JPS6091326A - Focus adjusting mechanism of optical system - Google Patents

Abstract

PURPOSE:To make a fine focus adjustment and to prevent eccentricity due to the adjustment by varying the tilt angles of two parallel flat plates on an optical axis reversely to each other. CONSTITUTION:When an image formation position is coincident with an image formation plane P while the parallel flat plates 2 and 3 are at an angle theta of 0 deg. perpendicular to the optical axis, light of infinite distance incident to a lens 1 has an image position before the image formation plate P as shown by broken lines, so the plates 2 and 3 are rotated counterclockwise and clockwise by theta1 respectively by rotating an adjusting gear 6 counterclockwise as shown by an arrow to prolong the length of the optical path, setting the image formation position on the image formation plate. Thus, an object image of infinite distance and an object image of short distance are formed on the same image formation plate P by adjusting the inclinations of the plates 2 and 3.

Description

[Detailed description of the invention] It is.

Recent trends in lens systems are toward higher performance, while there is also a strong desire for compactness and lower cost.

Conventionally, focusing mechanisms for lens systems include front focus, inner focus, rear focus, and so-called bank focusing, which changes the relative position of the focusing surface and the lens system. These methods are used depending on the application and purpose, taking advantage of their respective characteristics.

However, it is still insufficient for special purposes or when maintaining high precision.

SUMMARY OF THE INVENTION In view of the problems of the prior art described above, an object of the present invention is to provide a focus adjustment mechanism for an optical system that is less likely to cause decentering, maintains the optical axis with high precision, and enables delicate focus adjustment. shall be.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of an embodiment of a focus adjustment mechanism of an optical system according to the present invention, in which (a) shows an infinity state and (b) shows a short distance state.

In the figure, 1 is a lens group, 2 and 3 are parallel plane plates, which have the same refractive index and thickness, and are arranged on the optical axis between the lens group 1 and the imaging plane P. The parallel plane plates 2 and 3 are connected to gears 4 and 5, respectively, and the gear 5 meshes with the gear 4 and also with the adjustment gear 6.

Therefore, when the adjusting gear 6 is rotated manually or by a motor or the like, the parallel plane plates 2 and 3 are configured to be inclined at equal angles in opposite directions with respect to the optical axis direction.

Then, the refractive index n, perpendicular to the optical axis of a general optical system,
If a parallel plane plate with thickness t is inserted, the optical path will be extended by t(1--).

Furthermore, when such a parallel plane plate is tilted by θ with respect to the optical axis, the optical path is extended by %/csθ·(1--). Therefore, by tilting the parallel plane plate at an angle of θ from the perpendicular state to the optical axis, the optical path length is j/cpsθ.Focal adjustment is performed by fully utilizing such characteristics.

Therefore, the operation of this embodiment having the above configuration will be explained.

1. In Fig. 1(b), light from a certain short distance passes through lens group 1.
When the parallel plane plates 2 and 3 are perpendicular to the optical axis, that is, when the angle θ is 0, the image forming position is on the image forming plane P.
shall match.

When light from an infinite distance enters the lens group 1 with the parallel plates 2 and 3 perpendicular to the optical axis, the image forming position is as shown by the broken line in Fig. 1(a). Face P
Since the horizontal position is also in front of you, rotate the adjustment gear 6 in the counterclockwise direction of the arrow, and tilt the parallel plane plate 2t counterclockwise and the parallel plane plate 3 clockwise by θ1, respectively, to adjust the optical path length. The image forming position is corrected so that the image forming position becomes the image forming plane P as shown by the solid line in FIG. 1(a).

In other words, as shown in Figure 1(a), the object image at infinity and the first
As shown in Figure (b), an object image at a short distance can be formed on the same imaging plane depending on the degree of inclination of the parallel plane plates 2 and 3.

