JPS6031108A - Automatic focus adjusting method in camera and its device - Google Patents

Abstract

PURPOSE:To execute exactly and quickly a focal adjustment, especially, when a short focus lens is used, by moving roughly an original picture rack to a position being close to an optimum position, and subsequently, adjusting finely a lens against a lens rack. CONSTITUTION:As for a movement and stop control of an original picture rack 3, it is unnecessary to execute it with so high accuracy, and the original picture rack 3 is moved simultaneously with a movement of a lens rack 4, or moved so as to follow a little later. In case a lens selecting switch is set to a short focus side, a distance from a focused picture 34 in an actual spot position of the original picture rack 3 is measured by a rotary encoder 15 after the original picture frame 3 has stopped, and its value is transferred to an operating device. In the operating device, an error between the actual distance between a distance being an optimum value by a calculation is derived, and a corrected quantity of this error distance is derived. An operation of a motor is controlled basing on this value, and a lens 26 is moved from a reference position against the lens rack 4. In this way, the focus is adjusted automatically. As a result, a follow-up movement can be executed quickly at high speed, and the focus can be adjusted exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a camera such as a plate-making camera or a photographic enlarger, which uses a lens to form an image of an original image on a focusing surface, and exposes a photosensitive material placed on the focusing surface. In this paper, a method and apparatus for automatically adjusting focus are described.

In the conventional automatic focus adjustment method of this type, a lens holder and an original picture holder are provided so as to be movable in the optical axis direction with respect to the focusing plane, and by moving the lens holder, the distance between the lens holder and the focusing plane is adjusted. Based on the distance between the lenses and the focal length of the lens used, the optimal position for the original art rack is determined, and the original art rack is automatically moved to follow the movement of the lens rack so that the original art rack is located at the optimal position. There is something that makes me

However, using only this method, there is a problem in that it is difficult to accurately position the original picture rack at the optimum position.

In order to accurately stop the original drawing rack at the optimal position, it is possible to slow down the moving speed of the original drawing rack, but this causes another drawback in that the work cannot be done quickly.

The effect if the original picture rack is not exactly located at the optimum position is not so great in the case of a long focal length lens, but is noticeable in the case of a short focal length lens.

In view of the above-mentioned problems with the conventional automatic focus adjustment method, the present invention provides an automatic focus adjustment method for a camera that allows accurate and quick focus adjustment, especially when using a short throw lens. The present invention aims to provide such a device, and will be described below based on an embodiment shown in the accompanying drawings.

Note that this embodiment is a case where the present invention is applied to a photographic enlarger.

(1) is the main body, and in the center of its rear part there is a post (2) with a U-shaped cross section, and at the top and bottom of this post (2) there is an original picture rack (3) and a lens rack ( 4) are each independently mounted so as to be slidable in the vertical direction.

Inside the main body (1) below the lower end of the support column (2), a pair of left and right motors (586) capable of forward and reverse rotation are provided so as to face each other toward the center. Subrokets (?) (8) are fixed to the tips of the rotating shafts (5a) (6a) of the 5x6), respectively.

A pair of sprockets (9×10) are pivotally supported at the upper end of the support column (2) so as to correspond to the sprockets (7) and (8), with a common shaft (11) extending in the left-right direction.

Endless chains (12) and (13) are wound between the sprocket (7) and the sprocket (9), and between the sprocket (8) and the sprocket (lO), respectively, and one end of the endless chain (12) A part of the endless chain (13) is fixed to the original picture rack (3), and a part of the endless chain (13) is fixed to the lens rack (4).

Thus, motor (5), sprocket (7) (9),
Use an endless chain (12) etc. to attach the original picture rack (3) to the support (
The driving means for raising and lowering along the motor (6)
), Sprocket (8X10), Endless chain (13
) and the like form driving means for raising and lowering the lens frame (4) along the support column (2).

On the right side of the column (2), there is a rack (14) extending vertically.
) is formed, and this rack (14) has an original picture rack (3).
A binion (16) fixed to the rotating shaft of the rotary encoder (15) fixed to the lens frame (4), and a binion (18) fixed to the rotating shaft of the rotary encoder (17) fixed to the lens frame (4), They fit together so that they can be transferred.

This rack (14) and rotary encoder (15) (1
7) etc., the distance (a) from the focus plane (34) to the lens rack (4), which will be described later, and the distance (h) from the focus plane (34) to the original picture rack (3) are exactly 5- A high-precision length measuring instrument is formed.

Note that such a length measuring device may be one using a linear encoder or the like.

A light source (1) such as a halogen lamp is installed at the front of the original art rack (3).
A light source box (20) including a light source box (9) is attached, and an original image holder (22) for holding an original image (21) is attached to the lower end of this light source box (20).

A lens box (23) as shown in detail in FIG. 4 is attached to the front part of the lens rack (4), and in the center of this lens box (23) there is a vertical lens holding tube ( 24) is mounted so as to be slidable in the vertical direction by means of a key (25), but not rotatable around the central axis.

