US 5,168,401 A · Brightness conserving optical system for modifying beam symmetry

Abstract

An optical system for use in conjunction with a one or two dimensional array of high brightness sources where such sources are individually rotated by multiple reflective elements and in turn may be captured by beam filling optics and subsequently re-imaged by symmetric and asymmetric optics where the asymmetric optics preferentially image a single dimension while leaving the focus in the second dimension largely unaffected. In this manner and by properly selecting the spacing as well as the width of the line sources, and by properly designing the symmetric and asymmetric optics, the array of high brightness sources can be reformatted in a brightness conserving manner that allows the reformatted beam to simultaneously have an arbitrary ratio of image length to image width and arbitrary divergences in the respective dimensions. The multiple reflective elements provide the means of re-formatting between dimensions and in general consist of two reflecting surfaces that rotate sources such that the source axis initially parallel to the line passing through all sources is rotated to be perpendicular to the line passing through all sources. The system is particularly useful in reformatting beams from multiple sources of arrays of semiconductor lasers.

Claims60

Dependent claims

An optical system comprising,

multiple light sources arranged to form an array, said array defining a longitudinal direction parallel to a principal direction of propagation of light emitted from said sources, a lateral direction along an array axis passing through a line of said light sources and a transverse direction perpendicular to both said lateral and longitudinal directions, each of said sources emitting light that is characterized by a lateral and transverse light emitting dimension, and
multiple reflective elements arranged in front of said sources to form a corresponding array, said reflective elements positioned and oriented relative to one another and to said sources so as to cause a rotational transformation of light emitted from each source, said transformation being of such a nature that at least a component of said lateral and transverse dimensions of light emitted form each source is transposed into the other of said transverse and lateral dimensions of light emitted from that source.

An optical system comprising,

multiple light sources arranged in an array of similar sources that are equally spaced along at last one line of sources, any lines of sources in addition to one being equally spaced from one another in a second dimension, said array defining a lateral direction parallel to said at least one line of sources and a transverse direction corresponding to said second dimension perpendicular to said lateral direction and also perpendicular to a principal direction of propagation of light emitted from said sources, each of said light sources in said array emitting light characterized by lateral and transverse source size and divergence dimensions,
multiple reflective elements arranged in front of said sources to form a corresponding array, said reflective elements positioned and oriented relative to one another and to said sources so as to cause a substantially 90.degree. rotational transformation of light emitted from each source relative to an original orientation of said sources with respect to said array of sources, whereby said lateral and transverse dimensions of each source become the other of said transverse and lateral dimensions of the transformed light,
means for providing a collimated beam from transformed light corresponding to said multiple light sources, said beam collimating means including a lenslet array, each lenslet of said lenslet array positioned in front of a corresponding reflective element at a distance where diverging light emitted from each source intersects and begins to overlap light emitted from adjacent light sources in a line of sources and between any adjacent lines of sources, the light thereby substantially filling each lenslet of said lenslet array, said lenslets having a focal length which is substantially equal to the optical path length from the individual light sources thereto, whereby the light is fully collimated by said lenslets, and
means for reimaging said collimated beam into a modified beam, said reimaging means including asymmetric optics having lateral and transverse focal lengths selected to provide a specified lateral-to-transverse size ratio and a corresponding lateral-to-transverse divergence ratio for the modified beam.

