Orientation dependent radiation source

• US 6,384,908 B1
• Filed: 05/24/1999
• Issued: 05/07/2002
• Est. Priority Date: 08/15/1996
• Status: Expired due to Term

• Current Assignee: Go Sensors LLC
• Original Assignee: Go Sensors LLC
• Inventors: Armstrong, Brian S. R., Schmidt, Karl B.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/317,052
• Time in Patent Office: 1,079 Days
• Field of Search: 356/152.1, 356/139.03, 356/141.3, 356/141.5, 356/152.2, 356/152.3
• US Class Current: 356/152.3
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01D 5/30 the beams of light being detected by photocells
• CPC Class Codes: G01S 17/74 Systems using reradiation of electromagnetic waves other than radio waves, e.g. IFF, i.e. identification of friend or foe
• CPC Class Codes: G02B 5/09 Multifaceted or polygonal mirrors , e.g. polygonal scanning mirrors; Fresnel mirrors

Abstract

Methods and apparatus for producing orientation dependent radiation, and orientation detection systems are disclosed. An orientation dependent radiation source directs radiation to an observation area and facilitates a determination of the orientation of the orientation dependent source from the observation area. In particular, the orientation dependent source produces a radiation pattern having one or more detectable centroids that vary in position across an observation surface of the orientation dependent source as observed from the observation area, based on a rotation of the orientation dependent source about one or more axes of rotation. According to various embodiments, the orientation dependent radiation source may include one or more primary radiation sources or secondary sources, such as reflectors. One or more orientation dependent sources may be employed in an orientation detection system according to the invention which includes a radiation sensor located in the observation area to detect the orientation dependent radiation pattern produced by one or more orientation dependent radiation sources. Additionally, the radiation pattern produced by an orientation dependent source may be visibly observable, allowing an observer to qualitatively determine the orientation of the source from the observation area.

Claims

1. Apparatus comprising:

a first mask to substantially block radiation, the first mask defining an observation surface and including a first plurality of openings through which radiation is capable of passing; and

a second mask coupled to the first mask, the second mask including a second plurality of openings offset relative to the first plurality of openings such that radiation passing through at least the first plurality of openings produces an orientation dependent radiation pattern on the observation surface, the orientation dependent radiation pattern having at least one detectable centroid that varies in position across the observation surface based on a rotation angle of the first and second masks about at least one axis of rotation.

2. The apparatus of claim 1, wherein each opening of at least one of the first and second plurality of openings has a substantially rectilinear shape.

3. The apparatus of claim 1, wherein each opening of at least one of the first and second plurality of openings has an at least partially curved shape.

4. The apparatus of claim 1, wherein each opening of at least one of the first and second plurality of openings has a substantially circular shape.

5. The apparatus of claim 1, wherein each opening of the first and second plurality of openings is identically shaped.

6. The apparatus of claim 1, wherein at least some openings of the first and second plurality of openings are differently shaped.

7. The apparatus of claim 1, wherein the first plurality of openings is arranged as a first two-dimensional pattern.

8. The apparatus of claim 7, wherein the second plurality of openings is arranged as a second two-dimensional pattern.

9. The apparatus of claim 8, wherein the first two-dimensional pattern and the second two-dimensional pattern are arranged such that the at least one detectable centroid varies in position across the observation surface in two dimensions.

10. The apparatus of claim 9, wherein the observation surface has a rectangular shape.

11. The apparatus of claim 9, wherein the observation surface has a circular shape.

12. The apparatus of claim 9, wherein the observation surface has an elliptical shape.

13. The apparatus of claim 12, wherein:

the at least one axis of rotation includes a major axis and a minor axis in a plane of the observation surface; and

the first two-dimensional pattern and the second two-dimensional pattern are arranged such that a first sensitivity of the position of the at least one detectable centroid along the major axis based on a first rotation angle of the first and second masks about the minor axis is different from a second sensitivity of the position of the at least one detectable centroid along the minor axis based on a second rotation angle of the first and second masks about the major axis.

14. The apparatus of claim 1, further including a supply radiation source to direct the radiation toward the first mask and the second mask, the second mask being disposed between the source and the first mask to substantially block the radiation, the radiation passing through the second plurality of openings.

15. The apparatus of claim 14, wherein the supply source is coupled to the first and second masks.

16. The apparatus of claim 14, wherein the supply source includes a point source that radiates the radiation multidirectionally.

