JPH079531B2 - Autofocus device for micro film reader printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention provides a microfilm reader printer capable of forming a microfilm projection image on a visible projection surface and outputting the image to a printer. The present invention relates to an applied autofocus device.

(Technical background of the invention) A reader printer in which an image projection light of a microphotograph original image is formed on a screen or a photoconductor, and a magnified projection image is visually recognized on the screen or a photoconductor is formed to obtain a hard copy. There is. When an autofocus mechanism is provided in this type of device, only a partial area (focus zone) of the projected image is guided to the image sensor, this image sensor determines whether or not focus is achieved, and the focus state is set. Control the optical system of the projected image.

However, in order for such autofocus control to be possible, it is premised that an image suitable for autofocus control is included in the focus zone guided to the image sensor. For example, when the focus zone is a background area of uniform density, correct autofocus control cannot be performed.

It goes without saying that this problem can be solved by expanding the autofocus to the entire area of the screen or the image forming surface of the photoconductor, but in this case, the amount of relative movement of the image sensor with respect to the image becomes large, and focusing is completed. There is a problem in that the operation time of up to and the cost increase.

(Object of the Invention) The present invention has been made in view of such circumstances, and it is possible to guide an optimum area including an image as a focus zone to an image sensor, and it is possible to improve reliability of autofocus control. Another object of the present invention is to provide an autofocus device for a micro film reader printer.

(Structure of the Invention) According to the present invention, the object is to form a microfilm projection image on a projection surface through a projection lens so that the film projection image can be visually recognized on the projection surface, In a micro film reader printer capable of outputting to a printer, a manual zone setting means for designating a focus zone on the projection surface and a partial area of a film projection image passing through the projection lens are formed on an image sensor. A focus control optical system and control means for controlling the focus control optical system so as to guide the focus zone set by the zone setting means to the image sensor, and an exposure amount based on the output of the image sensor. Control and focus control of the projection lens are performed. This is achieved by the automatic focus device of the computer.

In order to guide the focus zone set here to the image sensor, the image sensor is moved, the imaging lens of the focus control optical system is moved, or a part of the projection light is divided into this autofocus system. It is possible to move the image dividing mirror.

(Embodiment) FIG. 1 is an overall schematic view of a reader printer which is an embodiment of the present invention, and FIG. 2 is a view showing its zone setting means.

In FIG. 1, reference numeral 10 is an original image of a micro photograph such as a micro fish or a micro roll film. Reference numeral 12 denotes a light source, and the light from the light source 12 is guided to the lower surface of the original image 10 via a condenser lens 14, a heat insulating filter 16, and a reflecting mirror 18.
In the reader mode, the transmitted light (image projection light) of the original image 10 is guided to the transmissive screen 28 as a projection surface by the projection lens 20, the reflecting mirrors 22, 24 and 26, and the original image 10 is enlarged and projected on the screen 28. Form an image. In the printer mode, the reflecting mirror 24 is rotated to the imaginary line position in FIG. 1, and the projection light is guided by the reflecting mirrors 22, 30 and 32 to the slit exposure type printer 34 of the PPC system. Photosensitive drum 36 of printer 34
The reflecting mirrors 22 and 30 move in synchronization with the rotation of the photosensitive drum 36.
A latent image is formed on it. This latent image is visualized with toner charged to a predetermined polarity, and this toner image is transferred onto the transfer paper.
Transferred to 38.

Reference numeral 40 denotes zone setting means, which is a focus zone A (second zone).
Mark 42) and the mark 42 on the screen
And a manual knob 44 for moving on. In this embodiment, the zone A can be moved up and down with the center of the screen 28 as the reference position, but it may be moved vertically and horizontally. The position a of the zone A is detected by the position detector 46 and sent to the control means 48.

A focus control optical system 50 includes a semi-transparent mirror 52 arranged on the optical axis of the image projection light, a projection lens 54, a CCD line sensor 56 as an image sensor, and a servo motor 58.
With. A part of the projection light that has passed through the projection lens 20 is guided to the line sensor 56 through the projection lens 54 by the semitransparent mirror 52. The line sensor 56 is movable by a motor 58 in a direction orthogonal to the optical axis. The projection lens 54
The focal length is determined so that the line sensor 56 is focused when the projection lens 20 is placed at a position where the projection light is focused on the screen 28 or the photosensitive drum 36.

