GB2232780A

GB2232780A - Opaque projector

Info

Publication number: GB2232780A
Application number: GB9008087A
Authority: GB
Inventors: Ritsuo Koga
Original assignee: Plus Corp
Current assignee: Plus Corp
Priority date: 1989-06-15
Filing date: 1990-04-10
Publication date: 1990-12-19
Anticipated expiration: 2010-04-10
Also published as: DE4013426C2; HK1000427A1; GB2232780B; FR2648577A1; DE4013426A1; JPH0311237U; GB9008087D0; CA2014370A1; CA2014370C

Abstract

An opaque projector for projecting an image of an illuminated object on a screen S1 comprises a stage 3 for the object and a mirror 8 and projection lens 1 for forming the image of the object on the screen S1. The stage 3 is pivotally supported on a shaft 4 at one end and the other end is engaged by an eccentric cam (6) that is rotatable by a lever (5), Fig. 1 (not shown), for adjusting the angle of the stage 3 to avoid having to correct the inclination phi 1 of the screen S1. <IMAGE>

Description

:; 12:3 2-7 L1 LO OPAQUE PROJECTOR The present invention relates to an

opaque projector having a stage which transmits illumination light from a light source and on which an object to be projected can be placed, a projecting mirror for reflecting light reflected by the object to be projected, and a projecting lens for converging. reflected light from the projecting mirror and imaging a projected image of the object on an external projection plane.

An opaque projector of the type described above is an apparatus arranged in such a manner that an original document placed on the stage is illuminated by a strong light source and scattered light thus generated by a projecting lens having a large apertvre original is projected on a screen. In use, projector must meet the following conditions:

(1) Since scattered light from the surface of -ilized, the efficiency of 1-:crht -- original document is ut L L11 LZ c i e n I%; insufficient. In order to compensate the insufJL lig-z efficiency, a light source of, for example, 1000 to 150OW is necessary in ordinary cases.

-'iciently converge scat- (2) In order to ef-L Uered light !l umin a tin sa =p is converged so that the an opaque -G reflected by the surface of the original document, the following projecting lens having a large aperture and a great f-number must be employed: (Practical Level) (illuminating light source 1000 to 150OW) Aperture: 100 to 140 f: 300 to 350 mm f-number: 1.4 to 3 (3) In order to use the above-described large aperture lens, the depth of focus of the projecting lens is very small as a result of a comparison made in terms of the OHP. For example, the practical depth of focus is 20 to 40mm in terms of the cost and the number of the lenses in the case where a lens of f = 330, the aperture is 120 4) and f-number is 2.9 is used.

As described above, since the depth of focus is very small in the conventional opaque projectors, the following adjustments and the arrangements are necessary in order to obtain a satisfactory projected image without any out of focus.

(1) The optical axis of the projecting lens and the screen is vertically instersected each other and the projection optical paths are the same length in any directions on the screen at the same distance from the optical axis (at least within the error of the depth of -3focus) - (2) The elevation angle of the projecting lens, that is, the elevation an, --,!-o-.AP the opaque projector body must be adjusted in accordance with the height of the body and the desired height of the plane of projection. Furthermore, the screen must be adjusted so as to be made vertical with respect to the opzical axis of the projecting lens, causing ficult and complicated an extremely di task to become necessary.

(3) The quality of the projected imacre considerably depends upon the structure of the screen whose angle can be adjusted. However, the maximum angle of the inclination of the screen is about 15 0 in consideration of the insufficient quality of the image due to the inclination of the screen caused from the size, the weight and the involved deflection of the surface of the screen.

(4) When a projection of an image is performed with making a certain elevation angle on a screen positioned vertically (the screen is positioned vertically in major cases), it is impossible to focus an object to be projected on the entire surface of the plane of projeezion, causing excessive inconvenience to occur.

An object of the present invention is to provide an opaque projector capable of easily and readily forming a - 4projected image without Out Of focus on the screen by adjusting the angle of the stage on which an original document is placed even if the screen -is not placed withou-z any correspondence to the elevation angle of the opaque _projector body, that is, the screen is not positioned vertically with respect to the optical axis of the projecting lens.

