JP2003195210A - Light source unit evaluation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluation device for a light source unit which is used for an image formation device or the like such as a copying machine and a printer, and efficiently and highly accurately evaluate temperature characteristics of the light source unit having a plurality of laser diodes. <P>SOLUTION: Light beams emitted from the light source units 1a and 1b loaded with a semiconductor laser array (LDA) are deflected and scanned by a polygon mirror 3 and made incident on light beam detection elements 7a and 7b composed of a photodiode (PD), a light beam detection signal (DETP) is outputted, beam position sensors (CCDs) 6a and 6b installed on an image formation surface are scanned and the scanning position of the light beam is measured. A mark position detection signal (MARKER) is outputted by marking executed on the upper surface of the polygon mirror 3 and lighting/ putting-out control is performed so as to polarize the light beam of a selected laser diode on a specified polygon surface of the polygon mirror 3 while measuring characteristics. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a digital PPC,
The present invention relates to an optical unit evaluation device for inspecting a light source unit used in a writing optical system of an image forming apparatus such as a laser printer, and particularly, to evaluate temperature characteristics of a light source unit having a plurality of light emitting elements with high accuracy and efficiency. The present invention relates to a light source unit evaluation device that enables the above.

[0002]

2. Description of the Related Art In an image forming apparatus such as a digital PPC and a laser printer, in order to speed up image recording, a plurality of laser diodes (LD) are used or a semiconductor laser array (LDA) having a plurality of laser diodes is used. Images are recorded with multiple light beams. As a semiconductor laser array, for example, one in which four semiconductor lasers are linearly arranged at intervals (pitch) of about 14 μm is known, and if such a semiconductor laser array is used, recording of four scanning lines can be simultaneously performed. Therefore, the recording speed can be quadrupled without changing the rotation speed of the polygon mirror.

To perform image recording using a plurality of beams,
In order to maintain high image quality, it is necessary that the characteristics related to the intervals (pitch) of the light beams emitted from the respective semiconductor lasers constituting the light source unit are uniform, and the characteristics related to the beam profile of each beam are uniform. . When the image forming apparatus is used, the temperature environment of the semiconductor laser array greatly changes depending on the use environment of the image forming apparatus, the manner of use, the frequency of use, etc., and therefore it is necessary to evaluate temperature characteristics. In the temperature characteristic evaluation, the evaluation device or the light source unit is housed in a constant temperature soda, the temperature of the semiconductor laser array is changed, for example, 25 ° C. → 45 ° C. → 25 ° C. → 10 ° C. → 25 ° C., and the characteristic at each temperature is measured. However, even if the temperature cycle is rotated by one cycle, it takes a considerable amount of time, and if the number of evaluations is large, it takes a huge amount of time to evaluate the characteristics.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a light source unit evaluation apparatus capable of efficiently and highly accurately evaluating a light source unit used in an image forming apparatus or the like. The purpose is to provide.
It is another object of the present invention to provide a light source unit evaluation device capable of aligning optical evaluation conditions of a light source unit while measuring characteristics of a plurality of light source units emitting a plurality of light beams. Furthermore, while measuring the characteristics of the light source unit,
An object of the present invention is to provide a light source unit evaluation apparatus capable of switching light beams at high speed and preventing deterioration of a semiconductor laser due to switching of light beams.

[0005]

The present invention has been made to achieve the above object, and the invention of claim 1 is to output light emitted from a plurality of light source units each having a plurality of light emitting elements. A scanning optical system that deflects the beam by a rotating polygon mirror and focuses it on each surface to be scanned, a light beam detection unit that detects the scanned light beam, and a light emitting element to be measured from the plurality of light emitting elements. A light beam switching means for selecting and emitting a light beam,
The light emitting control means includes a light emission control unit that controls lighting of the light emitting element so that the selected light beam is deflected on a predetermined polygonal surface of the polygon mirror, and a light beam sensor provided on the surface to be scanned. Is characterized by.

According to a second aspect of the present invention, in the light source unit evaluation device of the first aspect, the plurality of light source units are installed in substantially line symmetry with respect to a line passing through the rotation center of the polygon mirror. .

According to a third aspect of the present invention, in the light source unit evaluation apparatus according to the first aspect of the present invention, the light emission control means turns on the light emitting element so that the scanning of the light beam during measurement is always performed on the same polygon surface. It is characterized by controlling.

According to a fourth aspect of the present invention, in the light source unit evaluation apparatus according to the first aspect of the present invention, the light emission control means includes the light emitting element so that the scanning of the light beam during measurement is always performed on a preset specific polygon surface. The lighting of is controlled.

