FR2621710A1 - Combined device for chromatic analysis of a photographic negative film to be printed, for printing negative photographic films and for measuring the optical density in reflection of an exposed and developed photosensitive paper - Google Patents

Abstract

Device comprising: - an exposure light source 2, - a chromatic filtering system 3, - an array 11 of photosensitive cells 12, - an assembly for processing the signals transmitted by the photosensitive cells 12, intended to control the conditions of exposure of the negative film 1 to be printed; characterised in that it comprises: - an optical fibre 6, intended to convey a portion of the light leaving the light source 2 to the negative film 1 to be analysed, - a plurality of optical fibres 9, - an optical fibre 14, intended to convey a portion of the light leaving the light source 2 to the photosensitive paper 16 which is exposed and developed, - a shutter system 3, also arranged on the optical path A.

Description

COMBINED DEVICE FOR THE CHROMATIC ANALYSIS OF A FILM
PHOTOGRAPHIC NEGATIVE TO BE DRAWN, FOR THE DRAWING OF FILMS
PHOTOGRAPHIC AND DENSITY NEGATIVES
REFLECTIVE OPTICS OF INSULATED PHOTOSENSITIVE PAPER AND
DEVELOPED.

 The present invention relates to a device for chromatic and contrast analysis of a negative film on the one hand, and on the other hand for the correction of the exposure of said negative film with a view to its printing on photosensitive paper as a function of this analysis. , its actual printing on photosensitive paper, and finally, the measurement in optical density by reflection of an insulated photosensitive paper used as a test, intended to calibrate a machine for printing photographic films, in particular in color.

 When you take pictures with a camera, you form an image on the negative film. The quality of the image formed depends on various parameters, such as the brightness, the specific characteristics of the negative, and the camera settings when shooting.

 The image formed therefore has its own characteristics and possibly defects. However, to carry out a photographic test on paper with precise characteristics, these defects must be canceled.

 Currently, the chromatic analysis is done globally on the entire negative. This is certainly a satisfactory solution for a high percentage of so-called "normal" cases, that is to say normally exposed and of medium contrast. However, certain special cases cannot be treated, such as violent backlighting or highly contrasting subjects. Indeed, the corrections to be made are only statistical. One of the objectives of the invention is to be able to read the contrast of the image and its distributions, in its entirety.

 When the chromatic analysis is carried out, the exposure parameters (duration and intensity of the exposure) are thus determined. However, before proceeding to the actual printing phase, the characteristics of the photosensitive paper must be known. To do this, negative test films of value with known optical density have been used hitherto. These test films corresponded to variations in exposure, namely in general an underexposed view, a normally exposed view and an overexposed view. Once drawn, the optical density of each of the ranges was then measured and, as a function of the densities obtained, the exposure conditions were modified, namely the intensity of the light source and the duration of exposure respectively. However, such a device required different manipulations. In fact, it involved waiting for the thermal stabilization of the exposure lamp in addition to a prior calibration on the ranges of known optical density. This device was therefore a source of loss of time and involved the employment of personnel.

The present invention aims to overcome these drawbacks. It offers a combined device for the chromatic analysis of a photographic negative film to be printed, for the printing of photographic negative films and for measuring the optical density in reflection of an insulated and developed photosensitive paper, of the type comprising
- an exposure light source
- a chromatic filter system, arranged on the optical path between the light source and the negative film to be analyzed and drawn
- a first strip of obotosensitive cells
- a stepping motor intended to advance the negative film during the chromatic analysis phase
a set of processing of the signals transmitted by said photosensitive cells, intended to control the conditions of exposure of the negative film to be shot.

The present invention is characterized in that it comprises
- a plurality of optical fibers combined side by
dimension in the form of a second lon strip
width at least equal to the width of the negative film
each optical fiber being connected to a cell
photosensitive to form the first strip
transmitting information to all of
treatments;
- a sealing system also arranged on the tra
optical jet, intended to interrupt the light on
negative film when measuring in op density
sunstroke tick
- an optical fiber, intended to transfer one by
tie of light from the light source
on the insensitive and developed photosensitive paper
part of the light reflected by the
said paper then being picked up by means of a
plurality of optical fibers which transmit it
then to as many photosensitive cells of the
said barrette.

 In other words, the invention is characterized in that by means of an appropriate device, it is possible to carry out consecutively, using the same photosensitive cells, on the one hand, the chromatic analysis of the photographic negative film to be taken and on the other hand, a measurement in optical density of an insulated and developed photosensitive test paper, of the type on which the negative film is to be printed. It is also characterized in that the device according to the invention is used for printing photographic negative films after having carried out the two preceding steps.

