JPH0511179A - Projection device with focus detecting means - Google Patents

Abstract

PURPOSE:To obtain the projection device which has the focus detecting means of simple constitution which adjusts the focus of a projection image projected on a screen surface and easily obtains the projection image of good picture quality. CONSTITUTION:When an object image 4 lighted by a lighting means 1 is projected on the screen surface 15 through a projection lens 5, a luminous flux separating means 6 is provided in the optical path between the projection lens 5 and screen surface 15, part of luminous flux based upon the projected image 4 is passed through the luminous flux separating means 6 and reduced and imaged through an image forming lens, and the luminous flux is guided to a photodetecting means 10 arranged on the image formation surface; and the signal obtained by the photodetecting means 10 is utilized to adjust the image formation state of the projected image on the screen surface 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection device having a focus detecting means, and more particularly, it detects an image formation state of a projection image projected on a screen surface by a projection lens and always provides a good projection image in focus. The present invention relates to a projection device having a compact focus detection means suitable for a device such as a micro reader or a micro reader printer that can obtain the above.

[0002]

2. Description of the Related Art Conventionally, a microreader printer is roughly classified into a display unit for enlarging and projecting a projected image (image information) which is reduced and recorded on a microfilm onto a screen surface by a projection lens, and the projected image. And a printer section for projecting and recording the image on the photoconductor and outputting it as a copy.

In this micro reader printer,
In many cases, the focus detection means is used to detect the image formation state of the projection image formed on the screen surface or the photoconductor surface. As a focus detection method (focus adjustment) by the focus detection means, for example, a light receiving element is arranged on or near a projection surface of a screen portion or a photoconductor, and an arithmetic processing circuit uses an output signal from the light receiving element to perform arithmetic processing. Then there is a way to detect.

As described above, in the conventional micro reader printer, the focus detecting means is used to correct the deviation of the focus position of the projected image on the screen surface to obtain a good projected image in focus.

FIG. 9 is a schematic view of an essential part of an optical system of a micro reader as a projection device having a conventional focus detecting means.

In the figure, the luminous flux emitted from the light source means 91 comprising a halogen lamp or the like is a condenser lens 92.
Then, the effective illumination area of the projected image 94 made of microfilm or the like is uniformly illuminated via the cold mirror or the total reflection mirror 93. The light flux based on the projected image 94 is projected onto the two folding mirrors 9 by the projection lens 95.
The image is projected on a screen surface 98 through 6, 97.

In the microreader shown in the figure, the focus adjustment of the projected image 94 is performed near the screen surface 98 by a light receiving element 99 such as a line sensor (CCD) for focus detection.
Is arranged and the output signal from the light receiving element 99 is utilized. For example, the projection lens 95 is moved along the optical axis to a position where the contrast ratio of each pixel of the light receiving element 99 is maximized, thereby performing focus adjustment.

[0008]

However, in the conventional projection device such as a micro reader, the projected image 94 is generated.
Since a very large light receiving element 99 is provided in the vicinity of the screen surface 98 in order to detect the focus state on the screen surface, there is a problem that the entire apparatus tends to be large.

Further, each time the focus is adjusted, the light receiving element 99 must be installed in the area where the projected image is projected on the screen surface 98, which complicates the moving mechanism related to the apparatus. There was a problem that it was very difficult to make the whole compact.

According to the present invention, a light beam separating means is provided in the optical path between the projection lens and the screen surface, a part of the light beam separated by the light beam separating means is detected by the light receiving means, and the signal from the light receiving means is used. By doing so, it is an object of the present invention to provide a projection apparatus having a focus detection means capable of easily adjusting the image formation state of the projected image on the screen surface, that is, the focus adjustment while reducing the size of the entire apparatus.

[0011]

A projection device having a focus detection means of the present invention, when projecting an image to be projected illuminated by an illumination means onto a screen surface by a projection lens, the projection lens and the screen surface A light beam separating means is provided in the optical path between the two, and a part of the light beam based on the projected image is reduced and imaged by an image forming lens through the light beam separating means, and the light receiving means is arranged on the image forming surface. It is characterized in that the image formation state of the projected image on the screen surface is adjusted by guiding the light and utilizing the signal obtained by the light receiving means.

In particular, the light beam splitting means of the present invention is characterized by comprising a half mirror, a half prism, a rotatable half mirror, or a rotatable total reflection mirror.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part when a projection device having a focus detecting means according to a first embodiment of the present invention is applied to a micro reader printer, and FIG. 2 is an enlarged explanatory view of a part of FIG.

