JPS59148025A - Focus adjusting method - Google Patents

Abstract

PURPOSE:To vary the distance along an optical path up to an image formation surface and adjust a focus by moving at least two reflecting surfaces. CONSTITUTION:A reflecting mirror group 12 of one fixed reflecting mirror 12a and two movable reflecting mirrors 12b and 12c is arranged between a lens 10 and an image pickup tube 11. Those three reflecting mirrors 12a, 12b, and 12c reflect a light beam 14a passed through the lens 10 from a subject 13 successively to form an optical path 15 in the shape of a rectangle ABCD, generating a light beam 14b which travels to an image pickup tube 11 lastly. The reflecting mirrors 12b and 12c are moved properly to vary AB and CD, etc., and the optical path length from a point O to a point Q is varied to perform a focus adjustment.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a focus adjustment method.

BACKGROUND ART In general, a television camera basically has a structure consisting of a zoom lens 2 facing a subject 1, a master lens 3 in the next stage, and an image pickup tube 4, as shown in FIG. The position of the image 1A changes as the distance to the subject 1 changes. L is the imaging position of the subject 1 at position P1, and P2 is the imaging position of the subject 1 at position P2. Therefore, when taking an image, it is necessary to adjust the focus according to the distance of the subject so that the image 1A is formed on the imaging surface 4a of the imaging tube 4.

This focus adjustment is performed by (1) moving the front lens of the zoom lens back and forth, or (2) moving the master lens back and forth.

In addition, various methods are currently in use for automatically adjusting the focus instead of manually, but in all of these methods, the lens system described above is moved by a motor or the like and set at the in-focus position. This configuration adjusts the focus.

The above method of adjusting the focus by moving the lens system does not pose any particular problem when using the manual method, but since the lens system, which is the object to be moved, is heavy and difficult to move, in the automatic focus adjustment method, It takes a certain amount of time for the lens system to be moved convergently and set at the in-focus position, and the tracking characteristics for changes in distance to the subject are poor.

■ Requires a large torque motor.

■ Power consumption becomes large.

Because it uses an IV lens system, it is not possible to configure the camera with a C-mount or other interchangeable configuration.

There were problems such as.

Note that instead of moving the lens system, it is possible to adjust the focus by moving the image carrier tube back and forth, but since the image pickup tube is electrically connected to the outside, it is preferable to fix it and make it movable. Moreover, even if it were possible to move the lens system, there would be the same problems as when moving the lens system described above.

Means for Solving and Overcoming the Problems The present invention aims to provide a focus adjustment method that solves the above-mentioned problems. Among a plurality of reflective surfaces that are arranged between the image plane and reflect the light rays from the subject that have passed through the lens and direct them toward the image formation plane, at least two reflection surfaces are moved to The focal point is adjusted by varying the distance along the optical path i from the lens to the image forming surface without translating the optical axis of the light beam toward the image surface.

Embodiments Next, embodiments of the focus adjustment method according to the present invention will be described.

FIG. 2 shows an embodiment of the focus adjustment method of the present invention applied to a television camera.

In the figure, 10 is a lens in which a zoom lens and a master lens are incorporated, and 11 is an image pickup tube, which are arranged so that their respective optical axes are substantially perpendicular to each other and are fixed together.

Reference numeral 12 includes a reflecting mirror group C, which constitutes the main part of the present invention, and a lens 10.
and the image pickup tube 11, and the - fixed reflecting mirror 1
2a and two movable reflecting mirrors 12b.

12c and more. Three reflecting mirrors 12a, 12b.

12c is arranged so as to sequentially reflect the light rays 14a from the subject 13 that have passed through the lens 10 to form a rectangular ABCD optical path 15, and finally to the light rays 14b directed toward the image pickup tube 11.

In the above optical system, the optical path length from the center O of the lens 10 to the position Q of the imaging surface 11a of the image pickup tube 11 is OA, A
The length is the sum of B, BC, and CQ. Moreover, according to this optical system, AB can be achieved by appropriately moving the reflecting mirrors 12b and 12c.

It can be seen that by changing CD etc., it is possible to change the optical path length from point O to point Q. The present invention adjusts the focus by changing this optical path length.

Now, in the above television camera, when the subject 13 is at a close position P3, it is assumed that the image 13a is formed on the imaging surface 11a. When the subject 13 moves to the infinite position P4, the image is also formed at a position shifted by a dimension Δ2 from the imaging surface 11a, as shown by the broken line, and is out of focus. In this case, the optical path length from point O to point Q is the dimension Δ
By shortening the angle by .degree. C., it becomes possible to move the image 13a to the position of point Q and adjust the focus. The optical path length is shortened as described below.

The reflecting mirrors 12b and 12c are both moved in parallel at the point where a straight line parallel to the straight line BC intersects the optical axis at 8+.

Let it be C1. The reflecting mirror 12b is set at a position passing through the intersection B1 as shown by the two-dot chain line, and the reflecting mirror 12c is set at a position passing through the intersection C1. As a result, the optical path length is BB+ with no parallel shift in the optical axis toward the image pickup tube 11.
This means that it has been shortened by +CCI + (BC-B+ C+). If this shortened length matches the shift dimension Δ° C., the image 13a is moved onto the imaging surface 11a, and the focus has been adjusted.

When the subject moves from an infinite position to a closer position, the focus is adjusted by moving the reflecting mirrors 12b and 12C in the opposite direction to the above to lengthen the optical path length.