In addition, as mentioned above, the gears 4 and 5 are connected to the parallel plane plate 2.
and 3 are tilted at equal angles in opposite directions, the eccentricity caused by the parallel plane plate 2 is reversely corrected by the parallel plane plate 3, and eccentricity does not easily occur as a whole.

FIG. 2 shows a second embodiment of the present invention, which is similar to the first embodiment described above.
In the embodiment, the parallel plane plates 2 and 3 each are made into a set of two plates instead of one each, so that the optical path length can be changed even more.

namely, parallel plane plates 2a, 2b and 3a.

3b are arranged in pairs on the optical axis, and the total thickness of each pair is the same. The parallel plane plates 2a, 2b are gears 4a, 4b, respectively.
The gears 4a and 4b are connected to each other through a gear 7, and the parallel plane plates 3a and 3b are connected to gears 5a and 5b, respectively, and the gears 5a and 5b are connected to each other through a gear 8. Further, the gear 4b and the gear 5a are meshed with each other, and the gear 5b and the adjustment gear 6 are meshed with each other.

Therefore, by rotating the adjustment gear 6 manually or by a motor, the parallel plane plates 2a, 2b and 3a, 3
The lenses b are arranged in pairs and are tilted at equal angles in opposite directions with respect to the optical axis direction, so as to further change the optical path length.

Therefore, regarding the operation of this embodiment configured as shown below, when the parallel plane plates 2a, 2b and 3a, 3b are perpendicular to the optical axis and light from an infinite distance enters the lens group 1, As in the above-mentioned embodiment, the image forming position is in front of the image forming plane P as shown by the broken line in FIG. 2a,
2bt-counterclockwise, the parallel plane plates 3a and 3bt are tilted clockwise to extend the optical path length, and the image formation position is corrected to become the image formation plane P as shown by the solid line in Fig. 2, and the object distance is adjusted. It can be made to coincide with the image plane P depending on the situation.

FIG. 3 shows a third embodiment of the present invention, in which only the parallel plane plate 3 in the first embodiment described above is divided into two pieces to form a set, and the optical path length is This allows for large changes in the

That is, the plane-parallel plate 2 and the plane-parallel plates 3a and 3b are arranged on the optical axis, and the total thickness of the plane-parallel plates 3a+3b is the same as the thickness of the plane-parallel plate 2.

The parallel plane plate 2 is connected to the gear 4, while the parallel plane plates 3a and 3b are respectively connected to the gears 5a and 5b.
The gears 5a and 5b are meshed with each other via a gear 8, and the gear 5a is meshed with the gear 4, and the gear 5b is meshed with the adjustment gear 6, respectively.

Therefore, by rotating the adjustment gear 6 manually or by a motor, the parallel plane plates 2 and 3a+3b are tilted at equal angles in opposite directions with respect to the optical axis direction, and the optical path length is changed greatly. has been done.

The adjustment operation is performed in the same manner as in each of the embodiments described above.

As explained above, the present invention enables delicate focus adjustment, is less likely to cause eccentricity due to adjustment, and when used for flange bank adjustment, work efficiency and accuracy are significantly improved compared to methods that involve replacing washers. It has the effect of

[Brief explanation of the drawing]

The figure shows an embodiment of the focus adjustment mechanism of the optical system according to the present invention. FIG. 1 is a side view of the main part of the first embodiment, in which (a) is an infinity adjustment state, and (b) is a short distance adjustment state. The second
This figure and FIG. 3 are side views of essential parts of different embodiments, respectively. Torrens group, 2.2a, 2b, 3, 3a, 3b parallel plane plate, 4.4a, 4b, 5.5a, 5b... Gear, 6...
Adjustment gear. Figure 1 (a) (b) Figure 2 Figure 3

Claims (1)

[Claims] l Two sets of parallel plane plates each consisting of at least one are arranged on the optical axis of the lens group, and focus adjustment is performed by changing the inclination angle of each set of parallel plane plates in opposite directions. A focus adjustment mechanism for an optical system characterized by: