JPS60127441A - Apparatus for measuring radius mutual difference of rotary polyhedron mirror - Google Patents

Abstract

PURPOSE:To measure radius mutual difference rapidly and accurately, by allowing a rotary polyhedron mirror to position in a light beam path to detect the radius of a reflective surface on the basis of quantity of light blocked by the reflective surface. CONSTITUTION:A rotary polyhedron mirror 4 is arranged in the light path between a light source 11 and a light output measuring apparatus 12 so as to be partially blocked by the reflective surfaces 4a, 4b thereof. When light beam is emitted from the light source 11, it is partially blocked by the interposition of the reflective surface 4a and received by a measuring apparatus 12. An operation part 13 receiving the supply of this received light output signal operates the radius of the reflective surface 4a and similarly operates that of the reflective surface 4b. Subsequently, the operation part 13 operates the radius mutual difference from the radii of the reflective surfaces 4a, 4b. By this method, the radius mutual difference can be measured rapidly and accurately.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a rotating polygon mirror radius difference measuring device that accurately measures the radius difference of reflective surfaces by positioning the rotating polygon mirror in the optical path of a light beam. .

(Background Art) Rotating polygon mirrors for deflecting light beams at high frequencies are used in various devices such as printers. FIG. 1 shows an example of a laser recording device using a rotating polygon mirror.

This laser recording device includes a laser oscillator 17 that oscillates a parallel beam 16, and a laser oscillator 2-1 that oscillates the parallel beam 16 in all directions.
8a, 18b, 18c, 18d, a rotating polygon mirror 4 that is rotated by a motor or the like and deflects the parallel light #jll 6' (i=scanning direction), and a plurality of ←≠, 1- that controls the luminous flux of the parallel light 16. e-lens 20g, 20b.

20c, 20d, and 20e, a modulator 21 that modulates a parallel light beam 161 according to an image signal, and a photosensitive drum 22 on which an electrostatic latent image is formed by the light beam. In the above configuration, the parallel light beam 16 is emitted from the laser oscillator 17.
is oscillated, this parallel light ray 16 is reflected by the first mirror 18a.
and is displaced in that direction by the second mirror 18b,
The lens 20a'ii enters the modulator 21 via the lens 20a'ii and is modulated according to the image signal. This modulated light beam is transmitted through lens 2
After completely passing through 0b, it is displaced in the horizontal direction by the mirror 18C and reflected by the rotating polygon mirror 4 via the lens 20ck. The modulated light beam is deflected in the scanning direction by reflection from the rotating polygon mirror 4, travels through the lens 20d%20e, reaches the photosensitive drum 22 by the final mirror 18d, and forms a desired electrostatic latent image.

However, if there is a difference in the radius of the reflective surface of the rotating polygon mirror, a shift may occur in the scanning position on the photosensitive drum, which may reduce print quality. Therefore, the difference in radius of each reflective surface must be measured. .

As a method to measure the difference in radius of conventional rotating polygon mirrors,
For example, there are the following two methods.

(1) When using a contact displacement meter as shown in Figure 2.

This contact type displacement meter 1 consists of a shaft 2 that is movable in contact with a reflective surface 4a of a polygon mirror 4 that rotates around an axis 5,
The display section 3 displays the radius of the reflective surface 4a when the lift 2 is retracted. That is, in measuring the radius of the reflecting surface 4a, a rotating polygon mirror 4 and a contact displacement meter 1 are used.
Fix it in place. When the tip 2ak of the shaft 2 of the contact type displacement meter 1 is brought into contact with one reflective surface of the rotating polygon mirror 4, the display section 3 displays a value corresponding to the radius of the reflective surface 4a based on the amount of retraction of the shaft 2 at that time. show. Next, the rotating polygon mirror 4t is rotated, and the different reflecting surfaces 4b are all aligned with the shaft 2.
When the shaft 2 is in contact with the tip 2a, the display section 3 displays a value corresponding to the amount of retraction of the shaft 2 and the radius of the reflective surface 4b. This operation is repeated for the number of reflecting surfaces of the rotating polygon mirror 4 (eight times in FIG. 2), and the mutual difference in radius of each reflecting surface is measured.

However, in this method, the tip 2 of the shaft 2
Since the mirror is brought into contact with the reflective surface of the rotating polygon mirror, which requires a high mirror surface condition of 24 degrees af, there is a risk of damaging the reflective surface.

(2) When using a non-contact displacement meter as shown in Figure 3.

This non-contact type displacement meter 6 makes full use of eddy current and consists of a primary coil 7 and a secondary coil 8. The secondary coil 8 is provided with a display section 10 that measures all induced currents generated in the secondary coil and displays all of the values.

In the above configuration, the operation will be explained. When the -order coil 7 is joined with alternating current and made to face one reflective surface 4a of the rotating polygon mirror 4, the alternating magnetic field of the primary coil 7 (-order (magnetic field), eddy currents are generated. The alternating magnetic field generated by this eddy current 9 acts in the direction of the induction effect based on the primary coil 7 of the secondary coil 8, and the degree of reduction thereof changes depending on the distance between the rotating polygon mirror 4 and the displacement meter 6. Therefore, by measuring the induced current of the secondary coil 8, each reflecting surface 4a, 4bs4C%4d, 4e, 4f, 4
The mutual difference in radius between g and 4h can be measured.

