Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D11/00—Producing optical elements, e.g. lenses or prisms
  • B29D11/00009—Production of simple or compound lenses
  • B29D11/00269—Fresnel lenses
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/18—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical projection, e.g. combination of mirror and condenser and objective
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B3/00—Simple or compound lenses
  • G02B3/02—Simple or compound lenses with non-spherical faces
  • G02B3/08—Simple or compound lenses with non-spherical faces with discontinuous faces, e.g. Fresnel lens
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B3/00—Simple or compound lenses
  • G02B3/10—Bifocal lenses; Multifocal lenses
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/18—Diffraction gratings
  • G02B5/1866—Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/54—Accessories
  • G03B21/56—Projection screens
  • G03B21/60—Projection screens characterised by the nature of the surface
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/54—Accessories
  • G03B21/56—Projection screens
  • G03B21/60—Projection screens characterised by the nature of the surface
  • G03B21/62—Translucent screens

Definitions

• the invention applies to the field of Fresnel lenses intended for use in a rear projection system. It also applies to projection screens, an overhead projector and corresponding systems.
• a rear projection screen comprises two main components: a Fresnel lens that focuses or collimates the light and a lens array which distributes light towards the audience.
• the projector is arranged along the axis of the screen.
• the limit value for the numerical aperture of a Fresnel lens is approximately 0.6.
• the main reasons for this limitation are the losses and the shape of the reliefs of the Fresnel lens at high angles of incidence.
• a system of deflection mirrors (Figure 1) to fold the beam between the projection device and the screen of backprojection.
• the thickness or depth of such a device can be reduced to a third of the diagonal of the screen. For example, in 16/9 format, we can obtain a thickness of 17 inches for a screen of 50 inches diagonal.
• a projection is provided, for example off-axis (off-axis) on the rear face of the screen of backprojection. In this way, it is possible to reduce the thickness of the device to only one fifth of the diagonal of the screen.
• FIGS. 2a and 2b respectively represent overhead projection devices on the axis (on-axis) and off-axis (off-axis).
• One of the main problems to be solved in an off-axis configuration, or in a configuration where the image to be projected on the screen is off-center relative to the axis of the objective of the projection device, is to obtain that all the light projected on the screen is retransmitted to the spectators and that the emission is as uniform as possible. In particular, it this is to reduce the losses of the Fresnel lens which tend to increase when the angle of incidence of the illuminating light on the Fresnel lens increases.
• Patent application JP 59-000101 describes a Fresnel lens in which the faces of the prisms constituting the Fresnel lens form sufficiently large angles to allow easy release of the lens during manufacture by molding. More specifically, this document provides that one of the faces of each structure of the lens is parallel to the incident light rays. However, the operation of such a lens is limited when it is illuminated at high angles of incidence and these angles vary over a wide range of angles.
• the invention therefore relates to a Fresnel lens whose structure is simple and easy to implement industrially, and which makes it possible to operate under significant incidences.
• the invention therefore relates to a Fresnel lens comprising:
• each refractive structure is delimited by:
• the second face has several zones of refractive structures, at least two for example, distributed between the center of the concentric refractive structures and the periphery of the Fresnel lens:
• the lens comprises a third zone located between the second zone and the periphery of the lens.
• the first angle ( ⁇ ) of each first surface is such that the refractive structures refract the light in a direction making an angle ( ⁇ out) not zero and equal to the maximum value ( ⁇ max) relative to the determined direction,
• each first surface forms with each second neighboring surface an etching angle ( ⁇ ), this angle having a value determined in the second and in the third zone, and having a value greater than this value determined in the first zone.
• the invention makes it possible to produce Fresnel lenses which offer the best compromise between the highest level of optical performance and the lowest level of manufacturing costs thanks to a high etching angle of its refractive structures.
• the second zone and, where appropriate, the third zone each comprise at least one refracting structure.
• the first face of the Fresnel lens is preferably planar.
• This first face is also preferably covered with an anti-reflective layer optimized for a strong angle of incidence, in particular greater than or equal to 42 °.
