US4394683A
Expired / Lapsed
US
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New photodetector array based optical measurement systems
Assignee: Diffracto Ltd Canada
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Filing: 1980-06-26
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Granted: 1983-07-19
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Expires: 2000-06-26
Abstract
Abstract A method and apparatus are provided for analyzing the light pattern produced on a photodetector array. The signal produced by the array is filtered with a low pass filter and the output of the filter is differentiated to obtain either the first or second derivative of the filtered signal for one or more points in the pattern. The zero crossing of the differentiated signal is detected and the zero crossing point is timed relative to a further point, e.g., the start of the scan of the array, so as to obtain an output related to the position of the corresponding point or points in the pattern.
Inventors
- 👤 Nicholas Liptay-Wagner
- 👤 Roland Renaud
- 👤 Timothy R. Pryor
- 👤 Donald A. Clarke
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 08:47
CPC Classifications
B; B07; B07C; B07C5/00; B07C5/04; B07C5/10; B07C5/36; B07C5/363; B07C5/365; G; G01; G01B; G01B11/00; G01B11/02; G01B11/024
Claims Analysis
Total Claims: 60
Claim 1
Independent Claim
82 words
Method for analyzing a light pattern produced on a photo detector array, comprising the steps of: filtering the signal from said photodetector array with a low pass filter, differentiating the output of the low pass filter to obtain a derivative of said filtered signal at at least one point in said pattern, detecting the point of zero crossing of said differentiated signal, and timing said zero crossing point relative to a reference point to obtain the position of at least one point.
Claim 2
Dependent Claim
82 words
Method for analyzing a light pattern produced on a photo detector array, comprising the steps of: filtering the signal from said photodetector array with a low pass filter, differentiating the output of the low pass filter to obtain a derivative of said filtered signal at at least one point in said pattern, detecting the point of zero crossing of said differentiated signal, and timing said zero crossing point relative to a reference point to obtain the position of at least one point.
Claim 3
Dependent Claim
19 words
A method according to claim 1 wherein said photodetector array is a matrix, linear or circular array of photodiodes.
Claim 4
Dependent Claim
24 words
A method according to claim 1 wherein the clock rate of said timing step runs faster than the clock rate of said diode array.
Claim 5
Dependent Claim
17 words
A method according to claim 1 wherein said filter is a constant time delay low pass filter.
Claim 6
Dependent Claim
13 words
A method according to claim 4 wherein said filter is a Bessel filter.
Claim 7
Dependent Claim
23 words
A method according to claim 1 wherein the resolution of position of said points is greater than that of the photodiode inter-element spacing.
Claim 8
Dependent Claim
36 words
A method according to claim 1 incorporating the further step of storing the photodiode array detector level data in memory and reading said data back through said filter and a differentiator used in said differentiating step.
Claim 9
Dependent Claim
28 words
A method according to claim 7 wherein said photodetector array is a matrix array and said further step allows two axis edge pattern position data to be obtained.
Claim 10
Dependent Claim
46 words
A method according to claim 7 wherein said light spots are projected by means including a pair of beam projections and a lens, and wherein said matrix array further provides mensuration of images of said part in a plane perpendicular to the axis of said lens.
Claim 11
Dependent Claim
25 words
Method according to claim 1 wherein said light pattern is a diffraction pattern and said points in said pattern are the fringe maxima or minima.
Claim 12
Dependent Claim
13 words
A method according to claim 10 wherein said derivative is the first derivative.
Claim 13
Dependent Claim
45 words
A method according to claim 10 wherein a counter is actuated when a predetermined minima or maxima is detected and the instantanious count of said counter is selectively digitally latched to output ports, said latching being disabled when fringe maxima fall below a set threshold.
Claim 14
Dependent Claim
40 words
Method according to claim 1 wherein said light pattern is an image of one or more features of an object, said derivative is the second derivative and said points in said pattern are one or more points on said object.
