CA1318162C - Arrangement for imaging multiple arrays of light beams - Google Patents
Arrangement for imaging multiple arrays of light beamsInfo
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- CA1318162C CA1318162C CA000611247A CA611247A CA1318162C CA 1318162 C CA1318162 C CA 1318162C CA 000611247 A CA000611247 A CA 000611247A CA 611247 A CA611247 A CA 611247A CA 1318162 C CA1318162 C CA 1318162C
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Abstract
AN ARRANGEMENT FOR IMAGING MULTIPLE ARRAYS OF LIGHT BEAMS
Abstract Appartus for combining information beams by using a space variant mirror in the context of free space optical switching and computing, where lightbeams comprise beamlets that are focused onto surfaces to form arrays of light spots.
Beam combining is achieved by positioning the space variant mirror to coincide with the plane on which the spots are focused, and to thereby allow one beam to pass through the space variant mirror without loss and another beam to be reflected off the space variant mirror, also without loss.
Abstract Appartus for combining information beams by using a space variant mirror in the context of free space optical switching and computing, where lightbeams comprise beamlets that are focused onto surfaces to form arrays of light spots.
Beam combining is achieved by positioning the space variant mirror to coincide with the plane on which the spots are focused, and to thereby allow one beam to pass through the space variant mirror without loss and another beam to be reflected off the space variant mirror, also without loss.
Description
1 3 ~ 2 AN ARRANGEMENT FOR IMAGING MULI'IPLE
ARRAYS OF LIG~IT BEAMS
Background of the_InYention Harnessing the bandwidth of optics for transmission of information and for computing i5 very much at the forefront of current research and de~elop nent efforts.
This includes work in the area of "free space" optics, where the three-dimensional space S (formerly reerred to as "ether") is thc communication medium between light ernitting devices and light detecting devices. One advantageous characteristic of "free space" is that light beams can be intersected without comingling. Another advantageous characteristic is that a large number of beams can be handled in parallel, as a group, with a single optical setup. Still another advantage is that "free space" is indeed ~ee; it does 10 not need to be manufactured, and it costs nothing.
On the other hand, optics imposes its own constraints on the architecture oE the systems that are designed. These constraints have been overcome to some extent, as exemplified by systems described, for example, in U.S. Patent No. 4,943,909, issued July 24, 1990 to A. Huang, and U.S. Patent No. 4,917,456, issued April 17, 1990 to J. Jahns, et 15 al. These and other free space systems have one thing in common, and that is the use of plane arrays of optical devices, and corresponding arrays of light beams. Typically also, a number of different beam arrays are required because a usable logic device ~11"ngeneral, need at least two logical inputs. Depending on ths type of deYice, it may also require one or more optical bias beams. This is akin to a transistor logic gate, where one 20 employs a number of logic signals and a power supply source !~or operating the logic gate.
Hence, there is a need in the field of free space optical inforrnation handling to operate with a plurality of beams and, in particular, there is a need to arrange for multiple arrays of beams, with each array being derived possibly from a different source or sources, to be incident on a desired array of optical devices. In other words, there is a need to combine 25 beams and to separate beams.
- One approach is discussed hereinbelow with respect to the drawings.
Summar~ of the Invention This invention overcomes the drawbacks of prior art methods of cornbining inforrnation beams by using a space variant mirror in a new manner. More specifically, in 30 the context of free space optical switching and computing, where light beams comprise beamlets that are ~ocused onto surfaces to form arrays of light spots, this invention ~,~.r~
combines beams by appropriately positioning the space variant mirror to coincide with the plane on which the spots are focused. No loss occurs wi~h this method of beam combining because the mirror is positioned with its re~lected areas situated at the beam waists of the re~lected array of beamlets (in each of the three dimensions) and,S concurrently, the mirror is also positioned with its transmissive areas situated at the ~eam waists of the transmitted array of beamlets.
In one preferred embodiment the space valiant 90 rnirror is placed at an angle other than 90 with respect to the center axis of the beam that is transmitted through the mirror. The beam that is reflected is then appropriately arranged with respect to that center axis to combine the reflected beam with the transmitted beam to form a single beam that is applied to the image collection optics. Advantageously, the angle of the mirror with respect to that center axis is as close to 90~ as practical, and the beams (both the transrmissive and the rellective beams) are arranged to be very weakly divergent.
In another preferred embodiment, a beam splitter is used to permit the ~'! reflective beam to be arranged perpendicularly to the transmissive beam. In this arrangement, the beam splitter is interposed between the reflective beam and the rnirror, and the mirror is situated perpendicularly to the center a~s of the transmissive bearn.
Ihe beam splitter deflects the reflective bearn onto the space variant mirror.
To avoid losses associated with the beam splitter, a still another embodiment employs a beam splitter that is sensitive to the polarization of light. The re1ective beam is then arranged to be polarized in the mode that causes deflection in the beam splitter. To provide for a combined beam that is uniformly polarized, a quarter wave plate is placed between the beam splitter and the mirror, and the transmissive beam is arranged to have a circular polari~ation mode. The resulting combined beam passes through the quarter wave plate and the beam splitter without deflection, possessing a polarization mode that is orthogonal to the polarization mode of the incoming reflective ` beam.