According to a fifth aspect of the invention, in the light source unit evaluation apparatus according to the first aspect of the invention, the light beam switching means switches the light beam to be measured during a period in which the light emitting element is not lit. It is characterized by

According to a sixth aspect of the invention, in the light source unit evaluation apparatus of the first aspect of the invention, the light beam switching means switches the light emitting element by an analog switch.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
~ It demonstrates based on the Example shown in FIG. FIG. 1 is a schematic perspective view showing the overall configuration of a light source unit evaluation device according to an embodiment of the present invention. In the light source unit evaluation device,
A light source unit 1 equipped with a semiconductor laser array (LDA) having a plurality (for example, four) of semiconductor lasers (LD)
The light beams (laser beams) emitted from a and 1b are
After passing through the cylindrical lenses 2a and 2b and deflected and scanned by the rotating polygon mirror 3, the imaging elements 4a and
The beam position sensors 6a and 6b installed on the image plane are scanned by 4b and 5a and 5b to measure the scanning position of the light beam in the sub-scanning direction. Beam position sensors 6a, 6
An image sensor such as a CCD (charge coupled device) is used as b. Further, the scanned light beam is focused on the imaging element 4c,
The light beam detection signal (DET) passes through the image forming optical system composed of 4d, 5c, and 5d and is incident on the light beam detection elements 7a and 7b composed of, for example, photodiodes (PD).
P) is output.

Marking is made on the upper surface of the polygon mirror 3 to identify the rotational position of the polygon mirror 3, and the optical fiber sensor 8 detects the position of the mark and outputs a mark position detection signal (MARKER). The polygon mirror 3 has a hexagonal shape having six mirror surfaces (polygonal surfaces), but this is an example, and the regular polygonal shape having any number of surfaces such as eight and ten is not limited to six. Mirrors can be used, and the number of light source units is not limited to two, but can be three, four, five, etc., if the respective arrangements are made appropriate.

Here, the semiconductor laser array (LDA) 1
As a and 1b, for example, four semiconductor lasers are about 14 μm.
A linearly arranged m-spacing (pitch) is used as a measuring object, and as the beam position sensors 6a and 6b, a plurality of CCDs arranged in a straight line at an interval (pitch) of about 7 μm is used. It is possible to measure the change in the beam interval (pitch) on the beam position sensors 6a and 6b with respect to the temperature change of the array. By tilting the installation angles of the beam position sensors 6a and 6b by 45 ° with respect to the scanning direction of the light beam, the semiconductor laser interval becomes substantially 9.9 μm, and the beam position sensor can have higher resolution. . The beam position sensor 6
The a and 6b are not limited to those in which CCDs are one-dimensionally arranged as described above, but those in which CCDs used in CCD cameras are two-dimensionally arranged can also be used. In this case, in addition to the measurement of the beam interval (pitch), the linearity of the scanning line, the beam profile, etc. can be measured.

FIG. 2 is a block diagram showing an electrical schematic configuration of the light source unit evaluation apparatus according to the embodiment of the present invention. In FIG. 2, when the light beams emitted from the light source units 1a and 1b enter the light beam detection elements 7a and 7b, a light beam detection signal (DEPT) is generated. The light beam detection signal and the mark position detection signal (MARKER) of the polygon mirror 3 are input to the light emission control circuit 9. The light emission control circuit 9 is a semiconductor laser array (LDA).
The light emission of the laser diode selected as the measurement target from the plurality of laser diodes (LD) is controlled as follows. First, in order to count the polygon surface of the polygon mirror, the laser diode is caused to emit light at a predetermined position for each scanning line, and is turned off after the light beam detection signal is input. Secondly, in order to measure the light beam, light is emitted for the entire period of one scanning line (until the next beam position detection signal is input). The light emission control circuit 9 sends the LD lighting signal to the LD of the next stage.
It outputs to the drive circuit 10 and the LD switching circuit 11.

The LD drive circuit 10 outputs an LD drive current to cause the selected laser diode to emit light when the LD lighting signal is active. When the laser diode is switched on, when the laser diode is switched on, the LD switching circuit 11 delays the switching and controls the laser diode to be switched off after switching off.
Further, the unit switching circuit 12 switches the light source units 1a and 1b to be measured.