In the figure, reference numeral 1 is a light source means, which is composed of, for example, a halogen lamp or a fluorescent lamp. A condenser lens 2 condenses the light flux from the light source means 1. A cold mirror or a total reflection mirror 3 deflects the light flux from the condenser lens 2 in a predetermined direction.

Reference numeral 4 denotes a transmission type projected image (image information), which is made of, for example, a microfilm. Reference numeral 5 denotes a projection lens, which magnifies and projects the projected image 4 onto the screen surface 15 or the photosensitive drum surface 19. The projection lens 5 is moved by the driving means 102 based on a signal (output value) obtained by the light receiving means 10 which will be described later, as shown by the arrow A on the optical axis. Focus adjustment is performed.

Reference numeral 6 denotes a light beam separating means, which is composed of a half mirror, is provided in the optical path between the projection lens 5 and the screen surface 15, and separates a part of the light beam from the projection lens 5. .

In the present embodiment, the light flux based on the projected image 4 transmitted through the half mirror 6 is guided onto the screen surface 15 (or the photosensitive drum surface 19) and the projected image is formed on the surface. ing. The light beam reflected by the half mirror 6 is guided to the surface of a line sensor (CCD) 8 for focus detection which constitutes a part of a light receiving means 10 described later, and a projected image is formed on the surface.

The light receiving means 10 includes an imaging lens 7 and a light receiving element such as a line sensor (CCD) (hereinafter referred to as "line sensor").
Also called. ) 8 and receives a part of the light flux based on the projected image 4 reflected by the half mirror 6 to detect the image formation state (focus state) of the projection lens 5.

Reference numeral 101 denotes an arithmetic means, which calculates the position of the in-focus projection lens 5 on the optical axis using a signal from the light receiving element 8. Reference numeral 102 denotes a driving means, which drives the projection lens 5 based on a signal from the computing means 101.

A scanning mirror 11 vibrates as indicated by arrow B and scans the photosensitive drum surface 19 in the sub-scanning direction to form a projected image 4 on the photosensitive drum surface 19 as described later. The scanning mirror 11 also has a switching function of selecting and guiding the light beam transmitted through the half mirror 6 to the screen surface 15 or the photosensitive drum surface 19.

Numerals 12, 13 and 14 are mirrors for the reader, which reflect the light beam from the scanning mirror 11 and guide it on the screen surface 15. Reference numerals 16, 17, and 18 denote printer mirrors, which reflect the light flux from the scanning mirror 11 and guide the light flux onto the photosensitive drum surface 19.

In this embodiment, the luminous flux emitted from the light source means 1 is condensed by the condenser lens 2 and reflected by the cold mirror or the total reflection mirror 3, and then the effective illumination area of the projected image 4 is illuminated by the luminous flux. is doing. The projected image 4 through the projection lens 5 is incident on the half mirror 6, and the screen surface 15
(And the photoconductor drum surface 19) direction and the light receiving means 10 direction are separated.

The projected image 4 is displayed on the screen surface 15.
In the case of a reader for observing, the light flux transmitted through the half mirror 6 is reflected by the scanning mirror 11 toward the mirror 12, and then the screen surface 15 is passed through the mirrors 13 and 14.
An enlarged projection image is formed above.

When used as a printer for forming a projected image on the photosensitive drum surface 19, the scanning mirror 1 is used.
The light flux transmitted through the half mirror 6 by changing the inclination of 1 is reflected in the direction of the mirror 16, and then reflected by the mirrors 17 and 18 to be incident on the photosensitive drum surface 19. Then, an enlarged projection image is formed on the photosensitive drum surface 19.

At this time, the scanning mirror 11 is vibrated in the direction of the arrow B to scan the photosensitive drum surface 19 in the sub-scanning direction, whereby the image information of the entire projected image 4 is projected on the photosensitive drum surface 19. I am recording.

On the other hand, a part of the light flux based on the projected image 4 reflected by the half mirror 6 is made incident on the line sensor 8 by the imaging lens 7, and the projected image is formed on the surface thereof. At this time, in the present embodiment, the calculating means 101 uses the output signal (output value) from each pixel of the line sensor 8.
The contrast ratio of the projected image is calculated by, and the projection lens 5 is moved in the direction of arrow A on the optical axis to the position where the contrast ratio is maximized. As a result, focus adjustment is performed and a good projected image is formed on the screen surface.

