JPS5815766B2 - Sousakou Gakkei - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for optically scanning an object emitting electromagnetic waves, particularly visible light or heat rays, and is capable of scanning at high speed and with high scanning efficiency.

Various types of scanning optical systems have been known in the past, but there are many mechanical and optical difficulties in creating a scanning optical system capable of high-speed scanning and high scanning efficiency.

For example, as shown in FIG. 9, a rotating scanning optical system that scans by rotating a mirror drum can mechanically achieve high speed relatively easily.

However, if the beam diameter at the scanning position is large, the area of the reflective surface of the mirror drum must be made large to prevent the beam from crashing, and for this reason, the object must be constantly scanned in response to the rotation of the mirror drum. It becomes impossible to do things.

For example, in FIG. 9, although the angle that one reflective surface of the mirror drum makes with respect to the center of rotation O is 90 degrees, the rotation angle of the mirror drum used for scanning is ω,
This angle ω is considerably smaller than 90 degrees.

In other words, the ratio between the rotation angle of the mirror drum and the rotation angle used for actual scanning becomes difficult to maintain.

For this reason, methods of scanning by rotating a mirror drum generally tend to have low scanning efficiency.

In order to improve the scanning efficiency, it is conceivable to increase the number of mirror surfaces, but increasing the number of mirror surfaces increases the size of the optical system, resulting in the disadvantage that it becomes difficult to handle in use.

On the other hand, the vibration method that scans by vibrating a single mirror is
In general, high scanning efficiency is obtained, but in order to scan at high speed,
There are many mechanical difficulties in making a mirror vibrate at high speed.

The present invention aims to provide a scanning optical system which improves the above-mentioned drawbacks, and is characterized by a scanning optical system having a mirror surface that is a part of a paraboloid along the outer periphery of a cylinder. By synchronously rotating a deformed rotating mirror drum and a circular rotating prism whose thickness changes continuously, high-speed scanning and scanning with high scanning efficiency are made possible.

An embodiment of the present invention will be described below.

In FIG. 1, 10 is radiation from an object to be scanned (not shown).

Reference numeral 11 denotes an objective lens that images the radiation 10 onto a point on, for example, a mirror surface 12m of the deformed rotating mirror drum 12.

13 is a circular rotating prism, 13a is the thickest point of the prism, and 13b is the thinnest point.

The function of this prism will be explained in detail later.

A relay lens 14 forms an image of the radiation emitted from the circular rotating prism on the light receiving surface of the light receiving means 15.

22 is a drive means for rotating the modified rotating mirror drum 12, and 23 is a drive means for rotating the circular rotating prism 13.

Reference numeral 24 denotes a synchronization adjustment circuit, which functions to adjust the rotational state of the drive means 22 and 230, and when the mirror drum 12 is composed of four mirror surfaces as shown in the figure, the rotational speed of the rotating prism 130 is adjusted according to the rotational speed of the rotating prism 130. This is four times the rotation speed of .

Note that the objective lens 11 vibrates left and right to perform scanning in a direction perpendicular to the scanning direction by the deformable rotating mirror drum 12.

The modified rotating mirror drum 12 will be further explained.

In FIG. 2, reference numerals 12, 121, 12m, and 12n are four mirror surfaces, and although the figure shows the case of four mirror surfaces, the number is not necessarily limited to four.

Each mirror surface forms part of a quadratic curve, which will be explained below.

01-02 is the rotation axis of the mirror drum 120, and FIG. 3 is a plan view of the mirror drum.

In the figure, the angle γ corresponding to the shaded area is the angle used for actual scanning.

In the figure, since there are four reflective surfaces, one reflective surface for scanning in one direction, for example, reflective surface 12rn, is at the rotation center 0.
The angle between is 90 degrees.

In FIG. 3, the angle γ used for scanning is close to 90 degrees, and the angle γ' not used for scanning is made small, as shown in FIG. This can be easily achieved by making the angle of 02 close to 90 degrees.

Therefore, in the present invention, high scanning efficiency can be easily obtained.

FIGS. 4A and 4B are explanatory diagrams showing a state in which a light beam is reflected from a one-meter incident surface of the mirror drum 12. FIG.

In FIGS. 4A and 4B, the beam 10 incident on the symmetrical lens 11 forms an image on a straight line 1-1'.