A lens unit (27) including a lens (26) is mounted on the upper end of the lens holding tube (24) so that the optical axis (L) of the lens (26) coincides with the central axis of the lens holding tube (24). It is detachably mounted with a lens mount consisting of a plurality of set screws (28).

6. There is a male screw (24a) on the lower outer periphery of the lens holding tube (24).
This male thread (24a) is threaded into a female thread (30) threaded on the inner surface of the upper part of the rotating barrel (30) which is rotatably supported on the lens box (23) with a bearing (29) etc.
It is screwed into a).

A spur gear (30b) is connected to the lower end of the rotating barrel (30), and this spur gear (30b) is attached to the lens box (23).
It meshes with a spur gear (32) that is properly attached to a vertical rotation shaft (31a) of a high precision motor (31) such as a pulse motor that is supported by a motor (31) that can rotate in forward and reverse directions.

By rotating the rotating shaft (31a) of this motor (31) in forward and reverse directions, the rotary cylinder (30) is rotated in forward and reverse directions via the spur gears (32) (30b), and the internal thread ( 30a) and the male thread (24) of the lens holding tube (24).
Due to the screw feeding action with a), the lens (26) can be slightly moved in the vertical direction together with the lens holding cylinder (24), and these configurations allow the lens (26) to
A driving means for slightly moving the lens frame (4) is formed.

A translucent focusing glass (33) is provided horizontally just below the lens rack (4) in the main body (1), and the upper surface of this focusing glass (33) forms a focusing surface (34). .

On the optical axis (L) below the focusing glass (33), a reflecting mirror (35) tilting downward in the front is provided, and this reflecting mirror (35) allows the optical axis (L) hanging from above to be
) is reflected toward the center of a viewing window (36) formed in a slightly rearwardly inclined portion of the upper front surface of the main body (1).

A Fresnel lens (37) is attached to the opening of the viewing window (36).
is provided, and the original image (21) is imaged on the focus plane (34).
) image (21') can be enlarged and visually recognized.

(38) is a vertically expandable bellows whose ends are properly attached to the lens rack (4) and the top surface of the main body (1); (39)
(41) is a photosensitive material magazine that stores the photosensitive material (40) wound into a roll; 34) The photosensitive material (40) is conveyed to the top, cut to a required length, and the photosensitive material (40) that has been printed is transferred to the take-out chamber (42) provided in the main body (1).
) is a photosensitive material conveying device.

An operation panel (43) is provided on the front of the main body (1), and the operation panel (43) includes a power switch, a lens rack movement switch, a manual lens dial, an enlargement magnification display, a burn start switch, A color correction knob and various other switches and knobs are provided, and by operating these switches and knobs, the automatic control device (shown in the diagram) operates the drive means of each part in a timely manner and makes settings. Adjust the focus and adjust the photosensitive material (
40) etc. are automatically performed.

Next, the automatic focus adjustment method using the automatic control device will be explained in detail, and the overall operation and handling of the photo enlarger will be briefly explained.

First, on the operation panel (43), select the lens (
26) and the other setting conditions.

For example, focal length f = 50 mm, 75 mm, 13
Prepare three types of 5nun lenses (26), and if you actually use the f=50+nm lens (26), set the lens selection switch (path shown) to 5011II11 accordingly. .

In this case, if the lens selection switch is set to the short focal lengths of 50 mm and 75 mm, the lens (2
6) Perform fine adjustment on the side, but the long focus 1351110
When set to 1, the automatic control device is set so that this fine adjustment is not performed.

Next, operate the lens rack movement switch (path shown) to the upward or downward side.

Then, the motor (6) operates and the endless chain (13)
rotates, and the lens rack (4) is raised or lowered.

At this time, the distance from the focusing surface (34) to the lens rack (4), more precisely, from the focusing surface (34) to the lens (
26) is at a predetermined reference position with respect to the lens rack (4), the -l 〇- distance (a) to the lens (26) is determined by the rotary encoder (17), for example, in units of 0.01 mm. The measured value is
It is transmitted to the arithmetic unit of the automatic control device.

The arithmetic device uses the following calculation formula to set the focal plane (34) based on the value of this distance (a) and the focal length (f) of the lens (26) set by the lens selection switch mentioned above. The optimum distance (h) from the focus plane (34) to the original image (21) for forming an image (21') of the original image (21) and the enlargement magnification (m) at that time are calculated.

h=a+b ・・・・・・・・・ (1) Here b is
Lens (26) in reference position relative to lens rack (4)
This is the optimal distance from to the original picture (21).

From formula (2), m = ” ・・・・・・・・・・・・・・・・・・
・・・・・・ (5) The distance determined by the above formula (4) (
The value of h) is transmitted to the operation control device (shown in the figure) of the motor (5), and the motor (5) controls the original picture rack (3) so that it is in focus (
It is operated to move to a position close to the distance (h) from 34) and stop there.

The movement and stop control of the original picture rack (3) at this time does not need to be performed with very high precision; for example, ±0.0511II
It is sufficient to have an error of about 11.

The value of the enlargement magnification (m) determined by the above equation (5) is displayed on the enlargement magnification display section of the operation panel (43), for example, by a digital display.