Advantageously, in practice
- the number of photosensitive cells of the first strip intended for chromatic analysis is nine, distributed in three groups of three photosensitive cells, each of these groups carrying out the respective analysis for each of the three fundamental colors respectively red, blue and green
- The first strip further comprises two other additional photosensitive cells arranged thanks to optical fibers facing the lateral portion of the negative film, intended to read the bar code inscribed on said film
- the sealing system and the filtering system consist of a single disc, rotating around an axis parallel to the optical path, comprising
. three holes offset by 72 degrees, intended
to receive the filters corresponding to
three basic colors
. an orifice located in the vicinity of said axis, and
placed opposite one of the two op fibers
ticks transferring light from said orifice
up to the negative film at ana respectively
lyse during the chromatic analysis phase
and insensitive and developed photosensitive paper
popped up when measuring in optical density
The manner in which the invention can be implemented and the advantages which result therefrom will emerge more clearly from the exemplary embodiments given below by way of indication and not limitation, in support of the appended figure.

 Figure 1 is a schematic representation of the device according to the invention, materializing in particular the different optical paths from the light source.

 When the negative film (1) has been developed and dried, it is inserted into an exposure assembly forming a film holder (not shown). It then undergoes the chromatic analysis phase. To do this, the device according to the invention comprises a lamp (2) playing the role of light source and exposure lamp. The device according to the invention has on the optical path (A) defined by the lamp (2) and the negative (1) a disc (3) rotating around an axis (4) parallel to the optical path (A), driven by a stepping motor (not shown), and which acts as a filtering and sealing system. This rotating disc (3) is perpendicular to the optical path (A) defined above. It has through orifices, filled with filters (5), corresponding to the fundamental colors respectively red, blue and green. The disc (3) also has an orifice (17), arranged in the vicinity of its axis (4), and intended to be opposite an optical fiber (6) during the chromatic analysis phase, or an optical fiber (14) during the optical density measurement phase.

 During the chromatic analysis phase, the light coming from the light source (2) crosses the orifice (17) of the disc (3), and is received at the end of said orifice by an optical fiber (6), which 'routes to the negative (1) via a diffusing device (7). The light which diffuses through the negative (1) is received by a first strip (8) of optical fibers (9) extending over the entire width of the negative film (1). This strip (8) in fact comprises eleven optical fibers, conveying the light scattered by the negative (1) at the level of photosensitive cells (12, 13) also eleven in number, located in the vicinity of the chroma analysis unit. e, # is i- # r- ## i # the electronic assembly.

 Nine of these photosensitive cells (12) are intended for chromatic analysis proper. They are divided into three groups of three photosensitive cells, each of these groups carrying out a chromatic analysis in the three fundamental colors, namely red, blue and green. To do this, said photosensitive cells (12) are preceded by a filter of the corresponding fundamental color.

 The two remaining photosensitive cells (13) are intended to read the bar code (19) present on the side border (18) of the negative film (1). This barcode is presented in two lines, respectively indicating the brand of the negative film and its sensitivity. Thus, knowing these different parameters and having carried out the chromatic analysis, the device according to the invention allows access to a certain autonomy.

 A stepping motor (not shown) performing two hundred steps per revolution, therefore an advance of two tenths of a millimeter per step, causes the negative to advance in the film holder. Thus, each negative is divided into a multitude of small rectangles, analyzed by the photosensitive cells (12), and this in each of the three fundamental colors respectively red, green and blue.

 In addition, said photosensitive cells are able to identify the inter-view areas separating two shots on a negative. Thus, by the signal processing system which will be described later, one can proceed to the automatic positioning of each shot.

 On the other hand, when a shot has been analyzed as a whole by the nine photosensitive cells, the optical signals are transformed into electrical signals by means of said cells, these optical signals are then amplified by means of amplifiers, then selected. by means of a multiplexer (not shown). The electrical signal obtained is then converted into a digital signal by means of an analog-to-digital converter, which then transmits this digital signal to a microprocessor, which is programmed to restore data allowing the duration of exposure to be determined. in each of the three fundamental colors for the printing of the negative film (1) on a photosensitive paper. To do this, the microprocessor directly controls the stepping motor actuating the rotating disc (3) and is intended to allow the passage of light through the red, green and blue filters (5).