According to the present invention, there is provided an opaque projector having a stage which transmits illumination lich-. from a licrhz source and on which an object to be projected can be placed, a projecting mirror for reflecting ligh-L, reflected by the object to be projected, and a projecting lens for converging reflected light from the projecting mirror and imaging a projected image of the object on an external projection plane, the opaque projector comprising:. a mechanism capable of changing the angle of the stage on which the object to be projected can be placed in such a manner that the object to be projected, the optical axis of the projecting lens and the projection place meet a Scheimpflug condition.

The "Scheimpflug condition" means a condition in which the surface of the inclined object, the image plane, and the principal plane of lens (or their extension planes) coincide with one another on a line.

( 1 Other and further objects, features and advantages of the invention will be appear more" fully from the following description.

Fig. 1 is a perspective view which illus-LIrates the structure of an opaque projector according to the present invention; and Fig. 2 illustrates the operation of the opaque projector according to the present invention.

As shown in the drawing, the opaque projector according to the present invention comprises a projecting lens having a focus-adjustment lever 2 on its front surface, the opaque to be projector further having a stage 3 on which an object projected (omitted from illustration) can be placed on the upper surface thereof. An end portion of the stage 3 is pivoted by a supporting shaft 4 adjacent to the projecting lens 1 so that angle Q made from the upper surface ol the opaque projec-.or body is adjusted. The opaque projector body includes a reflecting mirror 8 for reflecting the original -document (an object to be projected) placed on the stage 3 at an inclination angle of 45 0 with respect to the optical axis 13 of the lens 1. As a result, light reflected by the reflecting mirror 8 is converged by the projecting lens 1 so ( 1 that the original document is projected on screen S 1 In this case, the stage 3 and the optical axis 13 of the projecting lens 1 run parallel to each other. A stage-angle adjustment mechanism for moving the stage 3 with respect to the supporting axis 4 comprises an eccentric cam 6 and a stage-angle adjus-z;ment lever 5 each of which is disposed in the opaque projector body supporting shaft 4 for the pulled downwards by a spring Furthermore, the stage indexes 10 and 11 at its above-described end portion 4.

Only a half portion of an illuminating light source 16 for illuminating the original document with respect to the stage 3 is illustrated in Fig. 1, and it is omitted from Fig. 2.

Then, the operation (adjustment means) of the opaque projector according to the present invention will be described with reference to Fig. 2.

As shown in Fig. 2, in the case where - an object is projected on the screen S 1 positioned vertically with an elevation angle (an elevation angle with respect to the optical axis 13 of the projecting lens 1) of the opaque projector according to the present invention arranged to be in a place opposite to the stage 3. The stag e 3 is always 7 so as to be stabilized. - 3 is provided with a focusing two end portions including the pivoted by the supporting shaft 1 e 2' the object to be projected and placed on the stage 3 is reflected by the reflecting mirror 8 so as to be projected on the screen S 1 by the projecting lens 1. Then, the focusing index 10 positioned above the supporting shaft 4 of the stage 3, whose back-focus distance projected in the upper portion of the screen S 1 is not changed, is adjusted by the focus adjustment lever 2. Then, the eccentric cam 6 is rotated by the stage angle adjustment lever 5 connected to the eccentric cam 6 of the stage angle adjustment mechanism so that the rear portion of the stage 3 is upwards moved. Thus, the stage angle Q is changed so as to gradually incline the stage 3. As a result, a stage position 31 is realized with which the focus adjustment index 11 is focused on the screen S 1 Thus, the focusing operation is ended.

The above-described operations are performed with the projecting mirror 8 disposed between the object to be projected and the projecting lens 1. That is, the above-described operations are the operations in which stage virtual images 3i and 3i' and focusing index virtual images 10i and 11i are being operated. In this case, the virtual image _of the object on the stage 31 and formed by the projecting mirror 8 is positioned on the stage 3il. Therefore, each of the extension plane of the stage 3i 1, the image surface of the screen Si. and the principal p lane of the projecting lens 12 coincide with one another on a line.

As a result, the Scheimpflug condition is satisfied.

A screen S 2 represents the inclination of the screen when the opaque projector having no stage angle adjustment mechanism is used with inclined by an angle of e2 to project the object. In this case, since the relationship E?, = e 2 must be held, the adjustment of the screen S 2 has been inconvenient.

