FR2491637A1 - DEVICE FOR FLASHING IMAGES IN A DRY PROCESSING FILM - Google Patents

Abstract

THE OPTICAL PROJECTION SYSTEM INCLUDES COLLIMATION AND GUIDANCE MEANS PLACED ALONG AN AXIS GOING FROM A LIGHT SOURCE TO A PROTECTIVE MASK AND WHICH PRESENT AN ENTRY WINDOW 12A, AN EXIT WINDOW 12B AND AN EXTENDED STRUCTURE WITH INTERNAL REFLECTION 12 PLACED BETWEEN THE SAID WINDOW AND AROUND THE AXIS TO GUIDE THE LIGHT FROM THE SOURCE TO THE MASK BY MULTIPLE REFLECTIONS INSIDE THE STRUCTURE.

Description

249163?

  The present invention relates to a training device

  lightning up images in an imaging film at

dry treatment.

  An apparatus for dry processing a flash imaging film having a layer of imaging material dispersible by radiation energy

  on its surface, is described in the US patent. No. 3,966,317.

  The apparatus represented in the patent comprises an image transfer station o a single image of a micro-film is interposed on a micro-image of a film strip forming a mask which

  is placed over a glass window. A short im-

  energy pulse, greater than a certain threshold, which is emitted by a Xenon flash tube through the glass window and the micro-image of the film strip forming a mask to reach the image on the microfilm which preferably presents the shape of a microfiche or a micro card. The radiation energy pulse emitted by the Xenon flash tube

  is absorbed and dispersed by the opaque areas of the micro-

  image of the film strip forming a mask so as not to actually reach the corresponding areas of material

  dispersible by the energy of the underlying image of the microfilm.

  However, the short pulse of radiation energy trav-

  easily pours the substantially transparent areas of the micro-image of the mask film strip to achieve

  25. the corresponding underlying areas of dispersed matter

  ble by the microfilm energy in which the energy pulse is absorbed. The absorption of the radiation energy pulse by these zones heats the energy dispersible material and at least brings it to a softened or molten state, so that the continuous layer of energy dispersible material at the level of these areas is broken up and is dispersed into small, relatively spaced globules to make these areas

  substantially transparent. The dispersion of the material

  persible by the radiation energy at the level of the zones

  heated is produced mainly by the over-voltage

  face of the heated material which causes this material once heated to form such small spaced globules. After

  that the globules were thus formed by the short pulse

  ion of energy emitted by the Xenon flash tube, these are rapidly cooled and remain in this globular state to create substantially transparent areas in the microfilm image.

  The energy gathering efficiency of the device

  tion of image formation on film and which is illustrated in the US patent. No 3 966 317 is about 49%, Considered differently, about 60% of the energy emitted by the Xenon flash tube used in the belon device the patent is

  dissipated and lost. It is therefore necessary to use

  read a longer width pulse and a higher operating voltage to provide a sufficient amount of film plane energy to obtain a dispersion of the energy dispersible imaging material

  radiation on the imaging film used in conjunction

  sound with the device. The need for larger width pulses and higher operating voltage not only agitate to shorten the useful life of the tube

  Xenon flash but also has a harmful effect

  ble on the energy cost of the device and on the finesse

produced images.

  The imaging device must have, in addition to a high efficiency of capturing the energy of

  radiation from a corresponding source, an irra-

  substantially uniform diance on the film strip forming a mas-

  as well as a high degree of collimation of the radiation output. The latter requirement arises from the fact that it

  there is an inevitable gap between the film strip

  mant mask and the active layer of the microfilm, due to the

  presence of a protective layer on the micro-film.

  According to a characteristic of the invention, a high degree of such collimation is obtained by passing the

  light from a Xenon flash lamp by a structure

  ture presenting divergent surfaces with internal reflection.

  By optimizing the angles of divergence, a series of multiple internal reflections generally occurs around

  the axis of propagation of the structure results in a weakness

  exit sign very well collimated and sensitive intensity-

  uniformly at the exit window of the structure. Good image resolution - and appropriate uniformity of

  the illumination is obtained by means of this process. The possibility

  bility of collimation by multiple internal reflections

  is a hitherto unrecognized characteristic of struc-

divergent tures.

  In accordance with a particular characteristic of the

  present invention, and as illustrated below by way of example

  ple, the imaging device comprises a body of

  transmission of radiation energy which has advantageous

  the shape of an elongated prismatic element full in shape

  me of trunk of cone or trunk of pyramid and which presents a facet of entry of the energy of radiation and a facet of exit of this energy as well as lateral facets

  which are inclined with respect to the longitudinal axis of the element

  prismatic. The adjacent side facets are cha-

  can be inclined at a different angle to the longitudinal axis of the prismatic element which results in

  to give a generally divergent guide structure.

