WO1993004396A1

WO1993004396A1 - Photographic enlarger and enlarging method

Info

Publication number: WO1993004396A1
Application number: PCT/GB1992/001530
Authority: WO
Inventors: Andrew Mark Jackson
Original assignee: Andrew Mark Jackson
Priority date: 1991-08-20
Filing date: 1992-08-19
Publication date: 1993-03-04
Also published as: AU2443792A; GB9117977D0

Abstract

A method and an apparatus for producing photographic enlargements for an original (3) in which at least part of the original (3) is illuminated whilst moving the original (3) in one direction and a portion of the original (3) is projected via a lens (5) onto a receiving medium (6) moving at a rate dependent on the rate of movement of the original (3) so that a complete image of the original (3) is formed on the receiving medium (6) with the required enlargement factor.

Description

PHOTOGRAPHIC ENLARGER AND ENLARGING METHOD

BACKGROUND OF INVENTION

This invention relates to a photographic enlarger to produce prints and films.

A conventional photographic enlarger projects the entire area of an original photographic image onto photographic paper, thus requiring a large objective lens with a correspondingly large focal length. As a result, conventional enlargers take up a substantial amount of floor space. This is a particular problem in the case of enlargers used for the production of poster-sized prints, for use e.g. on advertising billboards.

DISCLOSURE OF INVENTION

According to a first aspect of this invention, a method of producing enlargements from an original comprises the steps of illuminating at least part of the original whilst moving the original in one direction and, projecting a portion of the image of the original via a lens onto a receiving medium whilst simultaneously moving the receiving medium at a rate dependent on the rate of movement of the original so that a complete image of the original is formed on the receiving medium. Preferably, the original is mounted in a supporting frame and the supporting frame is moved in the one direction.

Preferably the lens is an inverting lens and the original is moved in one direction whilst the receiving medium is moved in the opposite direction. Alternatively a non-inverting lens may be used.

The present invention provides a photographic enlarger to produce prints and films which has a substantially reduced space requirement over conventional designs. An enlargement includes a 1:1 scale reproduction.

Preferably the drive for the original and the receiving medium is controlled by a microprocessor. The relative speeds are determined by the desired enlargement factor. Where required, image distortion, such as a shear in one direction, can be achieved by speeding up or slowing down the movement of either the original or receiving medium.

According to a second aspect of this invention a photographic enlarger apparatus for forming enlargements from an original comprises: means for supporting an original; an illumination source arranged to illuminate at least part of the original; a lens arranged to project a portion of the original; and, means for supporting a receiving medium to receive the image projected by the lens; means for moving the original in one direction, and means for moving the receiving medium simultaneously at a rate dependent on the rate of movement of the original so that a complete image of the original is formed on the receiving medium.

An adjustable aperture may be arranged between the lens and the receiving medium but preferably it is arranged between the illumination source and original so that only a portion of the original is illuminated thereby reducing the effect of lens flare. Preferably the source of illumination provides a field of illumination which is substantially uniform in brightness and colour along the length of the aperture.

The illumination source may be a tungsten or xenon lamp and may be stroboscopic and may include dichroic filters to achieve an overall colour hue.

Preferably the lens is a wide angle inverting objective lens which minimises the distance between the lens and receiving medium. The lens may also include an adjustable aperture.

Preferably, the means for supporting the original includes first transport means comprising a carrier mounted on a lead screw which is driven by a high ratio geared DC motor, the original being mounted on the carrier. Alternatively it may comprise a digitally encoded motor which drives a belt to move a linear bearing along a ground shaft supporting the original.

Preferably, the means for supporting the receiving medium includes second transport means comprising a pair of light-tight chambers each of which encloses a roller. A first chamber stores the unexposed receiving medium, an end of which is attached to the internal roller of the second chamber and a motor drive winds the receiving medium from the first chamber to the second as required during the enlargement process.

Overall exposure may be controlled by altering the width of the adjustable aperture, by varying the light intensity of the illumination source, by altering the aperture of the lens or altering the speed of both the original and receiving medium at proportionate rates.