17. The apparatus of claim 14, wherein:

the at least one axis of rotation includes a first axis of rotation; and

an amount of radiation radiated by the source varies in a direction orthogonal to the first axis.

18. The apparatus of claim 17, wherein:

the at least one axis of rotation includes a first axis of rotation and a second axis of rotation, the second axis being orthogonal to the first axis, the first and second axes intersecting at a point on the observation surface; and

the amount of radiation radiated by the source varies radially along the observation surface from the point.

19. The apparatus of claim 14, wherein the second mask is formed by a controllable transmissive liquid crystal display.

20. The apparatus of claim 19, wherein the controllable transmissive liquid crystal display includes the supply source.

21. The apparatus of claim 20, wherein the controllable transmissive liquid crystal display includes means for varying a color of the at least one detectable centroid across the observation surface.

22. The apparatus of claim 14, wherein the supply source includes at least one reflector.

23. The apparatus of claim 22, wherein:

the at least one axis of rotation includes a first axis of rotation; and

a reflectance of the at least one reflector varies in a direction orthogonal to the first axis.

24. The apparatus of claim 23, wherein a granularity of the at least one reflector varies in the direction orthogonal to the first axis such that a specular reflection of the at least one reflector varies in the direction orthogonal to the first axis.

25. The apparatus of claim 23, wherein:

the at least one axis of rotation includes a first axis of rotation and a second axis of rotation, the second axis being orthogonal to the first axis, the first and second axes intersecting at a point of the observation surface; and

the reflectance of the at least one reflector varies in directions parallel to both the first and second axes, such that an intensity of the orientation dependent radiation pattern varies radially along the observation surface from the point.

26. The apparatus of claim 22, wherein the at least one reflector includes at least one retro-reflector to return incident radiation in a direction parallel to the incident radiation.

27. The apparatus of claim 26, wherein the at least one retro-reflector includes a sheet of retro reflecting material adhesively coupled to the second mask.

28. The apparatus of claim 26, wherein the at least one retro-reflector includes a spreadable mixture of suspended retro reflecting particles coating the second mask.

29. The apparatus of claim 22, wherein the second mask and the at least one reflector are formed by a controllable reflective liquid crystal display.

30. The apparatus of claim 29, wherein the controllable reflective liquid crystal display includes means for varying a color of the at least one detectable centroid across the observation surface.

31. The apparatus of claim 22, wherein the at least one reflector includes a controllable movable micro-mirror assembly.

32. The apparatus of claim 22, wherein:

the second mask is disposed between the at least one reflector and the first mask; and

a surface of the second mask facing the at least one reflector includes a reflective coating.

33. The apparatus of claim 32, wherein the at least one reflector includes at least one retro-reflector to return incident radiation in a direction parallel to the incident radiation.

34. The apparatus of claim 22, wherein the at least one reflector includes a pattern of surface perturbations.

35. The apparatus of claim 34, wherein the pattern of surface perturbations is arranged in a predetermined manner relative to the first and second plurality of openings.

36. The apparatus of claim 34, wherein the pattern of surface perturbations includes at least one curved bump.

37. The apparatus of claim 34, wherein the pattern of surface perturbations includes at least one triangular bump.

38. The apparatus of claim 34, wherein the at least one reflector includes at least one retro-reflector to return incident radiation in a direction parallel to the incident radiation.

39. The apparatus of claim 34, wherein:

the second mask is disposed between the at least one reflector and the first mask; and

a surface of the second mask facing the at least one reflector includes a reflective coating.

40. The apparatus of claim 39, wherein the at least one reflector includes at least one retro-reflector to return incident radiation in a direction parallel to the incident radiation.

41. The apparatus of claim 1, wherein the second mask includes at least one reflector.

42. The apparatus of claim 41, wherein:

the second mask includes a retro reflective pattern; and

the first plurality of openings is offset relative to the retro reflective pattern.

43. The apparatus of claim 42, wherein the second mask includes a plurality of retro reflective patches.

44. The apparatus of claim 42, wherein the second mask is formed from a sheet of retro reflecting material adhesively coupled to the first mask.

45. The apparatus of claim 42, wherein the second mask is formed from a spreadable mixture of suspended retro reflecting particles.

