GB2136142A

GB2136142A - Producing Modified Prints

Info

Publication number: GB2136142A
Application number: GB08305959A
Authority: GB
Inventors: Maurice Clifford Heard
Original assignee: Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1983-03-03
Filing date: 1983-03-03
Publication date: 1984-09-12
Also published as: GB2136142B; GB8305959D0

Abstract

A modified print is produced on photosensitive material 7 by illuminating original 5 with light from lamp 1 after passage through diffuser 3 and LCD panel 4, panel 4 containing a matrix of elements individually rendered opaque or transparent to burn in or hold back desired parts of the print. A plurality of prints are produced in succession under the control of an electronic store into which information (dictating which elements are to be opaque or transparent for each print) has been keyed in by a skilled operator. <IMAGE>

Description

SPECIFICATION Apparatus for Forming an Image on a Photo Sensitive Member This Application relates to an apparatus for forming an image on a photo-sensitive member. It is particularly applicable to photographic projection printers, e.g. enlargers, but is also applicable to photographic or television cameras.

in the field of photographic enlargers there are some occasions when the operator encounters a negative which, although of normal average density and gamma (contrast), contains area which print too light or too dark. It has been the custom for many years for the operator to "burn in" or "hold back" these areas by casting a shadow, using the hands or using a piece of cotton wool held on a thin piece of wire. This process, although perfectly effective for a single print, does not lend itself to a run of say 1 00 identical prints. Furthermore the operator needs to have considerable skill and experience to get the required effect even for a single print. For a run of prints there is an additional problem of obtaining consistency.

This invention provides apparatus for forming an image on a photo-sensitive member, the apparatus comprising an array of liquid crystal elements and control means for individually controlling the translucency of the elements thereby controlling the amount of light incident on different parts of the photo-sensitive member.

By employing the invention it will readily be apparent that it is possible to set the array of liquid crystal elements so as to burn in or hold back the desired parts of a print and to repeat the printing process using the same setting so as to produce a run of identical prints. This can be done by a relatively unskilled operator once the correct setting has been formulated by a more skilled operator.

When the invention is applied to a photographic printer the apparatus preferably includes a store containing, for each of a plurality of possible pictures or patterns to be printed, information determining which elements shall be opaque and which shall be translucent. In such an arrangement it is possible for the skilled operator to programme into the store information for the burning in or holding back of parts of say 16 different photographs and then to pass the process on to an unskilled operator who uses the programmed information to carry out the printing process.

The apparatus preferably includes an indicator or display to indicate to the operator, as he is loading information into the store for use on a particular print, which elements he has determined to be opaque and which are to be translucent.

One way in which the invention may be performed will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic side view of a photographic enlarger constructed in accordance with the invention; Figure 2 is a schematic vertical cross-section through a liquid crystal display panel of Figure 1; Figure 2A is a plan view of the liquid crystal display panel of Figure 2; and Figure 3 is a schematic block diagram of a circuit for controlling the liquid crystal display panel.

Referring firstly to Figure 1 a source of light in the form of a lamp 1 illuminates a mirror 2 which directs the light towards a diffuser 3 and thence to a liquid crystal display panel 4 which will be described in detail later. After passing through the display panel 4 the light illuminates a photographic negative 5 and an image of this is focussed by a lens assembly 6 onto a sheet 7 of photo-sensitive paper supported on a baseboard 8.

In order to reduce the illumination of the photo-sensitive paper in areas where the negative 5 is very translucent, the diffuser 4 is designed to spacially modulate the light passing through it and to reduce the intensity of illumination in those areas of the negative. Referring to Figures 2 and 2A the liquid crystal display panel is formed (as is conventional) from five layers namely: a top polariser 9, a glass sheet 10, a nemetic liquid layer 11, another glass sheet 12 and a bottom polariser 1 3 whose direction of polarisation is normal to that of the polariser 9. Electrode strips extend along the bottom of the glass sheet 1 0 and, at right angles to the first mentioned strips, along the top surface of the glass sheet 1 2.It is thus possible, by applying suitable signals to selected strips of sheet 10 and sheet 1 2 to cause selected parts of the panel to become transmissive or opaque to light. Figure 2A shows the panel as a matrix of different parts, eleven of which are shown in their opaque condition these having been selected to correspond to particularly bright areas of a particular photograph to be printed.

Referring now to Figure 3, for a given photograph to be printed, the operator, using his personal judgement, selects successively each matrix element of the LCD panel 3 by pressing "row" and "column" selector controls 14 and 1 5 provided by a keyboard. For each matrix element he operates a further control 1 6 (also provided by the keyboard) which determines whether the selected matrix element is to be opaque or transparent. This information is passed to a circuit 1 7 which contains a 1 6 xl 6 bit matrix store 17 and the contents of this store is used to illuminate an LED display 1 8 via suitable drive circuits 1 8A and 1 8B. The LED display 1 8 is a representation of the LCD panel and indicates to the operator the contents of the store 17.

A further store 1 9 contains 1 6 individual 1 6x 1 6 bit matrix stores each identified by a particular address. The operator selects, using controls 20, 21 and 22, into which address he wishes the contents of store 1 7 to be written and then presses the "store" button 23 so as to load the contents of store 17 into the appropriate address of the store 19. The whole process described so far is repeated for different photographs up to a maximum of sixteen i.e. the number of 1 6x 1 6 matrices which can be contained in the store 1 9.

In operation of the enlarger, for a given photograph, a corresponding set of values from the store 1 9 is read, using the recall button 24, to an LCD interface chip 25 which converts the stored information, in known manner, to a form in which it can operate the LCD display panel 3.

Thus selected parts of the panel 3 are made opaque or transparent as indicated on Figure 2A thereby controlling the exposure of different parts of the photograph in different ways. For a different photograph a different set of values is recalled from the store 1 9.

In an alternative form of the invention it would be possible to control the individual elements of the LCD matrix so as to vary their translucency to intermediate values between the most extreme opacity and the most extreme translucency possible. Such an arrangement is however not preferred since it adds complexity and is not necessary in the illustrated embodiment of the invention since the diffuser 3 ensures that an opaque element of the LCD panel does not produce a harsh unexposed region on the photosensitive paper 7 but rather produces a diffuse region of reduced exposure. In other forms of the invention it would be possible for the control of the LCD panel to be effected automatically using a suitable exposure measuring device to detect regions of the photo-sensitive elements subjected to higher than normal exposure.

Claims

1. Apparatus for forming an image on a photosensitive member, the apparatus comprising an array of liquid crystal elements and control means for individually controlling the translucency of the elements thereby controlling the amount of light incident on different parts of the photo-sensitive member.

2. A photographic projection printer according to claim 1.

3. A printer according to claim 2 including a store containing, for each of a plurality of possible pictures or patterns to be printed, information determining which elements shall be opaque and which shall be translucent.

4. A printer according to any preceding claim in which the control means has, associated wtih it, an indicator for indicating to an operator, which elements are to be opaque and which to be translucent.

5. A photographic projection printer substantially as described with reference to the accompanying drawings and substantially as illustrated therein.