  The dimensions of the entry and exit facets as well

  if the length and the degree of inclination of the facets la-

  such as the energy collected by the element taken

  material is directed by multiple internal reflections

  between the side facets in a way calculated for assu-

  rer maximum use and optimal distribution and collimation of the radiation energy on the plane of the film located at the exit facet of the element

  prismatic so as to obtain an optimum image resolution

male.

  The use of divergent guide means, present

  both one form or another, in lighting systems is

  certainly well known. Thus, US patent N03 514 200 illus-

  be a light mixer in a rectangular pyramid trunk

  on two divergent planes. A precise examination of the patent shows what-

, VS.

4 2491637

  while the extreme rays are confined, so that they do not reflect on the divergent walls and that collimation is ensured by conventional optical lens means. The mixture is obtained by multiple internal reflections of the usual type on the two parallel surfaces.

  U.S. Patent No. 4,125,315 shows a compressed mixing system.

  of cylindrical and semi-cylindrical mixing elements

  arranged in series and in parallel, the elements in series can

  possibly before being joined by conical adaptation interfaces which "may or may not be diffusion surfaces"

  (see column 4, lines 3 to 9), and this document does not describe

  a recognized collimation property. In reality no such collimation effect could exist in geometry

  represented unless there is a large disparity of indi-

  those of refraction between the adaptation surfaces, and this requirement is in no way described. It is also by no means

  mentions a divergence to convergence report of the ele-

  which is a central aspect of this

  cription. In the previous document, a collima-

  tion of the output rays by conventional optical means with lenses. None of the previous documents refer to this

  which constitutes the environment of the present invention,

  see a collimated shadow projection system.

  According to another characteristic of the invention illus-

  Also by way of example, the lighting efficiency of the device is improved by mounting the prismatic element near a source of radiation energy such as a Xenon flash tube and by embedding, at least in part. , the

  source and the prismatic element inside means of-

  Terception and reflection of the radiation energy which are placed to form a reflecting cavity. The

  means of interception and reflection of ray energy -

  advantageously comprise reflecting bodies of general hemispherical shape each having centers

  of curvature optimally arranged. The hemispheric organs

  are preferably mounted in a housing and act

  feels to intercept and reflect the radiation energy from a corresponding source in the input facet of the prismatic element. The prismatic element then guides the radiation energy towards the exit facet through an opening formed in one of the reflecting members. An imaging mask is provided at the exit facet of the prismatic element and is placed between the

  output facet and the microfilm or the printing micro card

  cut to allow energy to be applied to the film

according to a preset mode.

  The prior art describes reflected cavities

  general aspherical health for lighting

  ge, for example in the form of projection lamps with reflective walls having an opening. By placing a guide member inside the reflecting cavity, it is however possible to use hemispherical reflecting members

relatively less expensive.

  The image forming device according to the invention

  tion collects, directs, collimates and shapes the energy of

  radiation emitted by a corresponding source such as a tu-

  be Xenon flash in a way that allows ma-

  ximal and an optimal distribution of the energy at the level of the film plane thus ensuring a distribution substantially

  uniform and instantaneous imaging material available

  persible by radiant energy on the imaging film. The energy gathering efficiency of the imaging device is more than 80%, i.e. about double that of the imaging arrangement on

  film described in US Patent 3,966,317. The effectiveness of ras-

  very high energy appearance of the device has a-

  significant economic benefits in what can be employed

  a shorter width pulse and a function voltage-

  If the Xenon flash tube is used as a source of radiation energy, the energy costs are reduced appreciably and the useful life of the flash tube is reduced. Xenon is more than doubled. Such results are also obtained while giving on

  the imaging film, images that have characteristics

  exceptionally high resolution ques. The device

  described is light and compact and it is particularly

  particularly suitable for use in the apparatus described

in U.S. Patent No. 3,966,317.

  The subject of the invention is therefore an optical projection system characterized by a projection mask and a light source allowing

  to light up this mask and form a shadow image of it

  ci on an image forming surface away from the mask,

  in which means for collimating and guiding the light

  are placed along an axis going from said source

  towards the mask, the collimation and guidance means

  taking an entry window and an exit window as well as an elongated structure with internal reflection placed between said windows and around said axis to guide the light going from the source towards the mask by multiple reflections inside the structure , this structure being formed to diverge, continuously, in all directions perpendicular to this axis with an increasing distance from the source, the divergence of this structure being

  as it directs, collimates and mixes the light passing through

  the collimating and guiding means so as to provide a maximum intensity of light collimated appropriately and distributed in a substantially uniform manner to the

level of said mask.