As described above, in this embodiment, a part of the light flux based on the projected image 4 reflected by the half mirror 6 is reduced and imaged by the imaging lens, and the line sensor 8 is provided on the imaging surface to receive light. By doing so, the image formation state of the projected image is detected. Accordingly, the line sensor 8 can be smaller than the line sensor for focus detection used in the conventional micro reader, and the light receiving means 10 can be miniaturized.

FIG. 3 is a schematic view of a part of a second embodiment of the present invention. In the figure, the same elements as those shown in FIG. 2 are designated by the same reference numerals.

The present embodiment differs from the first embodiment in that a half prism 36 having a semi-transmissive surface 36a inside is used as the light beam separating means instead of the half mirror 6, and other structures and optical elements are used. Action is Example 1
Is substantially the same as.

As described above, even if the half prism 36 is used as the light beam separating means to separate the light beams, the same effect as that of the first embodiment can be obtained.

FIG. 4 is a schematic view of the essential portions of Embodiment 3 of the present invention. In the figure, the same elements as those shown in FIG. 2 are designated by the same reference numerals.

The present embodiment is different from the first embodiment in that, instead of the half mirror 6 as a light beam separating means, a rotatable half mirror or a rotatable mirror 46 such as a total reflection mirror formed by rotatable aluminum vapor deposition is used. Is used, and the other configurations are substantially the same. In the figure, a half mirror is used as the rotating mirror.

That is, in this embodiment, the half mirror 46 is rotated by a predetermined amount so as to be positioned in the optical path between the projection lens 5 and the screen surface as indicated by arrow A only when focusing is performed. Then, while observing the image projected on the screen surface, a part of the light flux based on the projected image reflected by the half mirror 46 is guided to the light receiving means 10 and focus adjustment is performed in the same manner as in the first embodiment. ing.

FIG. 5 is an explanatory view of the light receiving means 50 of the fourth embodiment of the present invention. In the figure, 51a and 51b are half mirrors, 51c is a total reflection mirror, and 58a, 58b and 5 are shown.
Each of 8c is a line sensor (CCD).

In the present embodiment, the light receiving means 50 separates the light flux based on the projected image which has passed through the image forming lens 57 as shown in the figure by using two half mirrors 51a and 51b and one total reflection mirror 51c. Then, the images are formed on the surfaces of the line sensors 58a, 58b, 58c whose positions on the optical axis are different from each other.

That is, the optical path lengths from the image forming lens 57 to the respective line sensors 58a, 58b, 58c are made longer in order. For example, the distance from the projection lens to the screen surface and the line sensor 58b from the projection lens
The distance to the surface is said to be optically equidistant. At this time, if the position on the optical axis of the projection lens is set so that the projected image is focused on the surface of the line sensor 58b, the other two in the front-back direction on the optical axis with respect to the line sensor 58b are set. On the surfaces of the line sensors 58a and 58c, the image has a blurred spread width.

Therefore, in the present embodiment, when the spread widths of the images on the surfaces of the line sensors 58a, 58b, 58c at this time are respectively set to L1, L2, L3, L1 is obtained.
= L3, and the projection lens is moved to a position where the conditional expressions L2 <L3 and L2 <L1 are satisfied. By doing so, focus adjustment is performed, and a projected image in focus on the screen surface is obtained.

In this embodiment, the light flux from the imaging lens 57 is separated by using the two half mirrors 51a and 51b and the one total reflection mirror 51c, and is guided to the surface of each line sensor 58a, 58b and 58c. Although light is emitted, a member that can separate an incident light beam into at least two light beams, such as a half prism, may be used instead of the half mirror.

In the present embodiment, the light beam separating means may be configured by using the optical members shown in the above-mentioned second and third embodiments. FIG. 6 shows the light receiving means 60 of the fifth embodiment of the present invention. FIG. In the light receiving means 60 in this embodiment, the projection image formed on the point P (planned image forming plane) by the image forming lens 67 is lined by two re-imaging lenses 61a and 61b arranged symmetrically with respect to the optical axis 67a. Sensor 68
It is projected on the surface.

That is, in this embodiment, the projected images formed near the point P are formed as two projected images A and B on the surface of the line sensor 68 by the re-imaging lenses 61a and 61b. Then, the focus state is detected by obtaining the interval between the two projected images A and B at this time. For example, when the projection lens is in focus, the interval between the two projected images A and B has a preset value. When this interval is the reference interval D, the reference interval D can be calculated.

