Classifications

• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; 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
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B3/00—Simple or compound lenses
  • G02B3/12—Fluid-filled or evacuated lenses
  • G02B3/14—Fluid-filled or evacuated lenses of variable focal length
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; 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
  • G06K7/10712—Fixed beam scanning
  • G06K7/10722—Photodetector array or CCD scanning
  • G06K7/10732—Light sources
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
  • G06K2207/00—Other aspects
  • G06K2207/1013—Multi-focal

Definitions

• the present convention relates generally to autofocus scanning systems and, more particularly, concerns code scanners capable of reading effectively over a wide range distances from a near field to a far field.
• Barcode scanners are a common form of code scanner. Some scanners of this type are handheld and need to recognize codes on labels in a large range of sizes over a large range of distances. For example, a barcode reader should, ideally, to be able to read anything from a tiny label with a resolution of 0.127 mm at a distance of 50 mm (near field) to a huge label with a resolution of 1.4 mm at a distance of 3 m (far field). Some scanners need to recognize two-dimensional codes, which presents an even more stringent requirement.
• the fundamental problem is that the scanning system must retain sharp focus over a large depth of field (DOF), the distance, included in the near to far fields.
• DOF depth of field
• the effective DOF can be increased by a using an automatic focus or zoom focus mechanism, such as one having a voice coil motor, to operate the optics or, the like.
• they tend to have a relatively slow response (I do not think that this is true.), involve the use of moving parts (reliability issue) (If so all digital cameras and mobile phones have the same issues.), and have a relatively limited focal range (I do not think that this is true.). They are also not easily retrofitted into existing systems, since they must be introduced in the middle of the optics, requiring redesign of all the lenses.
• an object of the present invention to provide an optical code scanner which is capable of detecting a code image effectively over all distances from a near field to a far field. It is another object of the present invention to provide an optical code scanner which is capable of detecting a code image a relatively quickly, preferably in 20 ms, or less.
• a code scanner which illuminates a scanned code from a distance, includes a liquid lens which focuses the reflected image of the code on an image sensor.
• the scanner includes a range detector, preferably laser- based, which determines the distance to the scanned code, and the liquid lens is controlled to focus at the detected distance.
• a code scanner which illuminates a scanned code from a distance includes a range detector, preferably laser-based, which determines the distance to the scanned code, and the source of illumination is uncontrolled to maintain its intensity substantially constant, regardless of the distance of the scanned code. This can be achieved by controlling the intensity of illumination (directly), or the dispersal angle of illumination in relationship to the distance.
• FIG. 1 is schematic diagram illustrating a code scanner 10 embodying the present invention.
• the scanner 10 has a light source 12, which illuminates an optical code 14, such as a barcode, at a distance.
• the light L reflected from barcode 14 forms an image on image sensor 16, which is processed to decode the bar code 14.
• a liquid lens 18 is interposed in the light path L between bar code 14 and image sensor 16.
• this an electro optical type of device which has a optical interface between two transparent layers. Through the adjustment of an applied voltage, the shape of that interface maybe changed, changing the focal length of the lens.
• the distance between the lens 18 and image sensor 16 remains fixed, however, the distance to the left of lens 18 of the plain on which the lens will focus will vary with the applied voltage.
• a ranging apparatus which preferably comprises a laser device and a laser detector 24.
• Pulsing technology measures the delay time between the initiation of a laser pulse and the return of its reflection.
• Parallax technology projects a light beam to form a spot on a target and then measures the position of the detected spot on the target. The distance of the target can be determined from the position of the detected spot.
• laser device 22 and detector 24 define a parallax ranging subsystem.
• Laser 22 projects a light beam onto bar code 14 and detector 24 senses the position of the resulting dot and determines the distances of bar code 14. It then produces a signal representative of that distance, which is applied to controller 20. In response, controller 20 is then able to apply a voltage to lens 18 to focus it appropriately.
• the output signal of detector 24 is also applied to light source 12, the intensity of which is controlled accordingly.
• source 12 could be a ray of light emitting diodes, and the intensity could be controlled by the numbers of diodes on the array that are turned on (more simply by changing optical output power).
• the intensity of light source 12 could also be controlled by varying the dispersion angle of the light at the midst.
• Those skilled in the art will appreciate that that could be achieved mechanically by controlling the angle of vain- like devices or the like, or it can be achieved optically with a condensing lens. It would be possible to provide a plurality of condensing lens and select among them or to provide a zooming lens, possibly even a liquid lens.
• liquid lens 18 is ARCTIC-414 or ARCTIC-416 produced by Varioptic.
• liquid lenses may be utilized as well.
• the laser is mounted atop of the camera module, instead of at the sides or on the bottom. Additionally, the laser should be offset from the optical axis by an amount equal to 6-15 mm. Moreover, if a LEDs are used for illumination, they should be mounted on the opposite of the module from the laser, in order to minimize the effects of reflection.
• the present invention exhibits advantages over the prior art in that it is capable of focusing a code image more quickly; in that it avoids the use of moving parts, eliminating the associated reliability issues; in that it has a substantially greater focus range; and in that it is easily retrofitted into existing scanning systems

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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)
• Automatic Focus Adjustment (AREA)

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Citations (4)

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• 2007
  • 2007-11-08 CN CN200780101467A patent/CN101855639A/zh active Pending
  • 2007-11-08 WO PCT/US2007/084043 patent/WO2009061317A1/en not_active Ceased
  • 2007-11-08 JP JP2010533055A patent/JP2011504247A/ja active Pending
  • 2007-11-08 EP EP07844971A patent/EP2218033A4/en not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (1)

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