WO2010104510A1 - Système optique à foyer variable - Google Patents

Système optique à foyer variable Download PDF

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Publication number
WO2010104510A1
WO2010104510A1 PCT/US2009/036895 US2009036895W WO2010104510A1 WO 2010104510 A1 WO2010104510 A1 WO 2010104510A1 US 2009036895 W US2009036895 W US 2009036895W WO 2010104510 A1 WO2010104510 A1 WO 2010104510A1
Authority
WO
WIPO (PCT)
Prior art keywords
mirror
curvature
transducer
periphery
distance
Prior art date
Application number
PCT/US2009/036895
Other languages
English (en)
Inventor
Yo Tanaka
Ryuji Nagaoka
Original Assignee
Optoelectronics Co., Ltd.
Opticon, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Optoelectronics Co., Ltd., Opticon, Inc. filed Critical Optoelectronics Co., Ltd.
Priority to PCT/US2009/036895 priority Critical patent/WO2010104510A1/fr
Publication of WO2010104510A1 publication Critical patent/WO2010104510A1/fr

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
    • G02B26/0825—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a flexible sheet or membrane, e.g. for varying the focus
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
    • G06K7/10792—Special measures in relation to the object to be scanned
    • G06K7/10801—Multidistance reading
    • G06K7/10811—Focalisation