Using an appropriate illumination source, the present invention achieves greater evenness of light and colour over the entire enlargement, by comparison with conventional enlargers, no matter what the degree of enlargement is.

The present invention saves space by moving the receiving medium between the two light-tight chambers during exposure, keeping the image receiving area in a flat plane, and also by the use of a wide angle objective lens. A conventional enlarger objective lens has to cover the entire original being copied from corner to corner. With the present invention the objective lens only has to cover a portion of the original and thus the focal length of the objective lens required can be substantially shorter.

BRIEF DESCRIPTION OF DRAWINGS An example of a photographic enlarger in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a plan view of an example of a photo¬ graphic enlarger apparatus;

Figure 2 is a side elevation of an apparatus for controlling the projection of an original transparent image;

Figure 3 is a front elevation of the apparatus for controlling the movement and projection of the original transparent image with the main components of the super¬ structure omitted; Figure 4 is a perspective view of the loading of the original transparent image into a support framework;

Figures 5a and 5b are plan views of the apparatus for dispensing the receiving medium;

Figures 6a and 6b are front elevations of the apparatus for dispensing the receiving medium;

Figure 7 is a plan view of an illumination source; and

Figure 8 is a front elevation taken through A-A of one end of the illumination source.

DETAILED DESCRIPTION OF PREFERRED EXAMPLE

Figure 1 illustrates the general concept of a photographic enlarger apparatus in accordance with the present invention. A photographic enlarger apparatus shown in Figure 1 comprises an illumination source 1, an adjustable aperture 2, an original film 3 held on a first transport means 4, an inverting lens 5 and a receiving medium 6 held on a second transport means 7.

The exposing light is provided by a pair of lamps 8 which illuminate a light mixing area with reflective walls. The lamps may be tungsten or xenon and may be stroboscopic as required. Dichroic filters 9 may be placed in the light path to achieve an overall colour hue. A diffuser 10 may be used to achieve an even light intensity at the output. The light passes through the adjustable aperture 2 and illuminates a portion of the original film 3. The original film 3 is held on a first transport means 4. In this example, the first transport means 4 comprises a carrier 11 mounted on a lead screw 12 and is driven by a high ratio geared DC motor 13. The original 3 is able to be moved in the plane defined by the lead screw 12 but must not have any movement in any other plane, especially when making enlargements of a great magnitude.

The image of the portion of the original film 3 passes via the wide angle objective lens 5 onto the receiving medium 6. The lens position may be adjustable so that the image can be focused at the receiving medium. The lens 5 is positioned at a distance from the original 3 which is greater than the focal length of the lens 5. The receiving medium 6 is held on a second transport means 7 at a distance from the lens 5 dependent upon the degree of enlargement required. The second transport means 7 comprises a pair of light-tight chambers 14, 15 each of which encloses a roller 16, 17. A first chamber 14 stores the unexposed receiving medium 6, an end of which is attached to the internal roller 17 of the second chamber 15, and a motor drive (not shown) winds the receiving medium 6 from the first chamber 14 to the second 15 as required during the enlargement process. The second transport means 7 may also include a pair of material tension sensors 18 and a real time speed sensor 19. Both the receiving medium 6 and original 3 must be moved at very accurate speeds. The motors of both the first and second transport means are controlled by a microprocessor.

An enlargement of the original 3 is achieved by illuminating a portion of the original 3 whilst moving the original 3 in one plane defined by the lead screw 12 in one direction and projecting a portion of the image of the original 3 via the lens 5 onto the receiving medium 6 whilst simultaneously moving the receiving medium 6 in a spaced apart parallel plane in the opposite direction at a rate dependent on the rate of the movement of the original 3 so that a complete image of the original 3 is formed on the receiving medium 6. The rate is dictated by the enlargement magnification ratio. By speeding up or slowing down of either original 3 or receiving medium 6 the image will visually stretch or contract, i.e. it will be disproportionate to the original being copied. Exposure times are automatically compensated for, preferably by a microprocessor. Overall exposure can be altered by adjusting the size of the aperture 2, changing the intensity of light, altering the aperture of the objective lens 5 or altering the speed of the original and receiving medium.