Claim 15
Dependent Claim
15 words
A method according to claim 13 wherein said features are the edges of said object.
Claim 16
Dependent Claim
15 words
A method according to claim 13 wherein said features are defects on said object surface.
Claim 17
Dependent Claim
27 words
A method according to claim 13 incorporating the further step of moving said object in one or more axes to present further images on said photodetector array.
Claim 18
Dependent Claim
18 words
Method according to claim 1 wherein said light pattern is an image of a spot on an object.
Claim 19
Dependent Claim
21 words
A method according to claim 17 wherein said derivative is the second derivative and provides at least one spot inflection point.
Claim 20
Dependent Claim
27 words
A method according to claim 1 incorporating the further step of pulsing the source of illumination producing said pattern to effectively freeze the motion of said pattern.
Claim 21
Dependent Claim
19 words
A method according to claim 1 wherein both the first and second derivative positions are used in said analysis.
Claim 22
Dependent Claim
15 words
A method according to claim 1 wherein position width or spacing of bars are determined.
Claim 23
Independent Claim
15 words
A method according to 21 wherein said bars are a bar code on an object.
Claim 24
Independent Claim
15 words
A method according to 21 wherein said bars are a bar code on an object.
Claim 25
Independent Claim
18 words
A method according to 21 wherein said bars are imaged through an object surface whose properties are determined.
Claim 26
Independent Claim
18 words
A method according to 21 wherein said bars are imaged through an object surface whose properties are determined.
Claim 27
Independent Claim
31 words
A method according to 21 wherein said bars are projected onto a surface, said bars on said surface are imaged onto said photodetector array and contours of said surface are determined.
Claim 28
Independent Claim
31 words
A method according to 21 wherein said bars are projected onto a surface, said bars on said surface are imaged onto said photodetector array and contours of said surface are determined.
Claim 29
Dependent Claim
28 words
A method according to claim 1 wherein said low pass filter is designed to cut off at a frequency 1/10 of the diode array clock rate or less.
Claim 30
Dependent Claim
30 words
A method according to claim 25 wherein said pattern is at least one spot produced by a laser and said low pass filter is used to obviate effects of speckle.
Claim 31
Dependent Claim
14 words
A method according to claim 1 wherein said filter has a variable pass frequency.
Claim 32
Dependent Claim
24 words
A method according to claim 1 wherein the position of said at least one point is compared to a stored value using a microcomputer.
Claim 33
Dependent Claim
25 words
A method according to claim 1 wherein at least relationship between the positions of at least two of each points is determined using a microcomputer.
Claim 34
Dependent Claim
22 words
A method according to claim 1 wherein said low pass filter provides an instantaneous weighted average of a plurality of array elements.
Claim 35
Dependent Claim
34 words
A method according to claim 1 wherein the outputs of said photodetector array are scanned and a delay is provided at the start of the scan is delayed to allow for filter settling time.
Claim 36
Dependent Claim
47 words
A method according to claim 1 wherein a counter is actuated when a preselected point of zero crossing is detected and digital latching of the instantaneous count of the counter to selected outputs is provided, said digital latching being disable when the detector array is in saturation.
Claim 37
Dependent Claim
91 words
Apparatus for analyzing a light pattern produced on a photo detector array, comprising: low pass filter means for filtering a signal produced from scanning said photodetector array. means for differentiating said filtered signal to obtain a derivative of said signal at at least one point in said pattern, means for detecting the point of zero crossing of said differentiated signal, and means for timing the start of said zero crossing point from the start of the scan of array to obtain the position of one or more points in said pattern.
Claim 38
Dependent Claim
91 words
Apparatus for analyzing a light pattern produced on a photo detector array, comprising: low pass filter means for filtering a signal produced from scanning said photodetector array. means for differentiating said filtered signal to obtain a derivative of said signal at at least one point in said pattern, means for detecting the point of zero crossing of said differentiated signal, and means for timing the start of said zero crossing point from the start of the scan of array to obtain the position of one or more points in said pattern.
