JPH03220437A - Inclination measuring apparatus of surface of polygon scanner - Google Patents

Abstract

PURPOSE:To reduce noises due to the fluctuation of the air in an optical path by providing wind protecting pipes in a manner to allow optical axes between a first ftheta lens and a beam splitter and between a second ftheta lens and a prism mirror to pass therethrough. CONSTITUTION:This measuring apparatus detects the position of a light beam to measure the surface inclination of a polygon scanner. In this measuring apparatus, plastic pipes 5a, 5b (e.g., having the outer diameter of about 18.1mm and the inner diameter of about 13.5mm) or metallic pipes 5a, 5b are provided in optical pathes between an ftheta lens 4a and a prism mirror 8a and an ftheta lens 4b and a beam splitter 6, respectively. The air outside the pipes 5a, 5b are shut from the air where light beams L2, L3 pass, whereby noises resulting from the fluctuation of the air can be reduced, assuring highly accurate measure ment. If the inner shape of the pipes 5a, 5b in a longitudinal direction is like waves, the irregular reflection of the light beam scanned by a polygon scanner 3 within the pipes 5a, 5b can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a polygon scanner surface inclination measurement device that measures the surface inclination of a polygon scanner using a light beam.6 (Prior Art) As shown in FIG. An example of conventional technology is shown.

A beam splitter 2 is provided to split the nearly parallel light beam L1 emitted from the light source 1 into two, and the light beam L3 transmitted through the beam splitter 2 is reflected by the polygon scanner 3 and is reflected by the fθ lens 4b. The light beam L3a enters the beam splitter 6 through the
The light beam L3b is split by the first prism mirror 8b and made incident on the first and second sensors 9e and 9f, and the other light beam L3b is split by the second prism mirror 7 and sent to the third and fourth sensors 9c. , 9 d, and at the moment when the powers of the light beams at sensors 9 c and 9 d become equal,
The vertical light beam inclination is detected by e and 9f.

Furthermore, the light beam L2 reflected by the beam splitter 2 passes through the second fθ lens 4a, and then passes through the third prism mirror 8a.
The light beam is divided into two parts, and is made incident on the fifth and sixth sensors 9a and 9b to detect the tilt of the light beam in the vertical direction. sensor 9e first
, 9f is measured by subtracting the vertical light beam inclination detected by the sensors 9a and 9b from the vertical light beam inclination detected by the polygon scanner 3.

(Problems to be Solved by the Invention) In the conventional polygon scanner surface inclination measurement 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, and the measured value may vary. This appears as noise as shown in Figure 4. Since the noise caused by this air fluctuation was as large as 0.7' at maximum, it was not possible to measure the surface inclination with higher precision.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and will be explained with reference to FIGS. 1 and 2 corresponding to embodiments. A beam splitter 2 is provided to split the almost parallel light beam L1 into two, and the light beam L3 transmitted through the beam splitter 2 is reflected by the polygon scanner 3 and enters the beam splitter 6 via the fθ lens 4b. and the transmitted light beam L3
a is divided by the first prism mirror 8b, and the first and second
The other light beam L3b is incident on the sensors 9e and 9f of
is split by the second prism mirror 7 and made incident on the third and fourth sensors 9c and 9d to detect the respective light beam positions, and the light beam L reflected by the beam splitter 2
2 is divided by a third prism mirror 8a through a second fθ lens 4a, and is incident on fifth and sixth sensors 9a and 9b to detect the position of the light beam. , the first fθ lens 4b and the first
Windproof plastic or metal pipes 5a and 5b are installed so that the optical axis between the beam splitter 6 and the optical axis between the second fθ lens 4a and the third prism mirror 8a pass through. They are arranged respectively.

(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 caused by air fluctuations is reduced.

(Embodiment) FIG. 1 shows a configuration diagram of an embodiment according to the present invention, in which 1 is a light source, 2 is a beam splitter, 3 is a polygon scanner,
4a and 4b are fθ lenses, and 5a.

5b is a plastic pipe, 6 is a beam splitter, 7.8a and 8b are prism mirrors, and 9a.

9b, 9c, 9d, 9e, and 9f are sensors.

The surface inclination measuring device for a polygon scanner according to the present invention differs from the conventional surface inclination measuring device explained in FIG.
pipe 5 in the optical path between b and beam splitter 6.
A and a pipe 5b are provided.

FIG. 2 shows the noise measured by the device of this embodiment.

As a result of this noise measurement, the conventional polygon scanner surface inclination measuring device shown in FIG. The noise due to air fluctuations is reduced by providing the pipes 5a and 5b.

Note that the pipes 5a and 5b used in this example have an outer diameter of 18.
It is a plastic pipe with a diameter of 1 mm and an inner diameter of 13.5 mm.

Incidentally, if the internal shapes of the pipes 5a and 5b are wavy when viewed in the longitudinal direction, diffuse reflection of the light beam scanned by the polygon scanner 3 within the pipes 5a and 5b can be prevented.

(Effects of the Invention) As described above in detail, according to the present invention, the noise in the conventional polygon scanner measuring device is 0.7.
' However, by installing a plastic or metal pipe in the long optical path length part of the measuring device, the noise due to air fluctuations can be reduced to 0.26'. This has the advantage of enabling more accurate measurement using a polygon scanner.

[Brief explanation of drawings]

1 and 2 show a configuration diagram and noise measurement values of an embodiment according to the present invention, and FIGS. 3 and 4 show a configuration diagram and noise measurement values of a conventional example. 1... Light source 2, 6... Beam splitter 3... Polygon scanner 4a, 4b... fθ lens 5a, 5b... Plastic pipe 7.8a, 8b
...Prism mirror

Claims (1)

[Claims] A beam splitter 2 is provided to split the substantially parallel light beam L1 emitted from the light source 1 into two, and the light beam L3 transmitted through the beam splitter 2 is reflected by the polygon scanner 3 and then passed through the fθ lens 4b. The light beam L3a enters the beam splitter 6 and is transmitted through the beam splitter 6.
The light beam L3b is split by the first prism mirror 8b and made incident on the first and second sensors 9e and 9f, and the other light beam L3b is split by the second prism mirror 7 and sent to the third and fourth sensors 9c, 9f. 9d, the respective light beam positions are detected, and the light beam L2 reflected by the beam splitter 2 is
In a polygon scanner surface inclination measurement device in which the light beam is divided by a third prism mirror 8a through a second fθ lens 4a and incident on fifth and sixth sensors 9a and 9b to detect the position of the light beam, The windproof pipe 5a is arranged so that the optical axis between the first fθ lens 4b and the first beam splitter 6 and the optical axis between the second fθ lens 4a and the third prism mirror 8a pass through. and 5b, respectively.