Polarizing splitter device and application to a system for illuminating a liquid-crystal screen

Claim 2

Polarizing splitter device, comprising: a double prism constituted by a first prism and a second prism facing faces and a polarizing splitter, said first prism having an entry face for receiving an unpolarized light beam, said polarizing splitter transmitting the polarized light in a first polarization direction and reflecting the polarized light in a second polarization direction, the second prism having a reflection face provided with a mirror receiving the light polarized in the second polarization direction, said second prism having a reflection face provided with a mirror receiving the light polarized in the second polarization direction reflected by the polarizing splitter, the first prism and the second prism being mutually positioned to operate on the principle of total internal reflection and having an exit face transmitting the light transmitted by the polarizing splitter and the light reflected by the mirror.

Claim 3

Device according to claim 1, wherein the polarizing splitter is formed by a cholesteric filter located on the exit face of the double prism.

Claim 4

Device according to claim 1, wherein the polarizing splitter is formed by a holographic splitter or a cholesteric filter located between facing faces of the first and second prisms.

Claim 5

Device according to claim 1, wherein the exit face is adjacent to the entry face and the reflection face is opposite the exit face.

Claim 6

Device according to claim 1, wherein the exit face is opposite the entry face and the reflection face is adjacent to the entry and exit faces.

Claim 7

Device according to claim 3, wherein the reflection face includes a quarter-wave plate, the light polarized in the first polarization direction, transmitted by the holographic splitter, is transmitted to another additional reflection face which reflects the light onto the exit face via the facing faces forming a dioptric interface which separates the first and second prisms.

Claim 8

Device according to claim 4, wherein the exit face is not parallel to the reflection face.

Claim 9

Device according to claim 5, wherein the reflection face is not perpendicular to the exit face.

Claim 10

Device according to claim 5, wherein the first and second prisms of the double prism have unequal angles.

Claim 11

Device according to claim 9, wherein the angle of incidence of the unpolarized light beam is other than zero degrees.

Claim 12

Polarizing splitter device, comprising: a double prism constituted by a first prism and a second prism facing faces and a polarizing splitter, said first prism having an entry face for receiving an unpolarized light beam, said polarizing splitter transmitting the polarized light in a first polarization direction and reflecting the polarized light in a second polarization direction, the second prism having a reflection face provided with a mirror receiving the light polarized in the second polarization direction, said second prism having a reflection face provided with a mirror receiving the light polarized in the second polarization direction reflected by the polarizing splitter, the first prism and the second prism being mutually positioned to operate on the principle of total internal reflection and having an exit face transmitting the light transmitted by the polarizing splitter and the light reflected by the mirror, the polarizing splitter is formed by a holographic splitter or a cholesteric filter located between facing faces of the first and second prisms, the reflection face includes a quarter-wave plate, the light polarized in the first polarization direction, transmitted by the holographic splitter, is transmitted to another additional reflection face which reflects the light onto the exit face via the facing faces forming a dioptric interface which separates the first and second prisms, the additional reflection face makes an angle other than 90° with the exit face.

Claim 13

Polarizing splitter device, comprising: a double prism constituted by a first prism and a second prism facing faces and a polarizing splitter, said first prism having an entry face for receiving an unpolarized light beam, said polarizing splitter transmitting the polarized light in a first polarization direction and reflecting the polarized light in a second polarization direction, the second prism having a reflection face provided with a mirror receiving the light polarized in the second polarization direction, said second prism having a reflection face provided with a mirror receiving the light polarized in the second polarization direction reflected by the polarizing splitter, the first prism and the second prism being mutually positioned to operate on the principle of total internal reflection and having an exit face transmitting the light transmitted by the polarizing splitter and the light reflected by the mirror, the polarizing splitter is formed by a holographic splitter or a cholesteric filter located between facing faces of the first and second prisms, the reflection face includes a quarter-wave plate, the light polarized in the first polarization direction, transmitted by the holographic splitter, is transmitted to another additional reflection face which reflects the light onto the exit face via the facing faces forming a dioptric interface which separates the first and second prisms, the additional reflection face makes an angle other than 90° with the exit face.