• the refractive structures are preferably circular or nearly circular.
• the illumination radiation of the lens is divergent and comes from a point (in the absence of optical aberrations) or a quasi-point area (in the presence of optical aberrations) located on the axis of the lens or substantially on this axis.
• said determined value of the etching angle ( ⁇ ) is less than 70 °.
• the etching angle ( ⁇ ) is substantially between 30 and 50 °. According to an alternative embodiment, it is equal to 60 ° or between 55 ° and 65 °.
• the Fresnel lens is characterized in that the number of aperture (also called "F-number" in English) is at most double the ratio of the focal distance associated with a point of the lens over the distance from this point to the axis of the lens is less than or equal to 0.55.
• the invention is applicable to a rear projection screen of images comprising an input face and an output face to be directed towards viewers.
• a Fresnel lens as defined above is arranged along the entry face of the screen with the face of the lens carrying the diffraction structures facing the exit face.
• the invention also relates to a system for projecting images comprising:
• an imaging beam return mirror adapted to return said imaging beam to said Fresnel lens
• the Fresnel lens comprises:
• Each refractive structure is delimited by a first surface
• a first beam called the direct beam, coming from the imaging beam and which has not been reflected by the first face, the direct beam forming a first incident beam by transmission of the direct beam inside the Fresnel lens;
• a second beam called the parasitic beam, coming from the imaging beam and which has been reflected by the first face then by the deflecting mirror, the parasitic beam forming a second incident beam by transmission of the parasitic beam inside the Fresnel lens;
• the second incident beam makes an angle of entry ( ⁇ int ') different from zero degrees with the normal to said plane (P),
• the second angle ( ⁇ ) of the second face of each structure of the first set is greater than the entry angle ( ⁇ int ') of the second incident ray minus 10 degrees.
• the second angle ( ⁇ ) of the second face of each structure of the first set is less than an upper bound equal to the entry angle ( ⁇ int ') of the second incident ray plus 2 degrees.
• the invention allows the joint use of a folding mirror and a Fresnel lens without harming the quality of the projected image.
• the first incident beams and most of the second incident beams do not directly strike the second surface of the diopter but the first surface.
• the first incident beam is refracted in a preferred direction towards a potential spectator.
• the second incident beam corresponding to a stray beam striking the first surface with a different angle of incidence of the incident first beam is refracted in another direction and the viewer does not see generally.
• the quality of the image is thus improved by eliminating or greatly reducing the ghost images originating in particular from parasitic ray obtained by reflection of a useful imaging beam on the first face of the lens then on the folding mirror, while allowing easy manufacturing of the Fresnel lens.
• Tooling in English is increased) of the lens while eliminating stray rays.
• the second angle ( ⁇ ) of the second face of each structure of the first set is greater than five degrees.
• the second angle ( ⁇ ) of the second face of each structure of the first set is greater than ten degrees.
• the second angle ( ⁇ ) of the second face of each structure of the first set is equal to the entry angle ( ⁇ int ') of the second incident ray.
• the Fresnel lens comprises at least two parts, including:
• the second part is divided into two parts not affected by the parasitic rays obtained by reflection of a ray incident on the first face of the lens and on the folding mirror:
• the second part is connected and only comprises a peripheral zone.
• the lens includes then, for example, an area close to the axis of the lens, second angle ( ⁇ ) of the second face of each structure of a second set of structures is less than or equal to a predetermined value or the entry angle ( ⁇ int) of a second incident ray as it would have generated if an imaging beam from the source would have been reflected by a downward extension of the Fresnel lens and an extension, also towards the bottom, of the folding mirror.
• the second face comprises at least two zones of refractive structures distributed between the center of the concentric refractive structures and the periphery of the Fresnel lens: - a first zone close to the center in which the first angle ( ⁇ ) of each first surface is such that the refractive structures refract the first incident beam in a direction making an angle ( ⁇ out) zero with respect to a direction
• the system further comprises a lenticular screen itself comprising transparent filtering means for the first refracted incident rays by the Fresnel lens and filter the second incident rays refracted by the Fresnel lens, the filtering means being juxtaposed to the Fresnel lens.