Figure 2 shows a second example of an apparatus for controlling the projection of the original transparent image. An original 25.4cm x 20.3cm transparent image is held within a transport housing 20 by a first transport means.

A light box 21 containing an illumination source is mounted to one side of the transport housing 20 and is arranged to direct light through an adjustable aperture (not shown) into the transport housing 20, thereby illuminating a portion of the original transparent image. The aperture is mounted on the output side of the light box 21 and comprises a pair of sliding doors which define a slit. Both the width and height of the slit may be adjusted according to requirements. The light box 21 is illustrated in Figures 8 and 9, and comprises two banks of four vertically mounted lamps 210, eight sets of red, blue and green dichroic filters 211, three DC drive motors 212 with lead screws 213 and three brackets 214 each to hold eight dichroic filters of the same colour which are attached with mounting blocks 215 to the lead screws 213. The box itself has an opal diffuser 216 at the output to the original transport housing 20. The internal walls 217 of the light box are white. The motors 212 push and pull the dichroic filter brackets 214 in and out of the light path via the lead screws 213. This alters the overall colour of the light which eventually falls on the opal diffuser 216. A set of three photodiode detectors (not shown) , each with its own red, blue and green filter above the diode, sends a signal back to a microprocessor, which in turn controls the forward or backward movement of the motors 212 until a predetermined reading is detected by the micro¬ processor for a given set of colour values requested. The light is transmitted to the remote photodiodes via fibre optics to avoid electrical interference.

The result is that the light transmitted through the adjustable aperture is evenly distributed so that the quality of the enlargement is greatly improved.

The light box 21 may be moved away from the side of the transport housing 20 to allow for the loading of the original transparent image. An inverting lens 22 is mounted on the front of a flexible light shield 23 mounted on the other side of the transport housing 20 and is arranged to project the illuminated portion of the original transparent image onto a receiving medium (not shown) . The lens 22 may be provided with an adjustable aperture to adjust the output light intensity and the depth of focus. The lens 22 and light shield 23 may be moved along a track 24 to focus the image.

The lens 22, light shield 23, transport housing 20 and light box 21 are all mounted on a support frame 25. The whole support frame 25 can be moved along a pair of parallel rails 27 which are held above a floor surface 26 by means of a number of brackets 28. Sets of ball racers 29 are mounted underneath the support frame 25 and can run along the rails 27. The ball racers 29 only contact the rails 27 over a small area so that surface friction is minimised. Hence the whole apparatus may be moved along the rails 27 with minimum effort. As described above, movement of the original transparent image in a direction towards or away from the receiving medium controls the degree of enlargement for a given lens. Figure 3 shows the transport housing 20 mounted on the support frame 25 with the bellows and other components of the superstructure omitted for clarity. The original

25.4cm x 20.3cm transparent image 30 is held on a first transport frame 31. The first transport frame 31 includes a Hepco slider system which comprises wheels 32 mounted at each corner which cooperate with runners 33 mounted within a second transport frame 34. The Hepco system is made by

Bishop Wisecarver Corporation and is described in detail in U.S. Patent No. 3,661,431. The first transport frame 31 is therefore capable of being moved in the vertical plane in the horizontal the direction, X. The movement is extremely stable and smooth so that the original transparent image 30 remains in the same plane throughout the whole range of movement.

The second transport frame 34 is moveable in the vertical plane in the Y direction, orthogonal to the X direction. Each corner of the second transport frame includes a wheel 51 which cooperates with runners 52 mounted within a transport support frame 35. The wheels and runners are identical to those described above. In this manner, the vertical movement of the second transport frame 34 is extremely stable throughout the range. The weight of the first and second transport frames is supported by means of tensioned steel springs ribbon 36. The steel springs 36 are mounted on hubs at the top corners of the transport support frame 35 and are connected at their free ends to the respective top corners of the second transport frame 34 by means of a bracket. A belt 37 is connected to a top corner of the second transport frame 34. This belt is tensioned over a pulley 38 mounted to the transport support frame 35 and is connected to a drive pulley 39 mounted at the bottom corner of the transport support frame 35. In this example, the drive pulley 39 is turned by hand but it may be driven by a motor. In this manner, the vertical position of the original transparent image 30 can be adjusted. This will be described in more detail below.

