JPH08254753A - Picture projector - Google Patents

Abstract

PURPOSE: To provide a picture projector capable of obtaining uniform illuminance even in the case of using a light source with a tilted filament and projecting lenses having a different pupil position. CONSTITUTION: As for the picture projector provided with an illuminating optical system constituted of the light source 1 and illuminating lenses 2 and 3, etc., the projector is provided with a driving means 12 for driving at least one optical member 2 among plural optical members back and forth in an optical axis direction, an illuminance detecting means 11 for detecting the illuminance at the peripheral part of the projected picture, and a driving control means 13 for detecting the illuminance at the peripheral part of the projected image by the means 11 while moving the optical member 2 by the driving means 12, and then, stopping the optical member 2 at a position where the output of the illuminance detecting means 11 becomes the maximum value at the time of adjusting the illuminance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image projection apparatus for projecting an image of a transparent original such as a film on a projection surface such as a screen.

[0002]

2. Description of the Related Art Conventionally, there is a microfilm reader as an image projection apparatus of this kind, and an illumination optical system thereof is shown in FIG.

That is, the illumination light from the light source 101 is condensed by the condenser lens 102 and the field lens 103, and illuminates the microfilm F sandwiched by the film holding portion 104 of the glass plate pair. Then, the transmitted light is projected on the screen 106 by the projection lens 105.

As the illumination optical system, a so-called Koehler illumination optical system that obtains uniform illuminance to the corners of the screen 106 is used. The Koehler illumination optical system projects the image of the filament 101 a of the light source 101 to the pupil 105 of the projection lens 105.
The condenser lens 102, so as to form an image at the position a.
The field lens 103 is arranged.

[0005]

However, in such a Koehler illumination method, in order to prevent uneven illumination, the light source 101,
It is necessary to hold each optical component such as the condenser lens 102 and the field lens 103 with high accuracy and maintain their relative relationship with each other with high accuracy.

On the other hand, the light source 1 of the microfilm reader
A halogen lamp is generally used for 01. In the halogen lamp, an inert gas and a minute amount of halogen gas are sealed in the quartz bulb 101b together with the filament 101a. The quartz bulb 101b is heated and crushed in the portion where the inside and outside of the lamp are electrically connected to maintain the airtightness.

However, the filament 101a is affected by the crushed quartz bulb 101b in order to maintain airtightness.
Easily falls, and even if the position of the light source 101 is held with high accuracy, the position of the filament 101a varies.

9 and 10 are schematic views when a light source 101 in which a filament 101a is tilted is used for an illumination optical system.

FIG. 9 shows a virtual illumination light flux that can reach a point a on the optical axis of the screen 110 (a light flux passing through a point a'on the film F corresponding to the point a and the projection lens 105), and FIG. A virtual illumination light flux (a light flux passing through the point b ′ on the film F corresponding to the point b and the projection lens 105) that can reach the point b in the peripheral portion of 106 is shown.
That is, the light fluxes of FIGS. 9 and 10 represent light fluxes that are reflected in the pupil when viewed from the points a and b on the screen 106.

The filament 1 covers the entire area of the light flux in FIGS.
When 01a covers, high illuminance can be obtained, and when it lacks, it decreases. An upright filament shown by a thin line can sufficiently cover the light flux shown in FIGS.

However, in the fallen filament 101a,
Although the light flux in FIG. 9 almost covers, the filament 101a is deviated from the light flux in FIG. 10, and the light emitted from the filament 101a does not reach the peripheral portion of the screen 106 sufficiently. In other words, the fallen filament 1
With 01a, it was not possible to obtain uniform illuminance up to the corners of the screen 106.

Further, the projection lens 105 can be changed by changing the magnification.
In order to satisfy the Koehler illumination method and prevent illuminance unevenness when the position of the pupil 105a of the
It is necessary to adjust the illumination such as moving 02 in the optical axis direction.

Conventionally, the illumination lens 105 is manually moved and adjusted. However, when a zoom lens in which the position of the pupil 105a continuously changes is used as the projection lens 105, in order to prevent uneven illuminance, the illumination must be adjusted every time the magnification is changed, which complicates the operation. In addition, the operation was omitted, causing uneven illumination.