Claim 39
Dependent Claim
18 words
Apparatus according to claim 33 wherein said photodetector array is a matrix, linear or circular array of photodiodes.
Claim 40
Dependent Claim
26 words
Apparatus according to claim 33 wherein the clock rate of said timing means is faster than the cock rate used in scanning of said diode array.
Claim 41
Dependent Claim
17 words
Apparatus according to claim 33 wherein said filter means is a constant time delay low pass filter.
Claim 42
Dependent Claim
12 words
Apparatus according to claim 36 wherein said filter is a Bessel filter.
Claim 43
Dependent Claim
22 words
Apparatus according to claim 33 wherein the resolution of position of said points is greater than that of the photodiode inter-element spacing.
Claim 44
Dependent Claim
30 words
Apparatus according to claim 33 further comprising means for storing the photodiode array detector level data in memory and reading said data back through said filter means and differentiating means.
Claim 45
Dependent Claim
29 words
Apparatus according to claim 39 wherein said photodetector array is a matrix array and said storing and reading means allows two axis edge pattern position data to be obtained.
Claim 46
Dependent Claim
24 words
Apparatus according to claim 33 wherein said light pattern is a diffraction and said points in said pattern are the fringe maxima or minima.
Claim 47
Dependent Claim
12 words
Apparatus according to claim 41 wherein said derivative is the first derivative.
Claim 48
Dependent Claim
50 words
Apparatus according to claim 41 further comprising a counter which is actuated when a predetermined minima or maxima is detected and digital latching means for latching the instantaneous count of the counter to selected outputs, said digital latching means being disabled when the fringe maxima fall below a set threshold.
Claim 49
Dependent Claim
40 words
Apparatus according to claim 33 wherein said light pattern is an image of one or more feaures of an object, said derivative is the second derivative and said points in said pattern are one or more points on said object.
Claim 50
Dependent Claim
14 words
Apparatus according to claim 44 wherein said features are the edges of said object.
Claim 51
Dependent Claim
15 words
A method according to claim 44 wherein said features are defects on said object surface.
Claim 52
Dependent Claim
25 words
Apparatus according to claim 44 further comprising means for moving said object in one or more axes to present further images on said photodetector array.
Claim 53
Dependent Claim
18 words
Apparatus according to claim 33 wherein said light pattern is an image of a spot on an object.
Claim 54
Dependent Claim
25 words
Apparatus according to claim 33 further comprising means for pulsing the source of illumination producing said pattern to effectively freeze the motion of said pattern.
Claim 55
Dependent Claim
23 words
Apparatus according to claim 33 further comprising microcomputer means for comparing the position of said at least one point with a stored value.
Claim 56
Dependent Claim
25 words
Apparatus according to claim 33 further comprising microcomputer means for determining at least one relationship between the positions of at least two of said points.
Claim 57
Dependent Claim
21 words
Apparatus according to claim 33 wherein said low pass filter provides an instantaneous weighted average of a plurality of array elements.
Claim 58
Dependent Claim
20 words
Apparatus according to claim 52 wherein said derivative is the second derivative and provides at least one spot inflection points.
Claim 59
Dependent Claim
35 words
Apparatus according to claim 33 further comprising means for scanning the outputs of said photodetector array and for providing a delay at the start of the scan to allow for settling of said filter means.
Claim 60
Dependent Claim
49 words
Apparatus according to claim 33 further comprising a counter which is actuated when a preselected point of zero crossing is detected and digital latching means for latching the instantaneous count of the counter to selected outputs, said digital catching means being disabled when the detector array is in saturation.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-07-18 | 1987-01-17 | 1987-07-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-07-18 | 1991-01-17 | 1991-07-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-07-18 | 1995-01-17 | 1995-07-19 | $7700.00 | Window Closed / Lapsed |