1 more element

An optical system comprising,

multiple light sources arranged in a linear array of similar sources that are equally spaced along a single line of sources, said linear array defining a lateral direction along an array axis through said single line of sources and a transverse direction perpendicular to said lateral direction and also perpendicular to a principal direction of propagation of light emitted from said sources, each of said light sources in said array emitting light characterized by lateral and transverse source size and divergence dimensions, the number N of sources in said array and the lateral source size S.sub.H being selected such that
N.apprxeq.S.sub.H sin.theta..sub.H /S.sub.V sin .theta..sub.V,
where S.sub.V, .theta..sub.H and .theta..sub.V are respective transverse size, lateral divergence and transverse divergence dimensions of each source in said array.
multiple pairs of mirror surfaces arranged in front of said sources to form a corresponding linear array, one pair for each source, each pair of mirror surfaces having a first mirror positioned in the path of light emitted from a source and oriented at 45.degree. to said path so as to reflect said light by 90.degree. within a plane of emission along said line of sources, and a second mirror positioned in the path of light reflected by said first mirror and oriented at 45.degree. to said reflected light path so as to reflect said light by 90.degree. into a direction perpendicular to said plane of emission, said multiple pairs of mirror surfaces causing a substantially 90.degree. rotational transformation of light emitted from each source relative to an original orientation of said sources with respect to said linear array of sources, such that said lateral and transverse dimensions characterizing light emitted from each source become the other of said transverse and lateral dimensions characterizing the transformed light,
means for providing a collimated beam from transformed light corresponding to said multiple sources, said beam collimating means including a lenslet array, each lenslet of said lenslet array positioned in front of a second mirror of a corresponding pair of mirror surfaces at a distance where diverging light emitted from each source intersects and begins to overlap light emitted from adjacent light sources in said line of sources, the light thereby substantially filling each lenslet of said lenslet array, said lenslets being axially symmetric with focal lengths selected to provide collimation in both lateral and transverse dimensions, and
means for reimaging said collimated beam into a modified beam with a specified lateral-to-transverse divergence ratio and a corresponding lateral-to-transverse size ratio which are both equal to one, said reimaging means including
an axially symmetric convergent lens in front of said lenslet array, said lens having a diameter of at least a total width N .times. P.sub.o of said source array, where P.sub.o is the spacing of said sources, said lens also having a focal length L.sub.o selected such that [N.times.P.sub.o /2L.sub.o =tan .THETA..sub.H, where .theta..sub.H ] N.times.P.sub.o /2L.sub.o =tan .theta..sub.H ', where .theta..sub.H ' is a specifiable lateral convergence angle of the light after said collimated light has passed through said lens, and
an asymmetric lens positioned in front of said axially symmetric lens, said asymmetric lens having a lens size sufficient to capture the transverse divergence of the beam and a transverse focal length selected to provide a transverse waveguide angle .theta..sub.V in the reimaged beam about equal to .theta..sub.H and a transverse size S.sub.V in the reimaged beam about equal to S.sub.H, said asymmetric lens leaving said lateral convergence angle .theta..sub.H substantially unaffected.

5 more elements

A brightness conserving, asymmetry reducing, laser array system comprising

an array of collinear, laterally spaced apart, laser light emitting sources, said array defining a longitudinal direction along a principal direction of propagation of light emitted from said sources, a lateral direction along an array axis passing through a line of said collinear, laterally spaced apart sources, and a transverse direction perpendicular to both said lateral and longitudinal directions, each of said sources emitting light characterized by a lateral size dimension S.sub.H, a transverse size dimension S.sub.V, a lateral divergence angle .theta..sub.H, a transverse divergence angle .theta..sub.V, a lateral component of brightness B.sub.H proportional to (S.sub.H sin .theta..sub.H).sup.-1 and a transverse component of brightness B.sub.V proportional to (S.sub.V sin .theta..sub.V).sup.-1, the array characterized by an array axis passing through each of said sources, a total brightness B proportional to (1/N) .times. B.sub.H .times. B.sub.V and an intrinsic asymmetry ratio A=N.times.(S.sub.H sin .theta..sub.H)/(S.sub.V sin .theta..sub.V), where N is the number of sources in the array,
means disposed in front of said array of sources for optically transforming light emitted from said array of sources in a manner such that the virtual image of each laser light emitting source has been rotated in the transformed array on the array axis, whereby said lateral and transverse size dimensions and divergence angles have undergone a rotational transformation, the virtual images of the sources in the transformed array still being collinear and lateral spaced, each of the source virtual images in the transformed array characterized by a transformed lateral size dimension S.sub.H ', a transformed transverse size dimension S.sub.V ', a transformed lateral divergence angle .theta..sub.H ', a transformed transverse divergence angle .theta..sub.V ', a lateral component of brightness B.sub.H ' for the virtual image that is proportional to (S.sub.H ' sin .nu..sub.H ').sup.-1 and a transverse component of brightness B.sub.V ' for the virtual image that is proportional to (S.sub.V ' sin .theta..sub.V ').sup.-1, the transformed array characterized by an array axis passing through each of the source virtual images which is parallel to the array axis of the actual array, a total brightness B' proportional to (1/N) .times. B.sub.H ' .times. B.sub.V ' and an intrinsic asymmetry ratio for the reimaged array of A'=N .times.(S.sub.H ' sin .theta..sub.H ')/(S.sub.V ' sin .theta..sub.V '),
wherein said transformed array substantially conserves brightness such that B'.apprxeq.B, and wherein said transformed array has an intrinsic asymmetry ration A' which is substantially closer to unity than the intrinsic asymmetry ratio A of the actual array,
optics means for collimating the laser light from said reimaged array of sources, and
means for focussing said collimated light to a spot.

2 more elements

Dependencies are inferred from the claim text.

Brightness conserving optical system for modifying beam symmetry

Life of this patent

Brightness conserving optical system for modifying beam symmetry

Life of this patent

Abstract

Claims60