Dimensional measuring apparatus using optical scan especially for hardness testing

Claim 2

Apparatus for measuring a dimension of a surface reflectance discontinuity of a workpiece comprising; scanner means for causing an optical beam to scan a predetermined path on the surface of said workpiece, photodetector means operatively disposed in the plane of scan of said beam and in a position relative to the scanner means to respond to that portion of the beam which is reflected from said surface at an angle which is within a given range of reflectance angles, said photodetector means producing an electrical signal which varies with the intensity of energy reflected within said range, electronic means connected with the photodetector means for producing an output signal having a magnitude proportional to the time duration that said electrical signal has a value which is below a threshold level indicative of reflection of said beam, and means for indicating the magnitude of said output signal as a measurement of the length of said discontinuity along said path.

Claim 3

The invention as defined in claim 1 wherein said scanner means comprises; a source of optical energy, optical means operatively related with the source for developing an optical beam, and a rotatable mirror in the path of said beam.

Claim 4

The invention as defined in claim 1 wherein said electronic means includes means for selecting from said electrical signal a single electrical pulse corresponding to a selected discontinuity and includes averaging means for averaging the value of said pulse over the time period of the scan of said path.

Claim 5

The invention as defined in claim 1 wherein said scanner means includes means for causing the beam to scan the same path repeatedly in the same direction of scan whereby said photodetector means produces a train of electrical pulses.

Claim 6

The invention as defined in claim 3 including a second photodetector means, said second photodetector means being disposed in the path of said beam produced by said scanner means adjacent the starting position of the scan and adapted to produce a start of scan pulse for each scan of the path, a gate pulse generator connected with second photodetector means and adapted to produce a gate pulse in overlapping time relation with the electrical pulse from the first mentioned photodetector means, said electronic means including a gate circuit having one input connected with said level detector and the other input connected with said gate generator and the output being connected with said indicating means.

Claim 7

The invention as defined in claim 5 wherein said electronic means includes a constant amplitude pulse generator connected between said gate circuit and said indicating means and being adapted to produce a constant amplitude pulse having a duration proportional to said electrical pulse from the first mentioned photodetector in response to the occurrence of said electrical pulse.

Claim 8

The invention as defined in claim 6 wherein said electronic means includes a level detector circuit connected between said second photodetector means and said gate generator and adapted to respond only to a pulse exceeding the predetermined amplitude corresponding to the pulse amplitude produced by the first mentioned photodetector means in response to the selected discontinuity.

Claim 9

The invention as defined in claim 7 wherein said electronic means includes a set level circuit connected between the first mentioned photodetector means and a reference input on said level detecting means, said set level circuit comprising an averaging circuit and adjustable amplifying means whereby the threshold value of said level detector is automatically adjusted in accordance with variations in the peak value of said electrical pulse from the first mentioned photodetector means.

Claim 10

The invention as defined in claim 8 wherein said source of optical energy is a laser, and said optical means includes a beam expander and a focussing lens for developing a focussed beam impinging upon said scanner means.

Claim 11

In a hardness testing machine, apparatus for measuring the diameter of an impression in the surface of a workpiece, said apparatus including a support member, an indenting element and actuating means therefor moUnted on the support member, said indenting element being adapted to engage a workpiece and form an impression therein, an optical scanner mounted on said support member and including a source of optical energy, beam forming means operatively related to said source for developing an optical beam, scanner means in the path of said beam for causing said beam to traverse a scan path which intercepts the position occupied by the indenting element when actuated to form an impression in said workpiece, whereby the scan path crosses said impression near a diametral line thereof, the motion of said beam being at a substantially constant speed, photodetector means mounted on said support member and disposed relative to the scanner to respond to that portion of the beam which is reflected from said surface at an angle within a given range of reflectance angles in the plane of beam motion, said photodetector means producing an electrical pulse when there is a change of intensity of optical energy reflected within said range, whereby an impression formed by said indenting element will produce a pulse having a time duration corresponding to the diameter of said impression, and electronic means connected with said photodetector means and responsive to the time duration of said electrical pulse.

Claim 12

In a hardness testing machine, apparatus for measuring the diameter of an impression in the surface of a workpiece, said apparatus including a support member, an indenting element and actuating means therefor moUnted on the support member, said indenting element being adapted to engage a workpiece and form an impression therein, an optical scanner mounted on said support member and including a source of optical energy, beam forming means operatively related to said source for developing an optical beam, scanner means in the path of said beam for causing said beam to traverse a scan path which intercepts the position occupied by the indenting element when actuated to form an impression in said workpiece, whereby the scan path crosses said impression near a diametral line thereof, the motion of said beam being at a substantially constant speed, photodetector means mounted on said support member and disposed relative to the scanner to respond to that portion of the beam which is reflected from said surface at an angle within a given range of reflectance angles in the plane of beam motion, said photodetector means producing an electrical pulse when there is a change of intensity of optical energy reflected within said range, whereby an impression formed by said indenting element will produce a pulse having a time duration corresponding to the diameter of said impression, and electronic means connected with said photodetector means and responsive to the time duration of said electrical pulse.

Claim 13

The invention as defined in claim 10 wherein said actuating means is operative to extend and retract said indenting element to form said impression in the workpiece, locating means adapted to be seated against the surface of said workpiece and extending beyond said indenting element in its retracted position whereby the scan path of said beam is unobstructed by said indenting element.