Therefore, there has also been proposed an apparatus for automatically adjusting the illuminance by providing a pupil position detecting means using a variable resistor or the like corresponding to the position of the pupil 105a.

However, a pupil position detecting means having a complicated structure for discriminating a large number of pupil position information and a large storage capacity and a complicated control means for processing a lot of information are required, which is expensive and large. It has become a thing.

Further, such an apparatus was expensive and large in size, but did not improve the uneven illuminance due to the above-mentioned light source in which the filament fell.

The present invention has been made in order to solve the above-mentioned problems of the prior art. The first object is a simple structure, and a light source having a filament tilted or a projection lens having a different pupil position is used. An object of the present invention is to provide an image projection device that can obtain uniform illuminance.

A second object is to achieve the first object without performing a simple operation or a special operation.

[0019]

In order to achieve the above object, the first invention according to the present application comprises an original holding portion for holding a transparent original and optical members such as a light source, a reflecting mirror and an illumination lens. The illumination optical system is configured in an image projection device including an illumination optical system that illuminates the transparent original, and a projection lens that forms an image of transmitted light of the transparent original illuminated by the illumination optical system on a projection surface. Drive means for reciprocating at least one optical member of the plurality of optical members in the optical axis direction, illuminance detection means for detecting illuminance of the peripheral portion of the projected image, and drive means for adjusting the illuminance. Drive control means for detecting the illuminance of the peripheral portion of the projected image by the illuminance detecting means while moving the optical member, and stopping the optical member at the position where the output of the illuminance detecting means reaches the maximum value. It is characterized in.

The above light source is suitable for a halogen lamp.

The illuminance detecting means may be arranged beside the image projection light path of the transparent original, or may be arranged in the image projection light path.

The optical member reciprocated around the periphery of the image projection image optical path may be at least one of a light source, a condenser lens, a field lens and a reflecting mirror.

The second invention is characterized in that the drive control means operates when the power is turned on.

A third invention has a lighting adjustment switch,
The drive control means operates when the illumination adjustment switch is operated.

A fourth aspect of the invention is characterized in that it has means for detecting attachment / detachment of the projection lens, and the drive control means operates when the projection lens is mounted.

A fifth aspect of the invention is characterized in that it has a means for detecting the zoom operation of the projection lens, and the drive control means operates when the zoom operation is completed.

[0027]

In the present invention, at least one optical member of the illumination optical system is moved to detect the illuminance change in the peripheral portion of the projected image by the illuminance detecting means.

Even if the image is projected, the change in illuminance is more intense in the peripheral area than in the central area. Therefore, if the position where the illuminance in the peripheral area is maximized is selected, the uneven illuminance with the central area is minimized. The illuminance can be made uniform as a whole.

In the case of so-called Koehler illumination in which an image of the filament is formed at the pupil position of the projection lens, the illuminance detecting means detects the illuminance change. It can be adjusted optimally without it. In particular, it is suitable for a halogen lamp in which the filament tends to fall during the manufacturing process.

The illuminance detecting means may be arranged beside the image projection light path of the transparent original, or may be arranged in the image projection light path. When it is arranged in the image projection optical path, a half mirror or the like may be used, or a switching mirror or the like that guides the projection light to the illuminance detecting means may be used.

A plurality of illuminance detecting means may be provided.

As the optical member to be driven, a light source may be moved, an image forming lens system such as a condenser lens or a field lens may be moved, or a reflecting mirror may be moved.

According to the second aspect of the invention, the illumination is automatically adjusted when the power is turned on again, and no special operation is required when the power is turned on again, such as when the lamp is replaced.

According to the third aspect of the invention, the illumination adjustment switch is operated to arbitrarily adjust the illumination when it is desired to eliminate the illumination unevenness.

A fourth aspect of the invention is to automatically adjust the illumination according to the change of the pupil position due to the replacement of the projection lens.

A fifth aspect of the invention is to automatically adjust the illumination in accordance with the change in the pupil position caused by the zoom operation of the projection lens.

[0037]

Embodiments (First Embodiment) The present invention will be described below based on illustrated embodiments.

