JPS63147120A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To eliminate and the need for an optical system which splits and guides part of image projecting light beams to an image sensor and to reduce the size and weight of an optical system by allowing the image sensor to enter the optical path of the image projecting light beams reaching a screen. CONSTITUTION:A line sensor assembly 40 is equipped with a narrow-width reflecting plate 46 which refracts part of the image projecting light beams striking on the screen 28 by 45 deg. and a line sensor 48 as the image sensor ar ranged in parallel to the reflecting plate 46. A control means 50 makes a focus ing discrimination according to the output signal of the line sensor 48 to move a projection lens 20 to a focusing position as automatic focusing operation, controls a printer 34, moves reflecting mirrors 22, 24, and 30. Then a knob 44 is turned to plate the line sensor assembly 40 at the position where an area including the image of the projecting light is made incident on the line sensor 48, and then part of the projection light is guided to the line sensor 48 by the reflecting plate 46. Consequently, an independent optical system which guides the projecting light beams to the image sensor is not required and the device is reduced in size and weight.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is applicable to readers, league printers, cameras, microscopes,
The present invention relates to an autofocus device that is applied to an optical device such as a magnifying projector that focuses image projection light onto a projection surface.

(Technical Background of the Invention) A reader printer that forms an image of the image projection light of a microphotographic original onto a screen or a photoreceptor so that the enlarged projected image can be viewed on the screen or a hard copy can be obtained by forming the image on the photoreceptor. There is. When an autofocus mechanism is provided in this type of device, a part of the projected image is guided to an image sensor such as a line sensor, and it is determined whether or not the image is in focus based on the contrast of the image obtained from the output of this image sensor. It has been considered to control the optical system of the projected image so that it is in focus.

For example, while a first projection lens forms an image on a projection plane, a part of the projection light passing through the first projection lens is split from the optical path leading to the screen and is imaged on an image sensor by a second projection lens. I can do it. However, in this case, since an optical system for the second projection lens is required, there is a problem that the apparatus becomes larger and weighs more.

(Object of the Invention) The present invention was made in view of the above circumstances, and although a part of the image projection light is guided to an image sensor and the focus is determined based on the output of this image sensor, the optical system is simple. The purpose of the present invention is to provide an autofocus device that can be made smaller and lighter.

(Structure of the Invention) According to the present invention, this object is to guide image projection light to a screen through a projection lens, while guiding a part of the image projection light to an image sensor, and to perform focus control based on the output of the image sensor. In the autofocus device that performs
This is achieved by an autofocus device characterized in that the image sensor is disposed so as to be movable in and out of the optical path of the image projection light leading to the projection screen and movable within this optical path.

In other words, by entering the image sensor into the optical path of the image projection light that reaches the screen, there is no need for an independent optical system to split part of the image projection light from the optical path that leads to the screen and guide it to the image sensor. small size,
Enables weight reduction. Furthermore, by moving the image sensor out of the optical path leading to the screen, it is possible to prevent the image sensor from forming a shadow on the projected image of the screen.

(Embodiment) Fig. 1 is an overall schematic diagram of a reader printer which is an embodiment of the present invention, and Fig. 2 shows the transfer of the line sensor. This is the original picture. 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 1o via a condenser lens 14, a heat shielding 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 projection lens 20 and the reflecting mirrors 22, 24, 26.
8, an enlarged projected image of the original image 10 is formed. In the printer mode, the reflecting mirror 24 is rotated to the imaginary line position in FIG.
The projection light is guided to a PPC type slit exposure type printer 34 by reflecting mirrors 22, 30, 32. printer 34
The reflecting mirrors 22 and 30 move in synchronization with the rotation of the photosensitive drum 36, 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 line sensor assembly, and this assembly 40 is attached to the rotating end of a rotating arm 42 that rotates around the outside of the upper left corner of the screen 28 as a fulcrum. This rotating arm 42 is rotated by a manual knob 44 within the range of the shoulder line in FIG. 2, and can be fixed to the neck as appropriate.

As shown in FIG. 3, the line sensor assembly 40 includes a narrow reflecting plate 46 that refracts a portion of the image projection light hitting the screen 28 by 45 degrees, and an image sensor disposed parallel to the reflecting plate 46. A line 48 is provided. The reflecting plate 46 may be a semi-transparent mirror. The reflecting plate 46 and the line sensor 48 are arranged in the longitudinal direction of the rotating arm 42. Therefore, a portion of the image projection light is reflected by the reflecting plate 46 and enters the line sensor 48 .

Reference numeral 50 denotes a control means, which performs an autofocus operation that determines focus based on the output signal of the line sensor 48 and moves the projection lens 20 to the in-focus position, controls the printer 34, and moves the reflecting mirrors 22, 24, and 30. etc.

