JPH0785125B2 - Focus adjustment device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a focus adjusting device, and more particularly to a focus adjusting device suitable for reading an image on a microfilm or the like.

[Prior art]

An apparatus for electronically reading an image on a microfilm will be described with reference to FIG.

The film 1 is exposed by the light from the light source a through the lens b, further passes through the lens c, and then is selectively guided to the screen h and the reading side 3 by the movable optical path switching mirror d. The focus is adjusted by tilting the mirror d to the screen side x and adjusting the focus of the lens group c. After that, the optical path is switched to the reading side Y by tilting the mirror d, and the motor g moves the CCDf in the direction of the arrow, and the CCDf converts the intensity of the incident light into an electric signal. In addition, e is a mirror.

Here, the image formed on the CCDf and the screen h
Correspondence of the focus with the image formed above is adjusted by the adapter lens AL, and this adjustment is performed at the time of factory assembly. However, vibration during transportation and transportation,
For focusing and reading the image on the screen due to the mechanism of the temperature difference (optical path length), shrinkage, aging, etc.
There was a drawback that the focus on the CCD side could not be met.

For this adjustment, after installing the device to the user, a serviceman moves the adapter lens AL and adjusts it accordingly, but this work takes a lot of time and requires high technology. It was

Also, the adapter lens AL itself cannot recognize the state of whether or not the best focus state (hereinafter referred to as just focus) is obtained unless the film image is clearly formed on the screen h. , Adapter lens AL
Aberrations and distortions are required to be extremely small, and resolution is also required to be very high. Therefore, the processing of this adapter lens is required to be precise, and the cost is also very high.

On the other hand, as described above, the adapter lens AL and the screen h
Even if the adjustment of the correspondence between the upper image and the image on the CCDf is good, it was very difficult for an unskilled operator to set the image at the just focus point.

The operator moves the focusing lens up and down to change the distance to adjust the focus of the image on the microfilm 1. However, the power from the manual knob or the electric motor is reduced by a gear or the like. It has a mechanism to move. However, in this type of device, when the focus point is centered, the vertical movement of the focusing lens is several μm to several tens μm.
There is only the range (depth of focus) of
The image becomes out of focus, and the image information cannot be read accurately.

As described above, in this type of apparatus, there are many problems in setting the just focus point rather than forming an image only on the screen.

Further, in recent years, the digitization of documents has progressed, and so-called optical disc electronic file systems for electronically recording documents have come to be widely used. Needless to say, users who have recorded and filed documents from old times have recorded and utilized as microfilm until now, but this microfilm document must be converted into an optical disc electronic file, It is the microfilm electronic scanner that makes these possible.
In recent years, development of this type of product has begun.

However, as described above, it is very inconvenient and time-consuming to adjust the focus of the image on the microfilm, because it requires one frame, one frame, and manual adjustment by an expert's eye.

On the other hand, there is a method in which the focus adjustment lens is moved and set to the position set during factory adjustment by adjusting the thickness of the film to be used to eliminate the above defects and inputting the thickness of these films. To be

However, microfilms have different film thicknesses depending on each manufacturer, and even the same manufacturer has very large film thicknesses, such as silver film, diazo film, etc. With the method, usable films were limited, which was very inconvenient.

Also, due to aging etc. during use, the above settings will be misaligned, so call a service person on a regular basis,
It was very inconvenient because I had to make troublesome adjustments.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and picks up a part of the image formed by the image forming optical means and forms the image formed by the image forming optical means at a predetermined image forming position. And a distance between the image forming optical unit and the planned image forming position so that an image formed by the image forming optical unit according to the judging unit is formed at the predetermined image forming position. And an image suitable for the determination that the determination unit should pick up for the adjustment operation of the adjustment unit from the images formed by the image forming optical unit prior to the adjustment operation of the adjustment unit. And a focus adjusting means for setting focus distance between the image forming optical means and the predetermined image forming position at a predetermined distance when the search operation of the search means is performed. Provide the equipment It is an.

〔Example〕

 The present invention will be described in detail below with reference to the drawings.

2 to 8 are views showing a preferred embodiment of the present invention.

In FIG. 2, F is a microfilm having an image recorded on the front surface or the back surface thereof, and is illuminated by the light passing through the lens B by the light source P. FC is the main lens for focus adjustment, and has a mechanism that moves up and down using a drive mechanism that converts the rotary motion of the pulse motor into linear motion by an eccentric cam.

The image converged by the main lens FC is formed on the one-dimensional photodetection sensor CCD in which a plurality of light receiving elements are arranged in a line. The arrangement direction of the light receiving elements of the CCD, that is, the self-scanning direction is the main scanning direction.

