JPS63118132A - Automatic focusing control method - Google Patents

Abstract

PURPOSE:To improve the reliability of automatic focusing operation and to shorten an operation time by storing a past focusing position and moving a projection lens to the past focusing position prior to the automatic focusing operation. CONSTITUTION:When automatic focusing control wherein the projection lens which guides a microphotograph negative image to a screen 28 or printer 34 is moved automatically to its focusing position is performed, the past focusing position of the projection lens 20 is stored and the projection lens 20 is moved to the past focusing position prior to automatic focusing operation. When plural projection lenses are used, focusing position are stored by the projection lenses. The respective projection lenses may have internal memories for storing their focusing positions so that the contents of the memories are read in a device main body when the projection lenses are mounted. Consequently, the focusing position is detected speedily when the projection lens is very far away from the focusing position before the automatic focusing operation or when a projection lens differing in back focus is mounted, thus improving the reliability of the automatic focusing operation and shortening the operation time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an autofocus control method applied to a microphoto enlarging and restoring device such as a microphoto reader, reader printer, enlarger, or enlarger printer. .

(Background of the Invention and Prior Art) A reader that projects an enlarged image of a microphotograph onto a screen, a printer that guides the enlarged image to a printer to obtain a hard copy, or a one-da printer, an enlarger, an enlarger, etc. Microphoto enlargement and reconstruction devices are known for some time. In this type of apparatus, it has been considered to provide an autofocus mechanism that automatically moves the projection lens to a focusing position. This autofocus mechanism, for example, guides a part of the projection light to a CCD line sensor, finds the position of the projection lens where the contrast signal obtained from the output of the image sensor is maximum, and determines this position (
The projection lens is configured to move the projection lens to a focused position.

This contrast signal changes significantly in response to changes in the position of the projection lens before and after the focal position of the projection lens.

However, if the image is far away from the in-focus position of the projection lens and is significantly blurred, the change in the contrast signal will be very small.

For this reason, the autofocus mechanism cannot determine the direction of the focus position of the projection lens, resulting in problems such as the autofocus mechanism not operating correctly or requiring a long time to detect the focus position.

In general, microfilms have images on the front and back, so methods have been proposed to detect and control which side the image is on (for example, JP-A-57-1
No. 20926), but in reality, there are a variety of films with different thicknesses, so this existing proposal cannot cope with this problem.

Therefore, a method of storing the image plane and film thickness on a film holder (cartridge) or film was also proposed (Japanese Patent Application Laid-open Nos. 60-257438 and 61-55637).
However, this type of micro-photo enlarging and restoring equipment usually has multiple groups of interchangeable projection lenses, and each projection lens has a different focus position, so each time the lens is replaced, the camera automatically adjusts to avoid the above-mentioned extreme blurring. A focus operation will be performed. In particular, the back focus (distance f2I from one lens surface to the focal point) of projection lenses varies considerably depending on factors such as the characteristics of the lens used, variations in focal length, and assembly errors, and this variation is generally 1 mm. It will be about.

On the other hand, the focusing accuracy required from the depth of focus of the lens is 10 microns or less for a high magnification lens. For this reason, even if the back focus is adjusted to a fairly high degree of precision, significant blurring may occur due to lens exchange, and this problem has previously been unsolvable.

(Objective of the Invention) The present invention has been made in view of the above circumstances, and it can be used when the projection lens is far away from the in-focus position before autofocus operation or when a projection lens with a different back focus is replaced. It is an object of the present invention to provide an autofocus control method capable of quickly detecting a focus position, increasing the reliability of autofocus operation, and shortening operation time.

(Structure of the Invention) According to the present invention, this object is to provide an autofocus control method for automatically moving a projection lens that guides an image of a microphotographic original image to a screen or a printer to a focusing position. This is achieved by an autofocus control method characterized by storing a focus position and moving the projection lens to this past focus position prior to an autofocus operation.

Here, when a plurality of projection lenses are prepared, the focus position is stored separately for each projection lens.

Of course, the memory for storing this focus position may be provided in the main body of the device, but it is also possible to have a memory built into each projection lens and read the contents of this memory to the main body of the device when the projection lens is attached. It may be configured so that it is released.

(Function) The past focus position stored prior to the autofocus operation is read out, and the projection lens is moved to this past focus position. Therefore, the projection lens does not have to perform an autofocus operation from a state where the focus is significantly deviated, and the contrast signal changes greatly due to lens movement. Therefore, the direction of the focus position of the projection lens can be accurately determined, and the reliability of the autofocus operation is increased and the operation time is shortened.

(Example) Fig. 1 is a block diagram of an autofocus device that is an embodiment of the present invention, Fig. 2 is a flowchart of its operation, Fig. 3 is an overall schematic diagram of a league printer, and Fig. 4 shows an output waveform. The figure shown in FIG. 5 is a diagram showing a change in the contrast signal with respect to the lens position.

