Method and apparatus for reading invisible symbol

• US 20040155113A1
• Filed: 07/29/2003
• Published: 08/12/2004
• Est. Priority Date: 03/23/1998
• Status: Abandoned Application

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Domon, Tomokazu, Sano, Kenji, Nagai, Hideo, Fukuda, Hironori, Urano, Taeko I.
• Application Number:
  US10/628,441
• Publication Number:
  US 20040155113A1
• Time in Patent Office: Days
• US Class Current: 235/491
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence

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 loading or trailing edge of a binary function.

Claims

1. An article comprising

a substrate;

and

an invisible symbol on the substrate,

wherein the invisible symbol is formed by a compound which includes a cyano group and has an infrared absorption wavelength apart from that of the substrate when heated.

2. The article of claim 1, wherein the compound has a polymer containing a cyano group.

3. The article of claim 1, wherein the substrate is made of paper, polymer or cloth.

4. The article of claim 1, wherein the compound emits infrared light when heated to 50 degree in Centigrade or more.

5. The article of claim 1, wherein the invisible symbol is a barcode having minimum bar width about 250 micro-meter.

6. The article of claim 1, wherein the wavelength of infrared emission is around 4.5 micro-meter.

7. The article of claim 1, wherein the invisible symbol is printed on the substrate using a laser beam printer.