46. The apparatus of claim 42, wherein the at least one reflector includes a controllable movable micro-mirror assembly.

47. The apparatus of claim 1, wherein:

the second mask includes a plurality of polygon shaped rods, each polygon shaped rod having a plurality of faces and being aligned essentially parallel to a first axis of rotation of the first and second masks, each rod being laterally translatable along a direction parallel to the observation surface and orthogonal to the first axis, each rod being rotatable about a rod axis of rotation passing through a geometric center of the rod; and

the apparatus further includes at least one translational and rotational controller to independently rotate each rod about the rod axis and to independently translate each rod along the direction parallel to the observation surface such that the second plurality of openings is offset to the first plurality of openings.

48. The apparatus of claim 47, wherein:

each rod is a triangular shaped rod having three faces;

a first face of each rod includes a reflector;

a second face of each rod includes a retro-reflector; and

a third face of each rod includes a non-reflective material.

49. The apparatus of claim 48, wherein the at least one translational and rotational controller rotates the plurality of rods such that a same face of each rod is parallel to the observation surface.

50. The apparatus of claim 1, further including at least one orientation independent radiation source coupled to the first mask and the second mask to produce an orientation independent radiation pattern.

51. The apparatus of claim 50, wherein the at least one orientation independent radiation source produces the orientation independent radiation pattern on the observation surface.

52. The apparatus of claim 50, wherein:

the first mask, the second mask, and the at least one orientation independent radiation source form an assembly having opposing lateral surfaces orthogonal to the observation surface; and

the at least one orientation independent radiation source produces the orientation independent radiation pattern on at least one lateral surface.

53. The apparatus of claim 52, wherein:

each lateral surface has a first region and a second region;

a first orientation independent radiation source produces a first orientation independent radiation pattern in the first region of one lateral surface; and

a second orientation independent radiation source produces a second orientation independent radiation pattern in the second region of another lateral surface.

54. The apparatus of claim 50, wherein the at least one orientation independent radiation source is a reflector.

55. The apparatus of claim 1, further including a support structure to which the first mask and the second mask are coupled, the support structure being constructed and arranged so as to not obstruct the radiation.

56. The apparatus of claim 55, wherein the support structure is disposed between the first mask and the second mask.

57. The apparatus of claim 56, wherein the support structure is constructed and arranged as a lens.

58. The apparatus of claim 55, wherein:

the support structure includes a first surface and a second surface;

the first mask is coupled to the first surface; and

the second mask is coupled to the second surface.

59. The apparatus of claim 58, wherein the support structure is a substrate disposed between the first mask and the second mask, the substrate being substantially transmissive of the radiation.

60. The apparatus of claim 59, wherein a thickness of the substrate is variable during normal operation of the apparatus such that a first distance separating the first mask from the second mask is variable.

61. The apparatus of claim 60, wherein the substrate includes a temperature sensitive material such that the thickness varies with a substrate temperature.

62. The apparatus of claim 61, further including a temperature controller to control the substrate temperature.

63. The apparatus of claim 1, wherein the second mask is arranged substantially parallel to the first mask such that a surface of the second mask facing the first mask is substantially parallel to the observation surface, the second mask being separated from the first mask by a first distance.

64. The apparatus of claim 63, further including a lens coupled to the observation surface.

65. The apparatus of claim 63, wherein the first mask is substantially planar such that the observation surface is substantially planar.

66. The apparatus of claim 63, wherein the first mask is curved such that the observation surface is curved.

67. The apparatus of claim 66, wherein the second mask is curved and is arranged substantially parallel to the first mask.

68. The apparatus of claim 67, further including a curved reflector coupled to at least one of the first mask and the second mask and arranged substantially parallel to the first mask.

69. The apparatus of claim 67, wherein the observation surface has a concave shape.

70. The apparatus of claim 67, wherein the observation surface has a convex shape.

71. The apparatus of claim 70, wherein the first and second masks are constructed and arranged as concentric spherical shells, the second mask having a smaller radius than the first mask.

72. The apparatus of claim 71, further including a point source located within the concentric spherical shells to radiate the radiation multidirectionally.

73. The apparatus of claim 71, further including a reflective spherical shell coupled to at least one of the first mask and the second mask and concentric with the first and second masks, the reflective spherical shell having a smaller radius than the second mask.

74. The apparatus of claim 70, wherein the first and second masks are constructed and arranged as elliptical shells.

75. The apparatus of claim 63, wherein the first distance is variable during normal operation of the apparatus.

76. The apparatus of claim 75, wherein at least one of the first mask and the second mask are coupled to a translational controller to vary the first distance.