Next, in scanning (scanning) in a direction substantially perpendicular to the main scanning direction (sub scanning direction), the CCD is moved by the sub scanning motor M, the pulley Q, and the wire W in a direction perpendicular to the main scanning direction. It is done by As a result, one screen of the image on the film can be sequentially read line by line.

An image signal read by the CCD is subjected to predetermined processing by an amplifier G or the like, and then an image forming apparatus (not shown),
For example, it is output to a laser beam printer, an optical disk device, or the like.

The system controller SC outputs a control signal CC for driving the CCD, a control signal SM for driving the sub-scanning motor M, and a control signal FS for moving and controlling the main lens FC.

CCD drive circuit CT is a drive signal for driving CCD sensor
It also generates a DS and a reset signal RS for synchronizing a counter K for counting focus information, which will be described later.

The comparator COM constantly compares the output signal from the CCD with the voltage (set value) set by the value setting volume VR, and if it is larger than the set value TL, it is an "H" signal, and if it is smaller than the set value TL, it is " The L "signal is output as focus information CS.

The number of edges on the rising edge (or falling edge) of the "H" or "L" signal is referred to as focus information, and the counter K counts the number of edges.

Then, the focus lens is controlled so as to be moved so that the number of the edges becomes large, so that the autofocus operation is performed.

That is, paying attention to the fact that as the number of this edge increases, the direction in which the focus is achieved, the value counted by the counter K is judged by the CPU built in the system controller SC by the CPU, and the counted value becomes the maximum (peak point). Similarly, the focus adjustment lens FC is controlled to move.

Next, the operation will be described. FIG. 3 (a) shows film F
It is a part of the image information recorded above (the microfilm is usually a negative film, the black part in the figure allows light to pass through, and the white part does not allow light to pass through). FIG. 7A is an enlarged view, and the stripe patterns F ₁ , F ₂ , and F ₃ become thinner as the distance from the central portion increases. When this image information is read by the one-dimensional optical sensor (CCD) between l _{1 and} l ₂ (main scanning direction), an output waveform as shown in FIG. 4 (a) is obtained. The amount of stairs in the waveform corresponds to each CCD cell (light receiving element).

This output waveform is compared with the value TL by the comparator COM (2
When converted into a value, the output signal CS of FIG. 4 (b) is obtained. Next, this signal CS is input to the counter K. Counter K is
Reset signal RS from CCD drive circuit CT every time one scan of CCD is completed
Received and reset. The counter K has a built-in latch and always stores the previous value in synchronization with the reset.

In this way, the output of the counter K counts the number of edges in one scanning period each time the CCD is scanned (scanned) in the main scanning direction.

FIG. 5A shows the just-focused state, and FIG. 5B shows the out-of-focus state.

When the one-dimensional photosensor CCD performs main scanning between l _{1 and} l ₂ in (I) of FIG. 5 (a), a waveform as shown in (II) of FIG. 5 (a) is obtained. (The actual CCD output signal has a stepped shape, but it is omitted for ease of explanation.) When the value TL is binarized, an output signal CS as shown in (III) of FIG. 5A is obtained.
(At Just Focus) Next, FIG. 5 (b) at the time of out-of-focus will be described.

In FIG. 5 (b), (I) is an image formed on the CCD sensor surface, but in actuality, the main scanning is performed between l _{1 and} l ₂ . Here, in the output signal (II) from the CCD, the number of crossing the threshold value TL is reduced, and the output signal CS from the comparator COM is the fifth signal.
Figure (b) of the rising edge as (III) also e _'1, e'
_It can be seen that the number becomes ₄ and e'4, which is clearly smaller than the number of edges at just focus.

Therefore, the state of the focus can be known by counting the rising edges e.

The above focus information (count value) is used by the system controller
The CPU built into the SC moves and controls the focus adjustment lens FC so that it reaches the maximum point (peak point) and the just focus point
Set to JP.

Here, the fl ₁ -l ₂ curve in FIG. 6 is focus information obtained by reading the area between l ₁ -l ₂ on the film F in FIG. ₂ with a CCD. In this case, the image on the film F reads part of the characters "ABDFG" as focus information. Next, when the area between l' ₁ and l' ₂ (broken line) on the film F in FIG. ₂ is read, a part of "ACF" is read, and the broken line curve fl ' _1-in FIG.
The level of the curve becomes lower like l' ₂ .

Since the image on the film is read by the one-dimensional photosensor in this manner, the maximum counter value differs depending on the position where the image on the film F is read. However, even if the images on the film are different, the count value of the counter K will always be the maximum point (peak point) when the movement position of the focus adjustment lens FC becomes the JP point, so the CPU will set the maximum point (peak point). ) Is detected, the just focus point JP can be detected.

FIG. 7 shows a sequence flowchart of the autofocus operation of the system controller SC.

