EP0054170B1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method of correcting the positional error of a rotating polygon mirror
Assignee: Dr Ing Rudolf Hell GmbH
•
Filing: 1981-10-30
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Granted: 1985-05-29
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Expires: 2001-10-30
Abstract
Abstract Positional errors are corrected for a light beam which is deflected point and line-wise across a scanning surface by a polyhedral rotating mirror. For each mirror surface, the positional errors are measured in the line direction and perpendicular thereto at a plurality of measuring points oriented in the line direction in the area of the scanning surface. Correction values are generated which, during simultaneous error measurement, are changed until the positional errors are compensated by means of correction elements. The determined correction values are stored and are read out for continuous correction during the actual operation synchronously with the mirror surfaces simultaneously located in the beam path. Light deflectors are employed as correction elements. Employing the rotating mirror in a recording arrangement, transit time elements controlled by the correction values are disposed as correction elements in the signal path of the image signal for the correction of the positional errors in the line direction. If the image signal is stored, the frequency of the read clock can alternately be changed as a function of the correction values. The method is very accurate so that, in particular, errors caused by uneven mirror surfaces are corrected.
Inventors
- 👤 Heinrich Jürgensen
- 👤 Thomas Zelenka
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 17:58
CPC Classifications
G; G02; G02B; G02B26/00; G02B26/08; G02B26/10; G02B26/12; G02B26/127; G02B27/00; G02B27/0025; G02B27/0031
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
174 words
Process for the correction of positional errors of a light beam deflected dot-by-dot and line-by-line across an area by means of a deflector system comprising at least one reflector surface, which is displaced transversely to the direction of deflection with respect to the deflector system, in which positional errors are detected and these are corrected by appropriate correction values, characterized in that prior to actual operation, a number of positional errors is measured in the direction of deflection (X positional errors) and at right angles thereto (Y positional errors) at measuring points set in the line direction in the region of the area, for each reflector surface, that for correction of the positional errors, correction values are generated for each reflector surface and are modified under simultaneous monitoring of the positional errors until the positional errors are cancelled, that the modified correction values are stored and that for current correction during actual operation, the stored correction values allocated to the individual reflector surfaces are called up synchronously with the displacement of the deflector system.
Claim 2
Dependent Claim
174 words
Process for the correction of positional errors of a light beam deflected dot-by-dot and line-by-line across an area by means of a deflector system comprising at least one reflector surface, which is displaced transversely to the direction of deflection with respect to the deflector system, in which positional errors are detected and these are corrected by appropriate correction values, characterized in that prior to actual operation, a number of positional errors is measured in the direction of deflection (X positional errors) and at right angles thereto (Y positional errors) at measuring points set in the line direction in the region of the area, for each reflector surface, that for correction of the positional errors, correction values are generated for each reflector surface and are modified under simultaneous monitoring of the positional errors until the positional errors are cancelled, that the modified correction values are stored and that for current correction during actual operation, the stored correction values allocated to the individual reflector surfaces are called up synchronously with the displacement of the deflector system.
Claim 3
Dependent Claim
32 words
Process according to claim 1, characterized in that the X-position errors and Y-position errors are corrected by means of deflection of the light beam which are a function of the correction values.
Claim 4
Dependent Claim
65 words
Process according to claim 1, characterized in that the intensity of the light beam is modulated as a function of an image signal for the purpose of line-by-line recording on the area, that the Y-positional errors are corrected by a controlled deflection of the light beam and the X-position errors are corrected line-by-line by a controlled change of the transit time of the image signal.
Claim 5
Dependent Claim
79 words
Process according to claim 1, characterized in that the light beam is modulated in its intensity for the purpose of line-by-line recording on the area, as a function of image data which are read out of a storage medium by means of a read cycle, that the Y-position errors are corrected by a controlled deflection of the light beam, and that for the purpose of line-by-line correction of the X-position errors, the frequence of the read cycle is modified.
Claim 6
Dependent Claim
34 words
Process according to any of claims 1 to 4, characterized in that the read-out of the image data is started in each case, at the line start, by means of a synchronizing start pulse.
Claim 7
Dependent Claim
25 words
Process according to any of claims 1 to 4, characterized in that the corrective deflection is performed before the line-by-line deflection of the light beam.
Claim 8
Dependent Claim
31 words
Process according to any of claims 1 to 6, characterized in that a corrective function is generated for each reflector surface by interpolation from the correction values allocated to the same.
Claim 9
Dependent Claim
24 words
Process according to any of claims 1 to 7, characterized in that a multi-face rotary reflector (polygon reflector) is utilized as the deflector system.
Claim 10
Dependent Claim
60 words
Process according to any of claims 1 to 8, characterized in that for determination of the Y-position errors, use is made in each case of a photoelectric measuring element comprising two photosensitive areas placed transversely to the direction of deflection, and that the photo-currents are integrated, and the Y-position error is determined by establishing the difference of the integrated photo-currents.
Claim 11
Dependent Claim
17 words
Process according to claim 9, characterized in that a differential photodiode is utilized as the measuring element.
Claim 12
Dependent Claim
26 words
Process according to any of claims 1 to 8, characterized in that a positional detector comprising a highohmic photosensitive material is utilized as the measuring element.
Claim 13
Dependent Claim
30 words
Process according to any of claims 1 to 11, characterized in that the X-position errors are determined by measuring the duration differences of the light beam between the measuring points.
Claim 14
Dependent Claim
24 words
Process according to claim 3 or 4, characterized in that an acousto-optical modulator is utilized for simultaneous intensity-modulation and deflection of the light beam.
References Cited (Backward Citations)
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