The autofocus device includes a servomotor 60 that moves the projection lens 20 back and forth in the optical axis direction, and the projection light is projected on the screen 28.
Alternatively, a control means is provided so that the image is properly formed on the photosensitive drum 36.
Focus control by 48.

Next, the operation of this embodiment will be described. First, in the reader mode in which the reflecting mirror 24 is in the position shown by the solid line in FIG. 1, the projection light is guided to the screen 28, and a part of this projection light is guided to the line sensor 56 by the semi-transparent mirror 52. The user operates the knob 44 while looking at the screen 28, and moves the mark 42 so that the mark 42 overlaps the projected image.

Autofocus control is entered by operating a switch provided as appropriate. The control means 48 first reads the position a of the zone A set by the zone setting means 40, and controls the servo motor 58 so that the projection light of the area corresponding to this zone A enters the line sensor 56.

Then, the control means 48 adjusts the exposure amount. This exposure amount adjustment, for example, of the output voltage of each pixel of the line sensor 56,
This is performed by selecting the voltage of the pixel corresponding to the background area and adjusting the light quantity of the light source 12 so that this becomes a predetermined voltage.

Next, the control means 48 performs autofocus control based on the output of the line sensor 56. Various algorithms are possible for this control. For example, the maximum and minimum I (M) and I (m) of the brightness I obtained from the output voltage of each pixel of the line sensor 56 at a certain position of the projection lens 20 are obtained, and the following formula V (I (M) -I The "mountain climbing method" is used in which the position of the projection lens 20 having the maximum visibility V defined by (m)) / (I (M) + I (m)) is detected while sequentially moving the projection lens 20. Further, the projection lens 20 is moved once so as to cross the in-focus point, and the in-focus point is obtained from the half-value width of the luminance change characteristic curve at that time (half-value width method), or the projection lens 20 is moved once over the entire range. , The position where the brightness I is maximum may be obtained (full scan method).

When the printer mode is set in this focused state, the reflecting mirror 24 is rotated to the position of the virtual line in FIG.

Although the above embodiment is configured to move the line sensor 56 corresponding to the focus zone A, the present invention is not limited to this. For example, the projection lens 54 may be moved in the direction perpendicular to the optical axis of the servo motor 62. The image splitting mirror 52 can be moved by the servo motor 64. In particular, when the image splitting mirror 52 is moved, if only a partial region of the image splitting mirror 52 is configured to be a semi-transparent mirror and the other region is transparent, the position of the focus zone A is a shadow of the semi-transparent mirror region, and the screen 28 is a screen. Can be seen with. Therefore, the zone setting means only needs to mechanically move the image splitting mirror 52, and the mark 42 and the position detecting section 46 are unnecessary. In this case, it is needless to say that the image splitting mirror 52 needs to be retracted from the optical path in the printer mode.

Further, the zone setting means is not only mechanically manually set as in the above-described embodiment, but the position and order of movement is stored in an electronic circuit in advance, and each zone is circulated in order by operating a manual switch. Then, at the beginning of the control, it is possible to automatically return to the reference position in the center of the image.

(Advantages of the Invention) As described above, the present invention allows the focus zone to be set manually, so that the autofocus control can be performed using an image that is optimal for the autofocus control, and the control reliability can be improved. It is possible to improve the sex.

[Brief description of drawings]

FIG. 1 is an overall schematic view of a reader printer which is an embodiment of the present invention, and FIG. 2 is a view showing its zone setting means. 28: Screen as projection surface, 40: Zone setting means, 48: Control means, 50: Focus control optical system, 52: Image splitting mirror, 54: Projection lens, 56: As image sensor CCD line sensor.

Claims (1)

[Claims] 1. A microfilm in which a microfilm projection image is formed on a projection surface through a projection lens so that the film projection image can be visually recognized on the projection surface while the film projection image can be output to a printer. In the reader printer, manual zone setting means for designating a focus zone on the projection surface, a focus control optical system for forming a partial area of a film projection image passing through the projection lens on an image sensor, and the zone Control means for controlling the focus control optical system so as to guide the focus zone set by the setting means to the image sensor, the exposure amount control and the focus control of the projection lens based on the output of the image sensor. An autofocus device for a microfilm reader printer, which is characterized in that