• the system comprises an image projection screen comprising an entry face and an exit face to be directed towards spectators, the screen comprising the Fresnel lens, this Fresnel lens being arranged along the entry face of the screen with the face of the lens carrying the refractive structures oriented towards the exit face of the screen.
• the number of aperture (referred to as "F-number" in English) is at most double the ratio of the focal distance associated with a point of the lens on the distance of this point to the axis of said Fresnel lens is less than or equal to 0.55.
• the invention is particularly well suited to spotlights of shallow depth.
• the invention is also applicable to a rear projection apparatus comprising such a rear projection screen or such a projection system as well as a projection apparatus emitting a light beam in the direction of the input face.
• the projection apparatus is preferably arranged along the axis of the Fresnel lens and makes it possible to project an image on only part of the Fresnel lens located on one side of its axis.
• the pupil of the objective of the projection device is located substantially on the axis of the Fresnel lens and the optical axis of this objective is oriented towards a used part of the Fresnel lens located one side of the axis of the Fresnel lens.
• FIG. 3a represents a Fresnel lens LF comprising refractive structures of concentric prismatic shapes. As can be seen in this figure, only part of the circular plane of the lens is used, typically less than half.
• this LF lens comprises a first flat face arranged in a plane and opposite to this face, a second face parallel to the first face and comprising circular and concentric refractive structures. The first face is illuminated by a source PR located on the optical axis XX 'of the lens but of which only part of the lateral field of this source illuminates the lens.
• this source PR is situated on the axis XX 'of the lens LF and illuminates only part of this lens located above the axis XX'. It illuminates the lens at an oblique angle to the lens.
• the lower light ray 30 of the illumination beam has a relatively small angle of incidence ⁇ ext on the Fresnel lens while the upper ray 31 of the beam has a higher angle of incidence ⁇ ext.
• each element of the refractive structure is delimited by a surface b (or face b) constituting the refractive diopter of this structure and a surface c (or face c) which is not used optically in the reference to figures 4a and 4b.
• the Fresnel lens is delimited by a plane face a serving as an input face parallel to a reference plane P or plane of incidence, and by a face located to the right of the lens and carrying structures refractive each delimited by faces b and c.
• the faces such as c form an angle ⁇ of approximately 3 ° with the normal to the plane of incidence P.
• Such a structure has narrow, large prismatic refractive elements height h, ⁇ low angle and therefore difficult to make in large quantities.
• the angle ⁇ values such that for each refractive structure, the side c is parallel to the light rays that the refractive structure receives.
• the height of the refractive structures is reduced to a height h ′ and the angle ⁇ is significantly greater; the prismatic elements are then easier to produce.
• the angle ⁇ between the faces b and c of the prismatic refraction structures has a value greater than or equal to a limit value ⁇ lim of manufacture (FIG. 5a), below which it would become particularly difficult to economically manufacture the prismatic elements.
• This manufacturing limit value ⁇ lim depends in particular on the manufacturing processes used and the size of the lens.
• FIG. 5d represents a Fresnel lens incorporating the three structures of FIGS. 5a to 5c.
• a structure of the type shown in Figure 5a located near the optical center of the Fresnel lens where the incident angle of the light from the source PR is smallest. Then in an intermediate zone Z2, a structure such as that of FIG. 5b is provided. And finally in a distal area of the optical center of the lens, wherein the angle of incidence of the light PR is highest, there is provided a structure of the type shown in FIG 5c.
• angles ⁇ , ⁇ , and ⁇ according to the incidence angle of light ⁇ int on the second face of the Fresnel lens are the following:
• the output beam is parallel to the axis XX '.
• the angle ⁇ is less than a threshold value ⁇ lim.
• the output beam is slightly divergent with respect to the direction of the axis XX 'with an angle of divergence ⁇ out which is less than a maximum value ⁇ max which is fixed in advance. And the angle ⁇ is equal to the limit value ⁇ lim.