FIG. 3 is a circuit diagram showing a light emission control circuit, FIG.
Is an input signal (DETP) of the emission control circuit, (MARK)
7 is a timing chart showing ER) and an output signal (LD_ON). FIG. 3A is a circuit diagram of the LD control unit for synchronization, which in the light emission control circuit 9 causes the laser diode to emit light in order to count the polygonal surface of the polygon mirror 3. A light beam detection signal (D
ETP), system clock (s_clk), and clear signal (clear) are input, and a synchronization LD_ON signal is output. A line counter 3-1 composed of a down counter, a D-flip-flop 3-2, etc.,
A system clock (s_clk) that sets the timing for turning on the laser diode in the line counter 3-1
The number is set. The line counter 3-1 down-counts the set value each time the system clock (s_clk) is input after the light beam detection signal (DETP) is input, and when the count value becomes 0, the synchronization LD_
An ON signal is output and the laser diode is turned on. When the next light beam detection signal (DETP) is input, the LD_ON signal for synchronization is turned off and the laser diode is turned off.

In FIG. 3B, in the light emission control circuit 9,
FIG. 6 is a circuit diagram of a face selection / face identification LD control unit that always causes a laser diode to emit light for one scanning period on the same polygon face. The surface selection / surface identification LD control unit is a D-flip-flop group 3
-3, polygon mirror selection counter (PMS counter)
3-4, polygon mirror surface number counter (PMN counter) 3-5, polygon mirror counter controller 3-
6 and the like, and includes a light beam detection signal (DETP), a mark position detection signal (MARKER), a system clock (s)
_Clk) and a clear signal (clear) are input, and an LD_ON signal for measurement is output.

The D-flip-flop group 3-3 uses the same polygon surface every time the polygon mirror makes two revolutions.
Outputs a signal for performing one measurement. The polygon mirror selection counter (PMS counter) is composed of a down counter for setting the surface selection data when the laser diode is turned on at a specific surface of the polygon mirror. The polygon mirror surface number counter (PMN counter) 3-5 is The polygon mirror counter controller 3-6 counts the number of times the polygon surface has passed the light beam detection element due to the rotation of the polygon mirror, and the polygon mirror counter controller 3-6 outputs the light beam detection signal (DETP).
Polygon mirror selection counter (PMS counter) for 1 system clock (s_clk) after is input
3-4, Polygon mirror surface number counter (PMN counter) 3-5 is enabled. The surface selection / surface identification LD control unit causes the laser diode to emit light for one scanning period after passing the designated number of polygon surfaces from the input of the mark position detection signal (MARKER). If the MARKER signal is always held inactive (the mark position detection signal is not used), the surface cannot be specified, but the same polygon surface can be used for measurement during measurement.

FIG. 5 shows a laser diode switching circuit,
It is a block diagram which shows schematic structure of a light source unit switching circuit and a light source unit. The switching for selecting the laser diode to be measured is performed by the analog switch 11-1 controlled by the LD changeover switch 11-2 operated manually or by a personal computer. LD_for synchronization may damage the diode.
The ON signal or the LD_ON signal for measurement is output, and the switching is postponed when the laser diode is on, and the LD switching signal generation circuit 11-3 generates the LD switching signal when the laser diode is off.

The light source unit evaluation apparatus of the present invention can detect the light beams from all the light source units by providing a plurality of light beam detection means, and at the same time, the light source unit evaluation apparatus of the present invention can be realized. By adjusting the semiconductor laser array by using it, a light source unit having good characteristics can be obtained.

Further, by using the semiconductor laser array adjusted by using the light source unit evaluation apparatus of the present invention, an optical writing unit excellent in the sub-scanning pitch characteristic can be obtained as a result, and further such an optical writing unit can be obtained. By using the writing unit, it is possible to obtain an image recording apparatus with less sub-scanning pitch unevenness.

[0022]

As is apparent from the above description, the present invention has the following effects. According to the invention of claim 1, a scanning optical system for deflecting a light beam emitted from a plurality of light source units each having a plurality of light emitting elements by a rotating polygon mirror and condensing it on each surface to be scanned, and scanning. Light beam detection means for detecting the light beam, and light beam switching for selecting a light beam to be measured of the emitted light beam for selecting a light emitting element to be measured from the plurality of light emitting elements to emit the light beam Means, a light emission control means for controlling the turning on / off of the light emitting element so that the selected light beam is deflected on the set polygon surface of the polygon mirror, and a light beam installed on the surface to be scanned. By including a sensor, a plurality of light source units having a plurality of light emitting elements can be mounted at one time, and a plurality of light emitting elements of the light source unit can be mounted. Since it each characteristic measurement selected, it is possible to perform evaluation of a plurality of light source units with high precision and high efficiency.

According to the second aspect of the present invention, since the plurality of light source units are installed in substantially line symmetry with respect to the line passing through the rotation center of the polygon mirror, the optical evaluation conditions of the plurality of light source units can be aligned. it can.