In accordance with one aspect of the invention there is provided a beam combiner/splitter characterized by a first energy beam comprising beamlets that form a first pattern of waists at a first surface; a second ener~y beam comprising beamlets that form a second pattern of waists at a second surface; and a third beam comprisingbeamlets that form a third pattern of waists, related to a combination of said first and said " ~`, ~31~ ~2 second patterns of waists, at a third surEace that is spatially related to said first and second sur&ces; and a mirror having a collection of reflective areas and transmissi~e are3s with said reflective areas arranged in accordance with said first pattern and said transmissive areas arranged in accordance with said second pattem; with said mirror situated in first S proximity to said first surface, and having said reflective areas face said first beam, with said first proximity being such that loss due to three-dimensional misalignment of said waists and said re~ective areas is below a preselected first threshold, and crosstalk between the energy of the beamlets corresponding to the waists on said reflective areas is below a second preselected threshold, and in proximi~r to said second surface su- h that loss due to three-dimensional misalignment of said waists and said transmissive areas is below a preselected third threshold.
Brief l~escription ot the DrawinP
FIG. 1 shows a prior art approach to beam combining;
FIG. 2 shows the arrangement of light spots from two beam arrays that form the input to an optical logic array;
depicts one realization for a beam splitter in accordance with the principles of our invention;
FlGS. 4 and 5 illustrate enhanced embodiments of the realization presented in FlG. 3, FIG. 6 shows the use of our invention to combine more than two beams;
FIG. 7 presents a realization of our invention that employs a beam splitter;
and FIG. 8 illustrates a realization of our invention for combining three beams with the aid of one beam splitter.
l~etailed l~escl-ipffol~
One approach for combining or separating two beam arrays is to apply them to a beam splitter as shown, for example, in FIG. 1. Beam 11 is applied to cube beam splitter 10 at one face of the beam splitter, where it is split into beams 13 and 14.
Beam 12 is applied to beam splitter 10 at another face of the splitter (orthogonal to the first face), wherein it is split into beams 15 and 16. Beams 14 and 15 e~t beam splitter 10 at the same face (to the right) and thus they are combined. Alas, using simple beam splitters to achieve beam combining entails loss, since ener~y is diverted to beams 1~ and 16.
?~.
Polari~ation-dependent beam splitters can also be uxed to combine two beams, and such combining is achieved essentially but without loss. In the arrangement of FIG. 1 where the beam splitter is sensitive to the polarization mode of the incoming light, it can be arranged for the light of beam 11 to be so polarized that it passes through the S bearn splitter without deflection, thus placing no energy in beam 1~. Similarly, it can be arranged for the light of beam 12 to be so polarized that it is deflected in the beam splitter, thus placing no energy in beam 16. The resultant beam combining that occurs within beam splitter 10 is lossless, but the combined beam is partially polarized in one mode and partially polarized in another mode.
Dichroic beam splitters can be used7 in principle, to combine beams of different wavelengths without loss. In practice, however, we may not wish to be constrained to use dif~erent wavelengths for the different beams, and devices may not work if such different wavelengths are used.
In a different environment, and for a different purpose, image combining 15 has been accomplished with the use of a reflective grating. This approach is described in "Real Time Incoherent Optical-Electronic Image Substraction," Dashiell et al., ~ptics Communications~ June, 1973, pps. 105-108. The described approach passes one image through a reflective grating and re~lects another image through the same grating. The grating in effect samples both images. The combined sample images are then applied to 20 an image plane where the sampled combined image is converted to electronic signals and processed. This is akin to sampling a signal at a high rate (above Nyquist rate), combining the sampled signals, and filtering with an appropriate bandpass filter. Of course, there is loss associated with this approach because a portion of each image is missing. In fact, in its operation (vis-a-vis loss) the Dashiell et al. arrangement is identical to the arrangement 25 of Fig. 1, but optically more complex.
FIG. 2 depicts a possible arrangement where the principles of this invention can be utili~ed. Rectangle 20 represents a surface that contains optical logic elements 21, such as SEED devices. It is desired to apply to each logic element 21 two light spots, such as 22 and 23. Rectangle 25 represents the surface of light emitting devices 26. This can ~0 be a structure on there is place an array of LED, a source of light spots derived from a single laser beam, etc. Devices 26 correspond in number and relative position to light spots 22 of rectangle 20. It is realized, of course, that maglufication and reduction are possible, but for purposes of this description and for the sake of simplicity, a magnification .,~, , 1 3 ~
4a factor of 1 is assumed. Rectangle 27 represents another surface of light emitting devices 28, and these devices correspond to light spots 2~ of rectangle 20. It maybe noted that in FIG. 2 light sources 28 have a positional orientation within rectangle 27 that is slightly S shifted to the left when compared to the positional orientation of elements 26 in rectangle 25. This shift corresponds to the separation between light spots 22 and 2~ in rectangle 20.
In an actual realization, however, it is likely that the entire array (the rectangle and its associated light sources) would be shifted.
What is necessary to accomplish is tlhe combining of light sources 26 and 10 light sources 28 and to apply the combined energy onto rectangle 20.
FIG. ~ depicts one arrangement in accordance with the principles of this invention. In FIG. ~, light sources from rectangle 25 pass through an appropriate focusing lens to result in beam ~5 that focuses an array of spots onto a plane indicated by dashed line 36. Similarly, light sources from rectangle 27 pass through 15 an appropriate focusing lens and resulting beam ~7 that focuses an array of spots onto a plane represented by dashed line ~8. Mirror 24 is a thin glass plate on which reflective areas 29 are deposited. The front view of mirror 24 is shown in FIG. 2.
It may be noted that the reflective areas of mirror 24 for the FIG. ~ arrangements are elliptical, with the major a~is being~ times the mirror a~s. This accounts for the 20 tilt of the mirror with respect to reflected beam 3~. As arranged in FIG. ~, the light of beam ~5 passes entirely through the transmissive portion of mirror 24 while the light of beam ~7 is reflected in its entirety of~ reflective areas 29 of mirror 24. Also . . , as arranged in FIG. 3, beam 37 is approximately at right angles to beam 35 and mirror 24 is approximately an angle of 45 with respect to the center axis (34) of beam 35. That is, rnirror 24 is an angle that is half the angle between the center axes of beams 35 and 37. The light transmitted through mirror 24, combined with the S light reflected off mirror 24, is applied to focusing lens 40. Lens 40 f~uses light spots 22 and 23 onto plane 20.
