JPH0720571A - Method for controlling optical system of microfilm reader - Google Patents

Abstract

PURPOSE:To align the position of a control element of an optical system to a target position with high accuracy without detecting the position of the control element by using a costly position detector in the method for controlling the optical system of a microfilm reader by moving the control element to the target position while detecting the position of the control element with its driving motor. CONSTITUTION:The control element of the optical system is moved in one way by a moving quantity A larger than a play DELTAx of a control system (initializing action) and the moving quantity x0 required for the target position is determined in this state (moving quantity detection operation). The control element is moved in a backward direction by the sum (x0+B) of the quantity B larger than the play, DELTAx and the moving quantity x 0(return action) and thereafter, the control element is moved in the original direction by the quantity B (final positioning action). The control element may be a prism for image rotation or projecting lens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system control of a microfilm reader which detects the position of an optical system control element such as an image rotation prism or a projection lens by its drive motor and moves it to a target position. It is about the method.

[0002]

2. Description of the Related Art In a microfilm reader, an image rotating prism is provided in an optical system to correct the inclination of a projected image, and this prism is rotated by a motor so that the projected image has a correct inclination. Further, the projection lens for forming an image on the screen is controlled by the motor at the in-focus position.

It is known that a black frame of a projected image is detected by an image sensor such as a line sensor, the inclination of the image is obtained from the inclination of the black frame, and the image rotation prism is rotated so as to correct the inclination.

Also, the contrast of the image is obtained from the image read by the line sensor, the position of the projection lens at which this contrast becomes maximum is detected, and the projection lens is moved to this position (focus position) by a motor. Devices are known.

[0005]

2. Description of the Related Art When controlling a control element of an optical system such as an image rotation prism or a projection lens by a motor as described above, since there is play in these drive systems, the position of the motor is set to the target position. Even if they match, the positions of the image rotation prism and the projection lens do not necessarily match the target position. Therefore, the reproducibility of the position is deteriorated, and the position of the control element cannot be controlled with high accuracy.

In order to improve the positioning accuracy of these control elements such as prisms and lenses, the position of the control elements is not detected from the rotation of the drive motor, but is fed back to the motor using a position detector such as a linear encoder. It is also conceivable to control the motor. However, in this case, there is a problem that an expensive position detector is required and the number of parts is increased.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the position of the control element is accurately matched with the target position without detecting the position of the control element using an expensive position detector. An object of the present invention is to provide a method for controlling an optical system of a microfilm reader that can perform the above.

[0008]

According to the present invention, an object of the present invention is to provide an optical system control method for a microfilm reader which moves the control element to a target position while detecting the position of the control element of the optical system by its drive motor. A method for controlling an optical system of a microfilm reader, characterized in that the respective operations are sequentially performed: An initializing operation of moving the control element to one side only; (b) a moving amount detecting operation of obtaining the moving amount x ₀ to the target position by setting the control element to the initializing position; (c) moving the control element to the moving amount x ₀ And a return operation of moving the control element in a direction opposite to the initialization operation by a sum (x ₀ + B) of a distance B larger than the movement distance Δx of the control element due to play of the drive system; (d) the initialization of the control element. The same person who works The final positioning operation of moving the distance B in the above direction.

The control element is, for example, an image rotation prism or a projection lens. In the case of a projection lens, it is desirable to move the projection lens upward during the initialization operation.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an embodiment in which the present invention is applied to control of an image rotating prism, FIG. 2 is a flow chart of its operation, and FIG.
FIG. 4 is a diagram showing the relationship between the position of the image rotation prism and the image rotation position, and FIG. 4 is an operation explanatory diagram.

In FIG. 1, reference numeral 10 is a light source, and the light from this light source 10 is a condenser lens 12 and a heat insulating glass 1.
4, cold mirror 16, microfilm 18, projection lens 20, image rotation prism 22, mirrors 24, 2
It is guided to the transmissive screen 30 via 6, 28, and an enlarged image of the microfilm 18 is formed on this screen 30.

A CCD line sensor 32 is arranged on the back surface of the screen 30 so as to be movable left and right. That is, the line sensor 32 is arranged long in the direction crossing the screen 30, and the line sensor 32 reads out an image in the length direction (main scanning direction) and sequentially outputs the image signals as time series signals to perform main scanning. Sub-scanning is performed by moving the line sensor 30 in the left-right direction by the motor 34.

The microfilm 18 is supplied from the supply-side reel 36 contained in the cassette, and the winding-side reel 3
It is rolled up to 8. Between the reels 36 and 38, the microfilm 18 is guided by guide rollers 40 and 42 so as to horizontally traverse below the projection lens 20.

The image signal a output from the line sensor 32
Is input to the bandpass filter through signal processing such as correction for variations in each pixel, and further input to the CPU 44 via a rectifying circuit, an integrating circuit, an A / D converter, an input interface and the like. Reference numeral 46 denotes a memory, in which a program of the CPU 44 and the prism 22 are provided.
Alternatively, the data of the lens 20 is stored. For example, data such as the characteristic diagrams shown in FIGS. 3 and 6 are stored in advance.

In this embodiment, the prism 22 is rotated by a motor 48 to correct the tilt of the image. That is, the rotation of the motor 48 is transmitted to the prism 22 via the toothed belt 50, the small gear 52 and the like. Motor 48 here
Is composed of a stepping motor, a servo motor, or the like, and its rotation angle can be detected on the motor 48 side.

