GB2202960A

GB2202960A - Moving image projectors

Info

Publication number: GB2202960A
Application number: GB08802134A
Authority: GB
Inventors: Stephen Humphrey Savage
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-01-30
Filing date: 1988-02-01
Publication date: 1988-10-05
Also published as: GB8702099D0; GB8802134D0; JPS63271241A

Abstract

Optical images of a plurality of discrete images, of which at least some discrete images are to be projected while moving, are simultaneously projected. Each discrete image is mounted in a separate transparent carrier (16, 17, 18). Each carrier is adapted to be either stationary or to be capable of intermittent or regular motion, in a light path defined between a light source (11) and a projection lens (19) whereby images of discrete images in the light path can be projected and focused. One or more motors are provided for driving one or more of the carriers to provide the intermittent or regular motion. The thickness of each carrier and the discrete image incorporated with each carrier is kept to a minimum, at least in the direction of the light path, and the carriers and images are juxtaposed in combination in the light path so that the length of the light path occupied by the combination is less than that of the operational field of focus of the projection lens. The projected image may be that of a working clock. <IMAGE>

Description

IMAGE PROJECTORS This invention relates to a method and an apparatus for the projection of an optical image.

The development of optical projection lenses have led to still and cinematic projectors which allow for the projection in great detail of highly complex images. The images originate from a carrier comprising an image recording medium incorporated in or supported on or by a film or slide or the like.

Problems arise when images are projected from two or more discrete carriers. Each carrier absorbs some of the incident light falling upon it. Consequently if two or more carriers are superimposed a corresponding increase in incident light intensity is required if the projected image is to remain as bright as that arising from a single carrier. Even for a projector utilising a single carrier the heat generated by the lighting system is substantial. Any increase in projection power to enhance the brightness of the projected image will create yet more heat which will need to be carried away from a carrier such as conventional exposed film material which is sensitive to overheating.

To provide an enlarged projected image light having past through the or each carrier in a light path passes through a projection lens which provides enlarged images focused onto a suitable screen. If an image to be projected lies in the light path within the field of focus of the lens then an image of the object can be focused by the lens to provide a sharp image on a suitable surface located at a focal plane of the lens. An image from a single carrier is readily focused to give a sharp image. The provision of a second carrier in conjunction with the first results in the images to be projected being spaced apart along an optical axis of the system. In this situation with conventional projection arrangements while one carrier will lie within the field of focus the other carrier will lie outside it.Consequently focusing on a projection screen will either involve focusing one image carrier sharply to the detriment of the other carrier image or will involve the compromise of focusing on a focal plane intermediate those of the two carriers. The focusing problem increases as further carriers are added for projection. The focusing compromise for a plurality of discrete projected images can be overcome by reducing the projection lens aperture and consequently increasing incident light intensity. While this serves to increase the field of focus and so improve the projected definition the overheating problem inherent in increasing light power still arises.

According to a first aspect of the present invention there is provided a method of simultaneously projecting optical images of a plurality of discrete images of which at least some are to be projected while moving comprises the steps of: incorporating each discrete image in a separate transparent carrier; locating each carrier so that each discrete image incorporated thereby is either stationary, or is adapted for intermittent or regular motion, in a light path defined between a light source and a projection lens whereby images of objects in the light path can be projected and focused; providing means for driving one or more of the carriers to provide the intermittent or regular motion; and limiting the thickness of the carriers and the object incorporated with each carrier, at least in the direction of the light path and juxtaposing the carriers and objects in combination, such that the length of the light path occupied by the combination is less than that of the operational field of focus of the lens.

According to a second aspect of the present invention there is provided apparatus for projecting optical images of objects comprising: a light source; a lens; a light path defined between the light source and then lens; at least two carriers each carrier having a discrete image for projection incorporated therewith; at least one driver whereby at least one carrier can be moved so that the discrete image incorporated with the or each carrier can be displaced relative to to at least one other carrier; and the carriers and the discrete images incorporated being of a thickness and being juxtaposed in a working combination, at least when disposed in the light path, so that the overall length of the combination measured in the length of the light path in which they are disposed is less than that of the operational depth of focus of the lens.

In a first preferred form of the second aspect of the invention each carrier is fabricated from ultra-thin glass and the discrete image incorporated therewith is formed on one side of the carrier or in a mask element secured to one side thereof. Preferably in the combination at least an adjacent pair of carriers have the one side on which the object is formed or to which the mask element is secured facing one another.

The term "ultra thin" refers to a thickness of no more than one millimetre. Quartz glass is preferred with a thickness of about 0.25 millimetre. The length to be occupied by the combination will typically be of the order of 10 millimetres though this will depend on the projecting lens used.

Among the advantages of the present invention are its ability to utilise a reasonably powered light source already available for use in conventional projection systems without a need for additional costly or bulky cooling systems. A minimal cooling requirement stems from the use of a minimal depth of focus field. As a consequence a reasonable lens aperture together with the good transmission qualities of the thin glass carriers provides a sharp image without the need for an excessively powerful light source.

If desired the glass and the discrete image or both can be coloured or etched or both.

In its simplest form the apparatus has two carriers. One is fixed and the other caused to move relative to the first.