From FIG. 3 it is readily apparent that beams 35 and 37 must be very weakly converging because the waist of the beamlets of bearn 35 do not all coincide in space with the transmissive portions of mirror 24. The waists are at plane 36, 10 while the mirror is at a different plane (that is at a 45 angle thereto).
Correspondingly, the waists of the beamlets of beam 37 (at plane 38) also do not all coincide with the reflective areas of rnirror 24. Use of beams 3S and 37 that are not very weakly converging would result in two problems. First, with respect to beam35, some light rnight not be transmitted (when it expands to cover more than the15 transmissive portion of the mir~r) and the loss of light, when it occurs, would increase with the distance away from the center axis of beam 35. With respect tobeam 37, light might also be lost when the beam is wider than the reflective portion and, additionally, crosstalk can occur when the energy of one spot is comingled on the reflective por~ions of mirror 24 with the energy of another spot.
FIG. 4 illustrates an opdcal setup that minimizes the above problem. In FIG. 4, bearn 37 is situated at an angle ~ with respect to ~he centcr axis of beam 35 that is as close to 180 as is possible, and miIror 24 is situated at the angle ~/2.
~IG. S depicts an ar~angement that is similar to the arrangement ~ FIG.
4, but it includes field lenses 41 and 42. Lenses 41 and 42 image the pupil of the 25 source onto the pupil of the objective, which permit lens 40 to have a smaller diameter.
FIG. 6 presents an optical arrangement mocleled after FIG. 3 that may be employed when more than ~wo beams are to be combined. In essence, mirror 43 combines beams 44 and 45, to form combined beam 46, and miITor 47 combines 30 beam 46 and beam 48. A focusing relay lens 49 is placed between mirror 43 andmi~ror 47 and field lenses 49, 50, and 51 can also be included. The principles employed in FI{}. 6 can easily be extended to a larger number of beams to be combined. As an aside, it may be observed that the spatial arrangement of mirror 47 is different from that of mirror 43, with ~he folmer most lilcely having more 35 llansmissive areas than the latter.
J,~
Mirrors such as the ones described above, with arbitrary patterns of reflective and transmissive regions, can be fabricated by conventional lithographic techniques. In one conventional approach, for example, a metallic rcflective coating is deposited on a glass substrate, and photoresist is applied to the substrate. The 5 photoresist is then exposed in the usual manner with the appropriate pattern from a lithographic mask, etched away to expose the areas of rnetal to be removed, and the metal is then etched away. At this stage, an antireflection coating is conveniently evaporated onto the exposed glass substrate to rernove any residual reflectivity of the glass surface (or reduce it to acceptably low levels), and finally the remaining10 photoresist is removed. The back surface of the whole substrate could also beandreflection coated to reduce reflection off this surface as well. Similar results can be obtained using dielectric mirror coadngs in place of the metallic coating. Many other methods of making such space-variant mirrors would be obvious to those skilled in the art.
If the glass substrate is thick, allowance has to be made for ~he lateral displacement that the substrate would induce on the transmitted beams. This involves adjustments in the positioning of the preceding mirrors or incorporation of compensating plates.
FIG. 7 presents an optical setup that employs the principles of our 20 invention and also overcomes the drawbacks of the FIG. 3 optical setup. In FIG. 7, beam 37 is applied to a beam splitter (here, cubic be~m splitter 60) that is sensitive to the polarization of light. That is, it deflects light that is y-polarized and passes light that is x-polarized. Beam 37 is arranged to be y-polaIized and, accordingly, it is deflected to the right in beam spli~ter 60. At the ~ace of beam splitter 60 where 25 beam 37 exits there is an aIrangement comprising a quarter-wave plate 61, a focusing lens 62, and a space variant m~rr~r 63. Beam 35 is applied, as in FIG. 3, from the right of mi~ror 63. The light of beam 35 focuses to an array of spots at the plane of mirror 63, and mirror 63 is positioned to align the ~ransmissive areas of the mirrors with the waists of the focused beam 35. Beam 35 is circularly polarized.30 The light transmitted thlough mirror 63 is collimated in lens 62 and applied to plate 61. Plate 61 converts the circularly polarized light to x-polarization and applies that light to beam splitter 60. The x-polarized light passes through beam splitter 60.
Beam 37 is applied in the FIG. 7 optical setup from the top. It is collimated and possesses a y-pol~zation. The collimated light is deflected in beam 35 splitter 60 and passes through plate 61 where it is converted to circular polarization.
Lens 62 focuses the light of beam 37 onlo the reflective areas of mirror 63. That light is reflected, collimated in lens 62, converted to x-polarization in plate 61, and passes through beam splitter 60 together with beam 35.
It may be appreciated that the order of lens 62 and plate 61 can be 5 interchanged. Indeed, lens 62 can be positioned before the beam splitter, although such an alrangement must deal w~th divergent beams as they exit the beam splitter to the left (after being combined). It may also be appreciated that the FIG. 7 optical setup can be simplified when one is ~lling to accept loss. In such a ease, one can use a beam splitter that is not polarization sensitive and one can do without the 10 quarter wave plate. The polarization of light would be immaterial in such an optical setup.
The above descriptions illustrate and teach the principles of our invention, but it is realized that many extensions naturally flow from these teachings, both with respect to general manipulations of beams, and with respect to specific 15 realizations. For example, it is probably clear to the skilled ar~san that the beam combining principles described above apply equally well to beam splitting needs.Also, combining three beams with an optical setup aldn tO the setup of FIG. 7 isquite straightforward, as illustrated by FIG. 8.