77. The apparatus of claim 63, further including a fluid disposed between the first mask and the second mask.

78. The apparatus of claim 77, further including a controllable valve to vary a volume of the fluid such that the first distance is variable during normal operation of the apparatus.

79. The apparatus of claim 63, further including a gas disposed between the first mask and the second mask.

80. The apparatus of claim 79, further including a controllable valve to vary a volume of the gas such that the first distance is variable during normal operation of the apparatus.

81. The apparatus of claim 63, further including at least one reflector coupled to the first and second masks and arranged substantially parallel to the first and second masks, the second mask being disposed between the first mask and the at least one reflector and separated from the at least one reflector by a second distance.

82. The apparatus of claim 81, wherein the second distance is variable during normal operation of the apparatus.

83. The apparatus of claim 1, wherein the radiation is visibly observable.

84. The apparatus of claim 83, further including at least one substantially transparent color filter through which the radiation passes.

85. The apparatus of claim 84, further including a source of radiation to direct the radiation toward the first mask and the second mask, wherein:

the second mask is disposed between the source and the first mask to substantially block the radiation, the radiation passing through the second plurality of openings; and

the source includes the at least one color filter.

86. The apparatus of claim 84, wherein at least one of the first mask and the second mask includes the at least one color filter.

87. The apparatus of claim 84, further including a substrate to which the first mask and the second mask are coupled, the substrate including the at least one color filter.

88. The apparatus of claim 87, further including:

a source of radiation to direct the radiation toward the first mask and the second mask, the second mask being disposed between the source and the first mask to substantially block the radiation, the radiation passing through the second plurality of openings; and

a second color filter through which the radiation passes, the second color filter being disposed between the source and the second mask.

89. The apparatus of claim 84, wherein the at least one color filter is constructed and arranged such that a color of the at least one detectable centroid varies as a position of the at least one detectable centroid varies across the observation surface.

90. The apparatus of claim 89, wherein:

the at least one axis of rotation includes a first axis of rotation; and

the color of the at least one detectable centroid varies along the observation surface in a direction orthogonal to the first axis.

91. The apparatus of claim 89, wherein:

the at least one axis of rotation includes a first axis of rotation and a second axis of rotation, the second axis being orthogonal to the first axis, the first and second axes intersecting at a point on the observation surface; and

the color of the at least one detectable centroid varies radially along the observation surface from the point.

92. The apparatus of claim 1, further including at least one non-uniform polarizing filter through which the radiation passes.

93. The apparatus of claim 92, further including a source of radiation to direct the radiation toward the first mask and the second mask, wherein:

the second mask is disposed between the source and the first mask to substantially block the radiation, the radiation passing through the second plurality of openings; and

the source includes the at least one non-uniform polarizing filter.

94. The apparatus of claim 92, further including a substrate to which the first mask and the second mask are coupled, the substrate including the at least one non-uniform polarizing filter.

95. The apparatus of claim 92, wherein the at least one non-uniform polarizing filter is constructed and arranged such that a polarization of the at least one detectable centroid varies as a position of the at least one detectable centroid varies across the observation surface.

96. The apparatus of claim 95, wherein:

the at least one axis of rotation includes a first axis of rotation; and

the polarization of the at least one detectable centroid varies along the observation surface in a direction orthogonal to the first axis.

97. The apparatus of claim 95, wherein:

the at least one axis of rotation includes a first axis of rotation and a second axis of rotation, the second axis being orthogonal to the first axis, the first and second axes intersecting at a point on the observation surface; and

the polarization of the at least one detectable centroid varies radially along the observation surface from the point.

98. The apparatus of claim 95, further including at least one color filter through which the radiation passes, the color filter being constructed and arranged such that a color of the at least one detectable centroid varies as the position of the at least one detectable centroid varies across the observation surface.

99. The apparatus of claim 1, further including at least one neutral density filter through which the radiation passes.

100. The apparatus of claim 99, further including a source of radiation to direct the radiation toward the first mask and the second mask, wherein:

the second mask is disposed between the source and the first mask to substantially block the radiation, the radiation passing through the second plurality of openings; and

the source includes the at least one neutral density filter.

101. The apparatus of claim 99, further including a substrate to which the first mask and the second mask are coupled, the substrate including the at least one neutral density filter.

