JPH0682082B2 - Polygon scanner measuring device - Google Patents

Description

The present invention relates to an evaluation device for a laser scanning device using a polygon mirror used in a laser printer or the like.

(Prior Art) In a laser printer, high processing accuracy is required for each unit in order to maintain performance such as high resolution and high print quality. Above all, the laser scanner, which is the core of the laser optical system, processes and assembles with sub-micron accuracy.
The whole unit must guarantee high accuracy for a long time. In the scanner, the polygon mirror is directly connected to the spindle and rotates at high speed. Up to now, a method of statically measuring the optical characteristics such as the size of the scanner and the processing accuracy such as surface misalignment has been put into practical use. However, there is no effective means to measure the dynamic movement (including axial deviation) of the surface when the scanner is rotating at a high speed, and there is a method to judge the quality of the printing result on the device. I had no choice but to employ it.

(Problems to be Solved by the Invention) In the above-mentioned conventional method, work efficiency is low and improvement in productivity cannot be expected, and therefore, development of a method capable of measuring scanner characteristics at high speed and with high accuracy under dynamic conditions has been developed. I was coveted.

In addition, since the dynamic movement of the surface affects the rotation jitter, which is one of the important performances of the polygon scanner, the scanner that accurately measures the surface movement at the reflection point of the polygon mirror that actually measures the rotation jitter. It will be useful for evaluation and analysis.

(Means for Solving the Problems) The present invention has been made to solve the above problems,
The present invention will be described with reference to FIGS. 1 and 3A and 3B corresponding to the embodiment. According to the present invention, a laser beam L5 emitted from a first laser light source 2 is incident on a rotating polygon mirror 1 and reflected by the polygon mirror 1. The generated laser beam L6 is incident on the first position detector 10 for detecting the position of the laser beam after passing through the first cylindrical lens 12, and the laser beam L1 emitted from the second laser light source 3 is The laser beam L2 which has passed through the first half mirror 6 is made incident on the polygon mirror 1, the reflected laser beam L3 is made incident on the first half mirror 6, and its reflected light L4 is made first. And the laser beam L10 emitted from the third laser light source 4
Is incident on the rotating polygon mirror 1, and the reflected laser beam L11 is incident on the second position detector 11 for detecting the laser beam position after passing through the second cylindrical lens 13. Furthermore, the fourth laser light source 5
The laser beam L7 emitted from the second half mirror 8
Laser beam L8 that has passed therethrough is incident on the polygon mirror 1, the reflected laser beam L9 is incident on the second half mirror 8, and the reflected light L12 is reflected on the second half mirror 8.
A second dynamic surface entrance / exit measuring device configured to be incident on the trigger generator 9 of FIG.

(Operation) Before describing the operation of the present invention, a method for measuring the rotation jitter will be described with reference to FIG.

The laser beam L20 emitted from the laser light source 20 is incident on the mirror surface of the polygon mirror in the first state 24, the reflected laser beam L22 is incident on the first trigger generator 22, and the first trigger outputs a signal. Occur. The reflection point of the polygon mirror at that time is R1. Next, when the polygon mirror rotates counterclockwise to the second state 23, the reflected light L21 of the incident laser beam L20 is incident on the second trigger generator 21, and the second trigger signal is transmitted. To occur. The reflection point of the polygon mirror at that time is R2.

The rotation jitter measures the time between the first trigger signal and the second trigger signal.

As described above in detail, the reflection points of the polygon mirror at the rotation jitter measurement points are changed to R1 and R2. Therefore, according to the present invention, the emitted light L2 of the second laser light source 3 is
The reflected light L3 from the first reflection point R1 of the polygon mirror 1 is detected by the first trigger generator 7 as the reflected light L4 transmitted through the first beam splitter 6, and the fourth laser light source 5 The reflected light L9 from the second reflection point R2 of the polygon mirror 1 with respect to the emitted light L7 is detected by the second trigger generator 9 as the reflected light L12 that has passed through the second beam splitter 8, and the first trigger is generated. By detecting the time difference from the detection signal generated by the generator 7, it is possible to first perform the jitter measurement that does not include the surface entrance / exit component.

