HANNDHELD CODE READER WITH OPTIMAL OPTICAL READING DISTANCE

• US 20030039411A1
• Filed: 05/13/1999
• Published: 02/27/2003
• Est. Priority Date: 05/18/1998
• Status: Active Grant

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: NADA, YOSHIYUKI
• Granted Patent: US 6,571,025 B2
• Time in Patent Office: Days
• US Class Current: 382/313
• CPC Class Codes: G06K 7/10742 including a diffuser for diffusing the light from the light source to create substantially uniform illumination of the target record carrier
• CPC Class Codes: G06K 7/10772 Moved readers, e.g. pen, wand
• CPC Class Codes: G06K 7/10792 Special measures in relation to the object to be scanned

Abstract

In the optical system of a code reader, its MTF best position on the subject side at a spatial frequency corresponding to a code pattern is set to be present at a given distance from the end surface of the code reader. The light receiving surface of a photosensor is set larger than the image of one block of the code pattern which is formed through the optical system.

Claims

1. A code reader which is adapted to be used with a sheet-like recording medium on which data are recorded as an optically readable code pattern and to optically read the code pattern while being manually moved over the code pattern in contact with the recording medium, comprising:

an optical system for forming an optical image of the code pattern recorded on the recording medium onto a photosensor; and

said photosensor for converting the optical image formed by said optical system into an electrical signal,

wherein a modulation transfer function (MTF) best position on a subject-side of said optical system at a spatial frequency corresponding to the code pattern is set to be present at a given distance from that surface of the code reader which is brought into contact with the recording medium.

2. The code reader according to claim 1, wherein the MTF best position is set to be present outside the code reader and at a given distance from that end surface of the code reader which faces the recording medium.

3. The code reader according to claim 2, wherein the code pattern consists of an arrangement of a plurality of blocks each with a given area and capable of storing a predetermined amount of data;

each of the blocks comprises at least a data dot pattern consisting of a plurality of data dots, markers placed in a predetermined positional relationship with respect to the data dot pattern for detecting reference positions for reading the data dot pattern, and a block address pattern for identifying the corresponding block;

said photosensor is an area sensor; and

the area of the light receiving surface of said area sensor is larger than that image of one block in the code pattern which is formed on the light receiving surface through said optical system at least when the code pattern is present at the surface of the code reader of contact with the recording medium.

4. The code reader according to claim 2, wherein

the code reader is formed in the shape of a pen, and

the code reader surface of contact with the recording medium corresponds to the end surface of the pen.

5. The code reader according to claim 2, further comprising a diaphragm section having a fixed diaphragm value.

6. The code reader according to claim 3, wherein

the code reader is formed in the shape of a pen, and

the code reader surface of contact with the recording medium corresponds to the end surface of the pen.

7. The code reader according to claim 3, further comprising a diaphragm section having a fixed diaphragm value.

8. The code reader according to claim 1, wherein the code pattern consists of an arrangement of a plurality of blocks each with a given area and capable of storing a predetermined amount of data;

each of the blocks comprises at least a data dot pattern consisting of a plurality of data dots, markers placed in a predetermined positional relationship with respect to the data dot pattern for detecting reference positions for reading the data dot pattern, and a block address pattern for identifying the corresponding block;

said photosensor is an area sensor; and

the area of the light receiving surface of said area sensor is larger than that image of one block in the code pattern which is formed on the light receiving surface through said optical system at least when the code pattern is present at the surface of the code reader of contact with the recording medium.

9. The code reader according to claim 8, wherein

the code reader is formed in the shape of a pen, and

the code reader surface of contact with the recording medium corresponds to the end surface of the pen.

10. The code reader according to claim 8, further comprising a diaphragm section having a fixed diaphragm value.

11. The code reader according to claim 1, wherein

the code reader is formed in the shape of a pen, and

the code reader surface of contact with the recording medium corresponds to the end surface of the pen.

12. The code reader according to claim 1, further comprising a diaphragm section having a fixed diaphragm value.