102. The apparatus of claim 99, wherein the at least one neutral density filter is constructed and arranged such that an intensity of the at least one detectable centroid varies as a position of the at least one detectable centroid varies across the observation surface.

103. The apparatus of claim 102, wherein:

the at least one axis of rotation includes a first axis of rotation; and

the intensity of the at least one detectable centroid varies along the observation surface in a direction orthogonal to the first axis.

104. The apparatus of claim 102, wherein:

the at least one axis of rotation includes a first axis of rotation and a second axis of rotation, the second axis being orthogonal to the first axis, the first and second axes intersecting at a point on the observation surface; and

the intensity of the at least one detectable centroid varies radially along the observation surface from the point.

105. The apparatus of claim 102, further including at least one color filter through which the radiation passes, the color filter being constructed and arranged such that a color of the at least one detectable centroid varies as the position of the at least one detectable centroid varies across the observation surface.

106. The apparatus of claim 105, further including at least one non-uniform polarization filter through which the radiation passes, the non-uniform polarization filter being constructed and arranged such that a polarization of the at least one detectable centroid varies as the position of the at least one detectable centroid varies across the observation surface.

107. A system, comprising:

at least one orientation dependent radiation source to direct orientation dependent radiation to an observation area, the at least one orientation dependent radiation source having an observation surface from which the orientation dependent radiation is directed to the observation area, the at least one orientation dependent radiation source being constructed and arranged such that the orientation dependent radiation has at least one detectable property that varied with a rotation angle of the source about at least one axis of rotation, the at least one detectable property including a spatial distribution of the orientation dependent radiation on the observation superface; and

at least one radiation source located within the observation area to detect the orientation dependent radiation.

108. The system of claim 107, wherein the at least one orientation dependent radiation source includes a primary radiation source.

109. The system of claim 107, wherein:

the at least one axis of rotation includes a first axis passing through the at least one orientation dependent radiation source, the at least one orientation dependent radiation source having a reference position about the first axis;

the observation area is located at a radius from the first axis of rotation along a reference position normal extending from the observation surface when the at least one orientation dependent radiation source is in the reference position;

the observation area spans a first observation angle, relative to the reference position, about the first axis, the first observation angle being in a first plane orthogonal to the first axis and including the reference position normal;

the first observation angle is substantially less than a first maximum rotation angle of the at least one orientation dependent radiation source about the first axis, the first maximum rotation angle being relative to the reference position in the first plane; and

the at least one orientation dependent radiation source is capable of directing the orientation dependent radiation to the observation area at a plurality of first rotation angles about the first axis up to the first maximum rotation angle.

110. The system of claim 109, wherein:

the at least one axis of rotation includes a second axis of rotation passing through the at least one orientation dependent radiation source, the second axis of rotation being orthogonal to and intersecting the first axis;

the observation area spans a second observation angle, relative to the reference position, about the second axis, the second observation angle being in a second plane orthogonal to the second axis and including the reference position normal;

the second observation angle is substantially less than a second maximum rotation angle of the at least one orientation dependent radiation source about the second axis, the second maximum rotation angle being relative to the reference position in the second plane; and

the at least one orientation dependent radiation source is capable of directing the orientation dependent radiation to the observation area at a plurality of second rotation angles about the second axis up to the second maximum rotation angle.

111. The system of claim 107, further including at least one orientation independent radiation source to direct orientation independent radiation to the observation area.

112. The system of claim 111, wherein the at least one orientation independent radiation source is coupled to the orientation dependent radiation source.

113. The system of claim 107, wherein the at least one orientation dependent radiation source includes:

a first mask to substantially block source radiation, the first mask defining the observation surface and including a first plurality of openings through which the source radiation is capable of passing; and

a second mask coupled to the first mask, the second mask including a second plurality of openings offset relative to the first plurality of openings such that the source radiation passing through at least the first plurality of openings produces the orientation dependent radiation on the observation surface, the orientation dependent radiation including at least one centroid detectable from the observation area that varies in position across the observation surface based on the rotation angle of the orientation dependent radiation source about the at least one axis of rotation.

114. The system of claim 113, further including at least one orientation independent radiation source to direct orientation independent radiation to the observation area independent of the rotation angle, wherein the at least one radiation sensor detects the at least one centroid from the at least one orientation dependent radiation source and the orientation independent radiation.

115. The system of claim 114, wherein the at least one orientation independent radiation source is coupled to the at least one orientation dependent radiation source.