In FIG. 1.3, reference numeral 10 is an original image of a microphotograph such as microfiche or microroll film. 12 is a light source, and the light i12 is transmitted through a condenser lens 14. The original image 10 is passed through a heat shielding filter 16 and a reflecting mirror 18.
guided to the underside of

In the reader mode, the transmitted light (image projection light) of the original image 10 is guided to the transmission screen 28 by the projection lens 20 and the reflecting mirrors 22, 24, '26, and the enlarged projected image 24 of the original image 10 is projected onto the screen 28. It rotates to the imaginary line position in Figure 1, and the projected light is reflected by the reflecting mirror 22, 30, 32.
The image is guided to a c-type slit exposure printer 34. The reflecting mirror 22 synchronizes with the rotation of the photosensitive drum 36 of the printer 34.
．． 30 moves, and a latent image is formed on the photosensitive drum 36. This latent image is made visible by toner charged to a predetermined polarity, and this toner image is transferred onto the transfer paper 38.

40 is a zone setting means, which includes a mark 42 indicating a focus zone and a manual knob 44 for moving this mark 42 on the screen 28. The position a of the zone is detected by the position detection section 46 and sent to the control means 48.

Reference numeral 50 denotes a focus control optical system, which includes a semi-transparent mirror 52 arranged on the optical axis of image projection light, a projection lens 54, and C.
It includes a CD line sensor 56 and a motor 58. A portion of the projection light that has passed through the projection lens 20 is guided by a semi-transparent mirror 52 to a line sensor 56 through a projection lens 54 .

The line sensor 56 is movable by a motor 58 in a direction perpendicular to the optical axis. Further, the projection lens 54 is configured so that when the projection lens 20 is placed at a position where the projection light is focused on the screen 28 or the projection surface of the photosensitive drum 36, an image is accurately formed on the light receiving surface of the line sensor 56. Its focal length is determined.

The autofocus mechanism includes a motor 60 that moves the projection lens 20 forward and backward in the optical axis direction, and the projection light is directed to the screen 28.
Alternatively, the focus is controlled by the control means 48 so that the image is correctly formed on the projection surface of the photosensitive drum 36.

The control means 48 is constructed as shown in FIG. That is, the clock pulse outputted by the clock 62 is input to the CCD driver 64, and this CCD driver 64 is
The line sensor 56 is driven at the drive frequency commanded by the PU 76. This line sensor 56 outputs a pulse signal that changes approximately in proportion to the amount of incident light (exposure amount) of each pixel for each scan. This pulse signal varies from pixel to pixel even if the same amount of light is projected due to variations in the characteristics of each pixel. The signal processing circuit 66 corrects this variation in the characteristics of each pixel and shapes the waveform to produce the output signal V shown in FIG. 3(I). Note that in FIG. 3, the horizontal axis n indicates the pixel order of the line sensor 56.

The output signal V processed in this way is passed through a bandpass filter (
BPF) 68 and becomes the output W shown in FIG. 3 (II).

70 is a peak hold circuit (PH). This peak hold circuit 70 detects the maximum value of the output signal W, and this maximum value corresponds to the position χ of the projection lens 20 at this time.
becomes the contrast signal C (Fig. 3 (m)
reference).

This contrast signal C is converted into a digital signal by an A/D converter 72, and the contrast signal C is
It is input to PU76. In FIG. 1, 78 is a ROM that stores control programs for the CPU 76, 80 is a RAM, and 82
84 and 86 are D/A converters, and 88 and 90 are drivers for driving the motors 58 and 60, respectively.

92 is a memory attached to the projection lens 20, such as a non-volatile ROM or a battery-backed RAM. This memory 92 stores the focal position of the projection lens 20 determined in the previous autofocus operation.

In general, there are two types of microphotographic originals 10: those with images on the front and those with images on the back.

For example, in the case of an original image lO with an image on the front, the projection lens 2
0 is focused on the front side of the original image 10, and the contrast signal C at this time is determined by the lens position χ1 as shown in FIG. 5A.
Maximum at . Further, in the case of an original image lO having an image on the back side, the projection lens will focus on the back side, and the contrast signal C at this time will be maximum at the lens position χ2 as shown in FIG. 5B.

The memory 92 of the projection lens 20 stores two lens positions χ1, χ2 obtained in the previous autofocus operation, that is, in-focus positions χ1, χ2 for the front and back sides of the original image 10.
is memorized. This focus position may be rewritten and memorized with new data (focus position) each time autofocus is performed, or the focus position of each projection lens 20 may be determined by inspecting all of the projection lenses 20 before shipping from the factory. It may be entered in advance.

In FIG. 1, 94 is a front/back designation switch.0 The front/back designation switch 94 is used by the operator to manually input whether the image of the microphotographic original 10 to be used is on the front or back. The CPU 76 reads either the focus position χl or χ2 from the memory 92.

A focus switch 96 selects between autofocus mode and manual focus mode. In the manual focus mode, this switch 96 allows input of the moving direction and moving speed of the projection lens 20.
When 0 is far from the focus position ε, it can be brought together again at high speed, and when it is close to the focused position, it can be moved at low speed.

98 is a print switch, and by operating this switch 98, the printer 34 is operated to obtain a hard copy.

100 is a timer. Generally, the position χ of the projection lens 20
If the value does not change for a certain period of time or more, the lens lO is considered to be in the in-focus position. This is because if autofocus fails, the user is likely to perform autofocus or manual focus again.

