Imaging Device

Abstract

An imaging device for projecting individually controllable laser beams onto an imaging surface movable in an X-direction. The device includes a plurality of semiconductor chips each comprising a plurality of laser beam emitting elements arranged in a main array of M•N. The chips are mounted such that each pair of adjacent chips in the Y-direction are offset from one another in the X-direction and, if activated continuously, the emitted laser beams of the two chips of said pair trace on the imaging surface a set of parallel lines that are substantially uniformly spaced in the Y-direction. In addition to the M•N elements of the main array, each chip comprises at least one additional column on one or each side, each additional column containing at least one selectively operable element capable of compensating for any misalignment in the Y-direction in the relative positioning of the adjacent chips on the support.

1 . An imaging device for projecting individually controllable laser beams onto an imaging surface that is movable relative thereto in a reference X-direction, the device comprising:
 a support;   a plurality of semiconductor chips coupled to the support, each of the chips comprising a plurality of individually controllable laser elements arranged in a two dimensional main array of M rows and N columns, the laser elements in each row having a uniform spacing A r  and the laser elements in each column having a uniform spacing a c ;   the chips being arranged in at least one pair of rows such that the main array of each pair of chips that are adjacent one another in a reference Y-direction, transverse to the X-direction, are offset from one another in the X-direction, and such that the center of each two adjacent laser elements in the main arrays of both chips be uniformly spaced from one another in the Y-direction by a nominal distance A r /M, whereby the centers of laser elements of both chips do not overlap in the Y direction;   the chips within the two rows of the pair being aligned such that corresponding elements in any group of three adjacent chips in the X and Y-directions lie at the apices of congruent equilateral triangles and the distance in the Y-direction between corresponding elements equals nominally to N•A r ,where A r  is the nominal distance between any two adjacent laser elements in each row;   each chip further comprising at least one additional column in addition to the N columns of elements of the main array, the additional column being disposed on a side of the main array in the Y-direction, and containing at least one selectively operable laser element capable of emitting an additional laser beam that lies between respective sets of M•N laser beams of each pair of chips.   
     
     
         2 . An imaging device as claimed in  claim 1 , wherein each of the chips further comprises at least a second additional column in additions to the N columns of the respective main array, the second column being disposed opposite to the first column and containing at least one selectively operable laser element. 
     
     
         3 . An imaging device as claimed in  claim 1 , further comprising a plurality of lens systems, each serving to focus the laser beams of all the laser elements of a respective one of the chips onto the imaging surface, each lens system comprising at least one gradient index (GRIN) rod. 
     
     
         4 . An imaging device as claimed in  claim 3 , wherein the GRIN rod is of circular cross-section having a diameter equal to 2•N•A r . 
     
     
         5 . An imaging device as claimed in  claim 3 , wherein the lens systems have a magnification of absolute value equal or greater than 1. 
     
     
         6 . An imaging device as claimed in  claim 5 , wherein the lens systems magnification value is +1 or −1. 
     
     
         7 . An imaging device as claimed in  claim 3 , wherein the lens systems have a magnification of absolute value smaller than 1. 
     
     
         8 . An imaging device as claimed in  claim 3 , wherein each lens system is formed by a plurality of mutually inclined GRIN rods. 
     
     
         9 . An imaging device as claimed in  claim 8 , wherein light from each GRIN rod is directed to the next GRIN rod in the plurality of rods of the same lens system by at least one member. 
     
     
         10 . An imaging device as claimed in  claim 9 , in which the member is a prism having a higher refractive index than the highest refractive index of the GRIN rods. 
     
     
         11 . An imaging device as claimed in  claim 1 , wherein the support is fluid-cooled. 
     
     
         12 . An imaging device as claimed in  claim 1 , wherein the support is constructed of a rigid metallic or ceramic structure. 
     
     
         13 . An imaging device as claimed in  claim 1 , further comprising at least one lens associated with each chip of the pair of chips, wherein the respective lens focuses the laser beams emitted by all the elements of the associated chip onto the imaging surface. 
     
     
         14 . An imaging device as claimed in  claim 1 , wherein each chip has an equal number of rows and columns of laser elements in the main array. 
     
     
         15 . An imaging device as claimed in  claim 1 , wherein the surface of the support is formed of, or coated with, an electrical insulator, and further comprises a plurality of thin film conductors formed on the electrically insulating surface for supplying electrical signals and power to the chips. 
     
     
         16 . An imaging device as claimed in  claim 1 , wherein the laser elements are vertical cavity surface emitting laser (VCSEL) elements. 
     
     
         17 . An imaging device as claimed in  claim 1 , wherein each individually controllable laser element can emit a laser beam of at least four selectable levels of energy. 
     
     
         18 . A method of projecting individually controllable laser beams onto an imaging surface that is movable relative to an imaging device, the method comprising:
 providing an imaging device for projecting individually controllable laser beams onto an imaging surface, the imaging device and imaging surface being movable relative to each other in a reference X-direction, the imaging device comprising:   a support;   a plurality of semiconductor chips coupled to the support, each of the chips comprising a plurality of individually controllable laser elements arranged in a two dimensional main array of M rows and N columns, the laser elements in each row having a uniform spacing A r  and the laser elements in each column having a uniform spacing a c ;   the chips being arranged in at least one pair of rows such that the main array of each pair of chips that are adjacent one another in a reference Y-direction, transverse to the X-direction, are offset from one another in the X-direction, and such that the center of each two adjacent laser elements in the main arrays of both chips be uniformly spaced from one another in the Y-direction by a nominal distance A r /M, whereby the centers of laser elements of both chips do not overlap in the Y direction;   the chips within the two rows of the pair being aligned such that corresponding elements in any group of three adjacent chips in the X and Y-directions lie at the apices of congruent equilateral triangles and the distance in the Y-direction between corresponding elements equals nominally to N•A r , where A r  is the nominal distance between any two adjacent laser elements in each row;   each chip further comprises at least one additional column in addition to the N columns of elements of the main array, the additional column being disposed on a side of the main array in the Y-direction, and containing at least one selectively operable laser element capable of emitting an additional laser beam that lies between respective sets of M•N laser beams of each pair of chips.