JPH03131817A - Light beam scanning optical device - Google Patents

Abstract

PURPOSE:To relax the fitting accuracy of a photodetector by providing a luminous flux adjusting means so that the spot shape of a beam which is made incident on the photodetector is equal to a spot diameter on a scanned surface and larger in spot diameter in the vertical direction. CONSTITUTION:When the luminous flux of the light beam 14 is not adjusted, spots 27 on sensor surfaces 15 and 16 of the photodetector are the same as the spot on the scanned surface and an adjustment margin is L1. When the luminous flux of this light beam 14 is adjusted by a coating film 20, spots 28 on the sensor surfaces 15 and 16 of the photodetector are larger in diameter at right angles to a scanning direction as compared with the spots 27, so the adjustment margin is L2. Thus, the luminous flux in section perpendicular to the scanning-directional section of the light beam 14 traveling to the photodetector 9 is adjusted by the coating film 20. Consequently, the fitting accuracy of the photodetector is relaxes and the adjustment can be made easily and speedily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light beam scanning optical device used in a laser beam printer or the like.

[Conventional technology]

In scanning optical devices that scan light beams, rotating polygon mirrors and galvano mirrors are widely used as light beam deflectors. Conventionally, a method has been used in which a synchronization detection means is provided at a location where the data is scanned and the time interval from the inspection timing to the writing timing is set constant. At that time, a light receiving element such as a bin photodiode is used to detect the high-speed scanning light beam at daytime response speed, but the size of the light receiving element is small, about 0.5w square, and the light receiving element is small. In order to make the beam enter the element correctly, it is necessary to adjust the reflecting mirror and the light-receiving element. Furthermore, due to the configuration of the scanning optical device, when the light beam is incident on the light receiving element, a part of the light beam must be folded back, and the holding 9w of the reflecting mirror is required.
The disadvantage was that it became difficult to adjust the four-way order. As a solution to this problem, the reflecting mirror and the light receiving element are integrally supported.

For example, the technical idea disclosed in Japanese Unexamined Patent Publication No. 62-204221 is used, or the reflecting mirror is changed to an optical fiber.

For example, there is a technical concept disclosed in Japanese Patent Application Laid-Open No. 65-27i14.

[Problem to be solved by the invention]

However, in the method of integrally supporting the reflecting mirror and the light-receiving element as in the above-mentioned conventional technology, the position of the light-receiving element and the printed circuit board on which it is mounted must be determined by fixing members that are generally difficult to mount with precision. Therefore, even if the supporting member is finished with high precision, the effect is not fully realized. On the other hand, in the method of using optical fibers, the precision of mounting the light receiving element is ignored, but the cross section of the other optical fiber requires fine adjustment of the conventional reflecting mirror, and in this case as well, the effect is not fully realized. There were problems such as not appearing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light beam scanning optical device that has a simple configuration and can significantly reduce the accuracy of mounting a reflecting mirror and a light receiving element.

[Means to solve the problem]

In order to achieve the above object, the present invention makes the spot shape of the beam incident on the light receiving element the same as the spot diameter on the scanned surface in the scanning direction, and in the direction perpendicular to the scanning direction. In this embodiment, a light flux adjusting means is provided in a part of the second imaging optical system so as to increase the spot diameter.

[For production]

Generally, when focusing the original beam, the scanning spot diameter is j,
7.0 lens focal length! , the incident beam diameter and the wavelength λ, a linear relationship holds true.

d=ni・(f/D)・λ・・・・・・・・・・・・
・■However, is a constant of proportionality. Therefore, as is clear from equation (2), the scanning spot diameter d is inversely proportional to the incident beam diameter, and it can be seen that the scanning spot diameter d increases as the incident beam diameter is made smaller.

Here, FIG. 5 is a schematic diagram showing the spot shape of the light beam scanning optical device according to the present invention. Both the direction perpendicular to is d, and -1 for boat fishing.
It is around 00μ attack. On the other hand, (b) is a spot 26 on the light receiving element, and the spot diameter is d only in the direction perpendicular to the scanning direction by the above-mentioned light flux adjustment means according to the present invention.
'.

Note that the light flux adjusting means adjusts the light flux only in the direction perpendicular to the scanning direction (compared to ml) from the relationship of the above equation (2) so that (b) is smaller. As a result, the sensor of the light receiving element As shown, it is about 0.5 ■ square, and compared to (α), (
With bl, the light flux is easier to enter the sensor due to the larger spot diameter. In other words, by adjusting the luminous flux restriction amount so that the spot d' in (A) is equal to or larger than the sensor size Q, 5■, highly accurate synchronized detection can be obtained even if the mounting accuracy of the light receiving element is poor. I can do it.

