JPS62267716A - Scanning optical device - Google Patents

Abstract

PURPOSE:To miniaturize a scanning optical device, by making the scanning track of a reflecting mirror straight and, at the same time, controlling the rotational angle of the mirror in accordance with the displaced quantity of the mirror. CONSTITUTION:When a motor 12 is driven, a gear 14 moves in the scanning direction while rotating on the straight line of a scanning track XX' or on a track 11 provided in parallel with the line XX' and a reflecting mirror 6 moves along a straight track. As the mirror 6 moves, a worm wheel 21 coupled with the reflecting mirror 6 rotates in accordance with the displaced quantity of the mirror 6 and the inclination of the reflecting surface of the mirror 6 changes. Since the rotational angle of the reflecting mirror 6 is very small as compared with the moving distance of the mirror 6 in the scanning direction, the number of teeth of the gear 14 is made smaller than that of another gear 15 so that the rotation of the gear can be transmitted to the worm wheel after reduction in speed and the center point O of the reflecting surface of the mirror 6 can always be positioned on the straight scanning track XX' during scan. When the gear ratio between the gears 14 and 15 is changed, appropriate displacement of the reflecting mirror in rotational angle can be obtained in accordance with the displaced quantity of the mirror in the scanning direction.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to a reader printer, etc. in which a single lens is used to guide imaging light between an imaging lens and a virtual imaging surface to a predetermined position on a photoreceptor. The present invention relates to a scanning optical device that performs optical scanning by rotating or moving a reflecting mirror.

(Previous technology) Conventionally, this type of device for performing optical scanning using only one reflective mirror is disclosed in Japanese Patent Application Laid-open No. 126258/1982 and US Pat. No. 4,299,480. In such a conventional example, one reflecting mirror moves as the virtual imaging point moves, with the reflecting surface of the reflecting mirror coinciding with the perpendicular bisector of the line segment connecting the virtual imaging point and the exposure position. Therefore, optical scanning was performed.

That is, in order to perform optical scanning in the conventional example, as shown in FIG.
A reflecting mirror 106 is disposed approximately midway between the point on the virtual image forming surface 105 and the image forming point on the photosensitive drum 107 in synchronization with the rotational speed of the photosensitive drum 107. Reflection mirror 10 on the perpendicular bisector of the line segment connecting
Since the reflective mirror 106 needs to move while being aligned, the locus of the reflective mirror 106 becomes a curve SS'.

(Problems to be Solved by the Invention) However, in such conventional examples, the scanning optical device for moving the reflecting mirror is configured to control the pupil position of the lens or the exposure on the photosensitive drum by means of a connecting member that allows the reflecting mirror to slide. Since it is configured to be moved by being connected (linked) to a portion corresponding to the position, there are problems in that the device becomes larger and the degree of freedom in actual optical arrangement is reduced.

Therefore, the present invention has been made in order to solve the above-mentioned problems of the conventional example, and its purpose is to eliminate the member connecting the scanning reflecting mirror, the imaging lens, and the photosensitive drum. The objective is to reduce the size of the device and improve the degree of freedom in optical arrangement.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, by moving one reflective mirror disposed between the imaging lens and the imaging surface, In a scanning optical device that performs optical scanning, the scanning trajectory of the reflecting mirror is made linear, and the rotation angle of the reflecting mirror is controlled in accordance with the amount of displacement of the reflecting mirror.

(Function) In the present invention, the scanning trajectory along which one reflecting mirror moves is linear, and by controlling the rotation angle of the reflecting mirror according to the amount of displacement of this reflecting mirror, the reflecting mirror can be moved independently. It has been made possible to do so.

(Examples) The present invention will be described below based on illustrated embodiments. 6
mlI24 and FIG. 2 are schematic diagrams for explaining the principle of an embodiment of the scanning optical device according to the present invention. In the figure, 1 is an illumination lamp, and the light emitted from the illumination lamp 1 is A microfilm 3 is irradiated through a condenser lens 2, and an image of this microfilm 3 is projected onto a virtual imaging plane 5 through an imaging lens 4.

In this case, on the display surface of the microfilm 3, the second
As shown in the figure, point B on the optical axis of lens 4 and points A and C on both sides thereof are points B1 and AI on virtual image plane 5, respectively.
A reflection mirror 6 is disposed approximately midway between the lens 4 and the virtual imaging surface 5 to reflect the imaging light and form an image on the surface of the photosensitive drum 7. In order to
It is necessary to make the distance from the image forming point of the photosensitive drum equal to the distance from the image forming point of the photosensitive drum.

Therefore, in order to perform optical scanning, the reflection mirror 6 is synchronized with the rotational speed of the photosensitive drum 7 to move the virtual image plane 5.
Since the reflection surface of the reflection mirror 6 must match the perpendicular bisector of the line segment connecting the upper point and the imaging point on the photosensitive drum 7 while moving, the trajectory of the reflection mirror 6 follows the curve SS '. The shape of this curve SS' varies depending on the placement position of the photosensitive drum 7, but as shown in FIGS. 1 and 2,
The position of the reflecting mirror 6 is relatively close to the lens 4,
When the position of the photosensitive drum 7 is far from the virtual imaging plane 5 and close to the lens 4, the curve SS
′ can be regarded as a substantially straight line. Therefore, a method can be considered in which scanning is performed by moving the reflecting mirror 6 on a linear trajectory. At this time, in order to image the light that has passed through the lens 4 on the photosensitive drum 7 at all positions in the image area of the linear trajectory t, while rotating the angle of the reflecting mirror 6,
Furthermore, it is necessary to scan while changing the moving speed in order to synchronize with the photosensitive drum 7 which rotates at a constant speed.