The operation of this embodiment will be described below with reference to FIGS. This operation is divided into the following four operations. That is, (a) initialization operation (b) movement amount detection operation (c) return operation (d) final positioning operation.

In the initializing operation (a), the prism 22 is rotated by an amount A, which is larger than the play Δx of the driving system by α, in one direction, for example, the counterclockwise direction (+) shown in FIG. 4, to absorb the play Δx. (Step 100 in FIG. 2).

This operation (a) means rotating from the position P ₁ of the prism 22 before the start-up in FIG. 3 by the rotation amount A in the -x direction and moving to the position P ₂ on _one characteristic Q ₁ .

Next, in the CPU 44, the line sensor 32 detects the black frame of the projected image, and the inclination θ of the image from the black frame is detected.
Ask for ₁ . CPU44 the rotation angle theta ₂ required for further images in inclination theta ₁ to the correct target tilt theta ₂
−θ ₁ = θ ₀ is obtained (step 102 in FIG. 2).

Next, the CPU 44 finds the rotation amount x ₀ of the prism 22 required to rotate the image by this angle θ ₀ (FIG. 2, step 104). This calculation is the characteristic x in FIG. 3 showing the image rotation amount θ with respect to the rotation amount x of the prism 22.
= F (θ) is used for the calculation.

Next, the CPU 44 adds a fixed amount B to the obtained rotation amount x _0, and the prism 2 is added by this sum (x ₀ + B).
2 in the clockwise (+) direction (return operation, FIG.
Step 106). Here, the constant amount B is the sum B = Δx + β of the play Δx of the drive system of the prism 22 and the constant β.
This returning operation causes the prism 22 to move to the position P in FIG.
It moves to position P ₄ via position P ₃ on the characteristic Q _{2 which} is deviated from ₂ by play Δx.

Next, the CPU 44 moves the fixed amount B in the counterclockwise (-) direction (final positioning operation, step 108 in FIG. 2). By this operation, the position P of the prism 22
₄ returns to the amount of play Δx and then rides on the characteristic Q ₁ to position P
_{The process} moves from ₅ to the final target position P ₆ . As a result, the prism 22 can be moved to the position P ₆ where the target inclination can be accurately obtained.

In the above embodiment, as shown in FIG. 4, the initial position P _{1 of the} image is counterclockwise (-) relative to the final target position P _6.
The case of being on the side was explained. However, the same explanation can be made when the initial position P ₁ is on the clockwise (+) side of the final target position P ₆ . Figure 5 shows x-
FIG. 6 is a diagram showing the θ characteristic, and FIG. 6 is an operation explanatory diagram.

[0024] In this case the prism 22, the initial position P ₁ by the initialization operation (a) moves to the position P ₂ on the characteristic Q ₁ from the target position theta ₂ required rotational amount of up to θ ₀ = θ ₁ -θ ₂ The movement amount x ₀ = f (θ ₀ ) of the prism 22 corresponding to is calculated. Then, by returning only | x ₀ −B |, the prism 22 comes to the position P ₄ within the play Δx between the characteristics Q ₁ and Q ₂ (return operation c), but the prism 22 is moved by the next final positioning operation (d). When B is moved by B, the play | x ₀ -B | between the position P ₄ and the characteristic Q ₁ is absorbed and the final position P ₆ can be positioned.

The above description is for the case where the tilt of the image is corrected by rotating the prism 22, but the present invention is also applicable to other control elements of the optical system, such as the projection lens 20.

[0026]

As described above, according to the first aspect of the present invention, the control element of the optical system is moved to one side by the movement amount A larger than the play Δx of the control system (initializing operation), and in this state, the target position is reached. the amount of movement x ₀ required to seek the sum of the (movement amount detecting operation), play Δx larger amount B moving amount x ₀ of Toko (x ₀ +
After moving B) in the reverse direction (return operation), the amount B is moved in the original direction (final positioning operation). Therefore, even if there is play Δx in the control system, it is possible to accurately position the control element. Also, it is not necessary to directly detect the position of the control element using an expensive position detector.

The control element may be an image rotation prism (claim 2), but may be applied to other control elements such as a projection lens.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

[Fig. 2] Operation explanatory diagram

FIG. 3 is a relationship diagram between a prism position (x) and an image rotation position (θ).

[Fig. 4] Operation explanatory diagram

FIG. 5 is an operation flow chart showing another operation example.

FIG. 6 is an explanatory diagram of its operation.

[Explanation of symbols]

 18 Microfilm 22 Image Rotating Prism as Control Element 48 Motor

Claims (2)

[Claims] 1. An optical system control method for a microfilm reader which moves the control element to a target position while detecting the position of the control element of the optical system by its drive motor. A method for controlling an optical system of a characteristic microfilm reader: (a) An initialization operation for moving the control element from its current position x to one side by an amount A larger than a movement amount Δx of the control element due to play of a drive system; (b) A movement amount detecting operation for obtaining the movement amount x ₀ to the target position by setting the control element to the initialization position; (c) the control element, which is based on the movement amount x ₀ and play of the drive system. A return operation for moving the control element in the direction opposite to the initialization operation by the sum (x ₀ + B) of the distance B greater than the movement amount Δx of the control element; (d) the distance B in the same direction as the initialization operation. Just move The final positioning operation. 2. The optical system control method for a microfilm reader according to claim 1, wherein the control element is an image rotation prism and is rotatable around the optical axis of the optical system.