  - A lighting fixture comprising a light source

  is characterized by light mixing and guiding means and light reflecting means, said mixing and guiding means being arranged to guide the light coming from said source along an axis emanating from this source, said mixing and guiding means comprising an inlet window and an outlet window as well as an elongated structure with internal reflection disposed between said windows and generally around said axis so as to

  mix and guide the light from the ma-

  generally along the said axis by internal reflections

  multiple to produce lighting so that are of-

  substantially uniform density when it leaves said exit window, the light reflecting means being arranged

  around said source so as to form an image of the

  material from this source at a chosen image point located substantially on said axis and near the entrance window, said light reflecting means comprising a first reflector having the shape of a surface part of a first sphere and a second reflector having the shape of a surface portion of a second sphere, said second reflector having an access opening placed substantially in its axial region, said first reflector being placed with the center of said first sphere on a

  first point substantially on the axis and substantially mid-

  path between said source and said image point and having the central region of the first reflector disposed substantially on said axis at a second point, this second point being disposed on a line situated in the extension of said

  axis and extending from said guide means and from

  dipping across the source towards said second point, said second reflector being disposed with the center of the second sphere substantially at the intersection of said

  axis and source and presenting the center of said opening

  ture of access placed substantially on said axis at a third point, this third point being placed on a line located in the extension of said axis and extending from the

  source through the inlet opening towards said third

  sith point, said reflectors forming at least part of a reflecting cavity around said source, said mixing and guiding means being arranged with at least said entry window placed inside said cavity, a first part of the light coming from said source reflecting on the first reflector to focus, at said image point, a second part of the light

  from the source reflecting on the second reflec-

  tor to return to this source and from there to the first

  reflector to reach said image point, the input window

  very mixing and guiding means intercepting a substantial fraction of the light emitted by the source, this

  fraction crossing said access opening and said window

  exit to provide a maximum intensity of light distributed substantially uniformly from the exit window.

  Various other characteristics of the invention come out

  Besides, try the detailed description which follows.

  EMBODIMENTS OF THE OBJECT OF THE INVENTION

  are shown, by way of nonlimiting examples, to the

attached sins.

  Fig. 1 is a sectional elevation of a form of

  production of the device according to the invention.

  Fig. lA is a partial section on a larger scale illustrating an image-forming mask as well as the microfiche card in contact with it during the formation of a

image with the device.

  Fig. 2 is a section taken substantially along

line 2-2 of fig. 1.

  Fig. 3 is a plan view of an embodiment

  tion of the device illustrated in the previous figures.

  Figs. 3A, 3B and 3C are respectively views of

  bottom, side and top of the power transmission body

  radiation radiation illustrated in fig. 1 and 2.

  Fig. 4 is a partial top view showing the image forming mask used to form an image on a surface or area of a microfiche card placed with respect to the output facet of the energy transmission body of

radiation of the device.

  Fig. 5 is a partial section of part of the mas-

  than image formation in contact with part of the

microfiche card.

  Figs. 6A and 6B are geometric constructions illustrating the formation of multiple images of a point source and a double source by parallel reflection planes. Fig. 7 is a geometric construction illustrating the displacement of the source images when the planes of the

fig. 6 divergent.

  Fig. 8 is a perspective view of a column

  forming a radiation source illuminating a guide element

  divergent age, this figure showing the process of analyzing the

ray tracing.

  Fig. 9 is a geometric construction illustrating the location of the reflector for lighting the prism.

  The design of an exemplary embodiment according to the

  vention must provide suitable collimation means to reduce the distortion and the loss of resolution resulting from the inevitable distance between the strip of film forming a mask.

and microfiche film.

  Fig. 5 is a section of a part of the film strip 44 forming a mask, in contact with a part of a microfiche film 40. A protective layer 50 protects a dispersion layer 52 of the microfiche film 40 from any physical abrasion and atmospheric effect. The illumination of an element 53 of the image in the emulsion layer 54 of the mask band by parallel rays 56-56 of offset axes means that

  The image of the element is moved relative to the form element.

  mant the image, so that offset axis lighting gives rise

  distortion of the whole image.

  The illumination of a second element 58, by a beam of divergent rays 60-60-60, gives rise to penumbra effects on the dispersion layer 52, as shown, and causes a loss of resolution. The lighting system must therefore provide an appropriate collimation of the radiation energy as well as a remarkable uniformity of intensity over the surface on which the image is to be formed. The degree of collimation and the uniformity of intensity are regulated by the requirements of distortion, resolution and uniformity

lighting imposed on the system.

