Light module with optimized optical imaging for a pixellated spatial light modulator, intended for a motor vehicle
The light module for motor vehicle offers a light source associated with a first part of an imaging system so as to produce a reflected beam coincident with the reflection surface of a high definition pixellated spatial light modulator, which makes it possible to avoid unnecessarily lighting the periphery of the spatial light modulator. The light source consists essentially in one or more light emitting diodes and/or has a punctiform or virtually punctiform appearance. The reflected radiation arrives on a second part of the imaging system, this part characteristically consisting in an optical projection system, some of whose elements can form a back focussing system. The module remains compact and is clearly suitable for providing adaptive lighting in a homogeneous, efficient manner and with high resolution.
1. Light module for motor vehicle, intended to shape a light beam, the light module comprising:
a light source;
an imaging system suitable for creating an image of the light source;
a high definition pixellated spatial light modulator presenting a zone of reflection having a determined format,
wherein the imaging system includes at least two optical elements distributed upstream and downstream of the high definition pixellated spatial light modulator, following the direction of propagation of the light emitted by the light source, such that there is at least one element of the imaging system upstream, and at least one element of the imaging system downstream of the high definition pixellated spatial light modulator,
wherein the imaging system further includes, in a first imaging part, a lens for adjustment to a characteristic dimension of the determined format, suitable for concentrating a radiation from the light source, and
wherein the light module further includes a projection screen relative to a zone of reflection of the high definition pixellated spatial light modulator, a second part of the imaging system being suitable for creating said image on the projection screen, based on an intermediate image of the light source formed on the zone of reflection by using a first part of the imaging system, said intermediate image extending entirely inside a perimeter of the zone of reflection.
2. Light module according to claim 1 , wherein the high definition pixellated spatial light modulator is defined by a digital micromirror device having a zone of reflection whose largest dimension is greater than the largest dimension of the light source.
3. Light module according to claim 1 , wherein the determined format of said zone of reflection has a rectangular perimeter format.
4. Light module according to claim 1 , wherein at least one of the optical elements of the imaging system forms said first imaging part, which comprises:
the adjustment lens for adjustment to the determined format, designed and arranged so as to concentrate the radiation from the light source by defining a contour shape of the radiation that corresponds to the shape of a perimeter of the zone of reflection defined by the high definition pixellated spatial light modulator.
5. Light module according to claim 3 , wherein the first imaging part, arranged upstream of the high definition pixellated spatial light modulator has at least one transparent optical element with an anamorphosis effect.
6. Light module according to claim 3 , wherein the first imaging part, arranged upstream of the high definition pixellated spatial light modulator, has an anamorphosis effect mirror.
7. Light module according to claim 3 , wherein the high definition pixellated spatial light modulator comprises a digital micromirror device, the micromirrors of the digital micromirror device each being moveable between:
a first position wherein the micromirror is arranged so as to reflect light rays of a first radiation reaching it from the first imaging part of the imaging system, in the direction of an optical projection system including a second part of the imaging system,
and a second position wherein the micromirror is arranged so as to reflect the light rays of the first radiation reaching it from the first imaging part of the imaging system, away from the optical projection system.
8. Light module according to claim 1 , wherein the high definition pixellated spatial light modulator comprises a displaying reflective zone of the liquid crystals on silicon type.
9. Light module according to claim 1 , comprising an optical projection system,
wherein the high definition pixellated spatial light modulator comprises a matrix of micromirrors distributed in a plane, said matrix defining an optical axis, which spans in a central manner the optical projection system,
and wherein active micromirrors of the digital micromirror device are in an active state rotated through a determined angle, preferably comprised between 6 and 15°, towards an optical element of the convergent type situated upstream of the high definition pixellated spatial light modulator and which belongs to the imaging system.
10. Light module according to claim 1 , wherein a convergent type of optical element, situated upstream of the high definition pixellated spatial light modulator and which belongs to the imaging system,
defines, from the light emitted by the light source, a first radiation projected onto a zone of reflection of the high definition pixellated spatial light modulator, forming on this zone of reflection an intermediate image, which is distorted by said optical element of the convergent type,
extends comparatively further from the high definition pixellated spatial light modulator and nearer to another optical element onto which is directed a second radiation, coming directly from a reflection of the first radiation on the high definition pixellated spatial light modulator, the other optical element forming a first optical element of an optical projection system belonging to the imaging system.
11. Light module according to claim 10 , wherein the optical projection system comprises, successively in this order, along a distancing direction relative to the high definition pixellated spatial light modulator:
the first optical element arranged as an input lens of the optical projection system so as to capture the second radiation;
a pair of optical elements, making it possible to reduce the focal length of the optical projection system relative to a longer focal length that would be obtained for the optical projection system in the absence of this pair of optical elements.
12. Light module according to claim 11 , wherein the optical projection system furthermore comprises an achromat, preferably forming one of the optical elements of said pair of optical elements.
13. Light module according to claim 1 , wherein the light source is part of a unit for emitting light rays provided with at least one reflecting surface distinct from the high definition pixellated spatial light modulator and making it possible to orient the light source along a direction for distancing the light relative to a zone of reflection of the high definition pixellated spatial light modulator.
14. Light module according to claim 1 , wherein the light source consists essentially in one light emitting diode or in several light emitting diodes, grouped on a common mount.
15. Projector for motor vehicle, comprising a projector housing and at least one optical module according to claim 1 .
16. Light module according to claim 2 , wherein the determined format of said zone of reflection has a rectangular perimeter format.
17. Light module according to claim 2 , wherein at least one of the optical elements of the imaging system forms said first imaging part, which comprises:
the adjustment lens for adjustment to the determined format, designed and arranged so as to concentrate the radiation from the light source by defining a contour shape of the radiation that corresponds to the shape of a perimeter of the zone of reflection defined by the high definition pixellated spatial light modulator.
18. Light module according to claim 4 , wherein the first imaging part, arranged upstream of the high definition pixellated spatial light modulator has at least one transparent optical element with an anamorphosis effect.
19. Light module according to claim 4 , wherein the first imaging part, arranged upstream of the high definition pixellated spatial light modulator, has an anamorphosis effect mirror.