflect- scanned by the mirror 5 that is rotating at a high speed, pass an fθ lens 8 and converted so that the light spots are scanned on a photosensitive body drum 9 at the same speed. A light beam L which passes the lens 8 is reflected by a fixed mirror 10 and is led to a timing detection sensor 12 through a condenser lens 11. By making the width of the sensor surface of the sensor 12 to be smaller than the inner side pitch of each light beam which simultaneously scans, the timing deviation of an information writing is accurately detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam detecting device for detecting a light beam for each scanning in the case of simultaneously performing main scanning on multiple lines.

[0002]

2. Description of the Related Art Conventionally, a writing light beam is obtained from two semiconductor laser light sources, and the scanning position of each light beam on the surface to be scanned is shifted by a predetermined pitch in the sub-scanning direction.
A recording method is known in which two lines are simultaneously main-scanned while the light beam is on / off-modulated according to image information.

In such a recording method, good recording images cannot be obtained unless the starting points of the main scanning by the respective light beams are accurately aligned. Therefore, in order to align the starting points of the main scanning by the respective light beams, the two light beams are adjusted with extremely high precision and then deflected by the deflecting means, and the two light beams deflected prior to the main scanning are made into the same light beam. The main scanning is started at the same timing for each light beam based on the detection result detected by the detection element.

[0004]

However, in the above-mentioned conventional example, there is a limit to the precision of combining the light beams, and even if the light beams can be combined with high accuracy, the effects of vibration, dirt, etc. As a result, the accuracy of synthesis decreases with time, so it is difficult to always stably arrange the starting points of main scanning by the respective light beams. Moreover, since a plurality of beams are simultaneously radiated to one photo-detecting element, the respective light amounts vary due to dirt, vibration, etc., and high-precision detection becomes difficult.

The object of the present invention is to solve the above problems,
It is an object of the present invention to propose a multi-beam detection device capable of highly accurate detection by preventing a plurality of light beams from simultaneously striking a photo-detecting element in the multi-beam.

[0006]

A multi-beam detection device according to a first aspect of the invention for achieving the above object emits a data writing light beam from at least one or more semiconductor laser light sources, and outputs each light beam. When a plurality of lines are simultaneously main-scanned and recorded by shifting the scanning position on the surface to be scanned in the sub-scanning direction by a predetermined pitch, each light beam is controlled prior to the main scanning in order to control the timing of the main scanning by each light beam. In a multi-beam detection device for detecting the passage of beams, the width of the sensor surface of a photodetector element that receives a light beam and outputs an electric signal is smaller than the inner pitch of each light beam that scans at the same time. .

A multi-beam detector according to the second invention is
A data writing light beam is emitted from at least one or more semiconductor laser light sources, the scanning position of each light beam on the surface to be scanned is shifted by a predetermined pitch in the sub-scanning direction, and a plurality of lines are simultaneously main-scanned and recorded. At this time, in order to control the timing of the main scanning by each light beam, in a multi-beam detector that detects the passage of each light beam prior to the main scanning, a photodetector element that receives the light beam and outputs an electrical signal A slit member having a rectangular opening is provided immediately in front of the sensor surface, the rectangular opening is made sufficiently smaller than the sensor surface, and the width of the rectangular opening in the light beam scanning direction is smaller than the inner pitch of each light beam simultaneously scanned. It is characterized by having done.

The multi-beam detector of the first invention having the above-mentioned structure emits a plurality of light beams for writing data from at least one or more semiconductor laser light sources,
The main scanning position of each light beam on the surface to be scanned is shifted by a predetermined pitch in the sub-scanning direction, and when multiple lines are simultaneously main-scanned and recorded, prior to main-scanning, the inner pitch of each light beam scanned simultaneously is The passage of each light beam is detected by a photodetector having a sensor surface with a small width.

In the multi-beam detector of the second invention, a plurality of light beams for writing data are emitted from at least one or more semiconductor lasers, and each beam is subjected to main scanning on the surface to be scanned. When a plurality of lines are simultaneously scanned in the main scan and recorded at the same time, the slit member having a rectangular opening is arranged immediately in front of the sensor surface of the photodetector, and the slit is moved in advance in the main scan. The passage of each light beam is detected through a rectangular aperture that is sufficiently smaller than the sensor surface of the detection element and smaller than the inner pitch of each light beam that is simultaneously scanned.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 shows a configuration diagram of the first embodiment,
In front of a single point light source 1 composed of a semiconductor laser light source, a collimator lens 2 for converting a light beam from a divergent state to a parallel state, an aperture stop 3 for determining a beam diameter according to a stop shape, and a converging action in only one direction. A cylindrical lens 4 for linearly focusing light and a polygon mirror 5 rotating at high speed are sequentially arranged, and the polygon mirror 5 is rotationally driven by a motor 6.

A spherical lens 7, an fθ lens 8 forming a toric lens, and a photosensitive drum 9 are sequentially arranged in the reflecting direction of the polygon mirror 5, and between the fθ lens 8 and the photosensitive drum 9. The fixed mirror 10 is arranged in the direction of the light beam L from the image effective portion of the fθ lens 8, and the condenser lens 11 and the timing detection sensor 12 are arranged in the reflection direction of the fixed mirror 10.

The laser light from the point light source 1 is emitted while diverging, and is converted into parallel light by passing through the collimator lens 2. The beam diameter of the light beam emitted from the collimator lens 2 is determined by the shape of the aperture stop 3, and is transmitted through the cylindrical lens 4 to undergo a converging action in only one direction and is linearly condensed on the polygon mirror 5. The light beam reflected by the mirror surface of the polygon mirror 5 rotating at a high speed is deflected and scanned as the motor 6 rotates, passes through the spherical lens 7 and the fθ lens 8, and is reflected on the photosensitive drum 9 as a minute light beam. It is imaged as a spot.

