JPH06100710B2 - Focus control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a focus control method used in an optical device including both a manual focus control device and an autofocus device.

(Technical background of the invention) In an optical device such as a micro reader, an autofocus device using an image sensor such as a CCD line sensor has been proposed. Normally, only the projection light of a partial area (focus zone) of the image is made incident on the image sensor to perform the focus determination.

FIG. 4 is a diagram in which the change in resolving power F with respect to the projection lens position X is obtained for the vicinity of the optical axis (α) and the peripheral portion (β).

As is clear from this figure, a high resolving power F ₁ is obtained at the in-focus position A near the optical axis, but the resolving power F _{2 in} the peripheral portion at that time is low. Normally, focus control is performed in the focus zone near the center of the image, so the resolving power in the peripheral area is greatly reduced, and the difference between F ₁ and F ₂ is large, resulting in an uneven image overall .

Also, the projection lens may be slightly moved from the in-focus position depending on the user's preference or the quality of the current image. Therefore, there is a problem that even if the focus control is automatically performed on a specific part of the image, the image cannot be satisfied on the screen or on the hard copy.

Further, the mounting position of the image sensor in the optical axis direction and the position of the projection lens of the optical system for autofocus may be set so that the image sensor can be accurately focused when the projection light is focused on the projection surface such as a screen. is necessary. However, in reality, it is difficult to assemble them with high precision and the productivity becomes low, and there is also a problem that readjustment is required when moving the optical device.

Such a problem also occurs when an optical device having a printer such as a micro reader printer is used to obtain a hard copy. For example, although the preference of the line thickness of hard copy differs depending on the user, when the autofocus device is used, the line thickness cannot be changed.

(Object of the Invention) The present invention has been made in view of such circumstances, and even if the resolution on a projection surface such as a screen is homogenized over the entire surface, or even if an autofocus device is used, the user's preference can be obtained. So that the matching image is automatically obtained,
It is a first object of the present invention to provide a focus control method that does not require high precision in assembling an optical system and that can improve productivity and eliminate the need for adjustment.

Further, the present invention provides a focus control method for a reader printer or the like, which does not require optical adjustment of the printer not only in the reader mode but also in the printer mode and automatically obtains a hard copy desired by the user once set. The second purpose is to provide

(Structure of the Invention) According to the present invention, the first object is, in an optical device including a manual focus control device and an autofocus device, a setting position of a projection lens set by the manual focus control device, The deviation from the in-focus position of the projection lens set by the focus device is obtained, and thereafter, when the auto-focus device is operated, the in-focus position of the projection lens is obtained, and then the projection lens is moved by the deviation amount from the in-focus position. It is achieved by a focus control method characterized by moving only.

A second object of the present invention is to provide a micro-reader printer including a manual focus control device and an autofocus device, wherein the first setting position of the projection lens set by the manual focus control device in the reader mode and the manual setting in the printer mode. Detecting a second setting position of the projection lens set by the focus control device and a focusing position of the projection lens set by the autofocus device;
The deviations between the first and second set positions and the in-focus position are stored as a first deviation and a second deviation, respectively, and then, when the autofocus device is operating, after obtaining the in-focus position of the projection lens, This is achieved by a focus control method characterized in that the projection lens is moved by the first or second deviation from the in-focus position corresponding to each of the reader mode and the printer mode.

(Embodiment) FIG. 1 is an overall schematic view of a reader / printer which is an embodiment of the present invention, FIG. 2 is a block diagram of its control device, and FIG. 3 is a flow chart of its operation.

In FIGS. 1 and 2, 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 by the taking lens 20, the reflecting mirrors 22, 24 and 26, and the original image 10 is displayed on the screen 28.
To form an enlarged projection image of. In printer mode,
The reflecting mirror 24 is rotated to the position shown by the phantom line in FIG.
22、30、32 by PPC type slit exposure type printer 3
Guided by 4. The reflecting mirrors 22 and 30 move in synchronization with the rotation of the photosensitive drum 36 of the printer 34, and a latent image is formed on the photosensitive drum 36. This latent image is visualized with toner charged to a predetermined polarity, and this toner image is transferred to the transfer paper 38.

An autofocus control optical system 40 includes a semi-transparent mirror 42 arranged on the optical axis of the image projection light, a projection lens 44, a line sensor 46, and a servomotor 48. A part of the projection light that has passed through the projection lens 20 is guided by the semi-transparent mirror 42 to the line sensor 46 through the projection lens 44. Projection lens 44
Has a focal length such that when the projection lens 20 is placed at a position where the projection light is focused on the projection surface of the screen 28 or the photosensitive drum 36, an image is accurately formed on the light receiving surface of the line sensor 46. It has been decided.

The autofocus device is equipped with a servomotor 50 that moves the projection lens 20 back and forth in the optical axis direction so that the projection light is projected on the screen 28.
Alternatively, the focus is controlled by the control means 52 so that an image is correctly formed on the projection surface of the photosensitive drum 36. Reference numeral 53 is a mode switch for switching between the reader mode and the printer mode, and 54 is a manual focus control switch. 55 is a switch for changing the focus setting, and 56 is an autofocus selection switch.