• On the abscissa axis 600), we have plotted the values of the angles incidence ⁇ ext. Ordinate (axes respectively 601, 611 and 621) was carried respectively the values of the angles ⁇ , ⁇ , ⁇ .
• zone Z2 The zone where ⁇ ext is between 28 ° and 35 ° corresponds to zone Z2.
• zone Z3 The zone where ⁇ ext is between 35 ° and 63 ° corresponds to zone Z3.
• FIG. 7 provides curves illustrating the efficiency of transmission of the p and s polarizations by the Fresnel lens according to the invention.
• the two upper curves 73 and 75 represent the transmission of the polarization p.
• the lower two curves 72 and 74 represent the transmission of s-polarized.
• the curve in solid line 72 relates to a standard lens and the curve 74 surrounded by circles relates to the lens according to the invention. We see that up to 30 ° the efficiencies are the same. Between 30 ° and 45 °, the efficiency of the lens according to the invention is better. Beyond 45 ° the efficiencies are the same.
• the Fresnel lens according to the invention operates under high incidence illumination and its manufacture does not pose any delicate problem because of the angle ⁇ which is relatively large (of the order of 60 °).
• the Fresnel lens is more particularly applicable to a rear projection screen.
• Figure 8 shows an overhead projector.
• the Fresnel lens LF according to the invention arranged parallel to a plane P, is attached to the rear projection screen EC with its face carrying the refractive structures arranged towards the screen.
• the flat face of the LF lens is illuminated by a PR projection device. This is located along the optical axis XX 'of the lens and below it, of which only the useful part has been shown, that is to say the part illuminated by the projection apparatus PR which therefore illuminates the lens under relatively large incidence.
• the optical axis of the objective is collinear with the axis XX 'of the lens.
• the pupil of the objective is located on the axis XX 'of the Fresnel lens.
• the axis of the objective is not collinear with the axis XX 'of the lens.
• the objective can be oriented so that its axis passes through the center of the part used of the Fresnel lens, that is to say through the center of the screen.
• the lens is of course located at the level of the image provided by the objective and along the plane of this image. This configuration is, for example, illustrated by Figure 8.
• FIG. 9 illustrates a rear projection apparatus 5 according to a variant of the invention particularly well suited to the suppression of parasitic images which may be visible when parasitic rays are generated by reflection on the plane face of the Fresnel lens 54 and then on a folding mirror 53.
• This variant of the invention is also well suited to the production of particularly compact rear projection devices and offering good quality images as well as to corresponding Fresnel lenses which are easy to produce.
• backprojection unit 5 comprises imaging means 50 comprising a lens 51 which emits an imaging beam from a source CS of imaging (pupil center) to a first folding mirror 52 then a second folding mirror 53 (so as to make compact the apparatus 5) and the Fresnel lens 54.
• the display device 5 includes the Fresnel lens 54, a black matrix 58 (forming filtering means of stray rays) and a diffuser 59.
• the imaging beam has a rectangular section adapted to the projection screen and is limited in its lower part by a radius 57 and in its upper part by a radius 56 around the axis of the beam 52 offset from the lens optical axis 51.
• the angles of incidence of the imaging beam are particularly high.
• FIG. 10 specifies the propagation path of certain rays of the imaging beam.
• a direct incident ray 62 belonging to the imaging beam shown in solid lines
• a parasitic incident ray 60 belonging to a parasitic beam represented in dotted lines.
• the direct incident ray 60 comes from the source PR through the objective 51 after two successive reflections on the folding mirrors 52 and 53 respectively.
• the parasitic incident ray 60 is obtained by reflection of a direct incident ray 61 on the flat face from the Fresnel lens 54 at point N 'then on the folding mirror 53 at point N ".
• FIG. 11 represents a detail of an area of the Fresnel lens 54. According to this figure, the notations for the faces a, b and c, as well as for the angles ⁇ , ⁇ , ⁇ , ⁇ lim are the same as those presented with reference to Figure 4b.
