Optical interferometer

Claim 2

In an optical interferometer having a source for producing a beam of monochromatic light; a first reflector; means for dividing said beam into firSt and second parts that are directed along respective paths, one of said paths intersecting said first reflector, said first reflector being oriented with respect to said dividing means to redirect one of said parts from the dividing means for recombination with the other part in an interference field, the improvement comprising, a second reflector, the other of said paths intersecting said second reflector, means for translating said second reflector with respect to said dividing means so as to have at least a component of translation substantially normal to the light path therebetween, said second reflector having first and second substantially planar reflective surfaces normal to each other, the intersection of said surface planes forming a roofline, said reflective surfaces being elongated in the component direction of translation substantially normal to said respective light path, and parallel to said roof line, said component direction of translation being parallel to said roof line said second reflector being oriented with respect to said dividing means to redirect said other of said parts from the dividing means for recombination with said one part in an interference field, one of said reflectors being translatable with respect to said dividing means along the light path therebetween whereby the translation of said one reflector along the respective light path produces cyclic variations in the net intensity of light at a point in said interference field.

Claim 3

An optical interferometer in accordance with claim 1 wherein said second reflector is translatable along the light path between said dividing means and said second reflector.

Claim 4

An optical interferometer in accordance with claim 2 wherein said second reflector is a roof prism.

Claim 5

An optical interferometer in accordance with claim 1 wherein said light source is a coherent light source.

Claim 6

An optical interferometer in accordance with claim 1 wherein said second reflector is a roof prism.

Claim 7

An optical interferometer in accordance with claim 1 wherein said first reflector is a roof prism.

Claim 8

An optical interferometer in accordance with claim 6 wherein said second reflector is a roof prism.

Claim 9

An optical interferometer in accordance with claim 1 wherein the improvement further comprises a means for determining the amount of translation of said one reflector along said respective light path from the cyclic variations, said determining means including means for providing a first pair of interference signals having a sinusoidal cyclic variation corresponding to the cyclic variation in intensity of light at said point in the interference field that results solely from the translation of the one reflector along the respective light path, said first pair of sinusoidal interference signals being displaced in phase from each other; means responsive to said first pair of signals for providing a digital signal related to the translation of said one reflector along said light path, said digital signal providing means including weighted summing means operatively connected to said first signal pair providing means, said weighted summing means including means for providing a second pair of sinusoidal signals from said first signal pair which is a weighted sum of said first signal pair, and sensing means for providing said digital signal from both said first and second signal pairs in accordance with a predetermined signal pair condition.

Claim 10

An optical interferometer in accordance with claim 8 wherein said second reflector is a roof prism.

Claim 11

An optical interferometer in accordance with claim 8 further comprising: said dividing means which provides another interference field from recombination which is directed along a separate path from said first interference field; means for producing first and second electrical signals of magnitudes that correspond to the light intensity at said point in said first interference field and a respective point in said other interference field, respEctively; means responsive to said electrical signals for providing first and second interference signals respectively, each having a cyclic variation in intensity of light at the point in said respective interference field that results solely from the translation of the one reflector along the respective light path, said first and second interference signals having an average D.C. level; and means for combining the first and second interference signals to provide an interference signal having an average D.C. level of substantially less than the magnitude of the cyclic signal fluctuations.

Claim 12

In an optical interfometer having a source for producing a beam of monochromatic light; a first reflector; means for dividing said beam into first and second parts that are directed along respective paths, one of said paths intersection said first reflector, said first reflector being oriented with respect to said dividing means to redirect one of said parts from the dividing means for recombination with the other part in an interference field; a second reflector, the other of said paths intersecting said second reflector, said second reflector being translatable with respect to said dividing means along the light path therebetween and being oriented with respect to said dividing means to redirect said other of said parts from the dividing means for recombination with said one part in an interference field, whereby the translation of said second reflector produces cyclic variations in the net intensity of light at a point in said interference field, the improvement comprising: a means for determining the amount of translation of said second reflector along said respective light path from the cyclic variations, said determining means including means for providing a first pair of interference signals having a sinusoidal cyclic variation corresponding to the cyclic variation in intensity of light at said point in the interference field that results solely from the translation of the second reflector along the respective light path, said first pair of sinusoidal interference signals being displaced in phase from each other; means responsive to said first pair of signals for providing a digital signal related to the translation of said second reflector along said light path, said digital signal providing means including weighted summing means operatively connected to said first signal pair providing means, said weighted summing means including means for providing a second pair of sinusoidal signals from said first signal pair which is a weighted sum of said first signal pair; and direction sensing means for providing said digital signal from both said first and second signal pairs in accordance with a predetermined signal pair condition.