The control means 52 is constructed as shown in FIG. That is, the CCD driver 60 drives the line sensor 46 in synchronization with the clock pulse output from the clock 58. The run sensor 46 outputs a pulse voltage that changes in voltage corresponding to the amount of incident light on each pixel for each scanning. This pulse voltage 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 62 corrects variations in characteristics of each pixel and shapes the waveform.

The output signal thus signal-processed is converted into a digital signal by the A / D converter 64 and input to the CPU 68 via the input interface 66.

In FIG. 2, 70 is a ROM for storing the control program of the CPU 68,
72 is RAM, 74 is output interface, 76 is D / A converter,
A driver 78 drives the servo motor 50.

Next, the operation of this embodiment will be described with reference to FIG.

The user first selects a mode with the mode changeover switch 53, and inputs with the switch 55 whether or not to change the focus setting. If the mode is the reader mode (step 100) and the setting is to be changed (step 102), the controller 52
First, autofocus control (AF) is performed based on the output of the line sensor 46, the projection lens 20 is moved to the in-focus position A, and the position A is stored in the RAM 72 (step 10).
Four). Various algorithms are available for obtaining the in-focus position A. For example, it can be obtained as the position where the contrast of the image is maximum.

Next, the user operates the manual focus control switch 54 while looking at the screen 28 to perform the manual focus control (MF) so that the desired image can be obtained. The switch 54 outputs a pulse signal for adding / subtracting a counter in the CPU 68, for example, and the CPU 68 can be configured to drive the servo motor 50 to a position corresponding to the contents of the counter to move the projection lens 20. When the desired image is obtained on the screen 28 in this way, the position of the projection lens 20 at that time is stored in the RAM 72 as the first setting position B (step 10).
6).

The CPU 68 then obtains a deviation D = (AB) between the in-focus position A and the first set position B, and sets this as the first deviation in the RAM 72.
(Step 108).

If the user changes the setting for the other original image 10 (step 102), the above steps 104 to 108 are performed, and if the setting is not changed, the auto focus control (AF) is used. It is determined whether or not (step 110). Whether or not the autofocus control is performed is input by the user through the switch 56. If it is the auto focus control, the CPU 68 obtains the in-focus position A'for this new original image 10 (step 112). Then, the CPU 68 moves the projection lens 20 from the focus position A'by the first deviation D (step 11).
Four). As a result, the image in the state desired by the user set in step 106 appears on the screen 28.

If the auto focus control is not selected (step 110), the manual focus control (M
F) is performed (step 116).

When the printer mode is selected by the mode selector switch 53 (step 100), the operations of steps 202 to 214 are performed. Here, only step 206 is different from the case of the reader mode. That is, in this step 206, only the point where the position of the projection lens for bringing the hard copy of the printer into the preferable state is the second setting position B ′ is the step 106.
Since other operations are the same as those in the reader mode, the description thereof will not be repeated.

In the above embodiment, the present invention is applied to a reader printer so that not only the image on the screen 28 but also the image quality of hard copy can be changed according to preference. However, the present invention can also be applied to an optical device such as a micro reader that does not have a printer.

(Effect of the Invention) As described above, the invention of FIG. 1 stores the deviation D between the in-focus position A of the projection lens by the autofocus device and the set position B of the taking lens by the manual focus device, and thereafter, a new value is stored. For the original image, the focus position A ′ by the autofocus device is moved by the deviation D, so that the desired image is automatically displayed while the image on the projection surface is being viewed. Therefore, it is possible to obtain an image in which the resolution is homogenized over the entire surface according to preference. Further, even if the optical system for autofocus is not accurately set, if the desired image quality is set by the manual focus control, the desired image quality will always be obtained automatically even during the autofocus control. Therefore, high precision is not required for assembly, and productivity is improved. Further, it becomes unnecessary to readjust when the optical device is moved.

According to the second aspect of the invention, the desired image quality of the hard copy is preset not only in the reader mode of the reader / printer but also in the printer mode, so that the hard copy having the desired image quality can always be obtained even during the hard focus control. .

[Brief description of drawings]

FIG. 1 is an overall schematic view of a reader printer which is an embodiment of the present invention, FIG. 2 is a block diagram of its control device, and FIG. 3 is a flow chart of its operation. FIG. 4 is a diagram in which the change in resolving power F with respect to the projection lens position x is obtained for the vicinity of the optical axis (α) and the peripheral portion (β). 20 ... Projection lens, 40 ... Auto focus control optical system, A ... Focus position, B ... First setting position, B '... Second setting position, D ... Deviation.

Claims (2)

[Claims] 1. An optical device comprising a manual focus control device and an autofocus device, wherein a set position of the projection lens set by the manual focus control device and a focus position of the projection lens set by the autofocus device. The focus control method is characterized in that when the autofocus device is activated, the focus position of the projection lens is determined, and then the projection lens is moved by the deviation amount from the focus position. 2. A microreader printer comprising a manual focus control device and an autofocus device, wherein a first setting position of the projection lens set by the manual focus control device in the reader mode and the manual focus control device in the printer mode. The second set position of the projection lens set by the above and the focus position of the projection lens set by the autofocus device are detected, and the first set position is detected.
And a deviation between the second set position and the in-focus position are stored as a first deviation and a second deviation, respectively. After that, when the auto-focus device operates, the in-focus position of the projection lens is obtained, and then the reader mode and A focus control method characterized in that the projection lens is moved from the in-focus position by the first or second deviation corresponding to each printer mode.