The first transport frame 31 is connected via a bracket 40 to a DC motor driven lead screw 41 mounted on the second transport frame 34. A motor 42 drives the lead screw 41 which in turn moves the first transport frame 31, together with the original transparent image 30 along the runners 33. In this manner, the horizontal position of the original transparent image 30 can be controlled. This will be described in more detail below.

Figure 3 also serves to illustrate the manner in which the main support frame 25 can be moved along the rails 27. The design of the ball racers 29 is such that the load is evenly distributed. The rails 27 are supported above the floor surface by brackets 28 mounted in the floor 26.

Figure 4 illustrates the loading of the original transparent image 30 into the first transport frame 31 and the mechanisms by which its position may subsequently be adjusted. The original transparent image 30 is held in position within the original transport housing 20 on a frame 43 which is formed from two identical sections and which holds the original taut by means of spring tensioners 44a and clamps 44b located in each corner of the frame. These pull the original material outwards from the centre.

For practical loading of the original onto the frame 43, tension is applied via a cam 45 through the spring tensioners 44a, after the clamps 44b have been tightened onto each corner of the original. The frame 43 is removable and can be replaced with an alternative carrier to hold the original using two pieces of glass (not shown) . By this method more than one original can be sandwiched together e.g. to incorporate a text original with an image original. The frame 43 is held in position in a surrounding frame support 48 by a guide 46 at the bottom and two spring loaded retaining cams 47. The frame support 48 is generally rectangular, but has truncated radiussed corners, 48a to 48d which lie on a common circular arc. These provide surfaces generally orthogonal to the diagonal of the support. These surfaces engage rollers 49 mounted on the first transport frame 31.

The frame 43 and frame support 48 can be partially rotated to adjust the horizontal image plane i.e. to correct the horizon in a picture so that the image falls true on the receiving medium. The adjustment is made by loosening a frame angle clamp lock 50, so that the support 48 is free to move on the rollers 49 at its corners and rotating the frame support 48 by hand up to plus or minus fifteen degrees.

Figures 5 and 6 illustrate the apparatus for dispensing the receiving medium in the photographic enlarger of the present invention.

Figure 5a and 6a shows the dispenser in a load position. The apparatus comprises a chassis 53 made from a welded tubular box frame, a dispensing chamber 54, a receiving chamber 55, pinch rollers 56, take up rollers 57, a magnetic platen 58, support platen 59 and receiving medium 60. The unexposed receiving medium 60 may be negative or positive imaging material on opaque translucent or transparent film or paper bases typically manufactured by Kodak, Fuji or Agfa companies. Examples are those manufactured under the trade names Kodak Duratrans, Kodak Duraclear and Kodak Duraflex.

For both the dispensing and receiving chambers an AC or DC reversible motor may be used through a slipping clutch control mechanism (not shown) . Relatively low torque is required.

The speed of the receiving medium 60 is controlled through the two pinch rollers 56, one of which is driven by a high torque stepping motor through a flexible coupling. The stepping motor is synchronised at a rate relative to the movement of the original transparent image. This is controlled through software which takes account of the size of enlargement and lens used. The motor is similar to that used for the movement of the original transparent image having a 1.8 degree angle step with four phase construction. The steps are micro step controlled to ensure a smooth synchronous operation.

The chassis of the material synchronised dispenser is a very strong welded tubular box frame 53 which houses the support platen 59, dispensing chamber 54 which is mounted on a Hepco system 61, the receiving chamber 55, the pinch drive rollers 56 and the magnetic loading platen 58.