In FIG. 8, beam 53 is circularly polarized. It passes through space 20 variant rn~or 74, lens 72, and through ~uarter-wave plate 71 where it is conveIted to y-polari~adon. The beam is then applied to beam splitter 60 where it is deflected to the output of the beam splitter. Beam 37, which is y-polarized, is deflected in beam splitter 60, passes through quarter-wave pIate 61, is reflected off space variant mirror S3, and passes through plate 61 a second ~ime whereupon it assumes x-polalization.
25 Thereafter, the beam passes ~rough beam splitter 60, passes through plate 71, is reflected off mirror 74, and passes through plate 71 a second time, whereupon isassumes y-polarization. The beam then re-enters beam splitter 60 and is deflected to the output. Beam 35, possessing circular polarization, passes through mirror 63 and plate 61 and assumes x-polarizadon. Thereafter it follows the path taken by beam30 37.
ARRAYS OF LIG~IT BEAMS
Background of the_InYention Harnessing the bandwidth of optics for transmission of information and for computing i5 very much at the forefront of current research and de~elop nent efforts.
This includes work in the area of "free space" optics, where the three-dimensional space S (formerly reerred to as "ether") is thc communication medium between light ernitting devices and light detecting devices. One advantageous characteristic of "free space" is that light beams can be intersected without comingling. Another advantageous characteristic is that a large number of beams can be handled in parallel, as a group, with a single optical setup. Still another advantage is that "free space" is indeed ~ee; it does 10 not need to be manufactured, and it costs nothing.
On the other hand, optics imposes its own constraints on the architecture oE the systems that are designed. These constraints have been overcome to some extent, as exemplified by systems described, for example, in U.S. Patent No. 4,943,909, issued July 24, 1990 to A. Huang, and U.S. Patent No. 4,917,456, issued April 17, 1990 to J. Jahns, et 15 al. These and other free space systems have one thing in common, and that is the use of plane arrays of optical devices, and corresponding arrays of light beams. Typically also, a number of different beam arrays are required because a usable logic device ~11"ngeneral, need at least two logical inputs. Depending on ths type of deYice, it may also require one or more optical bias beams. This is akin to a transistor logic gate, where one 20 employs a number of logic signals and a power supply source !~or operating the logic gate.
Hence, there is a need in the field of free space optical inforrnation handling to operate with a plurality of beams and, in particular, there is a need to arrange for multiple arrays of beams, with each array being derived possibly from a different source or sources, to be incident on a desired array of optical devices. In other words, there is a need to combine 25 beams and to separate beams.
- One approach is discussed hereinbelow with respect to the drawings.
Summar~ of the Invention This invention overcomes the drawbacks of prior art methods of cornbining inforrnation beams by using a space variant mirror in a new manner. More specifically, in 30 the context of free space optical switching and computing, where light beams comprise beamlets that are ~ocused onto surfaces to form arrays of light spots, this invention ~,~.r~
combines beams by appropriately positioning the space variant mirror to coincide with the plane on which the spots are focused. No loss occurs wi~h this method of beam combining because the mirror is positioned with its re~lected areas situated at the beam waists of the re~lected array of beamlets (in each of the three dimensions) and,S concurrently, the mirror is also positioned with its transmissive areas situated at the ~eam waists of the transmitted array of beamlets.
In one preferred embodiment the space valiant 90 rnirror is placed at an angle other than 90 with respect to the center axis of the beam that is transmitted through the mirror. The beam that is reflected is then appropriately arranged with respect to that center axis to combine the reflected beam with the transmitted beam to form a single beam that is applied to the image collection optics. Advantageously, the angle of the mirror with respect to that center axis is as close to 90~ as practical, and the beams (both the transrmissive and the rellective beams) are arranged to be very weakly divergent.
In another preferred embodiment, a beam splitter is used to permit the ~'! reflective beam to be arranged perpendicularly to the transmissive beam. In this arrangement, the beam splitter is interposed between the reflective beam and the rnirror, and the mirror is situated perpendicularly to the center a~s of the transmissive bearn.
Ihe beam splitter deflects the reflective bearn onto the space variant mirror.
To avoid losses associated with the beam splitter, a still another embodiment employs a beam splitter that is sensitive to the polarization of light. The re1ective beam is then arranged to be polarized in the mode that causes deflection in the beam splitter. To provide for a combined beam that is uniformly polarized, a quarter wave plate is placed between the beam splitter and the mirror, and the transmissive beam is arranged to have a circular polari~ation mode. The resulting combined beam passes through the quarter wave plate and the beam splitter without deflection, possessing a polarization mode that is orthogonal to the polarization mode of the incoming reflective ` beam.
In accordance with one aspect of the invention there is provided a beam combiner/splitter characterized by a first energy beam comprising beamlets that form a first pattern of waists at a first surface; a second ener~y beam comprising beamlets that form a second pattern of waists at a second surface; and a third beam comprisingbeamlets that form a third pattern of waists, related to a combination of said first and said " ~`, ~31~ ~2 second patterns of waists, at a third surEace that is spatially related to said first and second sur&ces; and a mirror having a collection of reflective areas and transmissi~e are3s with said reflective areas arranged in accordance with said first pattern and said transmissive areas arranged in accordance with said second pattem; with said mirror situated in first S proximity to said first surface, and having said reflective areas face said first beam, with said first proximity being such that loss due to three-dimensional misalignment of said waists and said re~ective areas is below a preselected first threshold, and crosstalk between the energy of the beamlets corresponding to the waists on said reflective areas is below a second preselected threshold, and in proximi~r to said second surface su- h that loss due to three-dimensional misalignment of said waists and said transmissive areas is below a preselected third threshold.