Claim 14

Device according to claim 7, wherein the angle between the exit face and the reflection face is obtained by the use of an additional prism added to one of the first and second prisms of the double prism or by the use of a prism fulfilling the same function.

Claim 15

Device according to claim 8, wherein the reflection face includes a retroreflector.

Claim 16

Device according to claim 13, characterized in that the reflection face includes a λ/4 polarization device.

Claim 17

Device according to claim 1, wherein it includes a series of juxtaposed double prisms, the entry faces of the various double prisms lying in the same first plane and the exit faces of the various double prisms lying in the same second plane.

Claim 18

Polarizing splitter device, comprising: a double prism constituted by a first prism and a second prism facing faces and a polarizing splitter, said first prism having an entry face for receiving an unpolarized light beam, said polarizing splitter transmitting the polarized light in a first polarization direction and reflecting the polarized light in a second polarization direction, the second prism having a reflection face provided with a mirror receiving the light polarized in the second polarization direction, said second prism having a reflect ion face provided with a mirror receiving the light polarized in the second polarization direction reflected by the polarizing splitter, the first prism and the second prism being mutually positioned to operate on the principle of total internal reflection and having an exit face transmitting the light transmitted by the polarizing splitter and the light reflected by the mirror, a series of juxtaposed double prisms, the entry faces of the various double prisms lying in the same first plane and the exit faces of the various double prisms lying in the same second plane, two transparent dentate plates which fit together by their toothing, each tooth having a face perpendicular to the plane of the plate and an inclined face, the perpendicular faces of one of the plates at least being reflective.

Claim 19

Polarizing splitter device, comprising: a double prism constituted by a first prism and a second prism facing faces and a polarizing splitter, said first prism having an entry face for receiving an unpolarized light beam, said polarizing splitter transmitting the polarized light in a first polarization direction and reflecting the polarized light in a second polarization direction, the second prism having a reflection face provided with a mirror receiving the light polarized in the second polarization direction, said second prism having a reflect ion face provided with a mirror receiving the light polarized in the second polarization direction reflected by the polarizing splitter, the first prism and the second prism being mutually positioned to operate on the principle of total internal reflection and having an exit face transmitting the light transmitted by the polarizing splitter and the light reflected by the mirror, a series of juxtaposed double prisms, the entry faces of the various double prisms lying in the same first plane and the exit faces of the various double prisms lying in the same second plane, two transparent dentate plates which fit together by their toothing, each tooth having a face perpendicular to the plane of the plate and an inclined face, the perpendicular faces of one of the plates at least being reflective.

Claim 20

Device according to claim 16, wherein a plane face of one plate opposite the dentate face is provided with a polarizing filter.

Claim 21

System for illuminating a liquid-crystal screen, and applying a polarizing splitter device according to claim 1, comprising: a light source emitting an unpolarized light beam; a polarizing splitter device receiving the unpolarized light beam and retransmitting, onto the liquid crystal screen, a first and a second beam which are polarized in the same polarization direction, the axes of the two beams making a defined angle; a matrix of microlenses with one microlens for at least two adjacent picture elements in the liquid-crystal screen, each microlens directing that part of the first beam which it receives onto one of the two picture elements and that part of the second beam which it receives onto the other picture element.

Claim 22

System according to claim 18, wherein the screen lies in the focal plane of the microlenses.

Claim 23

System according to claim 18, wherein the microlenses are spherical.

Claim 24

System according to claim 18, wherein the microlenses are cylindrical and each enables two rows of picture elements to be illuminated.

Claim 25

System according to claim 18, wherein the polarizing splitter device includes a polarizing splitter which spatially separates the light from the source into two beams which are differently polarized, at least one reflector associated with a path of one beam, and a beam recombiner receiving the two beams and transmitting them onto the screen.

Claim 26

System according to claim 18, wherein it includes two reflectors each associated with the path of one beam.

Claim 27

System according to claims 22 or 23, wherein the reflectors are orientable.

Claim 28

System according to claim 22, wherein it includes a polarization-rotation device arranged in the path of one of the beams.