  Uniformity of lighting through an exit window

  tie can be provided by means well known in the art

  nique and it is easily obtained using srructu-

  light guiding res which cause the incoming radiation to undergo multiple internal reflections before it leaves the structure. Figs. 6A and 6E show the nature of this process

of mixtures.

  In fig. 6A, a source S is placed at a distance d from two plane and parallel reflecting walls 3-y and 3'-y 'separated by a distance 2d. An observer at point A,

  at a distance of 2d from S, will see a virtual source S1 reflected

  sucks in the 3-y plane, in addition to the source S. From the point

  B, at a distance of 6d from S, the sources S, S1 and S2 are visible

  sibles. The conjugate sources S1 and S2 are also visible by reflection in the 3-3 'plane. Thus, the longer the guide structure, the more sources will be visible from the exit plane yy '. Because the walls 3-y and 3'-y 'are perfectly reflective and parallel, it follows that all the radiation captured by the entry plane 3-y' must illuminate the exit plane yy '. The incident radiation at

  point B is thus that of the five sources and can be cal-

  abused from the latter by an appropriate summation.

  An observer at point B thus sees a network of seven sources subtending an angle 20 which is identical to the angle of capture subtended by the entry window 3 - 3 ′, seen from the source S. If the source S is replaced by two sources 0 and X of substantially different brightness, as shown in fig. 6B, then the lighting of the entry plane 3-3 ′ will present a significant non-uniformity on its surface. From point B, however, the observer therefore sees seven pairs of sources of different brightness at a significant distance giving rise to a significant average of the light intensity on the plane yy '. This is the origin of the process of mixing by multiple reflections in guide structures with walls.

  parallel. It should be noted, however, that the ray-

  The output at yy 'is not collimated, since it is dis-

  perse at an angle almost equal to the angle taken at the level

from the entry window 3-3 '.

  The present invention is partly based on what

  one can consider as a characteristic not re-

  known hitherto from multiple reflections in systems

  Reflective and divergent optical guide tems, namely the ability of such systems to collimate light from an extended source. If the reflecting walls are arranged to diverge as shown in fig. 7, the virtual sources of FIG. 6 are then placed over a length of arc of finite radius adjusted by the angle of divergence and the distance from the source to the input plane, as indicated by the geometric construction shown, and this may result in a marked reduction in the angle subtended by the

  equivalent source network seen from the exit plane Z -

  Z ', which results in a significant improvement in collimation. A concomitant loss of light intensity at Z - Z 'must also occur. In three dimensions, it is necessary to provide at least a second pair of reflecting and divergent planes to complete the structure. A complete analysis of the oblique rays is then necessary, because reflections of internal oblique rays imply,

  in general, all four walls. A computer calculation

  of angles and distances to obtain a

  optimal collimation and very good uniformity of light

  rage is therefore used to design an exemplary embodiment.

  The embodiment of the waveguide given to ti-

  example (see fig. 8) is designed to be used with a gas discharge flash source having a light column 62 20 mm long and 4 mm in diameter, with a minimum spacing from the entrance window 64 equal to 6 mm measured from the center of the column. Throughout the calculation, the spacing is set to this minimum value to optimize the efficiency of light gathering at the entry window 64 of the guide structure 12. The exit window 12b of the guide 12 is set equal to the standard format of 10 mm by 12.5 mm microfiche images thus giving the

  guides a configuration in a rectangular pyramid trunk.

  Due to major heating and

  cost and manufacturing tolerance, the guide 12 is preferably and advantageously manufactured in the form of an elongated prism in transparent quartz in which the reflections of the walls take the form of reflections

  total internal. The previous analysis remains valid; however

  the curvature of refraction of the light rays at the

  calves from entry and exit windows should be taken into

  account in the computer program.

  After establishing the spacing, the geometry of the exit window as well as the geometry of the source, the only remaining variable parameters are the length of the guide and the angles of divergence of the facets of the walls. For a given geometry, the source <represented in an approximate manner by a light plane 66 intersecting the source 62 in its middle,)

  the input window 12a and the output window 12b are decom-

  1.0 laid in mesh elements. By an appropriate summons

  performed on all source and window items

  We calculate the number, the angle and the intensity of each element of the beam of rays or "lobe" coming out at

  each element of mesh of output windows.