Brief l~escription ot the DrawinP
FIG. 1 shows a prior art approach to beam combining;
FIG. 2 shows the arrangement of light spots from two beam arrays that form the input to an optical logic array;
depicts one realization for a beam splitter in accordance with the principles of our invention;
FlGS. 4 and 5 illustrate enhanced embodiments of the realization presented in FlG. 3, FIG. 6 shows the use of our invention to combine more than two beams;
FIG. 7 presents a realization of our invention that employs a beam splitter;
and FIG. 8 illustrates a realization of our invention for combining three beams with the aid of one beam splitter.
l~etailed l~escl-ipffol~
One approach for combining or separating two beam arrays is to apply them to a beam splitter as shown, for example, in FIG. 1. Beam 11 is applied to cube beam splitter 10 at one face of the beam splitter, where it is split into beams 13 and 14.
Beam 12 is applied to beam splitter 10 at another face of the splitter (orthogonal to the first face), wherein it is split into beams 15 and 16. Beams 14 and 15 e~t beam splitter 10 at the same face (to the right) and thus they are combined. Alas, using simple beam splitters to achieve beam combining entails loss, since ener~y is diverted to beams 1~ and 16.
?~.
Polari~ation-dependent beam splitters can also be uxed to combine two beams, and such combining is achieved essentially but without loss. In the arrangement of FIG. 1 where the beam splitter is sensitive to the polarization mode of the incoming light, it can be arranged for the light of beam 11 to be so polarized that it passes through the S bearn splitter without deflection, thus placing no energy in beam 1~. Similarly, it can be arranged for the light of beam 12 to be so polarized that it is deflected in the beam splitter, thus placing no energy in beam 16. The resultant beam combining that occurs within beam splitter 10 is lossless, but the combined beam is partially polarized in one mode and partially polarized in another mode.
Dichroic beam splitters can be used7 in principle, to combine beams of different wavelengths without loss. In practice, however, we may not wish to be constrained to use dif~erent wavelengths for the different beams, and devices may not work if such different wavelengths are used.
In a different environment, and for a different purpose, image combining 15 has been accomplished with the use of a reflective grating. This approach is described in "Real Time Incoherent Optical-Electronic Image Substraction," Dashiell et al., ~ptics Communications~ June, 1973, pps. 105-108. The described approach passes one image through a reflective grating and re~lects another image through the same grating. The grating in effect samples both images. The combined sample images are then applied to 20 an image plane where the sampled combined image is converted to electronic signals and processed. This is akin to sampling a signal at a high rate (above Nyquist rate), combining the sampled signals, and filtering with an appropriate bandpass filter. Of course, there is loss associated with this approach because a portion of each image is missing. In fact, in its operation (vis-a-vis loss) the Dashiell et al. arrangement is identical to the arrangement 25 of Fig. 1, but optically more complex.
FIG. 2 depicts a possible arrangement where the principles of this invention can be utili~ed. Rectangle 20 represents a surface that contains optical logic elements 21, such as SEED devices. It is desired to apply to each logic element 21 two light spots, such as 22 and 23. Rectangle 25 represents the surface of light emitting devices 26. This can ~0 be a structure on there is place an array of LED, a source of light spots derived from a single laser beam, etc. Devices 26 correspond in number and relative position to light spots 22 of rectangle 20. It is realized, of course, that maglufication and reduction are possible, but for purposes of this description and for the sake of simplicity, a magnification .,~, , 1 3 ~
4a factor of 1 is assumed. Rectangle 27 represents another surface of light emitting devices 28, and these devices correspond to light spots 2~ of rectangle 20. It maybe noted that in FIG. 2 light sources 28 have a positional orientation within rectangle 27 that is slightly S shifted to the left when compared to the positional orientation of elements 26 in rectangle 25. This shift corresponds to the separation between light spots 22 and 2~ in rectangle 20.
In an actual realization, however, it is likely that the entire array (the rectangle and its associated light sources) would be shifted.
What is necessary to accomplish is tlhe combining of light sources 26 and 10 light sources 28 and to apply the combined energy onto rectangle 20.
FIG. ~ depicts one arrangement in accordance with the principles of this invention. In FIG. ~, light sources from rectangle 25 pass through an appropriate focusing lens to result in beam ~5 that focuses an array of spots onto a plane indicated by dashed line 36. Similarly, light sources from rectangle 27 pass through 15 an appropriate focusing lens and resulting beam ~7 that focuses an array of spots onto a plane represented by dashed line ~8. Mirror 24 is a thin glass plate on which reflective areas 29 are deposited. The front view of mirror 24 is shown in FIG. 2.
It may be noted that the reflective areas of mirror 24 for the FIG. ~ arrangements are elliptical, with the major a~is being~ times the mirror a~s. This accounts for the 20 tilt of the mirror with respect to reflected beam 3~. As arranged in FIG. ~, the light of beam ~5 passes entirely through the transmissive portion of mirror 24 while the light of beam ~7 is reflected in its entirety of~ reflective areas 29 of mirror 24. Also . . , as arranged in FIG. 3, beam 37 is approximately at right angles to beam 35 and mirror 24 is approximately an angle of 45 with respect to the center axis (34) of beam 35. That is, rnirror 24 is an angle that is half the angle between the center axes of beams 35 and 37. The light transmitted through mirror 24, combined with the S light reflected off mirror 24, is applied to focusing lens 40. Lens 40 f~uses light spots 22 and 23 onto plane 20.