• the face c of a diopter of this zone is parallel to the input beam of a parasitic incident ray 1120 obtained by refraction d a parasitic incident ray 112 on the flat face 110 of the Fresnel lens 54.
• the angle ⁇ is equal to the entrance angle of ⁇ 'int parasitic incident ray 1120.
• an incident ray of imagery 113 is divided into two rays by incidence on the flat face 110: an incident ray of imagery 1130 obtained by refraction of the ray 113 on the flat face 110 and a stray ray 1132 obtained by reflection on the flat face 110.
• the incident ray 113 and the parasitic ray 1132 make the same angle ⁇ extl with the normal to the flat face 110.
• the incident ray 112 makes an angle ⁇ 'extl smaller than ⁇ extl.
• the incident imaging ray 1130 makes an entry angle ⁇ int greater than ⁇ 'int ( ⁇ int and ⁇ 'int directly dependent on the angles ⁇ extl and ⁇ 'extl depending on the index of the material used for the Fresnel lens). It therefore strikes face b of the diopter considered and is refracted by face b by forming an exit radius 1131 parallel to the axis XX '(the exit angle ⁇ out is zero).
• the side c being parallel to the parasitic incident ray 1120, the latter also strikes the side b of the diopter considered and is refracted by the side b by forming an exit radius 1121 not parallel to the axis XX ' ( ⁇ 'out the exit angle is not zero).
• the ⁇ angle is between a lower limit equal to ⁇ 'int least 10 degrees and an upper limit equal to ⁇ 'int plus 2 degrees.
• a tolerance of 10 degrees is provided for the opening of the beam.
• the angle ⁇ being less than the entry angle ⁇ 'int plus 2 °, most of the stray rays are eliminated.
• the upper bound is equal to the entry angle ⁇ ′ int to eliminate all the parasitic rays obtained by reflection on the folding mirror 53.
• the angle ⁇ is greater than 5 degrees and preferably greater than 10 degrees.
• stray rays are taken into account for medium or high values of angles of incidence of stray rays.
• FIG. 15 illustrates the path of the refracted rays 1121 and 1131 in a top view of a detail of the black matrix 58 and of the diffuser
• the black matrix includes:
• the imaging beam is diffused towards a spectator by the diffuser 59 while most of the stray rays are eliminated.
• the diffuser makes it possible in particular to eliminate certain parasitic rays by diffusing them downwards or upwards so that they are not seen by a spectator situated in front of the projection apparatus.
• the means for filtering stray rays comprises, in addition to or in place of the black matrix 58, a filter comprising concentric circular black bands separated by transparent zones.
• This filter is placed between the lens 54 and the black matrix 58 or between the lens 54 and the diffuser 59 (in the absence of black matrix 58).
• a transparent area is placed opposite each diopter face b so as to allow the rays of the imaging beam refracted by the Fresnel lens to pass.
• An absorbent strip or black strip is placed between two transparent zones to eliminate parasitic rays (such as ray 118 or 1121) which could be transmitted in this zone.
• the lens 54 comprises three zones dependent on the angles ⁇ and ⁇ , similar to those described with reference to FIGS. 5a to 5d. It is noted, however, that the value of the angle ⁇ depends on the entry angle of a parasitic incident ray and not on the entry angle of a direct incident ray. Thus, the following zones are provided:
• the angle ⁇ is less than a limit value ⁇ lim.
• the output beam is slightly divergent with respect to the direction of the axis XX 'with an angle of divergence ⁇ out which is less than a predetermined maximum value ⁇ max.
• the angle ⁇ is equal to the limit value ⁇ lim.
• the values of the angles ⁇ , ⁇ , and ⁇ are therefore the following:
• the angle ⁇ is equal to the limit value ⁇ lim.
• the values of the angles ⁇ , ⁇ , and ⁇ are therefore the following:
• Figures 13 and 14 illustrate respectively a side view and a front view of the Fresnel lens 54 and folding mirror 53 according to a variant of the apparatus of backprojection 5 in a particular mode of realization of the invention.