Claim 14

The invention as defined in claim 11 wherein said locating means forms an enclosure for said indenting element, said enclosure defining an opening at the outer end for passage of the indenting element to engage the workpiece, said enclosure defining a slit extending in said plane of beam motion for admitting the beam to the surface of the workpiece, said enclosure defining a second slit on the opposite side thereof extending in said plane of beam motion for admitting the portion of the beam reflected from the surface to said photodetector means.

Claim 15

The invention as defined in claim 12 including means for selecting a single electrical pulse and including indicating means for displaying a value proportional to the time duration of the selected pulse.

Claim 16

The invention as defined in claim 10 wherein said scanner means includes means for causing the beam to scan the same path repeatedly in the same direction of scan whereby said photodetector means produces a train of electrical pulses.

Claim 17

The invention as defined in claim 13 wherein said electronic means includes means for indicating the time average value of the pulse over the time period of the scanning motion as an indication of the diameter of the impression.

Claim 18

The invention as defined in claim 15 wherein said electronic means comprises level detecting means connected between said photodetector means and said indicating means and adapted to produce an output pulse when said electrical pulse from the photodetector means exceeds a predetermined value.

Claim 19

The invention as defined in claim 16 including a second photodetector means, said second photodetector means being disposed in the path of said beam produced by said scanner means adjacent the starting position of the scan and adapted to produce a start of scan pulse for each scan of the path, a gate pulse generator connected with second photodetector means and adapted to produce a gate pulse in overlapping time relation with the electrical pulse from the first mentioned photodetector means, said electronic means including a gate circuit having one input connected with said level detector and the other input connected with said gate generator and the output being connected with said indicating means.

Claim 20

The invention as defined in claim 17 wherein said electronic means includes a constant amplitude pulse generator connected between said gate circuit and said indicating means and being adapted to produce a constant amplitude pulse having a duration proportional to said electrical pulse from the first mentioned photodetector in response to the occurrence of said electrical pulse.

Claim 21

The invention as defined in claim 18 wherein said electronic means includes a level detector circuit connected between said second photodetector means and said gate generator and adapted to respond only to a pulse exceeding the predetermined amplitude corresponding to the pulse amplitude produced by the first mentioned photodetector means in response to the selected discontinuity.

Claim 22

The invention as defined in claim 19 wherein said electronic means includes a set level circuit connected between the first mentioned photodetector means and a reference input on said level detecting means, said set level circuit comprising an averaging circuit and adjustable amplifying means whereby the threshold value of said level detector is automatically adjusted in accordance with variations in the peak value of said electrical pulse from the first mentioned photodetector means.

Claim 23

The invention as defined in claim 10 wherein said source of optical energy is a laser, and said optical means includes a beam expander and a focussing lens for developing a focussed beam impinging upon said scanner means.

Claim 24

Apparatus for measuring a dimension of an impression in the surface of a workpiece comprising; scanner means for causing an optical beam to scan a predetermined path on the surface of said workpiece, photodetector means disposed in a position relative to the scanner means to respond to that portion of the beam which is reflected from said surface at an angle within a given range of reflectance angles in the plane of the beam motion, said photodetector means producing an electrical signal which varies with the intensity of energy reflected within said range, electronic detector means adapted to respond only to signals above a predetermined threshold value and connected with the photodetector means for producing a pulse having leading and trailing edges corresponding respectively to the excursions of said signal above and below the predetermined threshold value whereby a group of pulses may be produced during the scan of said impression, pulse forming means for producing a single pulse having a duration extending from the leading edge of the first pulse of said group to the trailing edge of the last pulse of said group, and means for indicating a value proportional to the time duration of said single pulse as a measurement of the length of said impression along said path.

Claim 25

Apparatus for measuring a dimension of an impression in the surface of a workpiece comprising; scanner means for causing an optical beam to scan a predetermined path on the surface of said workpiece, photodetector means disposed in a position relative to the scanner means to respond to that portion of the beam which is reflected from said surface at an angle within a given range of reflectance angles in the plane of the beam motion, said photodetector means producing an electrical signal which varies with the intensity of energy reflected within said range, electronic detector means adapted to respond only to signals above a predetermined threshold value and connected with the photodetector means for producing a pulse having leading and trailing edges corresponding respectively to the excursions of said signal above and below the predetermined threshold value whereby a group of pulses may be produced during the scan of said impression, pulse forming means for producing a single pulse having a duration extending from the leading edge of the first pulse of said group to the trailing edge of the last pulse of said group, and means for indicating a value proportional to the time duration of said single pulse as a measurement of the length of said impression along said path.

Claim 26

The invention as defined in claim 22 wherein said pulse forming means comprises digital logic means for producing a pulse having leading and trailing edges upon the occurrence of the first and last excursions respectively of said signal above and below the predetermined threshold value within a given portion of said scan and for holding the pulse amplitude substantially constant between said edges.

Claim 27

The invention as defined in claim 23 wherein said digital logic means includes first and second flip-flops for producing first and second pulses respectively with the leading edge of the first pulse coinciding with the first excursion and the trailing edge of the second pulse coinciding with the second excursion, and means including a gate for producing a single pulse having leading and trailing edges coinciding with the aforementioned leading and trailing edges respectively.

Claim 28

The invention as defined in claim 23 wherein said means for indicating includes an averaging circuit for producing an electrical signal proportional to the time average value of the single pulse over the time period of the scanning motion as an indication of a dimension of the discontinuity.