Definitions

  • the present invention relates generally to optical systems and, more particularly, concerns an optical illumination system for code readers that provide increases depth of field (depth of read) through the use of an automatic beam focus and is free of moving parts.
  • optical code readers have been utilized in production lines where items are assembled, where they are inspected, where they are packaged, and the like. This application of optical code reading is far more demanding, as products move down a production line at a relatively high speed, for example, on a conveyor belt. In order to avoid the creation of a bottle neck on the production line, it is therefore important that accurate decoding of optical codes take place without reducing the speed at which the objects move down the production line. The speed at which an optical code can be decoded accurately therefore becomes a primary concern.
  • One form of optical scanner commonly used with linear barcodes projects a laser beam at a remote optical code and scans the beam linearly along the direction of the barcode. More of the laser beam is reflected from the light areas of the barcode than the dark areas (the bars), so the light reflected from the barcode, when sensed at the scanner, contains a sequence of bright and dark portions corresponding, respectively, to the spaces and bars of the barcode, respectively.
  • Accurate detection of the light and dark areas of the barcode requires that a well focused light source, typically one providing infrared laser light, be scanned over the barcode, to make an accurate determination regarding which areas are light or dark and, in particular, where the transition between the light and dark areas occurs.
  • a common approach is to focus the light source to a specific position where the barcode is expected to be and to restrict the beam diameter by passing the beam through an aperture of predefined size. Restricting the beam diameter increases the depth of field and, therefore, the operating range over which the light source provides illumination sufficiently focused to allow accurate decoding of the optical code.
  • the range can be increased by reducing the aperture, but only at the expense of reducing overall illumination. That is, a substantial increase in the brightness of the light source becomes necessary.
  • a typical laser beam illumination system 10 of this type is illustrated schematically in Fig.l.
  • a laser light source such as a laser diode 12 projects laser light forwardly.
  • the light impinges upon and passes through a focusing lens 14, in this case, a fixed lens and, forward of the lens is passed through an aperture 16.
  • a relatively narrow beam is projected from aperture 16 and exhibits a beam waist 18, or a minimum diameter, at a distance ZO from aperture 16, the actual value of ZO being determined, at a particular wavelength of light, by the focal length of lens 14 and the diameter of aperture 16.
  • an autofocus mechanism containing a lens which includes a movable lens element. This usually yields an effective operating range for many applications.
  • Fig. 2 is a schematic representation of a known variable focus laser beam illumination system 10'. That is, the system 10' produces a laser beam in which the distance of the beam waist from the aperture maybe be adjusted.
  • the light source 12 projects laser light forwardly onto and through a lens 20.
  • Lens 20 is mounted for axial movement towards and away from light source 12. Light emitted forwardly from lens 20 impinges upon an aperture 22, which is variable in diameter. Through the movement of lens 20 and the simultaneous adjustment of aperture 22, the distance of the laser beam waist from aperture 22 can be adjusted through a range of values.
  • the beam waist distance from the aperture 22 maybe adjusted through a range of values, so that it may be set at a distance corresponding to the distance of the target. As a result, the depth of field of the light source 10' is effectively increased.
  • lens 20 can be replaced by a system of lenses with one or more moving components.
  • the distance traveled by the moving component is, however, substantially longer, allowing more accuracy but making it difficult to miniaturize.
  • Durability of the system is low owing to the moving part, and an electrical mechanical actuator is still required to move the moving part.
  • a curved mirror preferably a cylindrical mirror is interposed into the path of light from the source of illumination of an optical illumination system.
  • the curvature of this mirror is varied by providing a mount system with piezoelectric transducers, so that the pressure applied to the curved lens may be varied through adjustment of the voltage applied to the piezoelectric elements.
  • FIG. 1 is a schematic representation of a typical an optical illumination system utilizing an aperture to restrict the diameter of a beam from a light source, increasing its depth of field;
  • FIG. 2 is a schematic representation of a known variable focus laser beam illumination system making use of a moveable lens
  • FIG. 3, comprising parts A and B is a schematic diagram illustrating the principle involved in the present invention
  • FIG. 4 is a schematic representation of a first embodiment of an automatic focus mirror structure 30 in accordance with the present invention.
  • FIG. 5 is an alternate embodiment 30' of an automatic focus mirror structure embodying the present invention.
  • FIG. 6 is a schematic representation of a automatic focus optical illumination system embodying the present invention.
  • FIG. 7 is a graph comparing the operating range of an automatic focus optical illumination system in accordance with the present invention ("New AF") with the operating range of an automatic focus optical illumination system employing single lens focusing system.
  • New AF automatic focus optical illumination system in accordance with the present invention
  • FIG. 3 is a schematic representation illustrating the principle involved in the present invention.
  • a mirror M will be utilized which is made of a material that can withstand some flexing, without breaking or exhibiting fatigue failure. For example, a somewhat flexible plastic material may be used or a metal which not experience fatigue over the range of distortion which it will experience.
  • Mirror M is provided with a finished reflecting surface F which can have the high reflectance ratio, preferably by virtue of using gold evaporation for finishing.
  • Mirror M is maintained in a flexed or curved position such that collimated light impinging on the mirror is reflected there from and focused at a distance forward of a mirror. The focused distance will be determined by the curvature of the mirror. For example, in FIG.
  • mirror M is in a relatively flattened state where its curvature is much lower. In this case, light impinging upon the mirror is focused at a substantially greater distance f 2 from the lens.
  • FIG. 4 is a schematic representation of a first embodiment of an automatic focus mirror structure 30 in accordance with the present invention.
  • Structure 30 has a mirror M of the type described previously, preferably a cylindrical mirror.
  • Mirror M is mounted in an arch to a curved position between the piezoelectric transducer elements 32, 32.
  • piezoelectric elements will produce a force (in this case, in the direction indicated by the arrows) which is related to a voltage applied to them.
  • mirror M is mounted so that where no signal is applied to the elements 32, 32 it will have a curvature calculated to place the beam waist position at a design maximum distance from mirror M.
  • a voltage is applied to the piezoelectric elements 32, 32 from a source 34.
  • the lens In the optical illumination systems utilizing an adjustable lens for automatic focus, the lens must be aligned axially with the light source, and the scanning mirror must then be spaced axially from the lens.
  • the light source, lens and scanning mirror must therefore be spaced and aligned linearly, introducing a dimension extending from the rear of the LED to the scanning mirror which cannot be reduced. This imposes a serious limitation on the ability to miniaturize. That limitation is not present in accordance with the present invention, since the scanning mirror can be positioned laterally of the mirror assembly 30 or 30', offering additional opportunities for space reduction.
  • FIG. 7 is a graph comparing the operating range of an automatic focus optical illumination system in accordance with the present invention ("New AF") with the operating range of a variable focus optical illumination system employing single lens focusing system.
  • New AF automatic focus optical illumination system
  • Three operational situations are illustrated: the top pair of curves illustrate the respective operating ranges when the lowest tolerable resolution is 20 mils; the middle pair of curves illustrate the respective operating ranges when the lowest tolerable resolution is 10 mils; and the bottom pair of curves illustrate the respective operating ranges when the lowest tolerable resolution is 5 mils.
  • the operating range of optical illumination system in accordance with the present invention is at least twice that of the system employing a lens.
  • the present invention not only achieves improved durability and greater reliability by virtue of eliminating moving parts and substantial reduction in size, but also offers a substantially greater operating range.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Theoretical Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Optical Scanning Systems (AREA)

