US3759618A
Expired / Lapsed
US
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Methods of and apparatus for effecting optical measurement and analysis
Assignee: National Research Development Corp UK
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Filing: 1971-07-29
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Granted: 1973-09-18
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Expires: 1991-07-29
Abstract
Abstract Optical analysis method and apparatus comprising a single photoelectric sensing means upon which the shadow of an optical grating is continuously cast through a composite grid having a plurality, preferably three, of different discrete sub-sections each having the same line repeat dimension and orientation but whose lines are progressively shifted relatively to those of the other sub-sections by chosen fractions of the line repeat dimension, and means for simultaneously casting the shadow of the optical grating on each of the sub-sections. There is also provided means for varying sinusoidally the intensity of the grating shadow incident upon each of the grid sub-sections so that the respective maxima and minima of the variations at such grid sub-sections are equally phase-displaced over the variation cycle, while means compares the resultant signal output from said photocell with a reference signal synchronised with the scanning cycle.
Inventors
- 👤 G Rogers
- 👤 Ens N Steph
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 23:29
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/36; G01D5/38
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
143 words
The method of determining the position of an optical grating which comprises the steps of continuously casting a shadow of such grating on to a single photoelectric sensing means through each of the sub-sections in turn of a composite grid whose separate sub-sections each have the same line repeat dimension and orientation as those of the grating but whose lines are progressively shifted relative to those of the other sub-sections by chosen fractions of the line repeat dimension, sinusoidally varying the intensity of the grating shadow incident upon each of said grid sub-sections so that the respective maxima and minima of the sinusoidal variations at such grid sub-sections are equally phase-displaced over the variation cycle and then directly comparing the electric signal output from said photoelectric sensing means with a reference signal which fluctuates sinusoidally in synchronism with the shadow intensity variation cycle.
Claim 2
Independent Claim
143 words
The method of determining the position of an optical grating which comprises the steps of continuously casting a shadow of such grating on to a single photoelectric sensing means through each of the sub-sections in turn of a composite grid whose separate sub-sections each have the same line repeat dimension and orientation as those of the grating but whose lines are progressively shifted relative to those of the other sub-sections by chosen fractions of the line repeat dimension, sinusoidally varying the intensity of the grating shadow incident upon each of said grid sub-sections so that the respective maxima and minima of the sinusoidal variations at such grid sub-sections are equally phase-displaced over the variation cycle and then directly comparing the electric signal output from said photoelectric sensing means with a reference signal which fluctuates sinusoidally in synchronism with the shadow intensity variation cycle.
Claim 3
Dependent Claim
46 words
The method according to claim 1 which includes the steps of cyclically changing a chosen characteristic of the light used to cast said shadow during each intensity variation cycle and then selectively filtering the light available at each of the different sub-sections of said composite grid.
Claim 4
Dependent Claim
20 words
The method according to claim 2 in which the cyclically changed characteristic is the direction of polarization of the light.
Claim 5
Dependent Claim
18 words
The method according to claim 2 in which the cyclically changed characteristic is the colour of the light.
Claim 6
Dependent Claim
178 words
Apparatus for determining the position of an optical grating or of the shadow cast thereby which comprises a composite optical grid which includes a plurality of separate sub-sections each having the same line repeat dimension and orientation as those of the grating but whose lines are progressively shifted relative to those of the other sub-sections by chosen fractions of the line repeat dimension optical means for simultaneously casting the shadow of said optical grating on to each of said sub-sections means for varying sinusoidally the intensity of the grating shadow incident upon each of said grid sub-sections so that the respective maxima and minima of the variations at such grid sub-sections are equally phase-displaced ovEr the variation cycle, a single photoelectric sensing means positioned to be responsive to the light of said cast shadow passing through each of said sub-sections, reference signal generating means for providing a reference signal which fluctuates in synchronism with the operation cycle of said intensity varying means and means for directly comparing the output signal from said photo-sensing means with said reference signal.
Claim 7
Dependent Claim
178 words
Apparatus for determining the position of an optical grating or of the shadow cast thereby which comprises a composite optical grid which includes a plurality of separate sub-sections each having the same line repeat dimension and orientation as those of the grating but whose lines are progressively shifted relative to those of the other sub-sections by chosen fractions of the line repeat dimension optical means for simultaneously casting the shadow of said optical grating on to each of said sub-sections means for varying sinusoidally the intensity of the grating shadow incident upon each of said grid sub-sections so that the respective maxima and minima of the variations at such grid sub-sections are equally phase-displaced ovEr the variation cycle, a single photoelectric sensing means positioned to be responsive to the light of said cast shadow passing through each of said sub-sections, reference signal generating means for providing a reference signal which fluctuates in synchronism with the operation cycle of said intensity varying means and means for directly comparing the output signal from said photo-sensing means with said reference signal.
Claim 8
Dependent Claim
58 words
Apparatus according to claim 5 which comprises means for cyclically changing a chosen characteristic of the light used to cast said shadow during each intensity variation cycle and filtering means adjacent each of said composite grid sub-sections for selecting only light having a chosen and different value of said characteristic for transmission to said single photoelectric sensing means.
Claim 9
Dependent Claim
17 words
Apparatus according to claim 6 in which said chosen characteristic is the polarization direction of said light.
Claim 10
Dependent Claim
16 words
Apparatus according to claim 6 in which said chosen characteristic is the colour of said light.
Claim 11
Dependent Claim
44 words
Apparatus according to claim 7 which includes a continuously rotatable disc of vectographic material disposed in the light beam forming the shadow incident on said composite grid and light polarization filters having suitably different polarization directions disposed in front of said composite grid sub-sections.
Claim 12
Dependent Claim
42 words
Apparatus according to claim 8 which includes a continuously rotatable colour modulating disc disposed in the light beam forming the shadow incident on said composite grid and colour filters of suitably different pass bands disposed in front of said composite grid sub-sections.
Claim 13
Dependent Claim
21 words
Apparatus in accordance with claim 9 which includes reference signal generator means coupled for operation by means rotating said rotatable disc.
Claim 14
Dependent Claim
32 words
Apparatus in accordance with claim 5 which includes means for providing a plurality of separate light beams whose respective intensities vary sinusiodally during each operation cycle with different instants of maximum intensity.
Claim 15
Dependent Claim
25 words
Apparatus in accordance with claim 12 which includes a plurality of separate light sources arranged for energization by different phases of a polyphase electric supply.
Claim 16
Dependent Claim
35 words
Apparatus in accordance with claim 12 which includes a single light source of constant intensity and a plurality of electric signal controlled light modulators arranged for control by different phases of a polyphase electric supply.
Claim 17
Dependent Claim
17 words
Apparatus according to claim 13 in which said polyphase supply is the normal three-phase public supply mains.
Claim 18
Dependent Claim
14 words
Apparatus according to claim 13 in which said polyphase supply is an electronic oscillator.
Claim 19
Dependent Claim
21 words
Apparatus in accordance with claim 10 which includes reference signal generator means coupled for operation by means rotating said rotatable disc.
Claim 20
Dependent Claim
43 words
Apparatus as described in claim 5 wherein the composite optical grid comprises a plurality of sub-sections, each respective sub-section having the same line repeat pattern, two sections being side-by-side and the third extending across one end of each of the aforementioned two sub-sections.
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) | 1976-09-17 | 1977-03-19 | 1977-09-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-17 | 1981-03-19 | 1981-09-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-17 | 1985-03-19 | 1985-09-18 | $7700.00 | Window Closed / Lapsed |