At this time, if the principal ray of the scanning light beam has an inclination between ±θ degrees with respect to the symmetric lens 110 element axis, and the direction of reflection of the reflected beam is at an angle α with respect to the optical axis, then 1 All you have to do is tilt one mirror surface.

In this example, α is 45°.

FIG. 4B shows the inclinations of the reflection points 12a, 12b, 12c, etc. on the mirror surface.

In the figure, the value X corresponding to the distance in the circumferential direction of the mirror drum is determined according to the rotation speed of the mirror drum, and the height y in the rotation axis direction is determined according to the inclination θ of the light beam. The reflection curved surface of the mirror surface is determined as the set of tangents at .

Therefore, the position of the reflection point as the mirror drum rotates is
Regarding the direction, it is always at the position 1-1', whereas
Regarding the direction, move on 1-1'.

The circular rotating prism 13 is provided to correct the variation in the optical path length due to the movement of the reflection point in the X direction.

FIG. 5 shows the circular rotating prism 13 shown in FIG. 1, and the direction of the arrow indicates the chief ray when the light beam reflected by the mirror drum passes through this prism.

Further, 01-02 is a rotation axis, and FIG. 6 shows a schematic diagram of this circular rotating prism developed.

Next, the principle of correcting the variation in optical path length will be explained using FIG. 7 and the developed view of the circular rotating prism shown in FIG.

In the figure, when the distances from the bottom of the prism to the reflection point are different, such as hl and h2 (h2>hl), by controlling the thickness of the prism, the luminous flux from point 12b in Figure 7 is is from 12b', point 12 in Figure 8
The light flux from a appears to be diverging from 12a'.

The distances from the bottom surface of the prism at the points 12a' and 12b' can be made equal to H by controlling the prism thickness.

Therefore, even if the distance hi from the bottom of the prism to the reflection point changes, by changing the thickness of the prism accordingly, the imaginary reflection point will always be kept at a constant distance H. .

In this way, if the thickness of the rotating prism is varied in accordance with the variation of the reflection point on the reflection surface of the mirror drum, the reflection point on the mirror drum can always be imaged on the light receiving means 15.

Hereinafter, the operation of this embodiment will be explained. A beam of light diverged from one point on an object is imaged by the objective lens 11.

These images are sequentially scanned by the mirror surface of the mirror drum 12, and the light beam reflected by this mirror surface is incident on the prism surface of the rotating prism 13.

At this time, the chief ray from the object becomes a light beam from one point on the image plane, that is, one point on the object, due to the inclination of the mirror, so that one direction of the object is sequentially scanned.

The light beams passing through the rotating prism 13 have their optical path lengths corrected so that they all appear to be reflected from the same distance, and can be imaged on the light receiving means 15 via the relay lens 14.

Furthermore, since the scanning speed of the deformed rotating mirror drum in the direction perpendicular to the scanning direction of the object surface may be considerably slower than the scanning speed of the mirror drum, it is possible to easily scan by vibrating the objective lens 11. .

As described above, the present invention is an excellent optical system that enables scanning at high speed and with high scanning efficiency by combining a mirror drum with a mirror surface with a special curve and a prism system that corrects fluctuations in reflection points. be.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the present invention. FIG. 2 is a perspective view of a modified rotating mirror drum according to an embodiment of the present invention, FIG. 3 is a plan view thereof, and FIGS. 4A and 4B are for explaining the configuration of a part of the embodiment of the present invention. An explanatory diagram. FIG. 5 is a perspective view of a circular rotating prism according to an embodiment of the present invention, FIG. 6 is a developed view thereof, and FIGS. 7 and 8 are diagrams for explaining the action of the circular rotating prism of the present invention. FIG. 9 is an explanatory diagram of scanning using the conventional rotation method. In the figure, 11...symmetrical lens, 12... deformed rotating mirror drum, 13... circular rotating prism, 14... relay lens, 15... light receiving means, 24... synchronous circuit.

Claims (1)

[Claims] 1. Reflection means for reflecting each radiation incident at various angles in the same direction, and when the radiation reflected by the reflection means is guided, a change in the position of the reflection point of the reflection means for each radiation is controlled. A scanning optical system characterized in that the reflection means and the correction means are synchronized to scan an object through a correction means that optically corrects the object by passing the object through a prism whose thickness changes continuously.