JPS60227241A - Microfilm reader - Google Patents

Abstract

PURPOSE:To match automatically focus by detecting the focusing state of the image projected by a microfilm reader on a screen and moving automatically an imaging lens thereby focusing said lens. CONSTITUTION:The luminous flux from a light source 2a is reflected 2b to pass through a condenser lens 2c, a reflecting mirror 2d and a condenser lens 2e and to irradiate a microfilm 2g held to a holder 2f. The light transmitted through the film 2g is enlarged by passing through the imaging lens 2h and is reflected by a mirror 2i by which the light is enlarged and imaged on the screen 2j. The quantity of the light detected by a photodetector 5 provided on the outside of the screen 2j is detected. A focusing judgement circuit 6 decides the focusing condition with the output of the photodetector 5 and runs forward or backward a motor 8 via a lens position control circuit 7 thereby moving the lens 2h along the optical axis and matching automatically the focus. The operator is thus able to devote himself to selection and reading of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a microfilm reader that automatically brings the entire focus into alignment.

[Prior art]

In conventional microfilm readers that are generally known, focusing is performed manually, and a mechanism for automatically matching the focus like a camera or the like has not been put into practical use. Focusing of this type of microfilm reader is necessary, for example, when using a film holder with insufficient precision, or when the film position deviates from the normal position when changing the film, or when changing the magnification. This is necessary when replacing the lens. However, the focusing of this Micro7IlA IJ-der is performed by operating a helicoid screw provided on the barrel of the imaging lens, and when there are many films, the focusing described above is performed for each film. This required a long time to perform the operations alone. As a result, reading only a few drops of film content caused eye fatigue, which was one of the causes of poor visual acuity.

〔the purpose〕

The present invention was made in view of the above-mentioned drawbacks of the conventional technology, and an object of the present invention is to provide a microfilm reader that automatically brings the camera into focus.

〔Example〕

The present invention will be explained below based on the drawings.

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

In the figure, 1 is a microfilm reader, 2 is an optical system, including a lamp la and a concave mirror 2b.

Condenser lens 2C1 illumination mirror 7d, condenser lens 2e1 film holder 2f, microfilm 2g
1, an imaging lens 2h, an optical path bending mirror 2+, and a screen 2j.

A lamp lighting circuit 3 is connected to a power source (not shown) via an outlet 4, and blinks the lamp 2a.

5 is COD (charge-coupled device
ce), which is disposed within the image circle 16 of the imaging lens 2h and outside the screen 2j. The light receiving surface 5a of the light receiving element 5 is on the same plane as the screen 2j, and detects the amount of light transmitted through the microfilm 2g. 6 is counter P1 memory iS A s memory MAX, memory MIN, memory A
The focus matching determination circuit is made up of the following, and determines whether or not the focus is matched based on the amount of light detected by the light receiving element 5.

The light receiving element 5 and the focus determining circuit 6 constitute a determining means A that determines whether or not the focus is in agreement. 7 is a lens position control circuit of the position determining means B for moving the imaging lens 2h to an appropriate position; it drives a motor 8 such as a pulse motor; and a lens moving mechanism 9 mechanically connected to the motor 8. This allows the imaging lens 2h to move.

Next, the operation will be explained based on the flowchart shown in FIG.

Microfilm 2g held by film holder 2f
When the lamp 2a is loaded and a switch (not shown) of the lamp lighting circuit 3 is turned on, the lamp 2a is lit. The light from the lamp 2a passes through a condenser lens 2C, and then is directed to an illumination mirror 2d.
and is guided to the condenser lens 2e. After passing through the condenser lens 2e, this light passes through the film holder 2f.

Pass through a microfilm 2g and an imaging lens 2h,
The light is reflected by the optical path bending mirror 21 and reaches the screen 2j. Then, the imaging lens 2 is placed on the entire surface of the image circle 16.
The image of microfilm 2g magnified by h is projected,
The light-receiving surface 5a of the light-receiving element 5 has an image, for example, as shown in FIG.
As shown in (b), part of the character 1 is projected. FIG. 3(a) shows an example when the focus matches, and FIG. 3(1)) shows an example when the focus does not match.

Normally, the color of the letters etc. on the microfilm 2g is white, and the output of the light receiving element 5 is highest at position 2 as shown in Figure 4, and when the focus is aligned, it is like curve a, and when it is not aligned, it is like curve a. is like song 5Llb or A-1, Nafu is Confucian fortune telling is 1. ? -J- The difference between the maximum value and the minimum value of the output of this machine with eccentricity becomes maximum.