According to the third aspect of the present invention, during the measurement of the characteristics of the light source unit, the lighting of the light beam is controlled so that the scanning of the light beam is performed on the same polygon surface of the polygon mirror. Positional variations can be reduced.

According to the invention of claim 4, the characteristic measurement of the light source unit is performed by controlling the lighting of the light beam so that the scanning of the light beam is always performed on the specific polygonal surface of the polygon mirror during the characteristic measurement of the light source unit. Whenever, the light beam is scanned on the specific polygonal surface, it is possible to reduce the variation of the scanning position due to the difference of the polygonal surfaces.

According to the fifth aspect of the present invention, when the light beam to be measured is switched, the light beam is switched while the light beam is not lit, so that deterioration of the light emitting element such as a laser diode can be prevented. it can.

According to the invention of claim 6, since the analog switch is used as the light beam switching means, the light beams can be switched at high speed.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an overall configuration of a light source unit evaluation device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical schematic configuration of a light source unit evaluation device according to an embodiment of the present invention.

FIG. 3 is a circuit diagram showing a light emission control circuit, which is shown in FIG.
Is a circuit diagram of a synchronization LD control unit in the light emission control circuit,
FIG. 3B is a circuit diagram of the surface selection / surface identification LD control unit in the light emission control circuit 9.

FIG. 4 is an input signal (DET) of the emission control circuit shown in FIG.
9 is a timing chart showing P) (MARKER) and an output signal (LD_ON).

FIG. 5 is a block diagram showing a laser diode switching circuit.

[Explanation of symbols]

1a, 1b ... Light source unit, 2a, 2b ... Cylindrical lens, 3 ... Polygon mirror, 3-1 ... Line counter, 3-2 ... D-flip-flop, 3-3 ... D-flip-flop group, 3-4 ... Polygon Mirror selection counter (PMS counter), 3-5 ... Polygon mirror surface number counter (PMN counter), 3-6 ... Polygon mirror counter controller, 4a, 4b, 5c, 5d ... Imaging element, 6a, 6b ... Beam position sensor , 7a, 7b ... Light beam detection element, 8 ... Optical fiber sensor, 9 ... Emission control circuit, 10 ... LD drive circuit, 11 ... LD switching circuit, 1
1-1 ... Analog switch, 11-2 ... LD changeover switch, 11-3 ... LD changeover signal generating circuit, 12 ...
Unit switching circuit.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/113 H04N 1/04 104A F term (reference) 2C362 AA03 AA16 AA75 BA54 BA56 BA66 BA69 BA89 BB31 BB32 BB33 2F065 AA01 AA21 AA51 BB29 CC21 DD06 DD16 FF04 FF65 GG06 GG13 HH04 JJ01 JJ02 JJ25 LL02 LL15 LL62 MM26 MM28 NN02 QQ25 QQ28 QQ51 UU06 2H045 BA22 DB03 DB02 DB03 DB02 DB02 DB02 DB02 DB02 DB02 DB07 DB02 DB02 DB02 DB02 DB02 DB02 DB02 DB02 DB02 DB02 DB02 DB02 DB03 DB02 DB03 HA13 HB01 HB08 HB13 HB20 XA01 XA05

Claims (6)

[Claims] 1. A scanning optical system for deflecting a light beam emitted from a plurality of light source units each having a plurality of light emitting elements by a rotating polygon mirror and condensing it on each surface to be scanned, and the scanned light beam. And a light beam switching means for selecting a light emitting element to be measured from the plurality of light emitting elements to emit a light beam, and the selected light beam is a predetermined polygon surface of the polygon mirror. 2. A light source unit evaluation apparatus comprising: a light emission control means for controlling lighting of the light emitting element so as to be deflected by the light beam sensor; and a light beam sensor installed on the surface to be scanned. 2. The light source unit evaluation device according to claim 1, wherein the plurality of light source units are installed substantially line symmetrical with respect to a line passing through a rotation center of the polygon mirror. 3. The light source unit evaluation device according to claim 1, wherein the light emission control means controls lighting of the light emitting element so that scanning of the light beam during measurement is always performed on the same polygon surface. Light source unit evaluation device. 4. The light source unit evaluation device according to claim 1, wherein the light emission control means controls the lighting of the light emitting element such that the scanning of the light beam during measurement is always performed on a preset specific polygon surface. A light source unit evaluation device characterized by: 5. The light source unit evaluation device according to claim 1, wherein the light beam switching means switches the light beam to be measured during a period in which the light emitting element is not lit. Unit evaluation device. 6. The light source unit evaluation device according to claim 1, wherein the light beam switching means switches the light emitting element by an analog switch.