 Beforehand, it is necessary before drawing any negative film, to calibrate the printing machine according to the photosensitive paper used. To do this, a negative test film is used, capable of restoring a "gray" on photosensitive paper. Once this print has been made, it must be analyzed in optical density in order to make the necessary corrections to the different exposure times in each of the three fundamental colors. To do this, the device according to the invention comprises an additional optical fiber ( 14), intended to capture the light immediately at the end of the disc (3), and to send it at the level of the insensitive and developed photosensitive paper (16) resulting from the printing of the negative test film. The light reflected by said paper ( 16) is picked up by three optical fibers! '5), which transmit 1 light thus ref1 # -' # hie to three photosensitive cells (12) of the same group mentioned previously.

 Thus, a new densitometric analysis is carried out, making it possible, as described above, to make corrections to the different exposure durations with a view to obtaining a perfect "gray".

 It is understood that the densitometric analysis of the photosensitive paper is carried out only once a day or at each change of the paper.

 On the other hand, during the optical density analysis phase of the insensitive photosensitive paper, the disc (3) is placed in such a way that it corresponds to a total blockage of the light coming from the source (2) in the direction of the negative, in order not to disturb the measurement - in optical density. Indeed, if the optical path were not blocked, the light coming from the light source (2) could reach the optical fibers (9), thus conveying a quantity of light to the photosensitive cells (12) intended in the case of species and at the moment, densitometric analysis of the paper (16).

 Thus, the device according to the invention makes it possible to correct two fundamental elements, namely, on the one hand, the color and this, locally and not globally, and on the other hand the exposure durations as a function measured contrasts, thus making it possible to draw any negative, whatever their contrast.

On the other hand, the present device has various advantages that the systems known to date did not allow to obtain. We can cite
- the use of optical fibers to obtain a compact electronic assembly that is well immunized against external parasites
- exposure times very well controlled due to the use of a stepper motor
- a substantial saving of material because the same material is used for several functions, in particular the photosensitive cells, the light source, etc .;
- automatic registration of the machine.

 All of these various advantages therefore immediately result in a lower cost of the resulting printing machine.

 Finally, it should be noted that this type of device is able to recognize special cases, such as for example a strong dominance of a localized subject, and therefore to proceed to their drawing.

Claims (4)

 1 / Combined device for the chromatic analysis of a photographic negative film to be printed, for the printing of photographic negative films and for measuring the optical density in reflection of an insulated and developed photosensitive paper, of the type comprising  - an exposure light source (2),  - a chromatic filter system (3), arranged on the optical path (A) between the light source (2) and the negative film to be analyzed and drawn (1)  - a first strip (11) of photosensitive cells (12),  - a stepping motor intended to advance the negative film (1) during the chromati analysis phase  a set of processing of the signals transmitted by said photosensitive cells (12), intended to control the conditions of exposure of the negative film (1) to be shot, characterized in that it comprises  - an optical fiber (6), intended to transfer a  part of the light from the light source  (2) at the level of the negative film to be analyzed (1)  - a plurality of optical fibers (9) joined together  side by side in the form of a second bar (8) of  length at least equal to the width of the film born  gative (1), each optical fiber (9) being connected  to a photosensitive cell (12) to form the  first bar (11) transmitting information  the treatment package  - an optical fiber (14), intended to transfer a  part of the light from the light source  (2) at the insensitive photosensitive paper and  developed (16), some of the reflected light  by said paper (16) then being picked up at  using a plurality of optical fibers (15) which  then transmit it to as many photo cells  sensitive (12) of said strip (11)  - a sealing system (3) also arranged on the  optical path (A), intended to interrupt the reading  on the negative film (1) during the measurement  in optical density of exposed and developed paper  (16)  2 / Device according to claim 1, characterized in that the number of photosensitive cells (12) of the first strip (11) intended for the chromatic analysis is nine, distributed in three groups of three photosensitive cells (12), each of these groups carrying out the respective analysis for each of the three fundamental colors respectively red, blue and green.  3 / Device according to one of claims 1 and 2 characterized in that the first strip (11) further comprises two other additional photosensitive cells (13) arranged with optical fibers facing the lateral portion (18) of the film negative (1), intended to read the bar code (19) written on the said film (1)  4 / Device according to one of claims 1 to 3, characterized in that the sealing system and the filtering system consist of a single disc (3) rotating around an axis (4) parallel to the optical path (A ), comprising  - three orifices offset by 72 degrees, intended for  receive the filters (5) corresponding to the three  basic colors  - an orifice (17) located in the vicinity of said axis (4),  and placed opposite one of the two opti fibers  ques (6,14) transferring the light from said orifice (17) respectively to the negative film to be analyzed (1) during the chromatic analysis phase and to the insulated and developed photosensitive paper (16) during the optical density measurement