Further, the reflected light L6 from the first reflection point R1 of the polygon mirror 1 with respect to the emitted light L5 of the first laser light source 2 is incident on the first position detector 10 via the first cylindrical lens 12. , The amount of entering and leaving the surface at the first reflection point R1 can also be measured at the same time.

Similarly, the reflected light L11 from the second reflection point R2 of the polygon mirror 1 with respect to the emitted light L10 of the third laser light source 4 is
By entering the second position detector 11 through the second cylindrical lens 13, it is possible to simultaneously measure the surface entrance / exit amount at the second reflection point R2.

(Example) Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment according to the present invention, and FIGS. 3A and 3B are block diagrams of the first and second dynamic surface entrance / exit measuring devices constituting the present invention, respectively. Hereinafter, the present invention will be described mainly with reference to FIGS. 3A and 3B.

3A and 3B respectively show the rotational position of the polygon mirror 1 at the time of measuring the rotational jitter, and the surface entrance / exit measurement points R1 and R2 are the same as the laser beam incident position at the time of the rotational jitter measurement. Since the configuration of the surface entrance / exit measurement is the same as in FIGS. 3A and 3B, the first dynamic surface entrance / exit measuring device will be described first with reference to FIG. 3A.

The substantially parallel laser beam L5 emitted from the first lasing light source 2 is incident on the rotation jitter measuring point R1 in the first state 24 of the polygon mirror 1. The incident laser beam L5 scans as the polygon mirror 1 rotates, but the polygon mirror 1
When the state becomes as shown in the figure, the reflected light L6 from the polygon mirror 1 passes through the cylindrical lens 12 and enters the laser beam position detector 10. This cylindrical lens
Reference numeral 12 is for reducing the output error of the beam position detector 10 due to the simultaneous occurrence of the surface tilt which causes the beam position deviation of the polygon mirror in the sub-scanning direction.

Further, the laser light L1 emitted from the second laser light source 3 passes through the half mirror 6 and the first state 24 of the polygon mirror 1
Incident on. This laser beam L1 also scans as the polygon mirror 1 rotates, but when the surface of the polygon mirror 1 and the incident laser beam L2 become vertical as shown in the figure, the reflected laser beam L3 is reflected by the half mirror 6. The reflected light L4 is incident on the trigger generator 7. Therefore, when the first state 24 of the polygon mirror 1 becomes a state as shown in the same figure, a trigger signal is generated from the trigger generator 7, and if the output signal of the beam position detector 10 at that moment is observed, the movement will occur. The amount of entry / exit is measured. Here, the calculation method of the surface entrance / exit amount will be described with reference to FIG. 4 using the laser beam La1 as an example. When the laser beam La1 is in the state A on the polygon mirror surface, the reflected light becomes like Lb1. Here, the reflected light when the surface is in state B is Lb2. Here, if the beam movement amount is d ₁ as shown in the figure, then the surface entrance / exit do becomes do ＝ d ₁ cos (θ / 2).

In this way, since the positional deviation of the reflected laser beams Lb1 and Lb2 can be measured, it is possible to obtain the entering / exiting amount of the surface.

Next, the second dynamic surface entrance / exit measuring device will be described with reference to FIG. 3B.

The substantially parallel laser beam L10 emitted from the third laser light source 4 enters the rotation jitter measurement point R2 in the second state 23 of the polygon mirror 1. The incident laser beam L10 scans with the rotation of the polygon mirror 1, but when the polygon mirror 1 is in the state as shown in the figure, the reflected light L9 from the polygon mirror 1 passes through the cylindrical lens 13 and passes through the laser. It is incident on the beam position detector 11. Since the cylindrical lens 13 simultaneously causes a surface tilt that causes a beam position shift of the polygon mirror 1 in the sub-scanning direction, the output error of the beam position detector 11 is reduced.

