Torque transducer utilizing differential optical sensing

Apparatus for detecting the direction and amount or rotation of a shaft and comprising:

• a pair of polarization means including,
• first polarization means having two areas of polarization oriented 90.degree. with respect to each other, and
• second polarization means having a single polarization oriented 45.degree. with respect to both areas of said first polarization means in null or unrotated orientation of said pair of first and second polarization means;
• light source means mounted on one side of said pair of polarization means;
• first and second photosensing means mounted on the other side of said polarization means and oriented in such a manner as to separately and respectively receive light transmitted through each of the two areas of said first polarization means and the single polarization of said second polarization means;
• said shaft being operatively associated with one of the first and second polarization means for rotating said one of the polarization means from said null position,
• circuit means connected separately to said first and second photosensing means and for generating an electrical signal proportional to the difference between the intensities of the light received by said first and second photosensing means, and
• indicator means in said circuit means for indicating, as a function of said signal the amount and direction of rotation of the shaft in response to the amount of light received by the photosensing means.

A method of measuring torque in a shaft, said method comprising,

• connecting a first polarizer disc to a first location on a shaft, said first polarizer disc having a first radially inner area of polarization and a second radially outer area of polarization with the first and second areas of polarization oriented 90.degree. with respect to each other,
• connecting a second polarizer disc to a second location on the shaft, said second polarizer disc having a single polarization oriented 45.degree. with respect to both areas of said polarizer disc when no torque is exerted on the shaft,
• mounting a light source on one side of said pair of polarizer discs,
• mounting photosensing means on the other side of said pair of polarizer discs,
• orienting the photosensing means in such a manner to separately receive light transmitted through each of the two areas of the first polarizer disc and the single polarization of the second polarizer disc,
• generating an electrical signal directly proportional to the difference in light intensity between the light transmitted through the two areas of the first polarizer disc, and
• reading the signal in terms of torque,
• thereby detecting the amount and direction of torques exerted on the shaft in response to the amount of light received by the photosensing means.

An instrument for measuring torque induced in a shaft coupled to torque-inducing means, including in combination:

• first and second discs mounted on said shaft for rotation with said shaft and spaced apart from each other axially thereon by a torsioning portion of said shaft,
• said first disc having an inner first annular light transmission control means and an outer second annular light transmission control means, said first control means and said second control means responding in an equal but opposite manner to torque induced in said shaft,
• said second disc having a third annular light transmission control means at least equal in area to the sum of said first and second control means,
• light source means mounted for sending light through both said discs and through all three said light transmission control means,
• light sensing means mounted on the opposite side of said discs from said light source means and including first photosensitive means for receiving only the light passing through said first and third light transmission control means and generating a first electrical signal, and second photosensitive means for receiving only the light passing through said second and third light transmission control means and for generating a second electrical signal,
• differential circuit means connected to said first and second photosensitive means for providing a third electrical signal proportional to the difference between said first and second electrical signals, and
• torque indicating means for indicating, in terms of torque, both the magnitude and direction of said third signal,
• said differential circuit means tending to cancel out inaccuracies due to variations in temperature, light source intensity, applied voltage, and aging.