  Fig. 8 shows a plot for a pair of spokes 74-

  74 from Source Elements 68-68, crossing the elements

  elements of mesh 70-70 of the entry windows and leaving by an element of exit mesh 70. For each element of exit meshes of this type, the elements of the beam of rays are subjected to an average in intensity and angle for provide

  light intensity ("emitting"), directing components

  average tion Ox etO of the ray beam, as well as the com-

  posing standard deviation angles O-x and O-Y of light rays coming from the middle direction and constituting a

  measure of divergence. The definitions of the previous parameters

  teeth as well as a general description of the optimization process

  can be found in the Applicant's publication

  "Tapered Light Guide Condenser: A Design Approach", Account-

  Render of the "Society of Photo-Optical Instrumentation Engineer $"

  Flight. 176 pages 161-167, April 17, 1979.

  A suitable prism that can be used in the device

* reil of the type described in US Patent Ne 3,966,317, derived from the preceding analysis, is shown in FIGS. 3A, 3B and 3C, and has a length of around 24 mm, a window or facet

  rectangular outlet 12b having lateral edges of

  about 12 mm and 12.5 mm in length, and a window or facet

  substantially square 12A inlet of about 9 mm side. The output face l2b is slightly beveled to avoid

  damaging the microfiche film 40. The angle of inclination of the narrower facets 12d-12d of the two pairs of lateral facets relative to the longitudinal axis of the guide or body for transmitting radiation energy 12 is approximate-

  10 30 '55 ", then believe the corresponding angle of the fac-

  these larger 12c-12c of the two pairs is approximately

28 '39 ".

  The values calculated for such a prism show a variation in emitter less than + 9%, a maximum deviation of the axis of the luminance lobe of 5 with an average of 3.5, a

  extent of the degree of fineness of "collimation" of the light lobe

  nance within an 8% range for both

  posing ux and Y, and an irregularity or "astigmatism" of the fineness of the profile of the luminance lobe measured by the

  disparity between the components g-x and o y less than 15%.

  Measured experimentally, the variation in luminance at the level of the output facet 12b is less than 6% over the entire format of the field, while the degree of collimation produces an image resolution suitable for solving 120

pairs of lines per millimeter.

  A very general reasoning can show that a means of guidance which diverges deeply in the two dimensions

  gives very little mixing. What is applied in this

  The invention is the recognition of the properties of collima-

  tion of a divergent system and optimization of the mixing and collimation properties in a moderately structured

  divergent designed appropriately.

  We get another improvement of the whole

  light output by interrupting and returning to facet-

  input te 12a (fig. 8) a significant fraction of the light

  from source 62, i.e. outside the year-

  grip of the entry facet. This is achieved by-

  the source S by a pair of spherical reflectors

  strips as shown schematically in FIG. 9.

  A hemispherical rear reflector 16a is placed with its center half-way between the source S, represented here ideally by a point source for the clarity of the presentation, and a point P very close to the entry facet 12a of the prism 12 A rear ray u reflecting on the rear reflector 16a is thus reflected towards the point P to strike the entry facet 12a. Strictly speaking, the re-

  rear flector should be an ellipsoid cup present

  both its foci at point S and P; however, the separation between points S and P is small enough with respect to the radius of the rear reflector 16a for image formation

  appropriate is obtained using a hemisphere. An eco

  considerable nomie is thus obtained by avoiding the use of an aspherical element. Front rays are returned by a hemispherical cup 16b having an opening and centered in S. A front ray v coming from the source S is brought back to S and provides an image in P in the same way as the rear ray u. Although the virtual source P is not optimally placed for collimation, experience has shown that the arrangement shown schematically at the

  fig. 9, and to scale in fig. 1 and 2, produces an increase

  significant illumination with glue properties

  acceptable limitation. A prior art lighting system, namely the Norelco 13120 C lamp (CXL / CXR) i

  uses an ellipsoid rear reflective wall for

  locate the rays reflected on a limit cone angle towards the front through the second focal point so as to allow

  free passage through a relatively distant opening

  swam in the anterior hemispherical reflecting wall.

  In the present invention, use has been made of the properties of

  internal bending of the energy transmission member to bring "the opening '", in this case the entry facet 12a eig. 8), close to the radiation energy source so as to avoid the need for a rear reflector

relatively expensive aspheric.

  The exemplary embodiment of the image forming device 13, shown in FIGS. 1 and 2 and indicated in its

  together by reference 10, includes a transmission element

  electromagnetic energy or prism 12, a source. of electromagnetic energy 14 and means of interception and reflection of energy indicated generally in 16. A

  housing 18 comprising a base part 20 and a su- part

  or cover 22 is provided to hold the parts

  of the function-forming image-forming device

  relative to each other.

  In the exemplary embodiment of the training device

  tion of images, the organ for transmitting radiation of

  gie 12 preferably includes a prismatic trunk element

  cone or pyramid trunk formed of a transmitting material

  both the radiation energy, and which is substantially trans-

  parent and resistant. While prism 12 can be manufactured

  qué in various materials, a particularly desirable material is a quartz of high purity, available in the

  trade under the designation "Amersil, Grade T-19, Suprasil".