Therefore, each time the lens rack (4) is moved and (a) is changed, the optimal value of (h) is calculated, and based on that value, the original picture rack (3) is adjusted to the position of the lens rack (4). At the same time as the movement or after a slight delay, the enlargement magnification (m) at that time is displayed on the operation panel (43).
displayed on the screen.

When the lens selection switch is set to the long focal length side, for example 135+am, after the original picture rack (3) has stopped with a certain degree of error as described above, the lens (26) is set to the lens rack ( While the photosensitive material (40) remains stopped at the reference position relative to 4), the photosensitive material (40), which will be described later, is printed, etc. This is because in the case of a long focal length lens, the influence of such errors can be almost ignored.

Set the lens selection switch to the short focal length side, for example 50III
Or if it is set to 75mm, use the original art rack (3
), the rotary encoder (15) measures the distance (h') from the focus plane (34) at the actual stop position of the original picture rack (3) to the unit of, for example, 0.01+nm, and calculates the value. Communicate to the device.

In the arithmetic device, the error between the actual distance (h') and the calculated optimum distance (h) is calculated by calculating the error Δh=h' - h,
The compensation 13-positive amount Δa of distance (a) for this error Δh is calculated using the following formula.

That is, by substituting h+Δh for h and a+Δa for a in the above equation (4), the following equation is obtained.

Determine Δa from this equation (6), and based on that value, the motor (
31) to move the lens (26) onto the lens rack (
4), it is moved by Δa (upward when positive, downward when negative) from the reference position.

Further, the enlargement magnification (m') at this time is calculated from the following equation, and the value is displayed on the operation panel.

In this way, after automatically adjusting the focus, the viewing window (
36) to the image (21'), then press the printing start switch and the photosensitive material (4
0) is automatically sent onto the bin 14-to surface (34) by the photosensitive material conveying device (41), and
In the optimum condition according to the conditions set by the various knobs on
Burning is done automatically.

In the above embodiment, a high-speed operation switch and a low-speed operation switch are provided as operation switches for moving the lens rack (4), and by selecting them, the motor (6) can be set to a high speed. It may also be possible to operate it at high speeds or at low speeds.

In addition, it is not possible to correct the out of focus when the original image curls in the original image holder (22) through the automatic adjustment described above, so after the automatic adjustment described above is completed, it is necessary to directly While looking at the image (21'), by adjusting the lens manual dial provided on the operation panel (43), the motor (31) is operated and the image (21') is adjusted.
) until the lens (26) is in focus
It would be even more convenient if it could be moved relative to.

As is clear from the above, in the present invention, based on the stop position of the lens rack and the focal length of the lens used, the original painting rack is moved roughly to the optimal position, and the calculated optimal position of the original painting rack is moved. The focus error caused by the error between the original picture frame and the actual stopping position of the original picture frame is corrected by finely adjusting the lens relative to the lens frame.

Therefore, an inexpensive motor or the like with low precision can be used as a driving means for the original picture rack, and the following movement of the original picture shelf can be quickly performed at high speed.
This is useful because the focus can be adjusted accurately even when a slight deviation in the position of the original image affects the image formation on the focal plane, such as with a short focal length lens.

[Brief explanation of drawings]

FIG. 1 is a front view showing an example of a photo enlarger to which the present invention is applied; FIG. 2 is a schematic central longitudinal side view; FIG. 3 is a schematic back view with a portion cut away; FIG. 4 is a central longitudinal sectional front view of the lens rack. (1) Main body (2) Post (3) Original picture rack (4) Lens rack (5) (6) Motor (7) (8) (9) (lO) Sprocket (12) (1
3) Endless chain (14) Rack (15) (17) Rotary encoder (16) (1B) Pinionk 20) Light source box (21) Original image (21') Image (22) Original image holder (23) Lens box (24) Lens holding tube (26
) Lens (27) Lens unit (30) Rotating tube (
30b) (32) Spur gear (31) Motor (33) Focusing glass (34) Focusing surface (40) Photosensitive material (43) Operation panel 17-

Claims (2)

[Claims] (1) In a camera in which a lens rack and an original picture rack are movable in the optical axis direction with respect to the focal plane, and the lens can be finely adjusted in the optical axis direction with respect to the lens rack,
determining the optimal position of the original art rack based on the distance between the focus plane and the original art rack and the focal length of the lens used;
By roughly moving the original picture rack to a position close to the optimum position and then finely adjusting the lens with respect to the lens rack, it is possible to eliminate the focus error caused by the error between the actual stopping position of the original picture rack and the optimum position. A method for automatically adjusting focus in a camera, characterized by correcting the focus. (2) a focusing surface formed inside the main body, a lens rack slidably provided along a support provided in the main body; and a driving means for raising and lowering the lens rack along the support; an original picture rack slidably provided along the support; a drive means for raising and lowering the original picture rack along the support; and a drive means provided on the lens rack so as to be able to move slightly in the same direction as the movement direction of the lens rack relative to the main body. What is claimed is: 1. An automatic focus adjustment device for a camera, comprising: a lens with a fixed angle; and a drive means for slightly moving the lens with respect to a lens frame.