116. The system of claim 113, wherein the at least one orientation dependent radiation source further includes a primary source to direct the source radiation toward the first and second masks, the second mask being disposed between the primary source and the first mask to substantially block the source radiation, the source radiation passing through the second plurality of openings to produce the orientation dependent radiation.

117. The system of claim 113, wherein:

the at least one orientation dependent radiation source includes a reflector coupled to the first mask and the second mask to reflect the source radiation, the second mask being disposed between the reflector and the first mask to substantially block the source radiation, the source radiation passing through the second plurality of openings to produce the orientation dependent radiation;

the at least one orientation independent radiation source includes at least one orientation independent reflector; and

the system further includes a primary source to direct the source radiation toward the at least one orientation dependent radiation source and the at least one orientation independent reflector.

118. The system of claim 117, wherein the primary source is located adjacent to the at least one radiation sensor.

119. The system of claim 117, wherein the at least one orientation dependent radiation source is coupled to an object.

120. The system of claim 107, wherein the spatial distribution includes a position of the orientation dependent radiation on the observation surface, wherein the position varies with the rotation angle.

121. The system of claim 107, wherein the at least one detectable property further includes an intensity of the orientation dependent radiation, wherein the intensity varies with the rotation angle.

122. The system of claim 107, wherein the at least one detectable property further includes a polarization of the orientation dependent radiation, wherein the polarization varies with the rotation angle.

123. The system of claim 107, wherein the at least one detectable property further includes a wavelength of the orientation dependent radiation, wherein the wavelength varies with the rotation angle.

124. The system of claim 107, wherein:

the orientation dependent radiation includes at least two centroids of radiation on the observation surface, each centroid being detectable from the observation area; and

the at least one detectable property further includes a distance between the at least two centroids of radiation, wherein the distance between the at least two centroids varies with the rotation angle.

125. The system of claim 107, wherein:

the at least one detectable property further includes at least one of an intensity of the orientation dependent radiation, a polarization of the orientation dependent radiation, and a wavelength of the orientation dependent radiation, wherein the at least one of the intensity, the polarization, and the wavelength varies with the rotation angle.

126. The system of claim 107, wherein:

the orientation dependent radiation includes at least two radiation patterns on the observation surface, each radiation pattern being detectable from the observation area; and

the at least one detectable property includes a differential property between the at least two radiation patterns, wherein the differential property between the at least two radiation patterns varies with the rotation angle.

127. The system of claim 126, wherein the differential property includes a differential polarization between the at least two radiation patterns.

128. The system of claim 126, wherein the differential property includes a distance between the at least two radiation patterns.

129. A method for producing an orientation dependent radiation pattern on an observation surface, comprising a step of:

varying a surface area of a radiation source exposed through the observation surface in response to a rotation of the observation surface about at least one axis of rotation to produce at least one detectable centroid having a position that varies across the observation surface corresponding to the rotation.

130. The method of claim 129, wherein the step of varying the surface area of the radiation source includes a step of filtering radiation passing through the observation surface.

131. The method of claim 130, wherein the step of filtering includes a step of selectively filtering the radiation such that an intensity of the at least one detectable centroid varies with the position.

132. The method of claim 130, wherein the step of filtering includes a step of color filtering the radiation such that a color of the at least one detectable centroid varies with the position.

133. The method of claim 130, wherein the step of filtering includes a step of polarization filtering the radiation such that a polarization of the at least one detectable centroid varies with the position.

134. The method of claim 133, wherein the step of filtering includes a step of color filtering the radiation such that both a color and the polarization of the at least one detectable centroid vary with the position.

135. The method of claim 130, wherein the step of filtering includes a step of passing the radiation through a first plurality of openings in the observation surface.

136. The method of claim 135, wherein the step of filtering further includes a step of passing the radiation through a second plurality of openings coupled to the observation surface, the second plurality of openings being offset relative to the first plurality of openings.

137. The method of claim 136, wherein the radiation source is a reflector.

138. The method of claim 135, wherein:

the radiation source is a reflective pattern; and

the step of filtering includes a step of coupling the reflective pattern to the observation surface such that the first plurality of openings is offset relative to the reflective pattern.

139. An apparatus, comprising:

at least one orientation dependent radiation source to direct orientation dependent radiation to an observation area, the at least one orientation dependent radiation source having an observation surface from which the orientation dependent radiation is directed to the observation area, the at least one orientation dependent radiation source being constructed and arranged such that the orientation dependent radiation has at least one detectable property that varies with a rotation angle of the source about at least one axis of rotation, the at least one detectable property including a spatial distribution of the orientation dependent radiation on the observation surface.