  In the embodiment of the training device

  tion of images 10 shown in fig. 1 to 3, the trans-

  radiation energy mission 12 is carried on the top part or cover 22 of the housing 18 through an opening 22a formed in the latter. The exit facet 12b of the orane 12 is substantially level with the upper surface of the top part or cover 22 while the entry facet 12a of the member 12 is kept apart from the source of energy 14. The energy source 14 shown is analogous to the energy source described in US Patent No. 3,966,317 and includes a Xenon flash tube such as tube No FX - 255 -.75 from the Company EG and G Companyi Le

  Xenon flash tube has a maximum electrical input

  mum of about 50 joules. The tube is preferably a type of broadband tube having a range from ultraviolet

  infrared with wavelengths between

  around 2000 and around 10,000 Angstroms.

  The ends of the flash tube 14 are held by spring clips 24-24 fixed on the base part 20 of the case 18. A trigger or excitation coil 26, connected to a power source not shown, is placed

  on the external surface of the flash tube 14 to excite this tube.

  Means of interception and reflection of energy

  radiation 16 of the imaging device 10

  take hemispherical reflectors 16a and 16b pre-

  each feeling a different center of curvature as represented

  tee respectively by arrows 30 and 32. The reflectors 16a and 16b can be formed from any suitable material for reflecting the radiation energy, for example

  mirror glass, metal or plastic.

  In the embodiment of the illustrated invention,

  the reflectors 16a and 16b are advantageously formed by

  shooting from a plastic material such as Plexiglas, the front surface of which has been coated with a layer of aluminum. The reflector 16a is carried by the base part 20 of the housing

  18 and presents its center of curvature located at a light point

  rement below the center of the input facet 12a of the member 12 at the top of the tube 14. The reflector 16b is carried by the upper part or cover 22 of the shoemaker 18 and its center. curvature is located directly below the center of curvature of the reflector 16a on the longitudinal axis of the flash tube 14. The radius of each of the reflectors 16a and 16b is long enough to prevent dispersion of the

  aluminum reflective layer on the surface of the reflective

  due to the high intensity energy emitted by the tu-

  be flash 14. In the embodiment of the device

  illustrated, the radius of each reflector is approximately 20.6 mm.

  The center of curvature of each of the reflectors 16a and 16b is

  offset in the manner described to allow the re-

  flexed emitted by the tube 14 to pass around this tube towards the entry facet of the organ 12. The extent of the displacement

  in the illustrated device is about 3 mm. The edges 16c-

  16c reflectors 16a and 16b are placed one against the other,

  and the reflectors thus form a chamber 34 for the fa-

  this inlet 12a of the element 12 and of the flash tube 14. To this end, the reflector 16b has an opening 36 at its pole to receive the member 12, the reflector 16b having opposite openings 38-38 at the ends of its axis of

  declination to receive the tube 14.

  As noted above, the I device

249 1,637

  imaging 10 according to the present invention is particularly

  specially designed to be used in conjunction with an appliance

  reil such as that described in US Pat. No. 3,966,317. As illustrated in the drawing, a micro-element preferably in the form of a microfiche card 40, of standardized size 10 X 15 cm and capable of receiving up to 96

  micro-images in a reduction ratio of 24, is pre-

  rence used for imaging with the device.

  Card 40 includes a synthetic plastic substrate

  substantially transparent and flexible tick such as Mylar

  (polyethylene glycol terephthalate), for example,

  as a thickness between approximately 0.075 or 0.375 mm and approximately 0.375 mm. The substrate is coated, preferably

  by vacuum deposition, a thin continuous layer of a material

  image dispersible by energy from

  radiation such as bismuth or a pre-bismuth alloy

  feeling a thickness of between 1000 and about 2000 A. The layer of imaging material dispersible by radiation energy is a heat absorbing layer and, in the case of bismuth, it has a melting point of about 2710C. An upper protective layer is advantageously applied to the layer dispersible by the radiation energy. The upper protective layer preferably comprises a plastic film

  synthetic, substantially transparent, in Saran, polyurethane-

  ne or similar material, and it has a thickness of

about 1 micron.

  Using the image forming device 10 to form an image on a surface or area 40a of the card

  40, a film strip forming a mask 44, carrying a micro-

  image, such as the strip described in the previously mentioned US patent, is placed between the exit facet 12b of

  the member 12 and the surface 40a of the card 40, see fig. 4.