From FIG. 3 it is readily apparent that beams 35 and 37 must be very weakly converging because the waist of the beamlets of bearn 35 do not all coincide in space with the transmissive portions of mirror 24. The waists are at plane 36, 10 while the mirror is at a different plane (that is at a 45 angle thereto).
Correspondingly, the waists of the beamlets of beam 37 (at plane 38) also do not all coincide with the reflective areas of rnirror 24. Use of beams 3S and 37 that are not very weakly converging would result in two problems. First, with respect to beam35, some light rnight not be transmitted (when it expands to cover more than the15 transmissive portion of the mir~r) and the loss of light, when it occurs, would increase with the distance away from the center axis of beam 35. With respect tobeam 37, light might also be lost when the beam is wider than the reflective portion and, additionally, crosstalk can occur when the energy of one spot is comingled on the reflective por~ions of mirror 24 with the energy of another spot.
FIG. 4 illustrates an opdcal setup that minimizes the above problem. In FIG. 4, bearn 37 is situated at an angle ~ with respect to ~he centcr axis of beam 35 that is as close to 180 as is possible, and miIror 24 is situated at the angle ~/2.
~IG. S depicts an ar~angement that is similar to the arrangement ~ FIG.
4, but it includes field lenses 41 and 42. Lenses 41 and 42 image the pupil of the 25 source onto the pupil of the objective, which permit lens 40 to have a smaller diameter.
FIG. 6 presents an optical arrangement mocleled after FIG. 3 that may be employed when more than ~wo beams are to be combined. In essence, mirror 43 combines beams 44 and 45, to form combined beam 46, and miITor 47 combines 30 beam 46 and beam 48. A focusing relay lens 49 is placed between mirror 43 andmi~ror 47 and field lenses 49, 50, and 51 can also be included. The principles employed in FI{}. 6 can easily be extended to a larger number of beams to be combined. As an aside, it may be observed that the spatial arrangement of mirror 47 is different from that of mirror 43, with ~he folmer most lilcely having more 35 llansmissive areas than the latter.
J,~
Mirrors such as the ones described above, with arbitrary patterns of reflective and transmissive regions, can be fabricated by conventional lithographic techniques. In one conventional approach, for example, a metallic rcflective coating is deposited on a glass substrate, and photoresist is applied to the substrate. The 5 photoresist is then exposed in the usual manner with the appropriate pattern from a lithographic mask, etched away to expose the areas of rnetal to be removed, and the metal is then etched away. At this stage, an antireflection coating is conveniently evaporated onto the exposed glass substrate to rernove any residual reflectivity of the glass surface (or reduce it to acceptably low levels), and finally the remaining10 photoresist is removed. The back surface of the whole substrate could also beandreflection coated to reduce reflection off this surface as well. Similar results can be obtained using dielectric mirror coadngs in place of the metallic coating. Many other methods of making such space-variant mirrors would be obvious to those skilled in the art.
If the glass substrate is thick, allowance has to be made for ~he lateral displacement that the substrate would induce on the transmitted beams. This involves adjustments in the positioning of the preceding mirrors or incorporation of compensating plates.
FIG. 7 presents an optical setup that employs the principles of our 20 invention and also overcomes the drawbacks of the FIG. 3 optical setup. In FIG. 7, beam 37 is applied to a beam splitter (here, cubic be~m splitter 60) that is sensitive to the polarization of light. That is, it deflects light that is y-polarized and passes light that is x-polarized. Beam 37 is arranged to be y-polaIized and, accordingly, it is deflected to the right in beam spli~ter 60. At the ~ace of beam splitter 60 where 25 beam 37 exits there is an aIrangement comprising a quarter-wave plate 61, a focusing lens 62, and a space variant m~rr~r 63. Beam 35 is applied, as in FIG. 3, from the right of mi~ror 63. The light of beam 35 focuses to an array of spots at the plane of mirror 63, and mirror 63 is positioned to align the ~ransmissive areas of the mirrors with the waists of the focused beam 35. Beam 35 is circularly polarized.30 The light transmitted thlough mirror 63 is collimated in lens 62 and applied to plate 61. Plate 61 converts the circularly polarized light to x-polarization and applies that light to beam splitter 60. The x-polarized light passes through beam splitter 60.
Beam 37 is applied in the FIG. 7 optical setup from the top. It is collimated and possesses a y-pol~zation. The collimated light is deflected in beam 35 splitter 60 and passes through plate 61 where it is converted to circular polarization.
Lens 62 focuses the light of beam 37 onlo the reflective areas of mirror 63. That light is reflected, collimated in lens 62, converted to x-polarization in plate 61, and passes through beam splitter 60 together with beam 35.
It may be appreciated that the order of lens 62 and plate 61 can be 5 interchanged. Indeed, lens 62 can be positioned before the beam splitter, although such an alrangement must deal w~th divergent beams as they exit the beam splitter to the left (after being combined). It may also be appreciated that the FIG. 7 optical setup can be simplified when one is ~lling to accept loss. In such a ease, one can use a beam splitter that is not polarization sensitive and one can do without the 10 quarter wave plate. The polarization of light would be immaterial in such an optical setup.
The above descriptions illustrate and teach the principles of our invention, but it is realized that many extensions naturally flow from these teachings, both with respect to general manipulations of beams, and with respect to specific 15 realizations. For example, it is probably clear to the skilled ar~san that the beam combining principles described above apply equally well to beam splitting needs.Also, combining three beams with an optical setup aldn tO the setup of FIG. 7 isquite straightforward, as illustrated by FIG. 8.