Here, for example, as shown in FIG. 7, the focus position of the projection lens is displaced and, for example, the image formation position is changed from point P to point P '.
If you move to 2
The interval between the two projected images A and B shifts from the reference interval D to the interval D ′.

Here, a method of detecting the gap D'will be described with reference to FIGS. 7 and 8. For example, as shown in FIG. 7, when the image forming position of the projection lens changes from the point P to the point P ′, the image has a blurred spread on the surface of the line sensor 68. The output signal (output waveform) from the line sensor 68 at this time is as shown in FIG.

Therefore, in this embodiment, a threshold level is set in the output signal obtained from the line sensor 68, and the intersections of the output signal from the line sensor 68 and the threshold level are respectively a, b, and
Assuming c and d, the distance between the intermediate position g between the intersection points a and b and the intermediate position h between the intersection points c and d is detected as the deviation interval D ′.

As another method of detecting the gap D ', as shown in FIG. 8, the output peak value e between the intersections a and b is shown.
It is also possible to detect the distance from the output peak value f between the intersection points c and d as the deviation interval D '.

Therefore, in the present embodiment, the change amount ΔD (deviation interval D'-reference interval D) at this time is obtained by a calculating means (not shown), and the change amount ΔD is 0 (ΔD = D'-D).
The projection lens is moved along the optical axis so that (0). As a result, a focused projection image is obtained on the screen surface.

Incidentally, the light beam separating means in this embodiment can be applied in the same manner as in the above-mentioned embodiment, using any optical member capable of separating the incident light beam in at least two directions.

[0047]

According to the present invention, as described above, the light beam separating means is provided in the optical path between the projection lens and the screen surface, and a part of the light beam based on the image projected through the light beam separating means is imaged. The image is reduced by a lens, guided to a light-receiving means on the image-forming surface, and the projection lens is moved using the output signal obtained by the light-receiving means to adjust the focus. It is possible to achieve a projection apparatus having a focus detection unit capable of obtaining a good projection image in focus on the screen surface with a simple configuration while achieving downsizing.

[Brief description of drawings]

FIG. 1 is a schematic view of main parts when a projection device having a focus detection unit according to a first embodiment of the present invention is applied to a microreader printer.

FIG. 2 is an enlarged explanatory view of a part of FIG.

FIG. 3 is a schematic view of a main part of a second embodiment of the present invention.

FIG. 4 is a schematic view of a main part of a third embodiment of the present invention.

FIG. 5 is a schematic view of a main part of a light receiving unit according to a fourth embodiment of the present invention.

FIG. 6 is a schematic view of a main part of a light receiving unit according to a fifth embodiment of the present invention.

FIG. 7 is a schematic view of a main part of a light receiving unit according to a fifth embodiment of the present invention.

FIG. 8 is an explanatory diagram showing an output signal from the line sensor.

FIG. 9 is a schematic view of a main part of an optical system when a projection device having a conventional focus detection means is applied to a micro reader.

[Explanation of symbols]

1 Light Source Means 2 Condenser Lens 3 Cold Mirror or Total Reflection Mirror 4 Projected Image 5 Projection Lens 6 Beam Separation Means (Half Mirror) 11 Scanning Mirrors 12, 13, 14 Reader Mirror 15 Screen Surface 16, 17, 18 Printer Mirror 19 photoconductor drum surface 36 light beam separating means (half prism) 46 light beam separating means (half mirror or total reflection mirror) 7, 57, 67 imaging lens 8.58a. 58b. 58c. 68 line sensor (CCD) 10, 50, 60 light receiving means 51a, 51b half mirror 51c total reflection mirrors 61a, 61b re-imaging lens 101 computing means 102 driving means

Claims (2)

[Claims] 1. When a projection image illuminated by an illuminating means is projected onto a screen surface by a projection lens, a light flux separating means is provided in an optical path between the projection lens and the screen surface, and the projection image is projected onto the projection image. A part of the light flux based on the light flux is separated and imaged by the imaging lens through the light flux separating means, guided to the light receiving means arranged on the image forming surface, and the signal obtained by the light receiving means is used to A projection apparatus having a focus detection means, characterized in that an image formation state of a projected image on a screen surface is adjusted. 2. The focus detecting means according to claim 1, wherein the light beam separating means comprises a half mirror, a half prism, a rotatable half mirror, or a rotatable total reflection mirror. Projection device.