JPH0254212A - Optical scanner - Google Patents

Abstract

PURPOSE:To sharply reduce the load to the driving mechanism of a mirror and, at the same time, to reduce the size and improve the reliability of an optical scanner by allowing the mirror to reflect a luminous flux two or more times. CONSTITUTION:A parallel luminous flux which is condensed to a detector 3 by means of an image forming optical system 2 is reflected at a reflecting angle which is twice as large as the angle of the reflecting surface of a polygon mirror 4, namely, the angle of rotation of the polygon mirror 4 and the luminous flux is again led to another mirror surface of the polygon mirror 4 by means of a telecentric optical system 5 constituted of lenses and mirrors. The optical system 5 is arranged so that the entrance pupil and exit pupil of the optical system 5 can be above the mirror surfaces of the polygon mirror 4. The parallel luminous flux led onto the mirror surface by means of the relay optical system 5 is again reflected at the angle which is twice as large as the angle of rotation of the polygon mirror 4. As a result, the load of the driving motor of the polygon mirror can be reduced and this optical scanner can be reduced in size and improved in reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to optical scanners, particularly raster scanning scanners.

[Conventional technology]

Conventionally, this type of optical scanner is mainly used in systems that acquire images in the far-infrared band.

As shown in FIG. 3, the infrared radiation from the scene (the beam 7 towards the center of the scanning range, the beam 8 redirected by the rotation of the mirror) is raster-scanned vertically and horizontally by an optical scanner 1; This allows the radiation from each point in the scene to be continuously transmitted to the detector 3 by the imaging optical system 2.
is imaged.

The detector 3 outputs an electric signal according to the infrared intensity,
An infrared image is displayed on a TV or the like from this electrical signal. In this system, raster scanning is often achieved by vibrating a plane mirror or rotating a polygon mirror.

FIG. 4 shows an example of scanning by the polygon mirror 4.

The light beam condensed onto the detector 3 is scanned by a polygon mirror 4, and the scanning angle is twice the rotation angle of the polygon mirror. At this time, the scanning angular velocity of the luminous flux is 4 πn(
rad/5ec) (n: rotation speed). Furthermore, the diameter and thickness of the polygon mirror are selected so that the effective diameter of the light beam does not become eclipsed over the entire required scanning angle range.

[Problem to be solved by the invention]

With the conventional optical scanner mentioned above, when scanning at TV rate (30 frames, 47 seconds, number of scanning lines: 525), the number of parallel detector elements is about 10 at most, so one polygon mirror usually has 20,000 to 20,000. 40°000
It needs to be rotated at RPM. Rotating a polygon mirror of the size necessary to achieve a high-quality image for the normally required angle of view (about 40 degrees) at the above rotational speed will result in large windage losses. This puts a large load on the drive motor, causing problems such as heat generation and shortened lifespan. In order to avoid this, if a method is adopted in which the polygon mirror is enclosed in a vacuum container to reduce air resistance and reduce the load on the motor, there is a drawback that the device becomes larger and more expensive.

An object of the present invention is to provide an optical scanner that solves the above problems.

[Means to solve the problem]

To achieve the above object, the present invention provides an optical scanner that scans a light beam by rotating or vibrating a mirror, in which the light beam is a parallel light beam, and the light beam reflected by the mirror is reflected again by the mirror, so that the light beam is It has an optical system that makes the scanning angle more than twice that of a single reflection.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

(Example 1) FIG. 1 is an optical path diagram showing Embodiment 1 of the present invention.

The optical scanner according to the present invention includes a polygon mirror 4 and a relay optical system 5, and the imaging optical system 2 and detector 3 are combined to form a scanner system. 7 is a light beam directed toward the center of the scanning range, and 8 is a light beam whose direction has been changed by the rotation of the mirror.

The parallel light beam condensed onto the detector 3 by the imaging optical system 2 is reflected at an angle of the reflecting surface of the polygon mirror 4, that is, at a reflection angle that is twice the rotation angle of the polygon mirror. This light beam is again guided to another mirror surface of the polygon mirror by a telesend link optical system composed of lenses and mirrors. This optical system is arranged so that its entrance pupil and exit pupil are respectively located on the mirror surface of the polygon mirror 4. The parallel light beam guided again to the mirror surface by the relay optical system 5 is further reflected at an angle twice the rotation angle of the polygon mirror 4. In this way, the light beam focused on the detector changes its scanning direction by the rotation of the polygon mirror 4, the angle of which is equal to four times the rotation angle of the mirror. In this case, the scanning angular velocity of the luminous flux is 8πn (rad
/5ee).

(Example 2) FIG. 2 is an optical path diagram of an example in which a vibrating mirror is used. The optical scanner according to the present invention includes a vibrating mirror 6 and a relay optical system 5, and the imaging optical system 2 and detector 3 are combined to form a scanner system. The vibrating mirror 6 is made of mirrors on the back and front, and the light beam focused on the detector 3 is reflected by one mirror, then transferred to the other mirror by the relay optical system 5, and reflected again. do. Therefore, the scanning angle of the light beam is four times the deflection angle of the vibrating mirror.

〔Effect of the invention〕

As explained above, the present invention allows the dimensions of the mirror to be reduced by 20 to 30% or more in order to obtain the same scanning angle with the same aperture by reflecting the light beam on the mirror twice or more, and furthermore, to obtain the same scanning angular velocity. In some cases, the rotation speed or vibration frequency can be lowered to 1/2 or less.

Therefore, the load on the mirror drive mechanism can be significantly reduced, and the optical scanner can be made smaller and more reliable.

[Brief explanation of the drawing]

Fig. 1 is an optical path diagram showing a first embodiment of the present invention, Fig. 2 is an optical path diagram showing a second embodiment of the invention, Fig. 3 is a block diagram showing a conventional optical scanner system, and Fig. 4 is a conventional optical scanner system. FIG. 2 is an optical path diagram showing an optical scanner. 1... Optical scanner 2... Imaging optical system 3.
・・Detector 4・Polygon mirror 5・
...Relay optical system 6...Vibration mirror 7...
Luminous flux toward the center of the scanning range

Claims (1)

[Claims] (1) In an optical scanner that scans a light beam by rotating or vibrating a mirror, the light beam is a parallel light beam, and the light beam reflected by the mirror is reflected again by the mirror, and the scanning angle of the light beam is changed to the time of one reflection. 1. An optical scanner characterized by having an optical system that increases the image quality by more than twice as much.