  The surface 40a of the card 40 is brought into contact with the strip of film forming a mask 44, and it is held in

  this position, during image formation, by the in-

  end of a mobile diver 46. The Xenon flash tube

  14 is then aroused by a weak pulse of energy.

  electromagnetic or radiation. The weak pulse of energy produced by the tube 14 is between approximately

  microseconds and about 1 millisecond and lasts, preferably

  rence, approximately 40 microseconds. Due to the efficiency - of combined high energy gathering of organ 12 and

  reflectors 16a and 16b, the lightning pulse can be increased

  due approximately 40% to 50% shorter than would otherwise be possible. At the same time, the excitation of the tube 14

  may take place at a lower operating voltage.

  These factors combine to extend appreciably the useful life of the tube 14 making it possible to obtain up to 000 flashes or more from a single Xenon tube of the

type described above.

  The short energy pulse emitted by the tube 14 is collected and reflected at the entry facet

  12a of organ 12. At the same time as the energy crosses the or-

  gane 12, it is collimated as best as possible and directed to

  the exit facet 12b from which it leaves in a form allows

  both maximum use and optimal distribution of energy at the level of the film. More specifically,

  with regard to this last point, the collimated energy comes out

  as long as the exit facet 12b of the member 12 is shaped in such a way that, if a grid or a network were placed at the level of the exit facet 12b, the energy would exit from this grid in the form of small inverted cones each of which

  vertical or longitudinal axis would be substantially perpendicular to

  re on the surface of the exit facet.

  As the energy leaves the exit facet 12b, it crosses the transparent surface of the mask 44, on which a micro-image is formed, to reach the layer of material dispersible by the radiation energy and which is on the surface or zone 40a of the card 40 where the energy is absorbed. The absorption of energy by the material dispersible by radiation energy at these surfaces causes the material dispersible by energy to become soft or to melt so that the solid layer continues to disperse material by sand. radiation energy at the surfaces of the zone 40 where the energy is absorbed is broken up and dispersed in small globules widely spaced so as to make these

  substantially transparent surfaces. The dispersion of the ma-

  The radiation energy dispersible material at the energy absorption surfaces is mainly caused by the surface tension of the heated material to form such small, widely spaced globules. Again, due to the very large combined energy gathering possibilities of the member 12 and the reflectors 16a and 16b, as well as the ability of the member 12 to collimate and direct

  energy towards the plane of the microfiche card 40, it

  due to a dispersion of the material dispersible by the radiation energy in the surfaces where the absorption of this energy takes place, and, consequently, the resolution of images occurs in a substantially uniform manner over the entire surface or area a. As indicated previously, after naked the globules were thus formed by the short pulse of energy coming

  of tube 14, these cool almost instantly

  and remain globular to provide a sharp, high-resolution microimage on the map corresponding to the

  micro-image of the film strip forming a mask 44.

  The invention is not limited to the embodiments presented and described in detail since various modifications

  can be made without departing from its scope.

  Thus, although we have indicated by way of example a rectangular output format and thus a trunk shape of

  rectangular pyramid, the guide means may include

  dre additional walls so that the fe-

  Our output conforms to the desired output format. The present invention can also be applied to geometries

  more generalized. So a hexagonal output format requires

  ter a hexagonal shape with six walls and, more generally at the limit, a circular or elliptical format would require

  a conical or elliptical-conical structure without various facets

  gentes with angles generating vertices calculated from ma-

  suitable for optimal collimation.

  R E V E N D 1 i A T I 0 E1 S I - Optical projection system comprising a projection mask and a light source making it possible to illuminate this mask and to form a shadow image of it on a

  imaging surface away from masks character-

  rised by means of collimating and guiding the ivy placed along an axis going from said source towards the mask, the collimating and guiding means comprising an inlet window (12a) and an outlet window (2ib)

  as well as an elongated structure with internal reflection (12)

  created between said windows and around said axis to guide

  the light going from the source rve-: the mask by reflections-

  multiple xions inside the structure, this structure

  ture being formed to diverge continuously in all

  are the directions perpendicular to this axis with a dis-

  tance increasing with respect to the source, the divergence of this structure being such that it directs, collimates and mixes the light passing through the collimating and guiding means so as to provide a maximum intensity of

  light collimated appropriately and evenly distributed

  substantially uniform at the level of said mask.

