Optical Information Reader and Optical Information Reading Method

• US 20120199655A1
• Filed: 01/31/2012
• Published: 08/09/2012
• Est. Priority Date: 07/31/2009
• Status: Active Grant

• Current Assignee: Optoelectronics Co Limited (Optoelectronics)
• Original Assignee: Optoelectronics Co Limited (Optoelectronics)
• Inventors: Fukuba, Ken
• Granted Patent: US 8,864,035 B2
• Time in Patent Office: Days
• US Class Current: 235/455
• CPC Class Codes: G02B 26/005 based on electrowetting
• CPC Class Codes: G02B 3/14 of variable focal length
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/10861 sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48

Abstract

A decoder 20 of a code scanner 1 measures a distance to a baggage 4 based on a reflection light by the baggage 4 of a laser light 15a outputted by a laser light generator 15, which is detected by a CMOS image sensor 13, adjusts focus of a focus lens 11 and irradiation light amount of illumination by a pulse LED 14 at image pickup based on the measured distance, analyzes the image including a code symbol 5 on the baggage 4 whose image is picked up under conditions after the adjustments, and decodes information indicated by the code symbol.

Claims

1-12. -12. (canceled)

13. An optical information reader which reads a symbol and decodes information indicated thereby, comprising:

an output device that outputs measuring light directed at the symbol to be read;

an illuminator that illuminates the symbol to be read;

an image pickup device that picks up an image of the symbol to be read, comprising an image sensor with a plurality of light responsive pixels, the image pickup having a shutter function controlling the start and stop of accumulation of charge substantially simultaneously in all pixels in accordance with an amount of light received by pixels;

a first controller that, in a first mode of operation, performs control in a first mode of operation, when reading the symbol, instructs said image pickup device to start periodic image pickup by said image sensor while turning on the measuring light output by said output device;

a distance measurement device that analyzes the image picked up by said image pickup device in said first mode and, when measuring light reflected by the symbol is detected in the image, measuring the distance to the symbol based on the position of the measuring light in the image;

a second controller that sets the amount of illumination produced by said illuminator based on the distance to the symbol as measured by said distance measurement device;

a third controller that, in a second mode of operation, turns on said illuminator with the illumination amount set by said second controller and causes said image pickup device to perform periodic image pickup via said image sensor, after distance measurement device detects measuring light in the image; and

a decoder that analyzes the image picked up by said image pickup device in the second mode and decodes the information indicated by the symbol.

14. The optical information reader according to claim 13, wherein the symbol is different in light reflectance from its surroundings.

15. The optical information reader according to claim 13, wherein the pixels are formed in a matrix.

16. The optical information reader according to claim 13, wherein the measuring light has a wavelength, intensity and focus that make it distinguishable, by the image sensor, in the picked up image.

17. The optical information reader according to claim 13, wherein the measuring light is laser light.

18. The optical information reader according to claim 13, further comprising:

an optical system with adjustable focus included in said image pickup device;

a device that stores a focus table in which the distance to the symbol to be read is associated with the value of a predetermined parameter for adjusting the focus corresponding to the distance to the symbol; and

said second controller adjusting the focus by driving the optical system based on the value of the parameter acquired by searching the focus table making use of the distance measured by said distance measurement device.

19. The optical information reader according to claim 18, wherein the value of the parameter corresponding to the distance in a predetermined range around a focal depth when the focus is set to a predetermined initial value is a fixed value corresponding to the predetermined initial value in the focus table.

20. The optical information reader according to claim 13,

said image pickup device further comprising a variable focus optical system forming an image of incident light on said image sensor and a device that adjusts focus of the optical system according to a value of a predetermined parameter, and

said second controller setting a value of the predetermined parameter for adjusting the focus of the optical system based on the distance to the symbol as measured by said distance measurement device.

21. The optical information reader according to claim 20, further comprising:

said optical system comprising a liquid lens the refractive power of which is adjustable by application of a voltage, and

wherein the focus is adjusted by adjusting the voltage applied to the liquid lens.

22. The optical information reader according to claim 13, further comprising:

a device that stores an illumination table in which the distance to the symbol is associated with a value of a drive control parameter for instructing said illuminator to perform illumination at an illumination amount suitable for the distance,

said second controller setting the illumination amount based on the value of the drive control parameter acquired by searching the illumination table making use of the distance measured by said distance measurement device.

