Fiber optics distance converting technique

Claim 2

Apparatus for producing at least one signal varying as a function of the distance from a reference face of the apparatus to a light reflecting surface comprising: a coherent light source; optical guide transmitter means having an emitting end at the reference face for transmitting a beam of coherent light rays from said source all with the same selected oblique incidence toward a surface so as to be reflected therefrom; optical guide receiver means having first and second receiving ends and first and second output means for transmitting a first flux of light issued from said emitting end and reflected by the surface from said first receiving end to said first output means to produce a first corresponding signal related to the distance from the reference face to the surface within one finite distance range outside which substantially no such first signal can be obtained, and for transmitting a second flux of light issued from said emitting end and reflected by the surface from said second receiving end to said second output means to produce a second corresponding signal related to the distance from the reference face to the surface within a second finite distance range outside which practically no such second signal can be obtained and which has an overlap section with said first finite range. said first and second receiving ends being laterally arranged with respect to said emitting end for producing said first and second corresponding signals which vary linearly witH distance with equal but opposite rates of variation within the overlap section of said first and second ranges for at least one value of said selected oblique incidence of said coherent light rays to provide a function of the variations in reflectivity of the light reflecting surface within this overlap section.

Claim 3

The apparatus of claim 1, further including means for producing a third signal functionally related to the sum of said first and second corresponding signals, which is representative of the reflectivity of the light reflecting surface within the overlap section of said first and second ranges.

Claim 4

The apparatus of claim 1, further including means for producing a third signal functionally related to said first and second corresponding signals, which provides a representation of distance from said reference face to the light reflecting surface, which representation is corrected for variations of reflectivity of the light reflecting surface.

Claim 5

The apparatus of claim 3, wherein said third signal producing means includes means for producing a fourth signal functionally related to the sum of said first and second corresponding signals and means for modifying a representation of said first signal in response to said fourth signal to produce said third signal.

Claim 6

The apparatus of claim 1, wherein said first and second output means include means for converting the first and second light fluxes into representative electrical signals to produce said first and second signals, said converting means having gains selected for producing said equal but opposite rates of variation.

Claim 9

The method of claim 6 further including: summing said one and other corresponding signals to obtain a signal varying with reflectivity and applying said reflectivity varying signal to correct one of said corresponding signals for variations of reflectivity to obtain an accurate indication of distance within said common distance range.

Claim 10

Apparatus for producing at least one signal varying as a function of the distance from a reference face of the apparatus to a light reflecting surface portion in a direction normal thereto comprising: light transmitting guide means having a light admitting end and a light emitting end at the reference face for passing light from said admitting end to said emitting end and transmitting light emerging from said emitting end to a light reflecting surface portion substantially parallel to the reference face for reflection of the transmitted light thereby; means for directing a collimated parallel beam of light toward said admitting end at an oblique incidence selected for transmitting rays of the light emerging from said emitting end all with essentially the same common angle of oblique incidence onto the reflecting surface portion; light receiving guide means having one light receiving end and one light output end for passing light from said one receiving end to said one output end, said one receiving end being disposed with respect to said emitting end for picking up light reflected by the surface portion over one finite range of distance from the reference face to the surface portion, for any given value of the selected oblique incidence producing such a common angle of oblique incidence for the light rays transmitted from said emitting end onto the surface portion; and photodetecting means for converting one flux of the light passed by said light receiving guide means to said one output end thereof into one electrical signal varying with the distance from the reference face to the surface portion over said one finite distance range in accordance with a relationship represented by one curve having distance as a coordinate and characterized by having a peak section about the center portion of said one distance range, a non-linear initial section at one end of said range, a non-linear final section at the other end of said one range, said other end being at a greater distance than said one end along the distance coordinate, and first and second linear section having slopes of opposite signs, said first linear section connecting said initial section to said peak section and said second linear section connecting said peak section to said final section, whereby said one signal may vary linearly with distance over two distinct portions of said one finite range on either side of the center portion thereof.