140. The apparatus of claim 139, wherein the spatial distribution includes a position of the orientation dependent radiation, wherein the position varies with the rotation angle.

141. The apparatus of claim 139, wherein the at least one detectable property further includes an intensity of the orientation dependent radiation, wherein the intensity varies with the rotation angle.

142. The apparatus of claim 139, wherein the at least one detectable property further includes a polarization of the orientation dependent radiation, wherein the polarization varies with the rotation angle.

143. The apparatus of claim 139, wherein the at least one detectable property further includes a wavelength of the orientation dependent radiation, wherein the wavelength varies with the rotation angle.

144. The apparatus of claim 139, wherein:

the orientation dependent radiation includes at least two centroids of radiation on the observation surface, each centroid being detectable from the observation area; and

the at least one detectable property further includes a distance between the at least two centroids of radiation, wherein the distance between the at least two centroids varies with the rotation angle.

145. The apparatus of claim 139, wherein:

the at least one detectable property further includes at least one of an intensity of the orientation dependent radiation, a polarization of the orientation dependent radiation, and a wavelength of the orientation dependent radiation, wherein the at least one of the intensity, the polarization, and the wavelength varies with the rotation angle.

146. The apparatus of claim 139, wherein:

the orientation dependent radiation includes at least two radiation patterns on the observation surface, each radiation pattern being detectable from the observation area; and

the at least one detectable property further includes a differential property between the at least two radiation patterns, wherein the differential property between the at least two radiation patterns varies with the rotation angle.

147. The apparatus of claim 146, wherein the differential property includes a differential polarization between the at least two radiation patterns.

148. The apparatus of claim 147, wherein the differential property includes a distance between the at least two radiation patterns.

149. An apparatus comprising:

a first orientation dependent radiation source to produce a first orientation dependent radiation pattern on a first observation surface of the first orientation dependent radiation source, the first orientation dependent radiation pattern varying in position across the observation surface in a first direction based on a rotation angle of the first orientation dependent radiation source about at least one axis of rotation; and

at least one additional orientation dependent radiation source coupled to the first orientation dependent radiation source, the at least one additional orientation dependent radiation source including a second orientation dependent radiation source to produce a second orientation dependent radiation pattern on a second observation surface of the second orientation dependent radiation source, the second orientation dependent radiation pattern varying in position across the second observation surface in a second direction based on the rotation angle of the first and second orientation dependent radiation sources, the first and second directions being different.

150. The apparatus of claim 149, wherein:

the first orientation dependent radiation pattern varies in position along a first axis;

the second orientation dependent radiation pattern varies in position along a second axis;

the first axis is parallel to the second axis; and

the first direction is opposite to the second direction.

151. The apparatus of claim 149, wherein:

the first observation surface defines a first plane;

the second observation surface defines a second plane; and

the first plane is parallel to the second plane.

152. The apparatus of claim 149, wherein the first and second observation surfaces are arranged so as to not substantially obstruct each other.

153. The apparatus of claim 152, wherein the first and second orientation dependent radiation patterns are each detectable from a same observation point.

154. The apparatus of claim 152, wherein the first and second observation surfaces are in a same plane.

155. The apparatus of claim 149, wherein each of the first orientation dependent radiation pattern and the second orientation dependent radiation pattern includes at least one detectable centroid of radiation.

156. The apparatus of claim 149, wherein each of the first and second orientation dependent radiation sources has an essentially rectangular shape, the rectangular shape having a long side and a short side.

157. The apparatus of claim 156, wherein the first and second orientation dependent radiation sources are arranged such that a long side of the first orientation dependent radiation source is adjacent to and parallel with a long side of the second orientation dependent radiation source.

158. The apparatus of claim 157, wherein:

a first axis passes through the first observation surface and is parallel with the long side of the first orientation dependent radiation source;

a second axis passes through the second observation surface and is parallel with the long side of the second orientation dependent radiation source;

the at least one axis of rotation includes a first rotation axis, the first rotation axis being perpendicular to both the first axis and the second axis; and

the rotation angle is about the first rotation axis.

159. The apparatus of claim 158, wherein:

the first orientation dependent radiation pattern varies in position along the first axis;

the second orientation dependent radiation pattern varies in position along the second axis; and

the first direction is opposite to the second direction.