In FIG. 8, beam 53 is circularly polarized. It passes through space 20 variant rn~or 74, lens 72, and through ~uarter-wave plate 71 where it is conveIted to y-polari~adon. The beam is then applied to beam splitter 60 where it is deflected to the output of the beam splitter. Beam 37, which is y-polarized, is deflected in beam splitter 60, passes through quarter-wave pIate 61, is reflected off space variant mirror S3, and passes through plate 61 a second ~ime whereupon it assumes x-polalization.
25 Thereafter, the beam passes ~rough beam splitter 60, passes through plate 71, is reflected off mirror 74, and passes through plate 71 a second time, whereupon isassumes y-polarization. The beam then re-enters beam splitter 60 and is deflected to the output. Beam 35, possessing circular polarization, passes through mirror 63 and plate 61 and assumes x-polarizadon. Thereafter it follows the path taken by beam30 37.
Claims (11)
1. A beam combiner/splitter characterized by a first energy beam comprising beamlets that form a first pattern of waists at a first surface;
a second energy beam comprising beamlets that form a second pattern of waists at a second surface; and a third beam comprising beamlets that form a third pattern of waists, related to a combination of said first and said second patterns of waists, at a third surface that is spatially related to said first and second surfaces; and a mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said first pattern and said transmissive areas arranged in accordance with said second pattern; with said mirror situated in first proximity to said first surface, and having said reflective areas face said first beam, with said first proximity being such that loss due to three-dimensional misalignment of said waists and said reflective areas is below a preselected first threshold, and crosstalk between the energy of the beamlets corresponding to the waists on said reflective areas is below a second preselected threshold, and in proximity to said second surface such that loss due to three-dimensional misalignment of said waists and said transmissive areas is below a preselected third threshold.
a second energy beam comprising beamlets that form a second pattern of waists at a second surface; and a third beam comprising beamlets that form a third pattern of waists, related to a combination of said first and said second patterns of waists, at a third surface that is spatially related to said first and second surfaces; and a mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said first pattern and said transmissive areas arranged in accordance with said second pattern; with said mirror situated in first proximity to said first surface, and having said reflective areas face said first beam, with said first proximity being such that loss due to three-dimensional misalignment of said waists and said reflective areas is below a preselected first threshold, and crosstalk between the energy of the beamlets corresponding to the waists on said reflective areas is below a second preselected threshold, and in proximity to said second surface such that loss due to three-dimensional misalignment of said waists and said transmissive areas is below a preselected third threshold.
2. A beam combiner/splitter characterized by a first beam that focuses into a first pattern of spots at a first surface;
a second beam that focuses into a second pattern of spots at a second surface; and a space variant mirror having a collection of reflective areas and transmissive areas, with said reflective areas arranged in accordance with said first pattern and said non-reflective areas arranged in accordance with said second pattern;
with said mirror situated in first proximity to said first surface, and having said reflective areas positioned to reflect said first beam, with said first proximity being such that loss due to mis-focus of said Spots on said reflective areas is below a preselected first threshold, and crosstalk between spots on said reflective areas due to mis-focus is below a second preselected threshold, and in proximity to said second surface such that loss due to mis-focus of said spots on said transmissive areas is below a preselected third threshold.
a second beam that focuses into a second pattern of spots at a second surface; and a space variant mirror having a collection of reflective areas and transmissive areas, with said reflective areas arranged in accordance with said first pattern and said non-reflective areas arranged in accordance with said second pattern;
with said mirror situated in first proximity to said first surface, and having said reflective areas positioned to reflect said first beam, with said first proximity being such that loss due to mis-focus of said Spots on said reflective areas is below a preselected first threshold, and crosstalk between spots on said reflective areas due to mis-focus is below a second preselected threshold, and in proximity to said second surface such that loss due to mis-focus of said spots on said transmissive areas is below a preselected third threshold.
3. Apparatus for combining a first beam that focuses into a first pattern of spots at a first surface and a second beam that focuses into a second pattern array of spots at a second surface comprising:
a space variant mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said first pattern and said non-reflective areas arranged in accordance with said second pattern;
with said mirror situated in first proximity to said first surface, and having said reflective areas face said first beam, with said first proximity being such that loss due to mis-focus of said spots on said reflective areas is below a preselected first threshold, and interference between spots on said reflective areas due to mis-focus is below a second preselected threshold, and in proximity to said second surface such that loss due to mis-focus of said spots on said transmissive areas is below a preselected third threshold.
a space variant mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said first pattern and said non-reflective areas arranged in accordance with said second pattern;
with said mirror situated in first proximity to said first surface, and having said reflective areas face said first beam, with said first proximity being such that loss due to mis-focus of said spots on said reflective areas is below a preselected first threshold, and interference between spots on said reflective areas due to mis-focus is below a second preselected threshold, and in proximity to said second surface such that loss due to mis-focus of said spots on said transmissive areas is below a preselected third threshold.
4. The beam combiner according to claim 3, further comprising collection optics and having said mirror further arranged so that spot energy reflected off said reflective areas and spot energy transmitted through said transmissive areas pass into said collection optics.
5, The beam combiner according to claim 4 where said first surface is a plane perpendicular to a first axis, said second surface is a plane perpendicular to said second surface, with said first axis forming an angle .theta. with respect to said second axis, and said mirror being situated at an angle with respect to said first axis that is substantially .theta./2.