That is, depending on the distance to the subject, the reflecting mirrors 12b, 12
The focus is adjusted by moving c so that the optical path length becomes shorter or longer by a length corresponding to the image shift length. In addition, in FIG. 2, anti-tA inhibitor l 2b ,
The movement of 12c is enlarged and shown in -C for convenience of illustration.

In addition to moving the reflecting mirrors 12b and 12c independently, the optical path length can also be changed in the same way by moving them φIIJ from point Sz to point S2 with the reflecting mirrors 12b and 120 fixed. Reflecting mirrors 12b, 1 fixed to each other
It is mechanically advantageous to move 2c integrally. In addition, anti-#JvA12b.

12c is manually moved, for example, by sliding a knob on the camera body with a fingertip. Also, reflecting mirror 1
The materials 2a to 12c are not limited to glass, but may also be aluminum or plastic vapor depositable. Furthermore, the reflecting mirrors 12a to 12c are not limited to ordinary reflecting mirrors;
The prism may be formed by vapor-depositing aluminum or the like on the surface of the prism, as long as it is a reflective surface.

In addition, although the optical path length can be varied by moving a single reflecting mirror, a parallel shift in the optical axis will always occur.Therefore, moving a single reflecting mirror is not practical. In the present invention, it is necessary to move at least two reflecting mirrors.

FIG. 3 shows a television camera with an automatic focus mechanism to which the focus adjustment method of the present invention is applied. In the figure, parts that substantially correspond to the mechanical parts shown in FIG. 2 are given corresponding symbols.

20 is a distance measuring device, 21 is a control circuit, 22 is a motor drive circuit, 23 is a motor, and 24 is a position detector. The movable reflecting mirrors 12b, 1, 2c have an integral structure, and the motor 23
is moved in the direction of arrow E.

A signal related to the distance to the subject 13 is applied from the distance measuring device 20 to the control circuit 21. A signal related to the position of the movable IJ'Jm 12b12c from the position detector 24 is also applied to the control circuit 21. The control circuit 21 outputs a signal to the motor drive circuit 22 in response to both of the above signals, and the circuit 22 operates to rotate the motor 23 in the forward and reverse directions, causing the reflector 12b,
12c moves in the direction of focusing, and the focus is automatically adjusted.

Here, since the reflecting mirrors 12b and 12c are much lighter and easier to move than the lenses, a small motor can be used as the motor 23.
It consumes less power, ■ It is possible to set the position where the reflectors 12b and 12c are in focus in an extremely short time, and it has excellent followability to changes in the distance to the subject. ■ Focus adjustment Can be operated stably ■ Since the lens does not need to be moved, it can be configured independently from the lens, and the camera can be used as a C-mount or other type of camera with interchangeable lenses.

etc. to the right effect.

Note that when the optical path is rectangular FGHI as described above, as shown in FIG.
When 2c is moved by a distance of 2, the imaging position moves by 2×8.

Further, as shown in FIG. 5, behind the reflecting mirrors 12a to 12C, the reflecting mirrors 12a and 121 are
The focal point can be adjusted in the same way by moving the mirror 1 in the direction of the arrow J. In this case as well, the imaging position and the reflecting mirror 12a, 1'2b are moved twice as far as the moving distance.

FIG. 6 shows an embodiment in which two reflecting mirrors 30a and 30b are arranged so that the optical path forms a right triangle KLM and are movable together. Also in this embodiment, the reflecting mirror 30
By moving a and 30b in the direction of arrow N, the optical path length is varied and the focus is adjusted. Reflector 30a, 3
0b by a distance Ill, the imaging position is 2g - t
Move an22,5' (1+CO345°).

The focus adjustment method described above is not limited to the O1 focus television camera, but can also be applied to, for example, a focus adjustment method used when assembling a television camera.

Effects As described above, the focus adjustment method of the present invention has the following features.

■ Compared to the method of moving the lens, it is easier and more stable.

(2) Since the reflecting mirror corresponding to the reflecting surface is much lighter and easier to move than the lens, it can be applied to an autofocus type pre-vision camera in 141 and has the C effect. That is, the focus can be adjusted in accordance with changes in the distance to the subject with good followability and stably, and moreover, a small motor is required, and power can be saved.

1[1;t- It becomes possible to make the Tono Orcus television camera into a type that allows for interchangeable lenses.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between changes in the position of a subject and changes in the imaging position in a television camera, and Fig. 2 shows an example of the focus adjustment method according to the present invention applied to a television camera. 3 is a diagram showing a television camera with an automatic focus adjustment device to which the focus adjustment method of the present invention is applied,
Figure 4 is a diagram showing the reflective mirror section in Figure 3, and Figure 5
FIG. 6 and FIG. 6 are four views each showing another arrangement of the reflecting mirrors applied to the focus adjustment method of the present invention. DESCRIPTION OF SYMBOLS 10... Lens, 11... Image carrier tube, 11a... Imaging surface, 12-... Reflection 81 group, 12a, 12b, 12c
, 30a, 30b--Reflector, 13... Subject,
14a. 14, b... Ray, 15... Rectangular optical path, 2o...
- Distance measuring device, 21... Control circuit, 22... Motor drive circuit, 23... Motor, 24... Position detector.

Claims (1)

[Claims] A plurality of lenses arranged between a lens facing the subject and an imaging plane on which the subject is to be imaged by the lens, and reflecting light rays from the subject that have passed through the lens and directing them to the imaging plane. Among the reflective surfaces, at least two non-conforming surfaces are moved to vary the distance along the optical path from the lens to the image forming surface without parallelly moving the optical axis of the light ray toward the image forming surface. A focus adjustment method characterized by adjusting the focus by