In addition, in the prior art, the spot diameter remains in the (-) state and the mounting accuracy is relaxed.

〔Example〕

The present invention will be explained below with reference to Examples.

FIG. 1 (,) is a perspective view showing a schematic configuration of a light beam scanning optical device according to an embodiment of the present invention, and #! Figure 1<h)
is an enlarged perspective view of the main part thereof. The optical device includes a light source 1
．． Combined lens 2. First imaging optical system 3° deflector (rotating polygon mirror 4. motor 5), second imaging optical system 6. Scanned object 7
．． Mirror for synchronization detection 8. Light receiving element 9. Coating film 2
0 (details shown in Figure 1 (bl)).

The light source 1 is a semiconductor laser in this embodiment, and the beam from this light source 1 is emitted as a diverging light.

The coupling lens 2 collimates the diverging light into #1
The light beam 10 is made into a substantially parallel light beam, and by adjusting its position in the optical axis direction, focus adjustment is performed to focus the light beam 10 on the surface of the object to be scanned 70 within a cross section in the scanning direction of the beam. The first imaging optical system 3 is composed of a cylindrical lens in this embodiment, has power only in a cross section perpendicular to the cross section in the scanning direction, and directs the light beam 10 to the rotating polygon in the deflector. The light is once focused near the mirror 40 reflection surface 11. At this time, since the first imaging optical system 5 has no power within the cross section in the scanning direction, the reflecting surface 11
The top is a line image.

The rotating polygon mirror 4 of the deflector is rotated by the motor 5 as shown in FIG.
By rotating in the direction of the arrow α) and changing the reflection angle of the reflecting surface 9, the light beam 10 is deflected. One scanning is performed while one reflecting surface is irradiated with the light beam 10, and while the rotating polygon mirror 4 rotates once, scanning is performed as many times as there are reflecting surfaces. In addition, the deflection scanning of the light beam 10 is based on the rotation axis of the deflector (i.e., the rotation center axis of the one-rotation polygon mirror 4).
The optical axis from the light source 1 to the first imaging optical system 3 is arranged within a cross section in the scanning direction.

The second imaging optical system 6 includes a second lens 1 in this embodiment.
3 and a second lens 13, and finally the light beam 10
The deflector is adjusted so that the reflection surface 11 of the deflector and the surface of the object 70 are in a conjugate relationship in the cross section in the sub-scanning direction.

The object to be scanned 7 corresponds to a photosensitive drum in a laser beam printer, for example, and exposes a signal with a light beam 10.

The coating @ 20 functions to adjust the luminous flux of the light beam 14 (t in the figure) in a cross section perpendicular to the cross section in the scanning direction, and the coating film 2
The light beam 14 whose luminous flux has been adjusted by 0 is reflected by the synchronous detection mirror 8 for each scan, and is received by the light receiving element 9 placed approximately at the focal position of the second imaging optical system 6. The light-receiving element 9 serves to determine the time point at which the recording signal starts, and a control circuit (not shown) generates a signal to start the recording signal after a certain period of time from the time of light reception. This signal causes light source 1
is modulated brightly and darkly according to a recording signal from a modulation circuit (not shown), and a latent image of a recorded image is formed on the object 7 to be scanned.

In this embodiment, the coating film 20 fills up the luminous flux in the cross section perpendicular to the cross section in the scanning direction of the light beam 14 directed toward the light receiving element 9, so that the accuracy of mounting the light receiving element can be greatly reduced. That is, adjustments can be made easily and quickly.

Figure 2 shows a comparison of the adjustment margin of the light receiving element when the luminous flux of the light beam 14 is adjusted and when it is not adjusted. In this case, the spot 27 on the sensor surface 15.16 of the light-receiving element is the same as the spot on the scanned surface, and the adjustment margin is 1.
According to this embodiment, the luminous flux of the light beam 14 is adjusted by the coating film 20,
Since the spot 28 on the sensor surface 15, 16 of the light receiving element has a larger diameter in the direction perpendicular to the scanning direction than the spot 27, the adjustment margin is set to L, and as a result, the mounting accuracy of the light receiving element is reduced. This will be significantly eased.

In this embodiment, the coating film 20 is applied to the scanned object 7 of the second lens 13 of the second imaging optical system 6.
Although it is provided on the side lens surface, the same effect can be obtained even if it is provided on the other lens surface, as shown in FIG.