The light beam deflected and scanned by the polygon mirror 5 at a constant angular velocity passes through the fθ lens 8 to
The light spot is converted so as to be scanned at a constant speed on the photosensitive drum 9, and the light spot is repeatedly scanned on the photosensitive drum 9 in the direction of the arrow. At this time, the light beam L passing through the image effective portion of the fθ lens 8 is reflected by the fixed mirror 10 and guided to the timing detection sensor 12 via the condenser lens 11. In this way, the timing deviation of information writing that occurs during repetitive scanning due to the division error of the reflecting surface of the polygon mirror 5 is recognized by detecting the light beam at the head portion deflected and scanned by each reflecting surface.

FIG. 2 is an enlarged view of the timing detection sensor 12. The timing detection sensor 12 has a vertically long shape and includes the first beam L1 emitted from the point light source 1 and the second beam L1.
For the inner pitch b of the beam L2, the sensor width a is a <b
In a relationship. With this setting, the sensor outputs O1 and O2 of the first beam L1 and the second beam L2 can be separated as shown in FIG. 3, so that the timing of each light beam can be accurately detected. You can

The pitch c of the first beam L1 and the second beam L2 in the sub-scanning direction is set according to the scanning density, and a laser unit including a point light source 1, a collimator lens 2 and an aperture stop 3 is rotated. I am adjusting to that value. Furthermore,
The inner pitch b of the first beam L1 and the second beam L2 is about 2 m
In m, this value can be calculated from the interval of a plurality of light emitting points formed in the point light source 1 of about 100 μm and the magnification of the optical system of about 20 times, and the width of the sensor 12 may be about 1.5 mm.

The above description has been made on the case of the semiconductor laser light source having two light emitting points, but the same can be applied to the semiconductor laser light source having three or more light emitting points.
Further, it can be applied to a case where a plurality of semiconductor laser light sources each having a single light emitting point are used to simultaneously scan a plurality of laser lights. In this case, when a plurality of light beams are scanned by the light deflecting device, the light beam incident position on the light deflecting device is set so that there is a difference of about 2 mm in the scanning direction. Can respond.

FIG. 4 shows a second embodiment of the condenser lens 1.
3 and the timing detection sensor 14 between the rectangular opening 15
A slit plate 15 having a is provided. The sensor surface 14a of the timing detection sensor 14 is sufficiently larger than the opening 15a, and the width d of the opening 15a is smaller than the inner pitch e of the first beam L1 and the second beam L2.
The condenser lens 13, the slit plate 15, and the timing detection sensor 14 are arranged on substantially the same central axis.

The first beam L1 and the second beam L2 scanned by the polygon mirror are focused on the surface of the slit plate 15 by the condenser lens 13, and the first beam L1 and the second beam L2 are imaged.
When the beam L2 passes through the opening 15a of the slit plate 15, the timing detection sensor 14 generates an electric signal. Since the sensor outputs of the first beam L1 and the second beam L2 at this time are separated as shown in FIG. 2, the respective detection timings can be accurately obtained.

By separating the sensor outputs of the plurality of light beams scanned by the slit plate 15 in this manner, no special sensor unit is required as the timing detection sensor 14, so that the timing detection sensor 14 is selected. Can have a degree of freedom.

[0020]

As described above, in the multi-beam detector according to the first aspect of the invention, the width of the sensor surface of the photodetector is smaller than the inner pitch of each light beam. It is possible to separate and detect the timings of a plurality of light beams without the incidence of the above light beams, and it is possible to perform accurate light scanning.

A multi-beam detector according to the second invention is
By making the rectangular opening of the slit member sufficiently smaller than the sensor surface of the light detection element and making the width of the rectangular opening in the light beam scanning direction smaller than the inner pitch of each light beam, a plurality of light detection elements can be simultaneously formed. The timing of a plurality of light beams can be separated and detected without the incidence of light beams, and accurate light scanning can be performed.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment.

FIG. 2 is an explanatory diagram of a timing detection sensor.

FIG. 3 is a graph of an output waveform of the sensor.

FIG. 4 is a perspective view of a second embodiment.

[Description of symbols] 1 semiconductor laser light source point light source 2 collimator lens 3 aperture stop 4 cylindrical lens 5 polygon mirror 8 toric lens 9 photoconductors 12 and 14 timing detection sensor 15 slit plate

Claims (2)

[Claims] 1. A light beam for writing data is emitted from at least one or more semiconductor laser light sources, a scanning position of each light beam on a surface to be scanned is shifted by a predetermined pitch in a sub-scanning direction, and a plurality of lines are simultaneously main-scanned. When scanning and recording, a multi-beam detector that detects the passage of each light beam prior to the main scanning for timing control of the main scanning by each light beam receives the light beam and outputs an electrical signal. The multi-beam detection device is characterized in that the width of the sensor surface of the light detection element is smaller than the inner pitch of each light beam scanned at the same time. 2. A light beam for writing data is emitted from at least one or more semiconductor laser light sources, and the scanning position of each light beam on the surface to be scanned is shifted by a predetermined pitch in the sub-scanning direction to simultaneously scan a plurality of lines simultaneously. When scanning and recording, a multi-beam detector that detects the passage of each light beam prior to the main scanning for timing control of the main scanning by each light beam receives the light beam and outputs an electrical signal. A slit member having a rectangular opening is provided immediately in front of the sensor surface of the light detecting element, the rectangular opening is made sufficiently smaller than the sensor surface, and the width of each of the light beams that simultaneously scans the width of the rectangular opening in the light beam scanning direction. A multi-beam detection device characterized by being made smaller than the inner pitch.