JPH03220439A - Measuring apparatus of jitter of polygon scanner - Google Patents

Abstract

PURPOSE:To reduce noises due to the fluctuation of the air by providing wind protecting pipes in a manner allowing three optical axes from a light source to a polygon scanner and an ftheta lens to prism mirrors 5a, 5b to pass therethrough. CONSTITUTION:A light beam L1 generated from a light source 1 is, after passing through a pipe 2a, reflected by a polygon scanner 3. Reflecting lights L2, L3 pass through an ftheta lens 4 and pipes 2b, 2c to be reflected by prism mirrors 5a, 5b and incident upon sensors 6a, 6b; 6c, 6d for a required time, respectively. The time interval from when the powers measured by the sensors 6a, 6b are equal to each other to when the powers measured by the sensors 6c, 6d become equal to each other is measured, so that jitters are calculated. Since there are plastic or metallic pipes 2a-2c in this apparatus, noises of a measured value due to the fluctuation of the air are reduced. If the pipes 2a-2c have wave-like inner shapes in the longitudinal direction, the irregular reflection of the light beam within the pipes 2a-2c can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polygon scanner jitter measuring device that measures the jitter of a polygon scanner using a light beam.

(Conventional technology) FIG. 2 shows an example of a conventional technique.

A substantially parallel light beam L1 emitted from a light source 1 is reflected by a polygon scanner 3, and a light beam L2 passes through an fθ lens 4 and is split by a prism mirror 5a within a certain period of time, and is split by a prism mirror 5a to a sensor 6a.

6b, and within another certain time, the prism mirror 5b
and enters the sensors 6c and 6d.

Jitter is detected by measuring the time interval from the moment when the powers of the light beams output from the sensors 6a and 6b become equal to the moment when the powers of the light beams output from the sensors 6c and 6d become equal.

(Problems to be Solved by the Invention) In the conventional polygon scanner jitter measuring device, the power of the light beam fluctuates due to fluctuations in the air in the portion where the light beam passes through the air with a long optical path length, causing noise in the measured value. appears. Because of the large noise caused by this air fluctuation, it was not possible to measure jitter with greater precision.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and will be explained with reference to FIG. 1 corresponding to an embodiment.
The almost parallel light beam L1 emitted from the polygon scanner 3 reflects the light beam L2, which passes through the fθ lens 4 and is split by the prism mirror 5a. Polygon scanner jitter is obtained by measuring the interval between the beam L1 reflected by the polygon scanner 3, the light beam L3 passing through the fθ lens 4, being split by the prism mirror 5b, and the time when equal power is detected by the sensors 6c and 6d. In the measuring device, from the light source 1 to the polygon scanner 3
and the optical axis between the fθ lens 4 and the prism mirror 5
Windproof plastic or metal pipes 2a, 2b, and 2c are respectively arranged so that the optical axis between the fθ lens 4 and the prism mirror 5b passes through the optical axis. .

(Function) According to the present invention, since the plastic or metal pipe is provided in the optical path of the measuring device so that the light beam passes through, the air outside the pipe and the air through which the light beam passes are blocked. Noise in measured values due to air fluctuations is reduced.

(Embodiment) Fig. 1 is a configuration diagram showing an embodiment according to the present invention, in which 1 is a light source, 2a, 2b, 2c are plastic or metal pipes, 3 is a polygon scanner, 4 is an fθ lens, 5
A and 5b indicate prism mirrors 6a, 6b, 6c, and 6d indicate sensors.

A light beam generated from a light source 1 is reflected by a polygon scanner 3 after passing through a pipe 2a. The reflected light passes through the fθ lens 4, passes through a pipe 2b, is split by a prism mirror 5a, enters both sensors 6a and 6b for the required time, passes through a pipe 2C, is split by a prism mirror 5b, and enters the sensor. The light is incident on both 6c and 6d for the required time. The jitter is calculated by measuring the time from the moment when the powers measured by the sensors 6a and 6b become equal to the moment when the powers measured by the sensors 6c and 6d become equal. Pipes 2a, 2b.

2c reduces noise in measured values due to air fluctuations.

Note that if the internal shape of the pipes 2a, 2b, and 2c is wavy when viewed in the longitudinal direction, the pipe 2a is scanned by the light beam by the polygon scanner 3.

Diffuse reflection within 2b and 2c can be prevented.

(Effect of the invention) According to the present invention, as described above in detail.

By installing a plastic or metal pipe in the long optical path length part of the measurement device, noise caused by air fluctuations can be reduced, making it possible to measure polygon scanner jitter with higher precision. It has the advantage of being

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional example. 1...Light sources 2a, 2b, 2c...Plastic or metal pipe 3...Polygon scanner 4...Fθ lenses 5a, 5b...Prism mirrors 6a, 6b, 6c, 6d -Sensors LL, L2. L3...Light beam

Claims (1)

[Claims] A substantially parallel light beam L1 emitted from a light source 1 is reflected by a polygon scanner 3, and a light beam L2 passes through an fθ lens 4 and is split by a prism mirror 5a.
the time when equal power is detected by the sensors 6a and 6b;
The light beam L1 is reflected by the polygon scanner 3, and the light beam L3 passes through the fθ lens 4 and is reflected by the prism mirror 5.
In the polygon scanner jitter measuring device, which measures the interval between the time when equal power is detected by the sensors 6c and 6d, the optical axis between the light source 1 and the polygon scanner 3, and from the fθ lens 4 A polygon scanner characterized in that windproof pipes 2a, 2b, and 2c are respectively arranged so that the optical axis between the prism mirror 5a and the optical axis between the fθ lens 4 and the prism mirror 5b pass through. Jitter measurement device.