23. The optical information reader according to claim 13, further comprising:

a device that outputs visible laser light and a device that outputs invisible laser light as said measuring light; and

a device that causes light output from said invisible laser device when there is no operation by a user, and switches to light output from said visible light laser device when there is a predetermined operation by the user.

24. The optical information reader according to claim 13, wherein, in said first mode, said image pickup device stops, after the start of the accumulation of charge in each pixel of said image sensor, the accumulation of charge in all pixels at a time when charge is at least equal to a predetermined reference value being accumulated in at least one of the pixels during a frame period.

25. The optical information reader according to claim 13,

wherein, in the first mode, said distance measurement device analyzes the image picked up by said image pickup device in a frame period and measures a distance to the object to be read by start of a next frame period, and

said second controller setting the illumination amount of said illuminator by the start of a frame period following a frame period in which the measuring light is detected.

26. The optical information reader according to claim 13

wherein said output device outputs a laser light as said light for sensing the object to be read and measuring distance to the object to be read.

27. A method for reading optical information in which other information is encoded, comprising the steps of:

a. directing a measuring light source at the optical information;

b. directing an illumination light source at the optical information;

c. controlling an image pickup device that picks up an image of the optical information, the device comprising an image sensor with a plurality of light responsive pixels, the control being exercised so as to start and stop accumulation of charge substantially simultaneously in all pixels responsive to light incident on pixels, periodic image pickup by the image sensor being started during predetermined frame periods;

d. analyzing an image picked up by the image pickup device in step c. and, when measuring light reflected from the optical information is detected in the image, measuring the distance to the optical information based on the position of the measuring light in the image;

e. setting the amount of illumination light based on the distance measured in step d.;

f. tuning on the illumination light source at the illumination light amount set in step e. during periodic image pickup after measuring light is detected in step d.; and

g. analyzing the image picked up by the image pickup device in step c. and decoding the other information.

28. The method according to claim 27 performed with an image pickup device in which the image sensor pixels are formed in a matrix.

29. The method according to claim 27 performed with a measuring light source in which the measuring light has a wavelength, intensity and focus that make it distinguishable, by the image sensor, in the picked up image.

30. The method according to claim 27 performed with a measuring light source which produces laser light.

31. The method according to claim 27, wherein at step e, the amount of illumination light is set based on a value of a drive control parameter acquired by making use of the distance measured in step d. to search an illumination table in which the distance to optical information is associated with the value of the drive control parameter.

32. The method according to claim 27, performed with a measuring light source providing both visible and invisible laser light, said method further comprising controlling the measuring light source to output invisible laser light when there is no operation by a user, and when there is a predetermined operation by the user, controlling the measuring light source to output visible laser light.

33. The method according to claim 27, wherein step c. comprises instructing said image pickup device, after the start of the accumulation of charge in a charge accumulation element in each pixel of said image sensor, to stop the accumulation of charge in charge accumulation elements in all pixels at a time when charge at least equal to a predetermined reference value is accumulated in at least one of the charge accumulation elements in a frame period.

34. The method according to claim 27 performed with an image pickup device including an optical system and a device that adjusts focus of the optical system to form an image of incident light on said image sensor according to a value of a predetermined parameter, step e. comprising setting the value of the predetermined parameter based on the distance to the object to be read measured by said distance measured in step d.

35. The method according to claim 34, wherein setting the value comprises searching a focus table in which the distance to the optical information is associated with a value of the predetermined parameter, making use of the distance measured at step d. to perform the search.

36. The method according to claim 35, wherein, the value of the parameter corresponding to distance in a predetermined range around a focal depth when the focus is set to a predetermined initial value is a fixed value corresponding to a predetermined initial value in the focus table.

37. The method according to claim 34 performed with an optical system which comprises a liquid lens, the refractive power of which is adjustable by application of a voltage, the focus being adjusted by adjusting the voltage applied to the liquid lens.

38. The method according to claim 27, wherein

step d. comprises analyzing the image picked up by said image pickup device in each frame period and measuring the distance to the optical code by the start of the next frame period, and

step e. comprises setting the amount of illumination light by start of a frame period next following a frame period in which the measuring light is detected.