Next, the operation of this embodiment will be explained. The user first uses reflector 2
4 is placed at the solid line position in FIG. 1, the reader mode is selected, and the target original image is projected onto the screen 28. and knob 4
4 to place the line sensor assembly 40 at a position where the area including the projected light image is incident on the line sensor 48. A portion of the projected light is guided to the line sensor 48 by the reflecting plate 46.

The control means 50 determines the exposure amount all based on the output of the line sensor 48. If the exposure amount is not appropriate, change the light amount and perform the exposure measurement again. This adjustment of the exposure amount can be done, for example, by selecting the output signal of the pixel corresponding to the background area from among the output signals of each pixel of the line sensor 48 and adjusting the light amount of the light source 12 so that this becomes a predetermined value. This is done by changing the driving frequency of 48.

Next, the control means 50 determines whether the projection light input to the line sensor 48 contains an appropriate image. This determination is made, for example, based on whether the number of times the image is inverted between black and white is greater than or equal to a predetermined value, and if it is greater than or equal to the predetermined value, it is determined that the image exists. When it is determined that there is no m-image, the control means 50 issues an alarm such as a buzzer or a lamp to request a change in the focus zone. The user operates the knob 44 while looking at the screen 28, and moves the assembly 40 so that the shadow of the line sensor assembly 40 overlaps the position where the projected image is located.

Next, the control means 50 performs autofocus control based on the output of the line sensor 48. Various algorithms are possible for this control. For example, the maximum and minimum brightness I (M) I (m) determined from the output voltage of each pixel of the line sensor 48 at the position of the projection lens 20 are determined by the following formula % formula % ()) A mountain climbing method is used in which the position of the projection lens 20 where the visibility V is maximum is detected while sequentially moving the projection lens 20. Alternatively, the projection lens 20 is moved once across the focused point, and the focused point is determined from the half-width of the luminance change characteristic curve at that time (half-width method).
The projection lens 20 may be moved over the range of the claws to find the position where the brightness is maximum (full scan method). When the autofocus control is completed in this manner, the control means outputs an appropriate signal such as sound or light to notify the user. The user can manipulate the knob 44 to move the line sensor assembly 40 out of the screen 28.

After viewing the enlarged projected image appearing on the screen 28, if the printer mode is selected, the reflecting mirror 24 is rotated to the position shown by the imaginary line in FIG. 1, and the image is transferred onto the transfer paper 38 to obtain a hard copy.

FIG. 4 is a sectional view showing a second embodiment of the line sensor assembly of the present invention. In this embodiment, the line sensor assembly 4
The OA is formed by a focusing fiber array 46A and a line sensor 48A disposed behind it (on the screen 28 side). According to this embodiment, the width of the assembly 4OA is reduced, and the shadow of the assembly 40A appearing on the screen 28 is reduced.

In the above embodiment, the position of the line sensor assembly 40.40A, that is, the force zone, is manually set while observing the shadow of the line sensor assembly 40.40A cast on the screen 28. It is not limited to this. For example, the presence or absence of an image is determined from the output of the line sensor 48, and if there is no suitable image, the line sensor assembly 40
The focus zone including the appropriate image may be automatically searched for by automatically rotating the camera by a predetermined angle.

(Effects of the Invention) As described above, the present invention allows an image sensor to enter the optical path leading to the screen to read out image information and perform autofocus. There is no need for an independent optical system to guide the sensor to the sensor, making it possible to make the device smaller and lighter. Furthermore, if the image sensor is moved out of the screen, its shadow will not appear on the screen.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a league sensor assembly according to an embodiment of the present invention, and FIG. 4 is a sectional view showing another embodiment of a line sensor assembly. DESCRIPTION OF SYMBOLS 10... Original picture, 20... Projection lens, 28... Screen, 48... Line sensor as an image sensor. Patent applicant Fuji Photo Film Co., Ltd. Agent Patent attorney Yama 1) Yu Moon Figure 1

Claims (4)

[Claims] (1) In an autofocus device that guides image projection light to a screen through a projection lens, guides a part of the image projection light to an image sensor, and performs focus control based on the output of this image sensor, wherein the image sensor An autofocus device characterized in that it is disposed so as to be movable in and out of the optical path of the image projection light that reaches the screen, and to be movable within the optical path. (2) The autofocus device according to claim 1, wherein the image sensor is arranged close to one side of the screen. (3) The autofocus device according to claim 1, wherein the image sensor is a CCD line sensor. (4) The image sensor is attached to a rotating end of a rotating arm that is rotatable around an outer corner of a rectangular screen.
Autofocus device as described in section.