• the zone Z1 of the Fresnel lens 54 is divided into three parts:
• the intermediate part 541 corresponds to a part of the Fresnel lens 54 capable of receiving parasitic incident rays as defined above: thus the lower part is defined by an arc of a circle to which a point G belongs.
• the point G is the point of impact on the Fresnel lens 54 of a parasitic ray 130 obtained by reflection of a direct incident ray 57 on the lower limit of the Fresnel lens 54
• the upper part of the intermediate zone 541 is defined by an arc of a circle to which points D and D "belong.
• the point D (respectively D") is the point of impact on the Fresnel lens 54 of a parasitic ray 141 obtained by reflection of a direct incident ray 140 on the Fresnel lens 54 at point B (respectively point B ”) then on an upper angle of the folding mirror 53 at point C (respectively C").
• the point D ' is located inside the part 541 below a point E' marking the upper limit of the portion 541.
• the point E is set on the same circular diopter that points D and D '. the folding mirror 53 being rectangular, point D 'is therefore not located on the limit of area 540.
• the intermediate part 541 extends beyond the possible target area of a parasitic radius.
• it can cover the entire lower part of the lens 54 and include the equivalent of the parts 542 and / or 540 and of the part 541 previously defined.
• the angle ⁇ is then equal to the angle ⁇ ′ int of a parasitic ray obtained by reflection of a beam coming from the illumination source PR on a plane to which the plane face of the Fresnel lens 54 belongs and then on a plane to which the folding mirror 53 belongs.
• FIG. 12 illustrates the angles (expressed in degrees along the axis 121) representative of a diopter as a function of the radius, r, of the circular refractive structure to which it belongs, along the axis 120 where the distances are expressed in millimeters.
• Curves 126 and 124 respectively represent the values of ⁇ and ⁇ int.
• the system being preferably off-axis, the object to be projected and the projected image are not on the axis.
• the curves are therefore defined for values of the radius r which are strictly positive.
• the invention is not limited to the embodiments described above.
• the Fresnel lens comprises at least one part where the angles ⁇ (made by the faces c of the dioptres, not optically useful with the normal to the plane of incidence) are equal to the entry angles of the stray rays obtained by reflection on the Fresnel lens and then on the last reflecting mirror.
• the angles of entry of these parasitic rays are therefore unambiguously defined as a function of the incoming imaging beam, of the positioning of the last fall-back mirror with respect to the Fresnel lens and of the shape of the last fall-back mirror.
• the folding mirror is plane, it is not necessarily parallel to the Fresnel lens.
• the Fresnel lens comprises, as a function of the maximum machining angles, ⁇ lim, diopters either a combination of the zones Z1, Z2 and Z3 as defined above, or a combination of the zones Z1 and Z2, or preferentially the zone Z1 alone when the machining limit value ("jogging" in English) allows it, the zone Z1 can be divided into several parts (each of the parts corresponding to a value of the angle ⁇ as a function of l 'angle of entry of an incident ray either direct or parasitic).

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Ophthalmology & Optometry (AREA)
• Mechanical Engineering (AREA)
• Overhead Projectors And Projection Screens (AREA)
• Projection Apparatus (AREA)
• Lenses (AREA)

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• 2003
  • 2003-05-20 FR FR0306064A patent/FR2855273A1/fr active Pending
• 2004
  • 2004-05-17 JP JP2006530441A patent/JP2007504515A/ja not_active Withdrawn
  • 2004-05-17 CN CNB2004800138887A patent/CN100426006C/zh not_active Expired - Fee Related
  • 2004-05-17 KR KR1020057021956A patent/KR20060021315A/ko not_active Application Discontinuation
  • 2004-05-17 EP EP04767828A patent/EP1625426A2/de not_active Withdrawn
  • 2004-05-17 WO PCT/FR2004/050199 patent/WO2004106992A2/fr active Application Filing
  • 2004-05-17 US US10/557,493 patent/US7342728B2/en not_active Expired - Fee Related
  • 2004-05-17 MX MXPA05012445A patent/MXPA05012445A/es active IP Right Grant

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