The support platen 59 keeps the image plane of the receiving medium 60 true whilst it is moving. The platen moves out of the way rearward for loading purposes so that the dispensing chamber 54 can be moved close to the receiving chamber 55 where a take up leader can be attached with relative ease.

A film leader is attached to the unexposed medium using low tack adhesive tape. Both receiving medium 60 and take up leader are held flat and lined up against a reference mark for loading purposes with magnetic bars attached to a magnetic platen 58, whilst a tape dispenser (not shown) makes the join.

When the dispensing chamber 54 is slid back to the exposing position, as shown in Figures 5b and 6b, the remainder of the leader is pulled across the support platen 59 under tension so that the leader does not sag. The support platen 59 is then brought forward to ensure the leader is in the image plane prior to exposure. Torque is also applied to the take up motor and the receiving medium is held stationary by the pinch rollers 56.

When the dispensing of the receiving medium begins, the pinch rollers 56 turn by a predetermined rate governed by the microprocessor control. As there is more torque and friction at the pinch rollers 56, the take up roller 57 only acts to roll the exposed material up and take out slack during the exposure. When the exposure is complete, all motors stop. The support platen 59 is moved rearwards and the motor on the dispensing chamber 54 takes up the unexposed receiving medium whilst pulling the chamber to the loading point where a micro switch stops the motor. The exposed receiving medium 60 can then be cut and be removed for processing. A new core and leader can be then loaded into the receiving chamber 55 ready for the next exposure.

In use, the photographic enlarger of the present invention is positioned in a darkroom with the original transparent image 30 and receiving medium 60 held in their respective carriers and distanced apart in parallel planes which are perpendicular to the plane of the floor surface 26. The support frame 25 is movable towards or away from the box frame 53 along the rails 27 to control the degree of enlargement for a given lens 22.

Once the receiving medium 60 and original transparent image 30 are loaded (as described in detail above) the original transparent image 30 is driven by the motor 42 to a position within the transport housing 20 which is clear of the aperture. A microprocessor is programmed with information relating to the enlargement and once the operation begins, the illumination source is activated and the original transparent image 30 and receiving medium 60 are driven by their respective motors in opposite directions in the horizontal plane at rates determined by the microprocessor.

For a given size of original transparent image 30, the slit height of the adjustable aperture may be set so that it extends across the height width of the image or only a part thereof. In the former case, the whole original transparent image 30 is effectively scanned in one movement of the first transport frame 31 across the width of the second transport frame 34 in a direction X. In the latter case, only a portion of the original transparent image 30 will have been scanned in the single pass. Therefore in this case, the illumination source must be deactivated, the movement of the receiving medium 60 must be stopped and the first transport frame 31 returned to the start position. Next, the second transport frame 34 must be raised or lowered accordingly in the direction Y within the transport support frame 35 to re-position the original transparent image 30 for the next scan. This process may be controlled automatically by the microprocessor which divides the original transparent image 30 into imaginary strips and makes the necessary adjustments in the tracking to scan the complete original transparent image 30 over several passes. This feature is particularly useful if the degree of enlargement is such that a single scan of the original transparent image 30 would not achieve the required enlargement.

Claims

1. A method of producing enlargements from an original comprising the steps of illuminating at least part of the original (3, 30) whilst moving the original (3, 30) in one direction and, projecting a portion of the image of the original (3, 30) via a lens (5, 22) onto a receiving medium (6, 60) whilst simultaneously moving the receiving medium (6, 60) at a rate dependent on the rate of movement of the original (3, 30) so that a complete image of the original (3, 30) is formed on the receiving medium (6, 60).

2. A method according to claim 1, wherein the lens (5, 22) is an inverting lens and the original (3, 30) is moved in one direction whilst the receiving medium (6, 60) is moved in the opposite direction.

3. A method according to claim 1 or 2, including the steps of mounting the original (3, 30) in a supporting frame (11, 31) and moving the supporting frame (11, 31) in the said one direction.

