Method and apparatus for reading invisible symbol
First Claim
1. A method for reading an invisible symbol comprising the steps of:
- heating an invisible symbol formed on a sample and containing a material which emits infrared light when heated;
detecting infrared light emitted from the invisible symbol;
calculating a differential coefficient of a detection signal corresponding to a position on the sample;
determining, based on upper and lower threshold values set for the differential coefficient, a maximum value of the differential coefficient in a region exceeding the upper threshold value and a minimum value of the differential coefficient in a region smaller than the lower threshold value; and
binarizing the detection signal by using the maximum or minimum value as a leading or trailing edge of a binary function.
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Abstract
An invisible symbol reading apparatus includes a heating unit for heating an invisible symbol formed on a sample and containing a material which emits infrared light when heated, a detecting unit for detecting infrared light emitted from the invisible symbol, and an arithmetic operation unit for binarizing a detection signal from the detecting unit. The arithmetic operation unit calculates a differential coefficient of the detection signal, that corresponds to a position on the sample. On the basis of upper and lower threshold values set for the differential coefficient, the arithmetic operation unit determines a maximum value of the differential coefficient in a region exceeding the upper threshold value and a minimum value of the differential coefficient in a region smaller than the lower threshold value. The arithmetic operation unit binarizes the detection signal by using the maximum or minimum value as a leading or trailing edge of a binary function.
89 Citations
18 Claims
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1. A method for reading an invisible symbol comprising the steps of:
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heating an invisible symbol formed on a sample and containing a material which emits infrared light when heated;
detecting infrared light emitted from the invisible symbol;
calculating a differential coefficient of a detection signal corresponding to a position on the sample;
determining, based on upper and lower threshold values set for the differential coefficient, a maximum value of the differential coefficient in a region exceeding the upper threshold value and a minimum value of the differential coefficient in a region smaller than the lower threshold value; and
binarizing the detection signal by using the maximum or minimum value as a leading or trailing edge of a binary function. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for reading an invisible symbol comprising:
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a heater configured to heat an invisible symbol formed on a sample and containing a material which emits infrared light when heated;
a detector configured to detect infrared light emitted from the invisible symbol; and
an arithmetic operation unit configured to binarize a detection signal from said detector;
wherein said arithmetic operation unit calculates a differential coefficient of the detection signal corresponding to a position on the sample, determines, based on upper and lower threshold values set for the differential coefficient, a maximum value of the differential coefficient in a region exceeding the upper threshold value and a minimum value of the differential coefficient in a region smaller than the lower threshold value, and binarizes the detection signal by using the maximum or minimum value as a leading or trailing edge of a binary function. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
said apparatus further comprises a conveyor configured to move the sample from a heating position of said heater to a detection position of said detector. -
10. The apparatus according to claim 8, further comprising a controller configured to turn off said heater before detection by said detector.
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11. The apparatus according to claim 8, further comprising:
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an optical modulator configured to optically modulate the infrared light emitted from the invisible symbol; and
said detector comprising a phase detector configured to detect a phase of a detection signal.
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12. The apparatus according to claim 8, further comprising a bandpass infrared filter for transmitting infrared light in a specific wavelength region of the infrared light emitted from the invisible symbol.
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13. The apparatus according to claim 12, wherein said bandpass infrared filter transmits infrared light near 4.5 μ
- m peculiar to a cyano group.
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14. The apparatus according to claim 8, further comprising a calcium fluoride lens.
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15. The apparatus according to claim 8, further comprising a Cassegrain lens.
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16. The apparatus according to claim 8, wherein said detector is a mercury cadmium tellurium detector.
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17. The apparatus according to claim 8, wherein said detector forms a focal plane array.
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18. The apparatus according to claim 17, wherein an element constructing said focal plane array is made of a material selected from the group consisting of platinum silicide and indium antimony.
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Specification