Claim 11

Apparatus for producing at least one signal varying as a function of the distance from a reference face of the apparatus to a light reflecting surface portion in a direction normal thereto comprising: light transmitting guide means having a light admitting end and a light emitting end at the reference face for passing light from said admitting end to said emitting end and transmitting light emerging from said emitting end to a light reflecting surface portion substantially parallel to the reference face for reflection of the transmitted light thereby; means for directing a collimated parallel beam of light toward said admitting end at an oblique incidence selected for transmitting rays of the light emerging from said emitting end all with essentially the same common angle of oblique incidence onto the reflecting surface portion; light receiving guide means having one light receiving end and one light output end for passing light from said one receiving end to said one output end, said one receiving end being disposed with respect to said emitting end for picking up light reflected by the surface portion over one finite range of distance from the reference face to the surface portion, for any given value of the selected oblique incidence producing such a common angle of oblique incidence for the light rays transmitted from said emitting end onto the surface portion; and photodetecting means for converting one flux of the light passed by said light receiving guide means to said one output end thereof into one electrical signal varying with the distance from the reference face to the surface portion over said one finite distance range in accordance with a relationship represented by one curve having distance as a coordinate and characterized by having a peak section about the center portion of said one distance range, a non-linear initial section at one end of said range, a non-linear final section at the other end of said one range, said other end being at a greater distance than said one end along the distance coordinate, and first and second linear section having slopes of opposite signs, said first linear section connecting said initial section to said peak section and said second linear section connecting said peak section to said final section, whereby said one signal may vary linearly with distance over two distinct portions of said one finite range on either side of the center portion thereof.

Claim 12

The apparatus of claim 8, wherein said light receiving guide means further comprises a second light receiving end and a second light output end for passing light from said second receiving end to said second output end, said second receiving end being disposed with respect to said emitting end for picking up light reflected by the surface portion over a second finite range of distance from the reference face to the surface portion, which has an overlap section with said one finite range for at least one value of said selected oblique incidence producing such a common angle of oblique incidence for the light rays transmitted from said emitting end onto the surface portion, and wherein, said photodetecting means is further arranged for converting a second flux of the light passed by said light receiving guide means to said second output and thereof into a second electrical signal varying with the distance from said reference face to the surface portion over said second finite range in accordance with a relationship represented by a second curve characterized by plural sections defined in a similar manner as for said one curve and including a peak section, non-linear and final sections and first and second linear sections, the first linear section of said second curve having a section of the distance coordinate in common with the second linear section of said first curve within the overlap section of said first and second finite ranges.

Claim 13

The apparatus of claim 9, further including means for combining said one and said second electrical signals to produce a third signal which varies with the reflectivity of the surface portion independently of the variations of its distance within said common distance coordinate section.

Claim 14

The apparatus of claim 8 wherein, said light receiving guide means has a second receiving end and a second output end for passing light from said second receiving end to said second output end, said second receiving end being disposed with respect To said emitting end for picking up light reflected by the surface portion over a second finite range of distance from the reference face to the surface portion, said second range having no overlap with said first finite range for at least one value of said selected oblique incidence producing such a common angle of oblique incidence for the light rays transmitted from said emitting end onto the surface portion, and wherein said photodetecting means is arranged for converting a second flux of light passed by said light receiving guide means to said second output end thereof into a second electrical signal varying linearly with distance from the reference face to the surface over a portion of said second range and outside said first distance range.