  2 - optical system according to claim 1, charac-

  terized by light reflecting means (16) placed

  around the source so as to form a bright image

  from this source at a selected imaging point located substantially on said axis and near the entrance window, said reflection means comprising a first reflector (16a) having the shape of a portion of surface of a first sphere and a second

  reflector (16b) having the form of a sur-

  face of a second sphere, said second reflector presents

  as an access opening placed substantially in its central zone, the first reflector being arranged with the center of said first sphere at a first point substantially on said axis and at. about halfway between said source

  and the imaging point and presenting the central area

  bale of the first reflector arranged substantially on said axis at a second point, this second point being placed

  on a line located in the extension of the said axis and runs

  tending from the collimating and guiding means through said source towards the second point, said

  second reflector being placed with the center of said segment

  cone sphere substantially at the intersection of said axis and said source and having the center of said access opening placed substantially on the axis at a third point, this third point being disposed on a line situated in the extension of said axis and extending from said source through the entry window towards the third point, the reflectors forming at least part of a cavity

  reflecting around said source, the means of colli-

  mation and guide being arranged with at least the window

  inlet placed inside said cavity, a first

  re part of the light coming from said source is reflected

  falling on said first reflector to focus at the image forming point, a second part of the light coming from said source reflecting on the second reflector to return to this source and from there

  to the first reflector to reach said point of formation

  tion of images, said input window of the colli-

  mation and guidance intercepting a sensitive part of the light emitted by said source, this fraction passing through the access opening and the exit window so as to

illuminate said mask.

  3 - Lighting apparatus comprising a light source

  neuse, light mixing and guiding means and light reflecting means, characterized in that said mixing and guiding means are arranged to guide the light coming from said source along an axis emanating from this source, said mixing means and

  guide comprising an entry window (12a) and a window

  exit window (12b) as well as an elongated structure with internal reflection (12) disposed between said windows and generally around the axis so as to mix

  and guide the light from the source in a general way

  249 1f? 7 line along said axis by multiple internal reflections to produce exit lighting which is of intensity

  substantially uniform when it leaves said exit window

  tie-, in that said light reflecting means are arranged around said source so as to form an image of the light coming from this source at an image point

  chosen being located substantially on said axis and close to

  tee of the entrance window, said light reflecting means comprising a first reflector (16a) having the shape of a surface part of a first sphere and a second reflector (16b) having the shape of a part

  of the surface of a second sphere, in that said second sphere

  flector has an access opening (36) placed sensi-

  in its central region, said first reflector being placed with the center of said first sphere at a first point substantially on said axis and substantially

  halfway between said source and said image point and pre-

  feeling the central region of the first reflector disposed substantially on said axis at a second point, this

  -second point being placed on a line located in the pro-

  lengthwise along said axis and extending from said guide and mixing means through said source towards said second point, said second reflector being disposed with the center of the second sphere substantially at the intersection of said axis and of source and having the center of said access opening placed substantially on said axis at a third point, this third point being placed on a line situated in the extension

  of said axis and extending from said source through the

  entry vertex towards said third point, in that

  that said reflectors form at least one part of a

  reflecting light around said source, said mixing and guiding means being arranged with at least said entry window placed inside said cavity, a first part of the light coming from said source reflecting on the first reflector for focus at said image point, a second part of the light

  from the source reflecting on the second re-

  flector to return to this source and from there to the

  said first reflector to reach said image point, in that the entry window of the leveling and guiding means intercepts a substantial fraction of the light emitted by the source, this fraction passing through said opening

  access and said exit window to provide an information

  maximum light density distributed appreciably

  uniform from the exit window.

  4 - Lighting apparatus according to claim 5,

  characterized in that the reflecting structure is con-

  formed to diverge in all perpendicular directions

  the said axes with an increasing distance from the

  source, the divergence of said structure being such that it

  produces a sensibly distributed light output

  clearly uniform and significantly collimated at the level of

said exit window.

  - Device according to one of claims I or 3,

  characterized in that the reflecting structure comprises four substantially planar reflecting side walls, these walls being arranged to form the lateral elements of an elongated trunk of straight pyramidal structure with rectangular base and vertex the rectangle defined by said walls at the level of the base constituting said exit window, and the rectangle defined by the walls at the level of the

  vertex constituting said entry window, the light

  trant through the entry window following inter-

  multiple on said walls in the direction of the window

be out.

  6 - Device according to one of claims I or 3,

  characterized in that said guide means feels

  read as a single full transparent body,

  said multiple reflections being inter-reflections

nes on the surface of said body.

  7 - Device according to one of claims I or 3, characterized in that the guide means have the

  shape of a single solid transparent body in the shape of a

  - 24 me which includes four facets with internal reflection and substantially planar arranged to form the lateral elements of a straight pyramid trunk with basic facets

  and with a rectangular top, the top facet is

  killing the entrance window and the basic facet constituting the exit window, the light entering the entrance window according to multiple internal reflections on said lateral facets in the direction of the window

Release.