Claim 13

In an optical interfometer having a source for producing a beam of monochromatic light; a first reflector; means for dividing said beam into first and second parts that are directed along respective paths, one of said paths intersection said first reflector, said first reflector being oriented with respect to said dividing means to redirect one of said parts from the dividing means for recombination with the other part in an interference field; a second reflector, the other of said paths intersecting said second reflector, said second reflector being translatable with respect to said dividing means along the light path therebetween and being oriented with respect to said dividing means to redirect said other of said parts from the dividing means for recombination with said one part in an interference field, whereby the translation of said second reflector produces cyclic variations in the net intensity of light at a point in said interference field, the improvement comprising: a means for determining the amount of translation of said second reflector along said respective light path from the cyclic variations, said determining means including means for providing a first pair of interference signals having a sinusoidal cyclic variation corresponding to the cyclic variation in intensity of light at said point in the interference field that results solely from the translation of the second reflector along the respective light path, said first pair of sinusoidal interference signals being displaced in phase from each other; means responsive to said first pair of signals for providing a digital signal related to the translation of said second reflector along said light path, said digital signal providing means including weighted summing means operatively connected to said first signal pair providing means, said weighted summing means including means for providing a second pair of sinusoidal signals from said first signal pair which is a weighted sum of said first signal pair; and direction sensing means for providing said digital signal from both said first and second signal pairs in accordance with a predetermined signal pair condition.

Claim 14

An optical interferometer in accordance with claim 11 further comprising means responsive to said digital signal to provide a display of the amount of translation of the second reflector along the light path with respect to a reference point.

Claim 15

An optical interferometer in accordance with claim 11 wherein said light source is a coherent light source.

Claim 16

An optical interferometer in accordance with claim 11 wherein said weighted summing means further includes means for providing a third pair of sinusoidal signals which is a different weighted sum of said first signal pair than said second signal pair.

Claim 17

An optical interferometer in accordance with claim 14 wherein said sensing means includes means for providing said digital signal from all of said signal pairs.

Claim 18

An optical interferometer in accordance with claim 14 wherein said respective signals of each pair have the same phase displacement with respect to each other.

Claim 19

An optical interferometer in accordance with claim 11 wherein said first signal pair is represented by the expressions cos theta and sin theta , each of said signals of said second signal pair is a different weighted sum of said first signal pair, the first weighted sum beinG represented by the expression sin( theta + phi ) sin theta cos phi + cos theta sin phi , and the other weighted sum being represented by the expression cos( theta + phi ) cos theta cos phi - sin theta sin phi , where phi is an arbitrary predetermined phase angle, and cos phi and sin phi are weighting constants.

Claim 20

An optical interferometer in accordance with claim 11 wherein said sensing means includes means responsive to said predetermined condition of a signal pair.

Claim 21

An apparatus in accordance with claim 18 wherein said condition responsive means includes means for providing a pulse signal each time a predetermined condition occurs for a signal of said condition providing pair, and means for combining said pulse signal and said other signal of said condition providing pair, said combining means including a first means responsive to a first set of logic combinations of said pulse signal with said other signal to provide an output pulse corresponding to translation in a given direction.

Claim 22

An apparatus in accordance with claim 19 wherein said combining means includes a second means responsive to a second set of logic combinations of said pulse signal with said other signal to provide another output pulse corresponding to translation in the opposite direction.

Claim 23

An optical interferometer in accordance with claim 18 wherein said condition includes a crossing of the midpoint in the magnitude of said cyclic variation of one signal of said condition providing pair.

Claim 24

An optical interferometer in accordance with claim 21 wherein said condition responsive means is responsive to the location of the other signal of said pair with respect to the midpoint in the magnitude of said cyclic variation of said signal when the crossing condition occurs for said one signal of said condition providing pair.

Claim 25

An optical interferometer in accordance with claim 21 wherein said means for providing said digital signal from said signal pairs includes bistable means for squaring the sinusoidal signals in said condition providing pair, said respective square signals having the same frequency as said respective sinusoidal signals.

Claim 26

An optical interferometer in accordance with claim 21 wherein said condition responsive means provides an output pulse when the crossing condition occurs for the one signal of the condition providing pair in combination with the occurrence of the location condition for the other signal of the condition providing pair.

Claim 27

An optical interferometer in accordance with claim 23 wherein said bistable squaring means comprises a Schmitt trigger, the D.C. component of the sinusoidal signals of the condition providing signal pair corresponding to the switching level of the Schmitt trigger.

Claim 28

An optical interferometer in accordance with claim 23 wherein said bistable squaring means comprises a bistable trigger for each signal of said condition providing pair, each of said bistable triggers providing a cardinal pulse as said square signal corresponding to the location condition; and said condition responsive means includes a monostable means to provide a pulse in response to a change of state in the respective bistable trigger corresponding to the crossing condition, and combining means responsive to the presence of both said cardinal pulse and said monostable pulse for providing said output pulse.