Claim 15

Apparatus for measuring the thickness of a transparent body having a first and a rear face opposite a reference face of the apparatus, comprising: light transmitting guide means having a light admitting end and a light emitting end at the reference face for passing light from said admitting end to said emitting end to emerge therefrom toward the transparent body; coherent light source means for producing a collimated parallel light beam directed toward said light admitting end at an angle of oblique incidence selected for transmitting rays of the light emerging from said emitting end toward the front face of the transparent body with a common angle of oblique incidence substantially equal to the selected angle of oblique incidence of the coherent light beam onto said admitting end, whereby a first fraction of the emerging light rays may be reflected by the front face at a common angle of reflection and a second fraction of the emerging light rays may be refracted a first time by the front face to travel through said transparent body to its rear face to be reflected thereby and travel back through the transparent body to the front face to be refracted a second time thereby and emerge from the front face at a common angle of emergence measured with respect to the normal direction to the front face; first light receiving guide means having a first light receiving end and a first light output end for passing a first flux of light picked up by said first receiving end to said first output end, said first receiving end being disposed with respect to said emitting end for picking up light rays from said first fraction reflected by the front face over a first finite range of distance from the reference face to the front face; second light receiving guide means having a second light receiving end and a second light output end for passing a second flux of light picked up by said second receiving end to said second output end, said second receiving end being disposed with respect to said emitting end for picking up light rays from said second fraction reflected by the rear face and refracted by the front face over a second finite range of distance from the reference face to the rear face, said first and second distance ranges having no overlap for the selected angle of oblique incidence of the coherent light beam; photodetecting means for converting said first and second fluxes into respective first and second electrical signals varying with the distances from said reference face to the front and to the rear face, respectively, over said first and second finite ranges in accordance with relationships represented by first and second respective curves having distance as a coordinate, each said curve including: a peak section about the center portion of the respective one of said first and second distance ranges, a non-linear initial section at one end of said respective one range, a non-linear final section at the other end of said respective one range, said other end being at a greater distance than said one end, and first and second linear sections having substantially equal slopes of opposite signs, said first linear section connecting said initial section to said peak section and said second linear section connecting said peak section to said final section, the first linear sections of said one and second curves having substantially the same slope and being displaced from one another along the distance coordinate by an amount equal to the average thickness of the transparent body, the second linear sections of said one and second curves having substantially the same slope, and the initial section of said second curve being separated from the final section of said first curve along said distance coordinate by a zone along which no such first or second signal can be obtained; and means for combining said first and second electrical signals to produce a third signal representative of the difference between distances from said reference face to the rear face and to the front face of the transparent body respectively, whereby an accurate measurement of the thickness of the transparent body can be obtained with substantially no light reflected by the front face interfering on said second signal.

Claim 16

Apparatus for measuring the thickness of a transparent body having a first and a rear face opposite a reference face of the apparatus, comprising: light transmitting guide means having a light admitting end and a light emitting end at the reference face for passing light from said admitting end to said emitting end to emerge therefrom toward the transparent body; coherent light source means for producing a collimated parallel light beam directed toward said light admitting end at an angle of oblique incidence selected for transmitting rays of the light emerging from said emitting end toward the front face of the transparent body with a common angle of oblique incidence substantially equal to the selected angle of oblique incidence of the coherent light beam onto said admitting end, whereby a first fraction of the emerging light rays may be reflected by the front face at a common angle of reflection and a second fraction of the emerging light rays may be refracted a first time by the front face to travel through said transparent body to its rear face to be reflected thereby and travel back through the transparent body to the front face to be refracted a second time thereby and emerge from the front face at a common angle of emergence measured with respect to the normal direction to the front face; first light receiving guide means having a first light receiving end and a first light output end for passing a first flux of light picked up by said first receiving end to said first output end, said first receiving end being disposed with respect to said emitting end for picking up light rays from said first fraction reflected by the front face over a first finite range of distance from the reference face to the front face; second light receiving guide means having a second light receiving end and a second light output end for passing a second flux of light picked up by said second receiving end to said second output end, said second receiving end being disposed with respect to said emitting end for picking up light rays from said second fraction reflected by the rear face and refracted by the front face over a second finite range of distance from the reference face to the rear face, said first and second distance ranges having no overlap for the selected angle of oblique incidence of the coherent light beam; photodetecting means for converting said first and second fluxes into respective first and second electrical signals varying with the distances from said reference face to the front and to the rear face, respectively, over said first and second finite ranges in accordance with relationships represented by first and second respective curves having distance as a coordinate, each said curve including: a peak section about the center portion of the respective one of said first and second distance ranges, a non-linear initial section at one end of said respective one range, a non-linear final section at the other end of said respective one range, said other end being at a greater distance than said one end, and first and second linear sections having substantially equal slopes of opposite signs, said first linear section connecting said initial section to said peak section and said second linear section connecting said peak section to said final section, the first linear sections of said one and second curves having substantially the same slope and being displaced from one another along the distance coordinate by an amount equal to the average thickness of the transparent body, the second linear sections of said one and second curves having substantially the same slope, and the initial section of said second curve being separated from the final section of said first curve along said distance coordinate by a zone along which no such first or second signal can be obtained; and means for combining said first and second electrical signals to produce a third signal representative of the difference between distances from said reference face to the rear face and to the front face of the transparent body respectively, whereby an accurate measurement of the thickness of the transparent body can be obtained with substantially no light reflected by the front face interfering on said second signal.