160. The apparatus of claim 149, wherein each of the first and second orientation dependent radiation sources includes:

a first mask to substantially block radiation, the first mask defining a respective observation surface and including a first plurality of openings through which radiation is capable of passing; and

a second mask coupled to the first mask, the second mask including a second plurality of openings offset relative to the first plurality of openings such that radiation passing through at least the first plurality of openings produces a respective orientation dependent radiation pattern on the respective observation surface.

161. In a system including at least two orientation dependent radiation sources coupled together, the at least two orientation dependent radiation sources including a first orientation dependent radiation source having a first surface area and a first observation surface, and a second orientation dependent radiation source having a second surface area and a second observation surface, a method for producing at least two orientation dependent radiation patterns, the method comprising steps of:

exposing the first surface area of the first radiation source through the first observation surface;

exposing the second surface area of the second radiation source through the second observation surface; and

varying the exposed first and second surface areas in response to a rotation of the first and second observation surfaces about at least one common axis of rotation to produce at least a first radiation pattern on the first observation surface and a second radiation pattern on the second observation surface, the first radiation pattern having a first position that varies across the first observation surface in a first direction in response to the rotation, and the second radiation pattern having a second position that varies across the second observation surface in a second direction in response to the rotation, the first and second directions being different.

162. An apparatus, comprising:

an orientation dependent radiation source to produce at least first and second orientation dependent radiation patterns on an observation surface of the orientation dependent radiation source, the first orientation dependent radiation pattern varying in position across the observation surface in a first direction based on a rotation angle of the orientation dependent radiation source about at least one axis of rotation, and the second orientation dependent radiation pattern varying in position across the observation surface in a second direction based on the rotation angle, the first and second directions being different.

163. A method for producing an orientation dependent radiation pattern on an observation surface, comprising steps of:

exposing a surface area of at least one radiation source through the observation surface; and

varying the exposed surface area of the at least one radiation source in response to a rotation of the observation surface about at least one axis of rotation to produce at least a first radiation pattern and a second radiation pattern, the first radiation pattern having a first position that varies across the observation surface in a first direction in response to the rotation, and the second radiation pattern having a second position that varies across the observation surface in a second direction in response to the rotation, the first and second directions being different.

164. In a system including at least one radiation sensor and at least one orientation dependent radiation source having a geometric center and at least two end faces, each end face located at a radius from the geometric center and including an end face radiation source to direct radiation radially outward from the geometric center, a method for measuring a rotational distance around a circular path from a reference point on the circular path, the circular path having the geometric center and the radius such that each end face of the at least one orientation dependent radiation source travels essentially along the circular path in response to a rotation of the orientation dependent radiation source about an axis of rotation passing through the geometric center, a first radiation sensor of the at least one radiation sensor located at the reference point, the method comprising steps of:

rotating the at least one orientation dependent radiation source about the axis of rotation; and

counting a number of radiation detection events as each end face radiation source passes by the first radiation sensor located at the reference point.

165. The method of claim 164, further including a step of determining the rotational distance traveled by the at least one orientation dependent radiation source based on the number of radiation detection events and the radius.

166. The method of claim 165, further including steps of:

measuring a time between each radiation detection event; and

determining a rotational speed of the at least one orientation dependent radiation source based on the measured time and the rotational distance.

167. The method of claim 165, wherein:

the at least one orientation dependent radiation source is constructed and arranged to produce at least one orientation dependent radiation pattern on at least one observation surface of the at least one orientation dependent radiation source, the at least one orientation dependent radiation pattern having a detectable property that varies in response to the rotation about the axis of rotation; and

the step of determining the rotational distance traveled by the at least one orientation dependent radiation source further includes steps of;

detecting the orientation dependent radiation pattern at the reference point; and

determining the rotational distance based on the detected orientation dependent radiation pattern, the number of radiation detection events, and the radius.

168. The method of claim 164, wherein the at least one orientation dependent radiation source has a polygon volumetric shape and includes a plurality of end faces, each end face located at the radius from the geometric center and including an end face radiation source to direct radiation radially outward from the geometric center, wherein the step of determining the rotational distance traveled by the at least one orientation dependent radiation source based on the number of radiation detection events and the radius includes a step of determining the rotational distance traveled by the at least one orientation dependent radiation source based on the number of radiation detection events, the radius, and the number of end faces.