In determining the actual linear trajectory, a linear regression line in which the deviation of the optical path length takes a minimum value at an arbitrary position is set as the scanning trajectory line for a curved trajectory equation that does not cause an optical path difference. In general, projection lenses for microfilm used in reader printers, etc. have advantages such as a narrower angle of view and deeper depth of field than lenses used in copying machines, etc., so the optical path created by a straight trajectory is The effect of deviation is almost negligible.

Next, in Fig. 3, regarding the control system of the reflecting mirror, a straight line xx' with an inclination of 12.5° with the image forming plane passes through a point on the optical axis at a position 650 mm from the image forming plane as the scanning trajectory straight line. FIG. 4 is a diagram showing the relationship between the moving displacement and angular displacement of the reflecting mirror on a straight line when the reflecting mirror is taken.

In this case, the reflecting surface of the reflecting mirror 6 rotates by a certain angle in a certain direction in accordance with the displacement of the reflecting mirror 6 in the linear scanning direction.

Note that the scanning speed of the reflecting mirror 6 is not theoretically constant unless the scanning straight line is taken parallel to the image plane, but if the slope of the scanning straight line is small as in the above embodiment, the scanning speed is constant. However, it actually has little effect.

Therefore, a specific device for scanning by moving the reflection mirror 6 as described above is shown in FIG. Guide rail members 9 and 10 are provided.

Reference numeral 8 denotes support members attached to both ends of the reflecting mirror 6, and guide rail members 9. IO guide holes 9a, 10a
The reflecting mirror 6 is moved by being guided by. Reference numeral 11 denotes a rack, and this rack 11 is arranged so that its pitch line coincides with or is parallel to the scanning trajectory straight line xx'. 12 is a motor as a driving source, 13 is a shaft of the motor 12, and a gear 14 is fitted to the tip of this shaft 13. The gear 14 meshes with the rack 11 and also meshes with the gear 15. The gear 15 connects to the bevel gear 1 via a connecting shaft 16.
7, and the bevel gear 17 meshes with the bevel gear 18. 20 is a worm, and a bevel gear 18 is fitted to one end of a shaft 19 of the worm 2o. Further, the worm 20 meshes with a worm wheel 21, and the worm wheel 21 engages with the worm wheel 21.
1 is attached to a support member 8.

In the above configuration, when the motor 12 is driven, the gear 14 moves in the scanning direction while rotating the rack 11-hi arranged on or parallel to the scanning trajectory straight line xx', so that the reflecting mirror 6 is moved along the linear trajectory. move. The worm wheel 21 connected to the reflecting mirror 6 rotates in accordance with the amount of displacement, thereby changing the inclination of the reflecting surface of the reflecting mirror 6. In addition, FIG. 5 is a configuration diagram of the main part of FIG. The rotation of the gear 14 is reduced in speed and transmitted to the worm wheel 21. In FIG. 5, the center point 0 of the reflective surface of the reflective mirror 6 is positioned on the scanning trajectory straight line xx' in the scanning chamber.

In the above embodiment, the control of the reflecting mirror was explained when the scanning trajectory straight line was set at a certain specific position.
Even if the setting position of the scanning trajectory straight line xx' is different, by changing the gear ratio of the configured gears, it is possible to obtain an appropriate rotation angle displacement of the reflecting mirror according to the movement displacement in the scanning direction. .

Therefore, in the above embodiment, the scanning trajectory of the reflecting mirror 6 is regarded as approximately a straight line within the allowable range of the geometric optical path difference, and the rack 11 is arranged on the scanning trajectory straight line or a straight line parallel thereto. gears 14, 15 and bevel gear 17.1 relative to rack 11.
8. The rotation angle of the reflecting mirror 6 is controlled by a deceleration mechanism composed of a worm 20 and a worm wheel 21.

(Effects of the Invention) The scanning optical device according to the present invention has the above-described configuration and operation, and not only makes the scanning trajectory of the reflection mirror linear, but also changes the rotation angle of the reflection mirror according to the amount of displacement of the reflection mirror. Since the control is performed, a member connecting the reflecting mirror, the imaging lens, and the photosensitive drum is not required, and the apparatus can be made smaller. In addition, by doing this, it is possible to interpose a reflective mirror that changes the direction of the light flux in addition to the reflective mirror that performs scanning between the imaging lens and the photosensitive drum, and the optical This has the effect that the degree of freedom in arrangement can be improved.

[Brief explanation of drawings]

1 and 2 are schematic diagrams for explaining the principle of an embodiment of the scanning optical device according to the present invention, and FIG. 3 shows the displacement of the reflecting mirror on the straight line of the scanning trajectory and the reflection at that time in the same embodiment. Figure i4 is a perspective view showing a specific example of the same embodiment; Figure 5 is a configuration diagram of the main part of Figure 4; Figure 6 is a conventional scanning FIG. 2 is a schematic diagram of an optical device. Explanation of symbols 4...Imaging lens 6...Reflection mirror 7...
・Photosensitive drum 11...Rack 14.15...
・Gear 17.18...Bevel gear 20...Worm 21...Worm wheel Figure 1 Figure 2 Figure 6

Claims (1)

[Claims] In a scanning optical device that performs optical scanning by moving a reflective mirror disposed between an imaging lens and an imaging surface, the scanning trajectory of the reflective mirror is made linear, and the reflective mirror A scanning optical device characterized in that the rotation angle of the reflecting mirror is controlled according to the amount of displacement of the reflecting mirror.