However, with this non-contact displacement meter 6, it takes time to position the measurement point without contacting the rotating polygon mirror, and the displacement meter must be set on the reflective surface. Therefore, quick measurements may not be possible. Furthermore, depending on the material used for the reflective surface, the generation of eddy current is so small that it is impossible to measure it.

(Objective and Structure of the Invention) The present invention has been made in view of the above, and is intended to quickly and accurately measure the mutual radius difference of a rotating polygon mirror without damaging the reflecting surface of the rotating polygon mirror. The present invention provides an apparatus for measuring the difference in radius of a rotating polygon mirror, which detects the radius of a reflecting surface based on the amount of light blocked by the reflecting surface by positioning the rotating polygon mirror in a passage.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

(Embodiment) FIG. 4 shows an entire embodiment of the present invention, in which the light beam 14a (i
) emitting light source 11 (for example, a beam diameter of Or ” l
+1llll T-1e-Ne laser gold) and a light output measuring device 12 (for example, a silicon photodetector with an outer diameter of about 2M) that receives the light from the light source 11 and measures the output of the received light. are provided at predetermined intervals.The optical output measuring device is connected to a calculation section 13 that inputs and calculates the measured optical output signal, and the calculation section 13 is connected to a display section 14 that displays all the calculation results. Light source 1
1 and the optical output measuring device] In the optical path between 2, there is a reflective surface 4a.
, 4b, 4c, 4d, 4e, 4f.

A rotating polygon mirror 4 is rotationally fixed about a shaft 5 so that 4 g % 4 h blocks a portion of the polygon mirror 4 .

In the above configuration, to fully explain its operation, the light source 11
When a light beam Ila'ji is emitted from the rotating polygon mirror 4, the light beam is partially blocked by the interposition of the reflecting surface 4a of the rotating polygon mirror 4 and is received by the light output measuring device 12, and the received light output signal is transmitted to the calculation unit 13. Enter. The input optical output signal is calculated in the calculation unit 13 based on a predetermined program, and the radius from the center point (axis 5) of the rotating polygon mirror 4 to the reflective surface 4a is displayed on the display unit 14. At that time, the intensity distribution of the cross section of the light beam lla is as shown in Fig. 5(a).
The light is strongest in the center of la), and Figure 5 (b) shows the light output measuring device f12 with and without light shielding.
This shows the change in light output at . Next, after the radius measurement of the reflective surface 4a is completed, when the rotating polygon mirror 4 is rotated clockwise, the reflective surface 4b is interposed in the optical path of the light beam lla. Similarly, the radius from the center point of the rotating polygon mirror 4 to the reflective surface 4b is displayed on the display section 14. In order to simplify the calculation operation of the calculation unit 13, the straight line part (A-B
range), 5μ for 1% change in optical output.
m reflective surfaces 4a, 4b, 4c, 4d, 4fs 4g.

This is done by measuring the inflow and outflow of 4h, that is, the mutual difference in radius. Figure 6 shows 8 reflective surfaces 1.2.3.4.5.6.7
．． Showing the results of measuring the radius of a rotating polygon mirror having 8,
The difference in radius can be determined by the envelope 15. The curve connecting each reflective surface 1 and book 3.4.5.6.7.8 is such that the light beam l1m is connected to each reflective surface 1.2.3.4.5, ξ7.
8 shows that the optical output varies due to the interruption by the boundary between the two.

(Effects of the Invention) As explained above, according to the rotating polygon mirror radius mutual difference measuring device according to the present invention, the rotating polygon mirror is entirely positioned in the path of the light beam, and the amount of light that is blocked by the reflecting surface is measured. Since the radius of the reflecting surface is detected by using the rotating polygon mirror, it is possible to quickly and accurately measure the difference in radius of the rotating polygon mirror without damaging the reflecting surface of the rotating polygon mirror.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a laser recording device using rotating polygon mirror sound.
2 and 3 are structural explanatory diagrams of a conventional radius mutual difference measuring device for a rotating polygon mirror, FIG. 4 is a structural diagram of a radius mutual difference measuring device according to the present invention, and FIG. 5 (a) is a light beam Figure 5 (b) is an explanatory diagram showing the change in the optical output of the optical output measuring device depending on the presence or absence of light shielding, and Figure 6 is an explanatory diagram showing the intensity distribution of the cross section of the rotating mirror. It is an explanatory diagram showing an envelope. Explanation of symbols 4...Rotating polygon mirror, 11...Light source, lla...
・Light beam, 12...Light output measuring device, 13...Calculating unit, 14...Display unit Patent applicant Fuji Xerox Co., Ltd. Agent Patent attorney Shin Matsubara 2 Patent attorney Kiyoshi Muraki Fellow Patent attorney Heisei 1) Patent attorney Atsushi Ueshima - Patent attorney Hitoshi Suzuki Figure 1 Figure 2

Claims (1)

[Claims] A light-emitting part and a light-receiving part are located in the middle of the rotating polygon mirror and transmit and receive a light beam whose cross-sectional area changes depending on the radius of the reflecting surface, and the amount of light received by the light-receiving part is 1. A calculation unit that calculates a mutual radius difference of the rotating polygon mirror based on the above-mentioned calculation unit.