6. A beam combiner according to claim 1, further comprising:
a third energy beam comprising beamlets that form a third pattern of waists at a third surface;
a fourth energy beam comprising beamlets that form a fourth pattern of waists at a fourth surface; and a second mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said third pattern and said transmissive areas arranged in accordance with said fourth pattern; with said third and fourth beams forming said second beam and said mirror situated in third proximity to said third surface, and having said reflective areas face said third beam, with said third proximity being such that loss due to three-dimensional misalignment of said waists and said reflective areas is below a preselected fourth threshold, and crosstalk between the energy of the beamlets corresponding to the waists on said reflective areas is below a fifth preselected threshold, and in fourth proximity to said fourth surface, with said fourth proximity being such that loss due to three-dimensional misalignment of said waists and said transmissive areas is below a preselected sixth threshold.
a third energy beam comprising beamlets that form a third pattern of waists at a third surface;
a fourth energy beam comprising beamlets that form a fourth pattern of waists at a fourth surface; and a second mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said third pattern and said transmissive areas arranged in accordance with said fourth pattern; with said third and fourth beams forming said second beam and said mirror situated in third proximity to said third surface, and having said reflective areas face said third beam, with said third proximity being such that loss due to three-dimensional misalignment of said waists and said reflective areas is below a preselected fourth threshold, and crosstalk between the energy of the beamlets corresponding to the waists on said reflective areas is below a fifth preselected threshold, and in fourth proximity to said fourth surface, with said fourth proximity being such that loss due to three-dimensional misalignment of said waists and said transmissive areas is below a preselected sixth threshold.
7. A beam splitter arrangement comprising:
a first energy beam comprising beamlets that form a first pattern of waists at a first surface;
a second energy beam comprising beamlets that form a second pattern of waists at a second surface;
a third beam comprising beamlets that form a third pattern of waists, related to a combination of said first and said second patterns of waists, at a third surface that is spatially related to said first and second surfaces;
a mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said first pattern and said transmissive areas arranged in accordance with said second pattern; and a beam splitter for diverting said first energy beam to said reflective areas of said mirror.
a first energy beam comprising beamlets that form a first pattern of waists at a first surface;
a second energy beam comprising beamlets that form a second pattern of waists at a second surface;
a third beam comprising beamlets that form a third pattern of waists, related to a combination of said first and said second patterns of waists, at a third surface that is spatially related to said first and second surfaces;
a mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said first pattern and said transmissive areas arranged in accordance with said second pattern; and a beam splitter for diverting said first energy beam to said reflective areas of said mirror.
8. A beam splitter arrangement comprising:
a first collimated energy beam comprising beamlets that, when focused, form a first pattern of waists at a first surface;
a second energy beam comprising beamlets that form a second pattern of waists at a second surface;
a third beam comprising beamlets that form a third pattern of waists, related to a combination of said first and said second patterns of waists, at a third surface that is spatially related to said first and second surfaces;
a mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said first pattern and said transmissive areas arranged in accordance with said second pattern;
a beam splitter for diverting said first energy beam to said reflective areas of said mirror; and a lens interposed between said beam splitter and said mirror.
a first collimated energy beam comprising beamlets that, when focused, form a first pattern of waists at a first surface;
a second energy beam comprising beamlets that form a second pattern of waists at a second surface;
a third beam comprising beamlets that form a third pattern of waists, related to a combination of said first and said second patterns of waists, at a third surface that is spatially related to said first and second surfaces;
a mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said first pattern and said transmissive areas arranged in accordance with said second pattern;
a beam splitter for diverting said first energy beam to said reflective areas of said mirror; and a lens interposed between said beam splitter and said mirror.
9. The arrangement of claim 7 wherein said first beam is polarized in a first mode, said second beam is polarized in another mode and said beam splitterreflects light that is polarized in said first mode and transmits light that is polarized orthogonally to said first mode.
10. The arrangement of claim 9 further comprising a quarter-wave plate between said beam splitter and said mirror.
11. Apparatus for combining a first energy beam comprising beamlets that form a first pattern of waists at a first surface, and a second energy beamcomprising beamlets that form a second pattern of waists at a second surface characterized by:
a mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said first pattern and said transmissive areas arranged in accordance with said second pattern; with said mirror situated in first proximity to said first surface, and having said reflective areas face said first beam, with said first proximity being such that loss due to three-dimensional misalignment of said waists and said reflective areas is below a preselected first threshold, and crosstalk between the energy of the beamlets corresponding to the waists on said reflective areas is below a second preselected threshold, and in second proximity to said second surface, with said second proximity being such that loss due to three-dimensional misalignment of said waists and said transmissive areas is below a preselected third threshold.
a mirror having a collection of reflective areas and transmissive areas with said reflective areas arranged in accordance with said first pattern and said transmissive areas arranged in accordance with said second pattern; with said mirror situated in first proximity to said first surface, and having said reflective areas face said first beam, with said first proximity being such that loss due to three-dimensional misalignment of said waists and said reflective areas is below a preselected first threshold, and crosstalk between the energy of the beamlets corresponding to the waists on said reflective areas is below a second preselected threshold, and in second proximity to said second surface, with said second proximity being such that loss due to three-dimensional misalignment of said waists and said transmissive areas is below a preselected third threshold.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US24846888A | 1988-09-23 | 1988-09-23 | |
| US248,468 | 1988-09-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1318162C true CA1318162C (en) | 1993-05-25 |
Family
ID=22939270
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000611247A Expired - Fee Related CA1318162C (en) | 1988-09-23 | 1989-09-13 | Arrangement for imaging multiple arrays of light beams |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH02244023A (en) |
| CA (1) | CA1318162C (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7499615B2 (en) * | 2007-08-01 | 2009-03-03 | Hewlett-Packard Development Company, L.P. | System and methods for routing optical signals |
| FR3012226B1 (en) * | 2013-10-18 | 2015-10-30 | Saint Gobain | MODULAR LASER APPARATUS |
-
1989
- 1989-09-13 CA CA000611247A patent/CA1318162C/en not_active Expired - Fee Related
- 1989-09-22 JP JP24540489A patent/JPH02244023A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02244023A (en) | 1990-09-28 |
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