FIG. 1 is a schematic view of a film reader to which the image projection device of the present invention is applied. Illumination light from a halogen lamp 1 which is a light source is condensed by a condenser lens 2 and a field lens 3 and is illuminated by a film holding portion 4 made of a glass plate pair or the like, and a microfilm F as a film forming a transparent original. .

The light transmitted through the microfilm F is projected by the projection lens 5 on the screen 6 arranged on the projection surface. The illumination optical path is bent by the reflection mirror 7, and the projection optical path is bent by the reflection mirrors 8 and 9, respectively.
It is stored in the machine casing 10. Further, the projection lens 5 is detachably held and can be replaced with another projection lens.

The condenser lens 2 is reciprocally movable in the optical axis direction (arrow C) by a driving mechanism 12 as a driving means. The drive mechanism 12 is composed of, for example, a pulse motor, a home position sensor, etc., and the position where the condenser lens 2 is closest to the halogen lamp 1 is the home position, and the position of the condenser lens 2 can be finely controlled. By arranging the condenser lens 2 in any of the moving ranges, it is possible to form an image of the filament 1a of the halogen lamp 1 on the pupil positions 5a of all the projection lenses 5 used.

In the halogen lamp 1, as described in the conventional example, an inert gas and a small amount of halogen gas are sealed in the quartz bulb 1b together with the filament 1a. The quartz bulb 1b is heated and crushed at the portion where the inside and outside of the lamp are electrically connected to maintain airtightness.

Further, a light receiving sensor 11 as an illuminance detecting means is fixedly installed outside the projection optical path below the reflecting mirror 9 so that the projection light immediately beside the projected image can be measured.

When adjusting the illuminance, the light receiving sensor 11 detects the illuminance of the periphery of the projected image while the condenser lens 2 is moved by the driving mechanism 12, and the output of the light receiving sensor 11 reaches the maximum value. Drive control means 13 for stopping the condenser lens 2 is provided.

2 to 4 are schematic views of the illumination optical system of the image projection apparatus of the present invention and virtual light fluxes that can reach the screen at the central portion a'and the peripheral portion b'on the film F.
In the figure, the peripheral portion b ′ is a position corresponding to the light receiving sensor 11. The reflection mirror 7 is omitted.

First, when the power of the apparatus is turned on, the halogen lamp 1 is turned on.

Subsequently, as shown in FIG. 2, the condenser lens 2 is moved to the home position La closest to the halogen lamp 1 by the driving means 11, and is moved away from the halogen lamp 1, as shown in FIG. The position Lc farthest from the halogen lamp 1 is reached. During this time, the light-receiving sensor 11 measures light at any time, and the output at this time is shown by the solid line in FIG.

When the condenser lens 2 is La shown in FIG. 2, the output of the light receiving sensor 11 is 0 because the filament 1a is not present in the virtual light flux of the peripheral portion b '.

Since the luminous flux at the peripheral portion b'decreases as the condenser lens 2 moves, when the filament 1a enters the peripheral luminous flux, the light receiving sensor 11 starts to rise. At the distance Lb shown in FIG. 3, since the filament 1a covers the entire peripheral light flux, the light receiving sensor 11
Output is maximum.

When the peripheral luminous flux continues to fall and the filament 1a begins to come out of the luminous flux, the output begins to decline,
Eventually, the distance Lc shown in FIG. 4 is reached. Then, the condenser lens 2 returns (Lc-Lb), stops at the position of Lb at which the maximum output of the light receiving sensor 11 is obtained, and the illumination adjusting operation ends.

In order to shorten the adjustment time, the condenser lens 2 may be controlled to stop at the moment when the output of the light receiving sensor 11 is other than 0 and the slope of the output curve becomes 0.

The output curve of the light receiving sensor 11 shown by the dotted line in FIG. 5 is obtained when the microfilm F in the photometric area of the light receiving sensor 11 has an image portion. Since the light receiving sensor 11 is arranged in the middle of the projection optical path, a sufficient light measuring area can be obtained on the film even if the light measuring area of the light receiving sensor 11 is small, and normal characters and figures are present in this light measuring area. However, the maximum output value can be sufficiently determined only by lowering the entire output curve.