Even if the inclination Q of the stage 3 is an optional angle, the focusing can be easily performed by adjusting the stage 3 as described above.

adjustment of the angle el eliminated.

Therefore, of. the screes the complicated S 2 can be In the case where the object to be projected is placed on the stage 3, the focusing can, also, be conducted with observing the focused state of the object after the focusing index 11 has been focused.

Although the reflecting mirror 8 and the optical axis 13 make an angle of 450 according to this embodiment, the present invention is not limited to this description.

As described above, it has been a great labor to adjust the angle of the screen since the screen is very large and heavy. Furthermore, since the angle must be adjusted in accordance with the elevation angle of the opaque projector body, a considerable skill has been necessary. However, according to the. present invention, out of focus can be G -g- prevented and the adjustment of the screen can be eliminated only by adjusting the angle of the stage.

Although the invention has been describe in its preferred form with a certain degree of particularity it is understood that the present disclosure of the preferred form can be changed in the details of construction and -the combination and arrangement of parts may be altered - without departing from the spirit and the scope of the invention as hereinafter claimed.

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Claims

CLAIMS:

-age which transmits 1. An opaque projector having a sI, L t from a light source and on which an object illumination lighl, to be projected can be placed, a projecting mirror for reflecting light reflected by said object to be projected, and a projecting lens for converging reflected light from said projecting mirror and imaging a projected image of said object on an external projection plane, said opaque projector comprising:

-age a mechanism capable of changing the angle of said st on which said object to be projected can be placed in such a manner that said object to be projected, the optical axis of said projecting lens and said projection plane meet a Scheimpflug condition.

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2. An opaque projector according to Claim 1, wherein a focusing index is provided above a supporting point of said stage angle changing mechanism.
3. An opaque projector according to Claim 2 wherein the projecting lens is provided with focus adjustment means.
4. An opaque projector according to any one of the preceding Claims wherein the stage is pivotally supported at one end portion and the other end portion is engaged by the angle adjustment means.

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5. An opaque projector according to Claim 4 wherein the stage is provided with a respective focusing index at each end portion.
6. preceding comprises An opaque projector according to any one of the Claims wherein the angle adjustment means a cam mechanism.
7. An opaque projector according to any one of the preceding Claims wherein the stage is resiliently biassed to a pre-determined or reference datum position.
8. An opaque projector comprising a stage for transmitting illumination light from a light source, a projecting mirror for reflecting light reflected by an object placed on the stage, a projecting leans for converging reflected light from the projecting mirror and imaging a projected image of the object on an external projection plane, and means for adjusting the angle of the stage relative to a pre-determined or reference datum position.
9. An opaque projector according to Claim 8 wherein the stage is pivotally supported at one end portion and the opposed other end portion is engaged by the angle adjustment means.
10. An opaque projector according to Claim 8 or Claim 9 wherein the angle adjustment means comprises a cam mechanism.

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11. An opaque projector according to Claim 10 wherein the cam mechanism comprises an eccentric cam engageable with the stage and rotatable by an operating lever.
12. An opaque projector according to any one of Claims 9 to 11 wherein the stage is provided with a respective focusing index at each end portion.
13. An opaque projector according to any one of Claims 8 to 12 wherein the stage is resiliently biassed to the pre-determined or reference datum position.
14. An opaque projector according to any one of Claims 8 to 13 wherein the projecting lens includes focus adjustment means.
15. An episcopic projector for projecting an image of an illuminated object on an external projection plane comprises a light transmitting stage for the object to be illuminated and adjustment means for adjusting the angle of the stage relative to a pre-determined or reference datum position.
16. An episcopic projector comprising a light transmitting stage for an object, a projection lens for projecting an inage of the object on an external projection plane or surface and adjustment means for adjusting the angle of the stage for correcting inclination of the projection plane or surface relative a plane extending normal to the optical axis of the projection lens, 1
17. An opaque projector substantially as hereinbefore described with reference to the accompanying drawing.

Published 1990 at The Patent Office, StateHouse.66171 High Holborn, LondonWClR4TP. Further copies maybe obtainedfrom The Patent office. Sales Branch, St Maxy Oray. Orpington. Kent BR5 3RD. Printed I)v multinlex technicues itcL St Marv Crav. Kent Con. 1/87