JPH077004B2 - Accuracy measurement method of rotation unevenness measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an accuracy measuring method of a rotation unevenness measuring device of an optical scanning device using a polygon mirror used in a laser beam printer.

(Prior Art) In general, a method of measuring the rotational accuracy of a scanner motor is as shown in FIG. 2, in which a polygon mirror 1 is irradiated with a laser beam L11 from a laser light source 2 and a reflected beam L12 is scanned.
Is received by the two trigger generators 13 and 14 arranged with a predetermined prospective angle with respect to the polygon mirror 1,
Obtain trigger signals S1 and S2.

The principle of the trigger generator 13 will be explained below.
As shown in the figure, the spot P of the scanned reflected beam L12 passes through the opening D of the trigger generator 13 from the left to the right in the figure, so that the analog signal Sa depending on the amount of light incident on the opening D is generated. Is obtained. This analog signal Sa is set to a predetermined level SL
And the digitized result is output as the trigger signal S1.

By inputting the two trigger signals S1 and S2 thus obtained to the input terminals A and B of the time difference measuring means (for example, a counter) 15, the reflected beam L12 as shown in FIG.
The average scanning time t for scanning the two trigger generators 13 and 14 and the fluctuation amount Δt are obtained, whereby the rotation accuracy J of the polygon scanner is obtained as (Δt / t).

(Problems to be Solved by the Invention) The signals S1 and S2 from the trigger generators 13 and 14 include components other than rotational fluctuations of the scanner (for example, noise of a photoelectric converter or circuit for generating a trigger). I often go out.

Therefore, in such a measurement system, components other than the rotational fluctuation of the scanner are included in the data, but until now, there was no means for grasping the quantitative magnitude of the component.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and a rotating polygon mirror is irradiated with a laser beam from a laser light source, and a scanned reflected beam is applied to the polygon mirror. On the other hand, two trigger generators arranged at a predetermined angle of view generate trigger signals respectively, and the trigger signals are converted into digital signals and input to the time difference measuring means, between the two trigger signals. In a rotation unevenness measuring device that measures the rotation accuracy of a polygon scanner from the average scanning time and fluctuation amount of the laser beam L1 emitted from the laser light source 2 to the rotating polygon mirror 1, the reflected laser beam is reflected. The beam L2 passes through the half mirror 5, and the passed laser beam La is incident on the trigger generator 4 to generate a trigger signal, and at the same time, the half mirror 5 is generated. The half mirror 5 and the trigger generators 4 and 3 are arranged close to each other so that the laser beam Lb reflected by the laser beam 5 enters the other trigger generator 3 to generate a trigger signal. Each of the trigger signals is converted into a digital signal and input to the time difference measuring means to measure the time difference between the two trigger signals and the variation amount.

(Operation) According to the present invention, the optical system is arranged so that the passed laser beam La and the reflected laser beam Lb are simultaneously incident on the trigger generators 4 and 3, and the trigger signals from the trigger generators 4 and 3 are generated. Convert it to a digital signal and input it to the time difference measuring means
By measuring the time difference between the two trigger signals and the fluctuation amount, it is possible to quantitatively evaluate the components other than the rotation fluctuation of the polygon mirror 1 included in the measurement data of the rotation unevenness measuring device.

(Embodiment) FIG. 1 is a diagram for explaining an embodiment of the present invention, in which a laser beam L1 emitted from a laser light source 2 is incident on a polygon mirror 1 and the reflected laser beam L2 is a polygon. Scanning is performed as the mirror 1 rotates in the direction of the arrow, and the laser beam La is incident on the half mirror 5 at a predetermined position and is divided into a laser beam La that has passed and a laser beam Lb that has been reflected. In this case, the half mirror 5 and the trigger generators 4 and 3 are arranged close to each other so that the laser beams La and Lb respectively enter the trigger generators 4 and 3 at the same time. The time difference and the amount of fluctuation of the trigger signals (not shown) from the trigger generators 4 and 3 thus obtained are measured by the time difference measuring means (for example, counter) 15 shown in FIG.

At this time, since the optical system is arranged so that the passed laser beam La and the reflected laser beam Lb are simultaneously incident on the trigger generators 4 and 3, two laser beams actually measured by scanning the laser beam are measured. The time difference between trigger signals and the amount of fluctuation are
That is, it is an error of the rotation unevenness measuring apparatus (for example, due to noise of a photoelectric converter or circuit for generating a trigger).

Because the half mirror 5, the trigger generator 4, and the trigger generator 3 are arranged close to each other, the influence of the distortion of the optical system fixing them can be ignored, and the same laser beam is simultaneously generated by the trigger generator. This is because the rotation fluctuation of the polygon mirror 1 does not enter the measurement amount because the laser beam is irradiated to the laser beam and the trigger signal is obtained by this laser beam.

(Effects of the Invention) As described above in detail, according to the present invention, it is possible to quantitatively evaluate the error of the measurement system other than the rotation fluctuation of the polygon mirror, that is, the rotation unevenness measuring apparatus for the polygon mirror. It is possible to measure the accuracy of the rotation unevenness measuring apparatus by quantitatively evaluating the error around the trigger generator included in the above. Therefore, the rotation irregularity of the polygon mirror can be obtained more accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a configuration diagram of a rotation accuracy measuring device of a scanner motor, FIG. 3 is a diagram for explaining the principle of a trigger generator, and FIG. 4 is a diagram showing a digitized trigger signal. 1 …… Polygon mirror 2 …… Laser light source 3,4,13,14 …… Trigger generator 5 …… Half mirror 15 …… Time difference measuring means

Claims (1)

[Claims] 1. A rotating polygon mirror is irradiated with a laser beam from a laser light source, and a reflected beam scanned is arranged at a predetermined angle with respect to the polygon mirror.
The trigger signals are generated by being received by two trigger generators, the trigger signals are converted into digital signals and input to the time difference measuring means, and the rotation of the polygon scanner is determined based on the average scanning time and fluctuation amount between the two trigger signals. In a rotation unevenness measuring device for measuring accuracy, a laser beam (L1) emitted from a laser light source (2) is incident on a rotating polygon mirror (1), and the reflected laser beam (L2) is reflected by a half mirror (1). Go through 5),
The passed laser beam (La) is a trigger generator (4)
To generate a trigger signal, and at the same time, the laser beam (Lb) reflected by the half mirror (5) enters another trigger generator (3) to generate a trigger signal. The trigger generators (4) and (3) are arranged close to each other, and the trigger signals of the trigger generators (4) and (3) are respectively converted into digital signals and input to the time difference measuring means, and two trigger signals are provided. An accuracy measuring method for a rotation unevenness measuring device, characterized by measuring a time difference between the two and a fluctuation amount.