Further, in a general film, light is slightly transmitted even with solid black. Therefore, as for the relationship between the maximum output from the light receiving sensor 11 and the position of the condenser lens 2, the same result can be obtained if a general film is projected.

The relationship between the position of the condenser lens 2 and the central illuminance is determined by the relationship between the central light flux and the filament in FIGS. The central illuminance is the position L of the condenser lens 2.
Since the central light flux is not completely covered by a, it falls a little, and the maximum value is obtained at the positions Lb and Lc. That is, screen 6
The optimum position of the condenser lens 2 that can obtain uniform illuminance from the four corners to the center is Lb.

FIG. 6 shows the position La of each condenser lens 2.
The relationship between Lc and the illuminance of the screen 6 is shown. The change in illuminance due to the movement of the condenser lens 2 is more intense in the peripheral portion than in the central portion. Therefore, in order to more accurately determine the optimum position of the condenser lens 2, it is better to measure the peripheral portion rather than the central portion.

It is also conceivable that the illuminance distribution will be reversed at the central portion as shown in FIG. 7 due to the matching between the projection lens 2 and the illumination optical system. In this case, optimal light adjustment cannot be performed even if the central portion is measured, but it is possible if the peripheral portion is measured.

Even when the projection lens 5 and the projection lens 5'having a different pupil position are set when the power is turned on, the illumination adjusting operation similar to the above is performed. By this operation, the optimum position (≠ Lb) of the condenser lens 2 is obtained for the pupil position 5a 'of the projection lens 5'.

Furthermore, when the projection lens 5 is replaced with a projection lens 5'having a different pupil position after the power is turned on, the illumination adjustment switch 14 is pressed by the operator to perform the above-mentioned illumination adjustment operation, and the optimum illumination state is obtained. Become.

In the apparatus as described above, even if the projection lens 5 is a zoom lens, even if the magnification is operated and the pupil position shifts and the illuminance becomes uneven, the illumination adjustment switch 14 is pressed to obtain the optimum illumination state. Therefore, uniform illuminance can be obtained.

Further, it is possible to deal with the same problem even after the filament 1a is replaced with a different lamp. Furthermore, by taking a large moving range of the condenser lens 2,
The mounting accuracy of the halogen lamp holding means in the optical axis direction can also be loosened. (Second Embodiment) In the first embodiment, the projection lens 5
The operator must press the illumination adjustment switch 14 every time the position of the pupil 5a is changed. Therefore, the illumination adjusting operation may be started when the projection lens attachment / detachment sensor 15 such as a micro switch detects the attachment / detachment of the projection lens 5, or when the zooming sensor 16 such as an encoder detects a zoom change of the projection zoom lens. .

In a device in which the projection zoom lens is electrically driven by a motor or the like, it is possible to easily detect that the zoom has been moved by the control means of the motor.

The present invention is not limited to the optical configurations of the first and second embodiments, and various configurations are conceivable. For example, the first and second
In the embodiment, the condenser lens 2 adjacent to the halogen lamp 1 moves, but depending on the configuration of the illumination optical system, the field lens 3, the halogen lamp 1, the reflecting mirror, or the like may be used.
A part of the illumination optical member may reciprocate in the optical axis direction.

Further, the light source 1 may be formed integrally with a reflecting mirror and a filament.

Further, in the first and second embodiments, the light receiving sensor 11 is arranged at a position right next to the image projection optical path so that the light amount can be measured. A mirror or the like may be used to measure the light amount of the peripheral portion in the image projection optical path. Further, a plurality of light receiving sensors 11 may be provided.

In the above embodiment, the case where the image projection device is applied to a microfilm reader for projecting a film image on a screen has been described. However, image reading in which a reading element such as CCD is arranged on the projection surface instead of the screen It can also be applied to the projection optical system of the device.

[0065]

As described above, according to the invention of the present application, at least one optical member of the illumination optical system is moved to stop the optical member at a position where the illuminance is maximized. Therefore, it is possible to prevent the illuminance unevenness and the illuminance change of the projected image due to the replacement of the light source and the magnification change of the projection lens with an inexpensive and simple configuration while the image is projected.