This timer lOO is for integrating this fixed time based on a command from the CPU 76.

Next, the operation of this embodiment will be explained. The CPU 76 first reads the position a of the zone set by the zone setting means 40, and controls the motor 58 so that the projected light of the area corresponding to this zone enters the line sensor 56 (see FIG.
Step 200). The user selects the reader mode in which the reflector 24 is placed at the solid line position in FIG. 1, and the target original image is projected onto the screen 28. A portion of this projected light is guided to a line sensor 56 by a semi-transparent mirror 52.

Based on the output of the front/back designation switch 94, the CPU 76
The focus position χ1 or χ2 corresponding to the front or back side is read from the ROM 92 and temporarily stored in the RAM 80 within the main body of the apparatus (step 202).

Then, the CPU 76 moves the projection lens 20 to the read focus position χ1 or χ2 (step 204).

If focus switch 96 has selected autofocus mode (step 206).

Auto exposure (AE), rain detection, auto focus (A
The operations F) are performed in sequence (step 208).

In auto exposure, for example, the exposure amount of the line sensor 56 is controlled by changing its driving frequency.
Control is performed so that the output level of No. 6 falls within an appropriate range. For rain detection, for example, based on the sufficiently large number of positive/negative fluctuations in the output W of the bandpass filter 68, it is determined whether or not the image is suitable for autofocus operation, and if the image is unsuitable, a warning is issued and the zone setting means 40 to request a focus zone change. Autofocus operation is performed using projection lens 2.
0 by a minute distance, find the lens position χ where the contrast signal C is maximum, and place the projection lens 20 at this position χ.
This is done by moving the .

When this autofocus operation is completed, timer 1
00 is set (step 210).

Then, the autofocus mode is selected again by the focus switch 96 (step 212), or
Is it possible to switch to manual focus mode? (Step 21)
4), if the original image 10 is moved (step 216
), it is determined that the result of the autofocus operation in step 208 is not satisfactory, and the timer 100 is reset (step 218). And again step 2
Return to 08. If autofocus mode is not selected again (step 212), manual focus mode is not selected (step 214), and the original image is not moved (step 216), if this state continues for more than the set time To of the timer 100, step It is considered that the autofocus result of step 208 is satisfactory (step 220). If the set time TO has elapsed, the timer 100 is reset (step 222), and the lens position χ at this time is stored in the memory 92 as the in-focus position (step 224). And prepare for the next operation.

FIG. 6 is an operation flowchart of another embodiment. In this embodiment, the focal position of the projection lens 20 is stored in the memory (RAM) of the main body of the apparatus.
80, etc.), only the type of the projection lens 20 is detected, and the focal position corresponding to this projection lens 20 is read out from the memory.

That is, first, after detecting the type of the projection lens 20 (step 300), if this lens 20 is the first one, the operations from step 206 onward are performed in the same manner as in FIG.
Step 302), if it is not the first lens, the past focusing position is read from the memory (step 304). Then, the lens is moved to this in-focus position (step 306), and the operations from step 206 onwards are performed. Note that since the operations from step 206 onwards are the same as those shown in FIG. 2, the description thereof will not be repeated.

In each of the following embodiments, when the autofocus operation is completed, the contents of the memory are replaced by the lens position (focus position) at that time. However, in the present invention, the focal position of the projection lens 20 is stored in advance at the time of shipment from the factory.
This includes information that is not rewritten each time an autofocus operation is performed. In addition to rewriting the memory after a certain period of time (To) has elapsed after the autofocus operation is completed, the memory may also be rewritten by operating the print switch 98 or by another independent manual switch that commands memory rewriting. Of course.

(Effects of the Invention) As described above, the present invention stores the past focus position and moves the projection lens to this past focus position prior to autofocus operation, so that the projection lens is in focus. This eliminates the need for autofocus operations to occur in a situation where the camera deviates greatly from its position and is in a so-called "baka-poke" state. Therefore, the reliability of the autofocus operation is improved and the operation time is shortened.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an autofocus device that is an embodiment of the present invention, Fig. 2 is a flowchart of its operation, Fig. 3 is an overall schematic diagram of a league printer, Fig. 4 is a diagram showing output waveforms, and Fig. 4 is a diagram showing output waveforms. FIG. 5 is a diagram showing changes in the contrast signal with respect to the lens position, and FIG. 6 is a flowchart of the operation of another embodiment. 20... Projection lens, 56... CCD line sensor, 76... CPU, 92... Memory. Patent applicant Fuji Photo Film Co., Ltd. Agent Patent attorney Yama 1) Yu Moon Figure 3

Claims (2)

[Claims] (1) In an autofocus control method in which a projection lens that guides an image of an original microphotograph to a screen or printer is automatically moved to a focusing position, the past focusing position of the projection lens is memorized and the autofocus operation is performed. An autofocus control method characterized in that the projection lens is moved to this past focusing position prior to. (2) The autofocus control method according to claim 1, wherein the projection lenses are replaceable, and each projection lens stores a past focus position of each projection lens.