On the other hand, when the microfilm 2b is loaded, a start signal is input to the focus determination circuit 6, and an operation for determining whether or not the focus is achieved is started.

First, the initial value o(
=p) and setting value 200←PI), memo IJ i S
A has an initial value of 0 or a value smaller than 0 (=i S
A) is set (STEP-1). When the lens position control circuit I inputs one pulse to the motor 8, the imaging lens 2h is moved a predetermined distance by the lens moving device #99 (
(hereinafter referred to as "scan"), and moves the entire distance with 200 pulses. On the other hand, the value obtained by adding 1 to the initial value, that is, l, is input to the counter P (STEP-2), and at the same time, the maximum and minimum values of the output from the light receiving element 5 are converted into A-Di, respectively, and stored in the memory MAX. and stored in memory MIIQ (STEP-3). Next, enter the maximum and minimum values in Memo IJ MAX and Memo! J.M.
Read from IN and calculate the difference SA 5TEP-4
(SA) obtained as a result of the L calculation is compared with the value iSA stored in the memory iSA. As a result of the comparison, if the difference SA is larger, the value of the difference SA is stored in the memory iSA.
5TEP-5), and at the same time, the number of pulses P1, that is, 1 in this case, is stored in memory A (STEP-6). On the other hand, when the value iSA stored in the memory isA is larger, the value iSA stored in the memory isA remains unchanged (STEP-5).
). Next, it is determined whether the imaging lens 2h has scanned the entire moving distance, that is, whether the value P stored in the counter P has become 200 or more (STEP-7).
. If it is not 200 or more, perform the basic operations from 5TEP-2 to 5TEP-7 until it becomes 200 or more, that is, scan the imaging lens 2h while scanning the light receiving element 5.
The difference SA between the maximum value and the minimum value of the output from
A is compared with the value iSA already stored in the memory iSA, and the larger value is stored in the memory iSA.

When this basic operation is repeated until the value of the counter P reaches 200, the imaging lens 2h, which has completed the entire movement distance, returns to the original scan start position, and at the same time, the imaging lens 2h returns to the original scan start position.
The value becomes 0 (STEP-8).

At this time, the memory A stores the pulse @p when the difference SA between the maximum value and the minimum value of the output from the light receiving element 5 is maximum, that is, the position of the imaging lens 2h when the focus matches on the screen 2j. is memorized.

The imaging lens 2h starts moving again when it returns to the scan start position, and stops moving when the number of pulses input from the lens position control circuit 1 to the counter P becomes the same as the value stored in the memory A. . At this time, screen 2j
A focused image of the microfilm 2g is projected onto it.

In the above embodiment, the case where one light-receiving element 5 was used was explained, but if a plurality of light-receiving elements 5, for example six as shown in FIG. The probability that an image or the like will be projected onto the light-receiving surface 5a of the light-receiving element 5 increases.

As a result, a more stable focusing operation can be performed than in the above embodiment.

[Not effective]

As explained above, this invention is capable of automatically aligning the focus, and eliminates the operation of aligning the focus and the need to look beyond the eye accompanying this operation, allowing the operator to concentrate on counting the contents of the microfilm. It has the effect of being able to

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a view seen from the direction of arrow P in FIG. 1, and FIGS. 3(a) and (b).
) is a diagram showing an example of a microfilm image projected near the light-receiving element. Figure 3(a) shows the image when the focus is aligned, and Figure 3('b) shows the image when the focus is out of alignment. A diagram showing an example of a projected image, Figure 4 is similar to Figure 3 (aL (b)
Figure 5 shows the relationship between the cell position of the light-receiving element and the output of the light-receiving element when an image is projected as shown in Fig.
FIG. 1...Microfilm reader 2...
...Microfilm 2h...Imaging lens 2j...Screen 5...Photodetector 6...Focus matching judgment circuit 7...Lens Position control circuit A... Judgment means B... Position determining means Fig. 3 (a) (b) Fig. 4 Fig. 6

Claims (2)

[Claims] (1) Position the imaging lens to capture the desired microfilm image! f- In a microfilm reader adjusted to be focused on a screen, a determining means for determining whether or not the focus is on the screen, and a position for determining the position of the imaging lens in the optical axis direction. A microfilm reader comprising a determining means, and based on the determination result of the determining means, all the position determining means are activated to automatically match the focus. (2) A patent characterized in that at least one of the determining means is disposed within the image circle of the imaging lens and outside the screen, and its light-receiving surface is on the same plane as the screen surface. Microfilm reader according to claim (1)