That is, in the case of so-called Koehler illumination in which the filament image is formed at the pupil position of the projection lens, it can be optimally adjusted without information about the position of the filament in the optical axis direction or the pupil position of the projection lens. it can. In particular,
It is most suitable for halogen lamps where the filament tends to fall during the manufacturing process.

According to the second aspect of the invention, the illumination adjustment is automatically performed when the power is turned on, and no special operation is required when the lamp is replaced and the power is turned on again.

According to the third invention, the illumination is adjusted by operating the illumination adjustment switch. In this case,
The illumination adjustment can be arbitrarily performed when illuminance unevenness occurs.

The fourth invention is to automatically adjust the illumination in accordance with the change of the pupil position due to the replacement of the projection lens.

The fifth aspect of the present invention is to automatically adjust the illumination according to the change of the pupil position by the zoom operation of the projection lens.

When applied to a film reader, it is possible to prevent unevenness in illuminance and change in illuminance due to replacement of light sources and change in magnification, and to make it easier to read images. In addition, the illumination can be adjusted while the film image is projected on the screen.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image projection apparatus of the present invention.

FIG. 2 is a diagram illustrating an illumination adjustment of the image projection apparatus of the present invention.

FIG. 3 is a diagram illustrating an illumination adjustment of the image projection apparatus of the present invention.

FIG. 4 is a diagram for explaining illumination adjustment of the image projection apparatus of the present invention.

FIG. 5 is a diagram illustrating an illumination adjustment of the image projection apparatus of the present invention.

FIG. 6 is a diagram showing illuminance at the time of illumination adjustment of the image projection apparatus of the present invention.

FIG. 7 is a diagram showing the illuminance at the time of adjusting the illumination of the image projection apparatus of the present invention.

FIG. 8 is a diagram illustrating a conventional example.

FIG. 9 is a diagram illustrating a conventional example.

FIG. 10 is a diagram illustrating a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Halogen lamp (light source) 2 Condenser lens F Micro film 5 Projection lens 5a Projection lens pupil 6 Screen (projection surface) 11 Light receiving sensor (illuminance detection means) 12 Driving means 13 Drive control means 14 Illumination adjustment switch 15 Projection lens attachment / detachment sensor 17 Zooming sensor

Claims (9)

[Claims] 1. An original document holder for holding a transparent original document, an illumination optical system for illuminating the transparent original document, which is composed of optical members such as a light source, a reflecting mirror, and an illumination lens, and the illumination optical system illuminated by the illumination optical system. An image projection apparatus comprising: a projection lens for forming an image of transmitted light of a transparent original on a projection surface, wherein at least one optical member of a plurality of optical members constituting the illumination optical system reciprocates in an optical axis direction. Driving means, an illuminance detecting means for detecting illuminance around the projected image, and an illuminance detecting means for detecting the illuminance around the projected image while moving the optical member by the driving means when adjusting the illuminance. The image projection apparatus further comprises drive control means for stopping the optical member at a position where the output of the illuminance detection means has a maximum value. 2. The image projection apparatus according to claim 1, wherein the drive control means operates when the power is turned on. 3. The image projection apparatus according to claim 1, further comprising an illumination adjustment switch, wherein the drive control unit operates when the illumination adjustment switch is operated. 4. The image projection apparatus according to claim 1, further comprising a detection means for detecting attachment / detachment of the projection lens, wherein the drive control means operates when the projection lens is attached. 5. The image projection apparatus according to claim 1, further comprising a detection unit for detecting a zoom operation of the projection lens, wherein the drive control unit operates when the zoom operation is completed. 6. The image projection device according to claim 1, wherein the light source is a halogen lamp. 7. The image projection apparatus according to claim 1, wherein the illuminance detection means is arranged beside an image projection optical path of the transparent original. 8. The image projection apparatus according to claim 1, wherein the illuminance detection means is arranged in the image projection optical path of the transparent original. 9. The image projection apparatus according to claim 1, wherein the optical member reciprocated around the periphery of the image projection image optical path is at least one of a light source, a condenser lens, a field lens, and a reflecting mirror.