Claim 29

An optical interferometer in accordance with claim 26 wherein said sensing means includes inverter means operatively associated with one of said bistable triggers for providing the complement of said trigger output signal in addition to said uninverted output signal; said monostable means being associated with said inverter for additionally providing a pulse in response to a change in state in said inverted output corresponding to an opposite change in state in said uninverted output to said combining means; and a means for providing inverted pulses from said monostable Pulses to said combining means, said combining means being responsive to a first set of logic combinations of said pulse signals to provide an output pulse corresponding to the translation of the second reflector along the respective light path in one direction.

Claim 30

An optical interferometer in accordance with claim 27 wherein the interference signal pair providing means provides a pair of sinusoidal interference signals for one direction of translation of the second reflector along the respective light path, said interference signals being displaced 180 degrees from the phase displacement of the first pair of signals for the opposite direction of translation along the path; and said combining means includes a first means responsive to the first set of logic combinations of said pulse signals for providing an output pulse corresponding to translation in said one direction; and a second means responsive to a second set of logic combinations of said pulse signals for the opposite direction of translation of the second reflector along the respective light path to provide another output pulse corresponding to translation in the opposite direction.

Claim 31

An optical interferometer in accordance with claim 11 wherein said second pair providing means includes an operational amplifier means having an associated impedance network, said operational amplifier network providing the weighted sum of said first sinusoidal signal pair as said second sinusoidal signal pair.

Claim 32

An optical interferometer in accordance with claim 29 wherein said operational amplifier means comprises an operational amplifier and associated impedance network for each signal of the second signal pair, the respective operational amplifier network providing a weighted sum from the first signal pair for each of the signals of the second signal pair.

Claim 33

An optical interferometer in accordance with claim 11 wherein said means for providing a first pair of interference signals includes: photoelectric means for producing a first pair of signals of a magnitude that corresponds to the light intensity at said point; and means responsive to said photoelectric produced signal pair.

Claim 34

An optical interferometer in accordance with claim 11 wherein said sensing means includes means responsive to a predetermined condition of each signal pair for providing a pulse signal for each signal pair in accordance with the occurrence of said condition; and combining means operatively associated with said responsive means and said respective pulse signals for providing an interlaced output signal from said respective pulse signals having a period which is less than the periods of the respective pulse signals.

Claim 35

In an optical interferometer having a source for producing a beam of monochromatic light; a first reflector; means for dividing said beam into first and second parts that are directed along respective paths, one of said paths intersecting said first reflector, said first reflector being oriented with respect to said dividing means to redirect one of said parts from the dividing means for recombination with the other part in an interference field; a second reflector, the other of said paths intersecting said second reflector, said second reflector being translatable with respect to said dividing means along the light path therebetween and being oriented with respect to said dividing means to redirect said other of said parts from the dividing means for recombination with said one part in an interference field, whereby the translation of said second reflector produces cyclic variations in the net intensity of light at a point in said interference field, the improvement comprising: said dividing means which provides another interference field from recombination which is directed along a separate path from said first interference field; means for producing first and second electrical signals of magnitudes that correspond to the light intensity at said point in said first Interference field and a respective point in said other interference field, respectively, said first and second electrical signals comprising first and second interference signals, respectively, each having a cyclic variation in intensity of light at the point in said respective interference field that results solely from the translation of the second reflector along the respective light path, said first and second interference signals having an average D.C. level, said cyclic variations being substantially 180* out of phase and means for combining the first and second interference signals to provide an interference signal having an average D.C. level of substantially less than the magnitude of the cyclical signal fluctuations.

Claim 36

In an optical interferometer having a source for producing a beam of monochromatic light; a first reflector; means for dividing said beam into first and second parts that are directed along respective paths, one of said paths intersecting said first reflector, said first reflector being oriented with respect to said dividing means to redirect one of said parts from the dividing means for recombination with the other part in an interference field; a second reflector, the other of said paths intersecting said second reflector, said second reflector being translatable with respect to said dividing means along the light path therebetween and being oriented with respect to said dividing means to redirect said other of said parts from the dividing means for recombination with said one part in an interference field, whereby the translation of said second reflector produces cyclic variations in the net intensity of light at a point in said interference field, the improvement comprising: said dividing means which provides another interference field from recombination which is directed along a separate path from said first interference field; means for producing first and second electrical signals of magnitudes that correspond to the light intensity at said point in said first Interference field and a respective point in said other interference field, respectively, said first and second electrical signals comprising first and second interference signals, respectively, each having a cyclic variation in intensity of light at the point in said respective interference field that results solely from the translation of the second reflector along the respective light path, said first and second interference signals having an average D.C. level, said cyclic variations being substantially 180* out of phase and means for combining the first and second interference signals to provide an interference signal having an average D.C. level of substantially less than the magnitude of the cyclical signal fluctuations.

Claim 37

An optical interferometer in accordance with claim 33 wherein the combining means includes means for providing an interference signal having average D.C. level of 0 volts.

Claim 38

An optical interferometer in accordance with claim 33 wherein: said electrical signal producing means comprises a first photoelectric means for producing the first electric signal; and a second photoelectric means for producing the second electrical signal.