4. A method according to any preceding claim, wherein the original (3, 30) and receiving medium (6, 60) are driven by digitally controlled motors and the relative speeds of the original (3, 30) and receiving medium (6, 60) are controlled by a microprocessor.

5. A method according to any preceding claim, wherein the relative speeds of the original (3, 30) and receiving medium (6, 60) are controlled to vary the proportions of the enlargement.

6. A method according to any preceding claim, further comprising varying the illumination of the original (3, 30) in accordance with the speed of the receiving medium (6, 60) so as to maintain a desired level of exposure at the receiving medium.

7. A photographic enlarger apparatus for forming enlargements from an original comprising: means (4, 20) for supporting an original; an illumination source (1, 21) arranged to illuminate at least part of the original (3, 30); a lens (5, 22) arranged to project a portion of the original (3, 30); and, means (7, 53) for supporting a receiving medium (6, 60) to receive the image projected by the lens (5, 22), means for moving the original (3, 30) in one direction, and means (16, 17, 54, 55, 56) for moving the receiving medium (6, 60) simultaneously at a rate dependent on the rate of movement of the original (3, 30) so that a complete image of the original (3, 30) is formed on the receiving medium (6, 60) .

8. A photographic enlarger apparatus according to claim 7, in which the means (4, 20) for supporting the original include first transport means arranged to be driven in the one direction.

9. A photographic enlarger apparatus according to claim

6, wherein an adjustable aperture (2) is arranged between the illumination source (1, 21) and the original (3, 30) so that only a portion of the original (3, 30) is illuminated.

10. A photographic enlarger apparatus according to claims

7, 8 or 9 wherein the illumination source (1, 21) comprises one of a tungsten or xenon lamp (8, 210).

11. A photographic enlarger apparatus according to claim 10, wherein the illumination source (l, 21) is strobo- scopic.

12. A photographic enlarger apparatus according to claims 10 or 11, wherein the illumination source includes operatively insertable dichroic filters (9, 211).

13. A photographic enlarger apparatus according to any one of claims 7 to 10, wherein the lens (5, 22) is a wide angle inverting objective lens.

14. A photographic enlarger apparatus according to any one of claims 7 or 13, wherein the lens (5, 22) includes an adjustable aperture.

15. A photographic enlarger apparatus according to any one of claims 8 to 14, wherein the first transport means comprises a carrier (2, 31) mounted on a lead screw (12, 41) which is driven by a high ratio gear DC motor (13, 42) , the original (3, 30) being mounted on the carrier (2, 31).

16. A photographic enlarger apparatus according to any one of claims 7 to 15, including digitally controlled motors arranged to drive the original medium (3, 30) and the receiving medium (6, 60) , and a microprocessor arranged to control the motors.

17. A photographic enlarger apparatus according to claim 16, in which the microprocessor is arranged to vary the exposure depending on the speed of the receiving medium (6, 60) so as to maintain a desired level of exposure at the receiving medium (6, 60).

18. A photographic enlarger apparatus according to any one of claims 8 to 17, wherein the first transport means comprises a digitally encoded motor which drives a belt to move a linear bearing along a ground shaft supporting the original.

19. A photographic enlarger apparatus according to any one of claims 7 to 18, wherein the means (7, 53) for supporting a receiving medium (6, 60) comprise second transport means comprising a pair of light tight chambers (14, 15, 54, 55) each of which encloses a roller.

20. A photographic enlarger apparatus according to claim 19, wherein a first chamber (14, 54) stores the unexposed receiving medium (6, 60) and a second chamber (15, 55) is adapted to receive and house the receiving medium (6, 60) once it has been exposed.

21. A photographic enlarger apparatus according to claim 17, wherein the second transport means further comprises a pair of pinch rollers (56) to control the speed of the receiving medium from the first chamber (54) to the second chamber (55) during exposure.

22. An apparatus according to claim 21, further comprising a support platen (59) to ensure that the receiving medium (60) is held in a given plane during its travel between th first and second chamber and a magnetic platen (58) t allow a film leader and the receiving medium (60) to b attached together prior to exposure.