FIG. 3 is a perspective view of the main part of FIG.
A coating film for adjusting the luminous flux of No. 4 may be provided at either the position A (used in the above explanation) and the position B of the second lens 13, or the position C and the position D of the second lens 13. A similar effect can be obtained. Further, in this embodiment, the second imaging optical system 6 includes the second lens 12 . Although the second lens 13 has a two-lens configuration, it goes without saying that any number of lenses may be used. Furthermore, in this embodiment, the first
The imaging optical system 3 creates a line image on the reflective surface 11 of the rotating polygon mirror 4, and the second imaging optical system creates a so-called troublesome image in which the reflective surface 11 and the surface 7 of the object to be scanned are in a conjugate relationship. Although a distortion correction optical system is shown, this is not necessarily necessary, and the first imaging optical system 3 may be removed.

Here, in the above embodiment, the coating film 20 was used as the luminous flux adjusting means, but the same effect can be obtained by using the luminous flux adjusting means shown in FIG. 4. Figure 4 shows
When the second lens 13 of the second imaging optical system (not shown) is attached to the lens fixing base 17 using the lens holding member 21 (usually a plate spring, etc.), the lens is directed toward the light receiving element (not shown) by the nuclear lens holding member 21. It has five configurations to adjust the luminous flux in the direction perpendicular to the scanning direction of the light beam 14. With this configuration, the steps for providing the coating film described above can be reduced.

In these embodiments, a rotating polygon mirror is used as the deflection device, but the present invention can also be applied to the case where another deflection device using a reflecting mirror such as a galvanometer mirror is used. Furthermore, in this embodiment, the explanation is based on the case where it is applied to an optical device for a laser beam printer, but it is not limited to the optical device of this building, and is applicable to other optical devices related to recording and reproducing information such as images. It can be applied to various optical devices.

〔Effect of the invention〕

As described above, according to the present invention, in a light beam scanning optical device, by adding a light flux adjusting means with a very simple configuration, optical adjustment for properly guiding the detected light flux to the detection means can be easily performed. Its industrial value is enormous.

[Brief explanation of the drawing]

FIG. 1(α) is a perspective view showing a schematic configuration of the entire device according to an embodiment of the present invention, FIG. 1<b> is an enlarged fR view of the main part of FIG. 1(α), and FIG. FIG. 5 is a perspective view of the main part of FIG. 1 (a), FIG. 4 is a perspective view of the main part showing another embodiment of the invention, and FIG. It is a diagram explaining the principle of the invention. 1 ・・・・・・・・・・・・・・・ 2 ・・・・・・・・・・・・・・・ 3 ・・・・・・・・・・・・・・・ 4 ・・・・・・・・・・・・・・・・ 5 ・・・・・・・・・・・・・・・ 6 ・・・・・・・・・・・・・・・ 7 ・・・・・・・・・・・・・・・ 8 ・・・・・・・・・・・・・・・ 9 ・・・・・・・・・・・・・・・ 10.14 ・・・・・・ 12 ・・・・・・・・・・・・ 13 ・・・・・・・・・・・・ 15.16 ・・・・・・ 17 ・・・・・・・・・・・・・ 18 ・・・・・・・・・・・・・ 20 ・・・・・・・・・・・・ 21 ・・・・・・・・・・・・ 25 ・・・・・・・・・・・・・ 26 ・・・・・・・・・・・・ 27.28 ・・・・・・ Light source coupling lens First imaging optical system Rotating polygon mirror motor Second imaging optical system For scanning object synchronization detection Mirror light-receiving element Light beam Second lens Second lens Sensor of light-receiving element Lens fixing space Screw Coating film Lens holding member Spora on the scanned surface Spora spot on the light-receiving element 2nd gray (α) 1st (b) 1st? times / 6 light receiving blue ÷ sensor no 16 light receiving element) sensor diagram q receiving blue man diagram diagram Cα) (b)

Claims (1)

[Claims] 1. A light beam generation source (1, 2), a first imaging optical system (3) that forms a linear image of the light beam generated from the light beam generation source; a deflector (4, 5) having a reflective surface (11) near the first imaging optical system; and a second focusing device for focusing the light beam deflected by the deflector onto the object to be scanned. A light beam scanning optical device comprising an image optical system (6) and an object to be scanned (7), and further comprising a synchronization detection mirror (8) for the light beam and a light receiving element (9),
The spot diameter on the light-receiving element is shaped into an elliptical or linear shape that is thicker only in the direction perpendicular to the scanning direction by restricting only the luminous flux in the direction perpendicular to the scanning direction of the light beam directed toward the synchronization detection mirror. A light beam scanning optical device characterized in that the second imaging optical system is provided with a light flux adjusting means. 2. The light flux adjusting means includes a coating film (20) formed on a part of the lens surface of the second imaging optical system in a shape that limits the light flux. Light beam scanning optical device. 3. The light flux adjustment means according to claim 1, wherein the light flux adjustment means has a configuration in which a part of the lens holding member (21) of the second imaging optical system or itself is provided with a shape that limits the light flux. Light beam scanning optical device.