The laser light L7 emitted from the fourth laser light source 5 passes through the half mirror 8 and is in the first state of the polygon mirror 1.
Incident on 24. This laser beam 7 also scans as the polygon mirror 1 rotates, but when the surface of the polygon mirror 1 and the incident laser beam L8 are perpendicular to each other as shown in the figure, the reflected laser beam L9 is transmitted to the half mirror 8. The reflected light L12 is incident on the trigger generator 9. Therefore, when the second state 23 of the polygon mirror 1 becomes a state as shown in the same figure, a trigger signal is generated from the trigger generator 9, and if the output signal of the beam position detector 11 at that moment is observed, it will move. The amount of entry / exit is measured.

Therefore, the laser beam L1 emitted from the laser light source 3 is incident on the mirror surface of the polygon mirror 1 in the first state 24, the laser beam L3 reflected at the reflection point R1 is incident on the half mirror 6, and its reflected light L4 When the polygon mirror 1 is in the second state 23, the reflected light L9 of the incident laser beam L7 is incident on the half mirror 8, and The reflected light L12 is the trigger generator 9
By detecting the time difference between the second trigger signal obtained by incidence on and the second trigger signal, it is possible to perform the jitter measurement that does not include the surface entrance / exit component.

Further, the reflected light L6 from the first reflection point R1 of the polygon mirror 1 with respect to the emitted light L5 of the first laser light source 2 is incident on the first position detector 10 via the first cylindrical lens 12. , The amount of entering and leaving the surface at the first reflection point R1 can also be measured at the same time.

Similarly, the second reflected light L11 from the second reflection point R2 of the polygon mirror 1 with respect to the emitted light L10 of the third laser light source 4 is
The second position detector 1 through the cylindrical lens 13 of
It is possible to simultaneously measure the amount of entering / exiting the surface at the second reflection point R2.

(Effect of the Invention) As described in detail above, according to the present invention, by using two sets of the dynamic surface entering / exiting measuring device, the surface entering / exiting amount that affects the rotation jitter of the polygon scanner can be directly measured. .

Also, by measuring the time of two sets of trigger signals of two sets of trigger generators for the dynamic surface entrance / exit measurement, it is possible to measure jitter without surface entrance / exit components at the same time, that is, on the same reflecting surface. Therefore, the number of parameters for quantifying the rotation characteristics of the polygon scanner is increased by one, which has the advantage of providing a measuring instrument effective for evaluation and analysis of the polygon scanner.

[Brief description of drawings]

FIGS. 1 and 3A and B are block diagrams of an embodiment according to the present invention,
FIG. 2 is a diagram for explaining the measurement principle of rotation jitter, and FIG. 4 is a diagram for explaining the operation principle of this embodiment. 1 …… Polygon scanner 2,3,4,5,20 …… Laser light source 6,8 …… Half mirror 7,9,21,22 …… Trigger generator 10,11 …… Laser beam position detector 12,13 …… Cylindrical lens 23,24 …… Polygon mirror

Claims (1)

[Claims] 1. A polygon mirror (1) rotating a laser beam (L5) emitted from a first laser light source (2).
To the first position detector (10) for detecting the position of the laser beam after passing through the first cylindrical lens (12), and further to the second laser beam (L6). The laser beam (L1) emitted from the laser light source (3) passes through the first half mirror (6),
The passed laser beam (L2) is incident on the polygon mirror (1), the reflected laser beam (L3) is incident on the first half mirror (6), and the reflected light (L4) is first reflected. And a laser beam (L10) emitted from a third laser light source (4), the rotating polygon mirror ( 1), the reflected laser beam (L11) is passed through the second cylindrical lens (13), and then is incident on the second position detector (11) for detecting the position of the laser beam after passing through it. The laser beam (L7) emitted from the laser light source (5) of No. 4 passes through the second half mirror (8),
The passed laser beam (L8) is made incident on the polygon mirror (1), the reflected laser beam (L9) is made incident on the second half mirror (8), and the reflected light (L12) is made second. A second dynamic surface entrance / exit measuring device configured to be incident on the trigger generator (9) of (4), and a polygon scanner measuring device.