When the moved carrier is a disc rotating about its centre then the locus of an off centre discrete image associated with the carrier will be a circle. A carrier can also include a masking element adapted to serve on its own or in combination with parts of other carriers to govern the projected images.

It will be apparent that the proposed method enables a wide range of moving effects to be achieved using only a single projection lens system rather than a multiplicity lens systems as is required in existing systems.

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings of an analogue clock face projector of which: Figure 1 is a diagrammatic longitudinal section; and Figures 2A to D show a number of components referred to in connection with Figure 1.

Figure 1 shows a projector housing 10 in which is mounted a conventional light source 11 in the form of a low voltage high intensity tungsten halide lamp mounted in a focusing reflector 12 which serves to project a cone of light 13 onto an object combination 14 lying on light path P. The combination 14 is made up of mounting 15 and carriers 16, 17, 18 which are shown in more detail in Figure 2. An adjustable lens 19 mounted in housing 10 focuses light from the combination 14 onto a conventional screen positioned in the direction of arrow 20 The combination 14 is now considered in greater detail with particular reference to the items making up Figure 2.

Mounting 15 is secured to housing 10 and serves to support a clock movement C. The mounting 15 incorporates a carrier 15A of quartz glass which is about 0.5 millimetres thick.

Carriers 16, 17 and 18 are of similar material with a thickness of about 0.20 millimetres.

The carriers 16, 17 and 18 are mounted within cogs (respectively cogs 21, 22 and 23) which are driven by means of shaft S from clock movement C powered by a synchronous electric motor. Each carrier 15A, 16, 17, 18 has an etched stainless steel lamina (respectively lamina 24, 25, 26, 27) bonded to its surface. The lamina are in the form of concentric rings which, when superimposed, serve to block any light from passing out of the combination 14 towards lens 19 save for that which passes through etched areas of the laminae. Lamina 24 has apertures corresponding to the conventional 12 hour clock face. Lamina 25 has apertures corresponding to a conventional clock hour hand. Lamina 26 has apertures corresponding to a conventional minute hand.

Lamina 27 has apertures representing the name of the manufacturer. Alternatively it can represent a conventional second hand or serve an advertising, motto or descriptive function The parts of the cogs 21, 22 23 on which the carriers are mounted are recessed to provide for the cogs to nest one within the other so that the carriers 15a, 16, 17, 18 are juxtaposed as closely as possible along the light path P to provide for the assembled carriers to occupy the shortest possible length within the field of focus 28 of the lens 19.

Once the carriers 15A to 18 are assembled and the light source 11 illuminated the laminae disclose a clock face which is enlarged and projected by way of the lens 11. The cogs 21 to 23 are driven by way of the clock movement C to ensure that the relevant carrier, and so the etched lamina it bears, rotate at the correct speed relative to the other laminae.

Being disposed in the field of focus of the lens 19 the images generated by the etched laminae are projected by way of the lens onto a screen or other surface to provide a well defined projected image of a working clock.

Claims

CLAIMS 1A method of simultaneously projecting optical images of a plurality of discrete images of which at least some discrete images are to be projected while moving comprises the steps of: 1 incorporating each discrete image in a separate transparent carrier; 2 locating each carrier so that each discrete image incorporated thereby is either stationary, or is adapted for intermittent or regular motion in a light path defined between a light source and a projection lens whereby images of discrete images in the light path can be projected and focused; 3 providing means for driving one or more of the carriers to provide the intermittent or regular motion; and 4 limiting the thickness of the carriers and the discrete image incorporated with each carrier, at least in the direction of the light path, and juxtaposing the carriers and discrete images in combination in the light path, such that the length of the light path occupied by the combination is less than that of the operational field of focus of the lens. 2 Apparatus for projecting optical images of combined discrete images comprising:

1 a light source;

2 a lens;

3 a light path defined between the light source and the lens;

4 at least two carriers each carrier having an discrete image for projection located thereon;

5 at least one driver whereby at least one carrier can be moved so that the discrete image associated with the or each carrier can be displaced relative to at least one other carrier; and

6 the carriers and the discrete images associated therewith being of a thickness, and juxtaposed in working combination, at least when disposed in the light path, so that the overall length of the combination measured in the direction of the light path in which they are disposed is less than that of the operational depth of focus of the lens.

3 Apparatus as claimed in Claim 2 wherein each carrier is fabricated from ultra-thin glass and the discrete image associated therewith is formed on one side of the carrier or in a lamina element secured to the one side thereof.

4 Apparatus as claimed in Claim 3 wherein in the combination in an adjacent pair of carriers the one carrier of the pair has the one side on which the discrete image is formed or to which the mask element is secured faces a similar side on the other carrier of the pair.

5 Apparatus as claimed in Claim 2, 3 or 4 wherein the driver comprises a motor adapted to drive the carrier by way of transmission system.

6 Apparatus as claimed in Claim 5 equipped with at least two carriers adapted for being driven by the transmission wherein the transmission serves to drive at least two of said carriers at different relative speeds.

7 Apparatus as claimed in any of preceding claims 2, 3, 4, 5, or 6 wherein the discrete images represent the working display elements of a clock whereby the apparatus serves to project an optical image of an analogue clock.