Claim 19

The method of claim 13 further comprising the steps of transmitting light rays emerging from said light emitting end onto a second light reflecting surface portion to be reflected thereby, said second surface portion being substantially parallel to said one surface portion and spaced further away than said one surface portion with respect to said reference face; receiving light reflected by said second surface portion with second light receiving guide means having a second light receiving end disposed with respect to said emitting end for picking up rays of the light reflected by said second surface portion over a second predetermined finite range of distance from the reference face to said second surface portion which does not overlap said one finite range for the selected angle of incidence; and passing the light rays picked up by said second receiving end through said second light receiving guide means for producing a second signal having a magnitude varying with the distance from the reference face to said second light reflecting surface over said second finite distance range in accordance with a relationship which is linear over at least one portion of said second range.

Claim 20

The method of claim 14, wherein said one and second surface portions belong to the front and rear facEs of a transparent body opposite said reference face and further comprising the step of producing a third signal functionally related to said one and second signals which is representative of the distance between said front and said rear faces of the transparent body to obtain a representative of the thickness thereof.

Claim 21

The method of claim 15, wherein said transparent body is a transparent plate floating on a light reflecting bath of liquid material.

Claim 22

The method of claim 14, further including the step of modifying the selected angle of incidence while still producing light rays emerging from said emitting end which have a common oblique angle of incidence onto the one surface portion for achieving a fine adjustment of portions of said first and second ranges over which said one and second signals vary linearly with distance from said reference face to said one and second surface portions respectively.

Claim 23

The method of claim 13, further including the steps of: receiving light rays reflected by the one surface portion with a second light receiving guide means having a second light receiving end disposed with respect to said emitting end for picking up rays of the light reflected at said common angle of reflection over a second predetermined finite range of distance from the reference face to said one reflecting surface portion, said first and second ranges having an overlap section; and passing light rays picked up by said second receiving end through said second light receiving guide means for producing a second signal having a magnitude varying with the distance from said reference face to said one surface portion over said second finite distance range in accordance with a relationship represented by a second curve characterized by a plurality of sections defined like those of said one curve and including a peak section, non-linear initial and final sections, and first and second linear sections, said one signal varying in accordance with at least a portion of the second linear section of said one curve when said second signal varies in accordance with at least a portion of the first linear section of said second curve within the overlap section of said distance ranges.

Claim 24

The method of claim 18, wherein said one surface portion belongs to the front or the rear face of a transparent plate floating on a light reflecting bath.

Claim 25

The method of claim 13 further including using a source of coherent light for producing said directed beam of light rays.

Claim 26

The method of claim 20, wherein said one surface portion belongs to one of the front and rear faces of a transparent plate floating on a bath of a melted light reflecting medium, further including the step of detecting in the light passed through said one light receiving means only that portion having a selected wave length present in the coherent light beam.