IE43781B1

IE43781B1 - Apparatus for viewing film strips

Info

Publication number: IE43781B1
Application number: IE24376A
Authority: IE
Original assignee: Vredeborch Gmbh
Priority date: 1975-02-06
Filing date: 1976-02-06
Publication date: 1981-05-20
Also published as: DE2504913B2; IT1056609B; FR2300352B1; FR2300352A1; JPS51106435A; DE2504913C3; DE2504913A1; ES444923A1; IE43781L

Abstract

The device is to allow viewing to a narrow gauge film having a light source with a condenser lens to act as the film illuminator by means of which the projected image of the film can be directed in a projection lens onto a transparent viewing screen, has at least one divergent lens (13) inserted into the light path (7) which runs from the projection or image lens (8) to the projection screen (12). This lens (13) is mounted in a movable manner and has a device by means of which it can be moved into or out of the light path (7).

Description

This invention relates to apparatus for viewing film strips ;omprising an illumination unit consisting of a light source with condenser, for projecting images from a film strip onto a display creen along a single light path of constant length by way of an mage optical system adapted to the length of the light path; a ivergent lens which can be rfioved at will into and out of the light ath; and actuating means adapted to move the divergent lens into nd out of the light path.

In addition to general film viewing, devices of the aforeentioned type also serve for assembling individual film scenes into film scenario. Generally such film viewers comprise a prism moved y the film, which transforms the continuous film movement as the film s run through into a succession of individual images, so that a equential movement is obtained. - 2 The image appearing on the display screen is much magnified in comparison with the image on the film. The extent of the magnification depends on the length of the optical path between the image optical system of the apparatus and the display screen, mirror deflection being used to enable the display screen to be situated in the frontal plane of the apparatus in order to bring it as close as possible to the viewer and to keep the dimensions of the apparatus small. For the purpose of more precise observation of individual film scenes it is often expedient and desirable to selectively magnify the projected film image still further. Known film viewers however, have the disadvantage that the length of the optical path, limited by their outer dimensions, cannot be as large as desired and therefore corresponding limits are set on the extent of the magnification. Even though the desired additional magnification would be possible by the use of a specially constructed optical system, such an optical system would influence the cost of the film viewer unfavourably.

The object of the invention is to provide apparatus of the aforementioned type which is capable of providing additional magnification of the image projected on to the display screen, without the optical path being correspondingly extended and without the necessity of employing a costly optical system.This is achieved in the apparatus according to the invention in that a transparent plate is provided, disposed so as to be movable into and out of the said light path in front of the image optical system, and that the actuating means is coupled to the transparent plate in such a manner that when the divergent lens is located in the light path, the plate is located out of the light path.

By means of the divergent lens, the optical path necessary for attaining the desired magnification of the film image is so shortened that the overall size of the total apparatus is considerably smaller than would otherwise be the case. The additional magnification of the image, for improved viewing of the film image which is very desirable for accurate film cutting in assembling individual film scenes, for example into a film scenario, may thus be achieved according to the Invention.

The divergent lens may be movably coupled to an operating device for swinging it into and out of the optical path. - 3 Automatic definition correction is obtained by inserting or removing che transparent plate, which may be a glass or elastics plate of high refractive index, into or from the region above the image optical system, i.e. into or out of the optical path, when the divergent lens is situated out of or in the optical path respectively.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view of a film viewer of a known kind.

Figure 2 is a diagrammatic illustration of part of the optical path shown in Figure 1, as modified according to the invention,showing the means for automatic definition compensation when swinging in the movable divergent lens.

Figure 1 shows the schematic construction of a film viewer and illustrates the optical path thereof. A film strip 1 to be viewed is itoved continuously through the film viewer in the direction of the arrow. Above the film there is disposed a light source 2, under which there is a condenser 3 in the form of a converging lens. The light from the light source is led through the condenser 3 and against the Film which is slidable on a film platform 4, the film thus being illuminated at a determined position. A toothed disc 5 engages in the Film perforations, not shown, and is coupled by a corresponding gear transmission to a prism 6,. which is rotatably disposed in the film rlatform and when a predetermined turning position has been reached transmits the light passing through the film from the light source along :he optical path 7 in the direction of the arrow to an image optical :ystem 8. The optical path is deflected at a mirror 9 and the image of :he film 1, illuminated by the light source, is projected on to the lisplay screen 12 by way of further mirrors 10 and 11.

Figure 2 shows the means for automatically compensating the lefinition of the projected image in apparatus according to the invention, n this, a divergent optical system consisting of two divergent lens 13 nd 14 is mounted between the deflecting mirrors 9 and 10. Of these, the - 4 . 370 1 lens 14 may be swung into the optical path and is connected to a glass plate 16 disposed above the image optical system 8 in such a manner that when operating means (not illustrated) is operated to swing the lens 14 into the optical path, the glass plate 16 is swung out of the optical path above the image optical system 8.

Claims

1. Apparatus for viewing film strips, comprising: - an illumination unit consisting of a light source with a condenser, for projecting images from a film strip onto a display screen along a single light path of constant length by way of an image optical system adapted to the length of the light path; - a divergent lens which can be moved at will into and out of the light path; - actuating means adapted to move the divergent lens into and out of the light path; - and a transparent plate disposed so as to be movable into and out of the said light path in front of the image optical system; the actuating means being coupled to the transparent plate in such a manner that when the divergent Tens is located in the light path, the plate is located out of the light path.

2. Apparatus according to claim 1, wherein the actuating means is adapted to swing the divergent lens into and out of the light path.

3. Apparatus according to claim 1 or 2, wherein the transparent plate is a glass plate.

4. Apparatus according to claim 1 or 2, wherein the transparent plate is a plastics plate.

5. Apparatus for viewing stripe, substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.