Abstract

Un miroir incurvé est intercalé dans le trajet de la lumière depuis la source d'éclairage d'un système d'éclairage optique. La variation de la courbure de ce miroir permet de modifier la distance focale de la lumière réfléchie par le miroir, ce qui modifie la distance focale ou la position du col du faisceau de lumière émis par le système d'éclairage. La courbure du miroir est de préférence modifiée par aménagement d'une monture sur laquelle des transducteurs piézoélectriques sont montés de manière que la pression appliquée au miroir incurvé par les éléments piézoélectriques peut être modifiée au moyen d'un ajustement de la tension appliquée aux éléments piézoélectriques.
PCT/US2009/036895 2009-03-12 2009-03-12 Système optique à foyer variable WO2010104510A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US2009/036895 WO2010104510A1 (fr) 2009-03-12 2009-03-12 Système optique à foyer variable

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2009/036895 WO2010104510A1 (fr) 2009-03-12 2009-03-12 Système optique à foyer variable

Publications (1)

Publication Number Publication Date
WO2010104510A1 true WO2010104510A1 (fr) 2010-09-16

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ID=42728606

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2009/036895 WO2010104510A1 (fr) 2009-03-12 2009-03-12 Système optique à foyer variable

Country Status (1)

Country Link
WO (1) WO2010104510A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103364945A (zh) * 2013-08-07 2013-10-23 北京理工大学 一种元件不动型变焦稳像一体化成像光学系统
CN116454718A (zh) * 2023-06-13 2023-07-18 深圳市镭硕光电科技有限公司 激光器

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4939356A (en) * 1989-05-02 1990-07-03 Spectra-Physics, Inc. Bar code scanner with asterisk scan pattern
US6053409A (en) * 1996-03-07 2000-04-25 Accu-Sort Systems, Inc. Dynamic focusing apparatus for an optical imaging system using a deformable mirror
US6304316B1 (en) * 1998-10-22 2001-10-16 Anvik Corporation Microlithography system for high-resolution large-area patterning on curved surfaces
US20060028703A1 (en) * 2003-07-30 2006-02-09 Asml Holding N.V. Method of using deformable mirror using piezoelectric actuators formed as an integrated circuit
US20060092393A1 (en) * 2004-10-28 2006-05-04 Asml Holding N.V. Lithographic apparatus having an adjustable projection system and device manufacturing method
US20070295817A1 (en) * 2006-06-22 2007-12-27 Intermec Ip Corp. Automatic data collection apparatus and method for variable focus using a deformable mirror

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4939356A (en) * 1989-05-02 1990-07-03 Spectra-Physics, Inc. Bar code scanner with asterisk scan pattern
US6053409A (en) * 1996-03-07 2000-04-25 Accu-Sort Systems, Inc. Dynamic focusing apparatus for an optical imaging system using a deformable mirror
US6304316B1 (en) * 1998-10-22 2001-10-16 Anvik Corporation Microlithography system for high-resolution large-area patterning on curved surfaces
US20060028703A1 (en) * 2003-07-30 2006-02-09 Asml Holding N.V. Method of using deformable mirror using piezoelectric actuators formed as an integrated circuit
US20060092393A1 (en) * 2004-10-28 2006-05-04 Asml Holding N.V. Lithographic apparatus having an adjustable projection system and device manufacturing method
US20070295817A1 (en) * 2006-06-22 2007-12-27 Intermec Ip Corp. Automatic data collection apparatus and method for variable focus using a deformable mirror

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103364945A (zh) * 2013-08-07 2013-10-23 北京理工大学 一种元件不动型变焦稳像一体化成像光学系统
CN116454718A (zh) * 2023-06-13 2023-07-18 深圳市镭硕光电科技有限公司 激光器
CN116454718B (zh) * 2023-06-13 2023-08-11 深圳市镭硕光电科技有限公司 激光器

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