In FIG. 7, when starting the autofocus operation,
First, in step S1, a pulse motor for moving the lens FC is set at a set position. That is, the lens FC for focus adjustment is previously positioned at a limited reference position. Next, in step S2, the movement of the CCD sub-scanning motor M from the origin is started and the CCD main scanning reading is executed.

Then, in step S3, a point where the count value of the counter K for each line scanning is equal to or larger than a predetermined number is searched for. That is,
An image line suitable for autofocus detection on the film F is detected. If there is a position where the count value is equal to or more than a predetermined number, the process proceeds to step S4, and the motor M is not operated to stop the sub-scan at that point. And This allows the CCD sensor to read a position suitable for autofocus detection.

Next, in step S5, the pulse motor for moving the lens FC is driven to set the lens FC at the starting point SP. And step
The main scan of the CCD sensor is performed in S6. At this time, the CCD sensor is not moved in the sub-scanning direction. The count value (the number of focus information) of the counter K is taken in every main scanning of one line of the CCD sensor and stored in the built-in memory. At this time, the number of steps of the pulse motor is also stored. And step
In S7, it is determined whether or not the lens FC is at the end point EP. End EP
If not, the process proceeds to step S8, the pulse motor for moving the lens FC is operated by one step, and the lens is moved by one step from the start point to the end point. Then, again in step S6, the CCD sensor is caused to perform main scanning, and focus information is counted and stored in the memory. When this is repeated until the lens FC reaches the end point EP, the count value of the counter K in each of the plurality of main scans in each step in which the lens FC moves from the start point to the end point is stored in the memory.

When the lens FC reaches the end point, the process proceeds to step S9, the maximum value of the count value stored in the memory for each main scan is searched, and the step number of the pulse motor corresponding to the maximum value is recognized. Then, the pulse motor is driven to move the lens FC to the position of the recognized number of steps. As a result, the lens FC is set to the just focus position.

FIG. 8 shows an example in which a two-dimensional optical detection sensor (CCD-2) is used as the optical sensor for focus detection and the optical sensor for image reading. The principle of focus adjustment is the same as the example using the one-dimensional (row-shaped) optical sensor described above, but in the case of this method,
Since sub-scanning and main scanning can be performed electronically (each element is switched electronically) when reading an image and detecting a focus, mechanical scanning is performed by a sub-scanning motor as shown in FIG. It will get better without doing it.

Also in the focus detection operation in this case, the focus state can be detected by reading the entire surface of the two-dimensional sensor CCD-2 or a specific area portion and counting the number of the edges.

In the case of this example, a 5000-element sensor was used as the one-dimensional light detection sensor (line sensor), and a 500-element × 500-element sensor was used as the two-dimensional sensor.

In the present embodiment, a microfilm reading device has been described as an example, but it goes without saying that it can also be applied to a normal 35 mm film reading device. In addition, since focusing can be performed manually without the need for a monitor screen for focusing.

Further, in addition to reading a film image, it can be applied as an autofocus for image reading of a system in which a book, a document or the like is read by its reflected light.

Moreover, since it can be used with one-dimensional and two-dimensional optical sensors, it can be applied to an image pickup tube, especially a video camera, and when applied to a video camera, a separate sensor for focus detection is used. Since it can be used without being provided, it can be applied to a ready-made Kamla.

[Correspondence between Example and Invention]

In the above embodiment, steps S5 to S9 of the system controller SC are the judging means of the present invention, step S10 of the system controller SC is the adjusting means of the present invention, and steps S2 to S5 of the system controller SC are the searching means of the present invention. The step S1 of the system controller SC corresponds to the setting means of the present invention.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a focus adjustment device that can perform focus adjustment appropriately and accurately.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of a conventional microfilm reader. FIG. 2 is a diagram showing a configuration example of a microfilm reading device according to the present invention, FIG. 3 is a diagram showing an image of a microfilm, FIGS. 4 and 5 are diagrams showing an output state of a sensor, and FIG. The figure which shows the distribution of the count value, Figure 7 the flowchart figure which shows the control procedure of the system controller,
FIG. 8 is a diagram showing the configuration of another embodiment of the present invention, P
Is a light source, FC is a focusing lens, F is a microfilm,
CCD is a one-dimensional sensor, COM is a comparator, K is a counter, and SC is a system controller.

Claims (1)

[Claims] 1. A judging means for picking up a part of an image formed by the image forming optical means and judging an image forming state of the image formed by the image forming optical means at a predetermined image forming position; Adjusting means for adjusting the distance between the image forming optical means and the predetermined image forming position so that an image formed by the image forming optical means according to the means is formed at the predetermined image forming position. Search means for searching for an image suitable for the determination that the determination means should pick out from the images formed by the imaging optical means before the adjustment operation for the adjustment operation of the adjustment means. A focus adjusting apparatus comprising: a setting unit that sets a predetermined distance between the image forming optical unit and the planned image forming position during operation.