Optical information reader
In an optical information reader which optically reads an information code, a first polarizing unit arranged on the light-exit side of a lighting unit is configured to polarize illumination light therefrom in a predetermined polarization direction. In addition, a second polarizing unit arranged on the light-reception side of a light receiving sensor is configured as a switchable polarization unit, in which the switchable polarization unit is capable of performing a switchover between a polarized state in which light reflected from the information code is polarized in a direction different from the predetermined polarization direction and a passing state where the reflected light passes therethrough without being polarized.
1. An optical information reader, comprising:
a lighting unit configured to emit illumination light to an information code;
a first polarizing unit arranged on a light-exit side of the illumination unit;
a light receiving unit configured to receive light reflected from the information code;
a second polarizing unit arranged on a light-reception side of the light receiving unit; and
a reading unit configured to read the information code based on light reception results at the light receiving unit, wherein
the first polarizing unit is configured to polarize the illumination light in a predetermined polarization direction, and
the second polarizing unit is configured as a switchable polarizing unit which is switchable to either one of a state where the reflected light is polarized in a direction different from the predetermined polarization direction and a state where the reflected light passes through the second polarizing unit without being polarized.
2. The optical information reader of claim 1 , wherein the first polarizing unit is provided with a diffusion unit which diffuses the illumination light and a reflection polarizing unit which, of light diffused by the diffusion unit, allows i) light in the predetermined polarization direction to pass therethrough and ii) remaining light which is other than the light in the predetermined polarization direction to be reflected towards the diffusion unit.
3. The optical information reader of claim 1 , wherein
the light receiving unit is provided with a light receiving sensor and an imaging lens which forms an image on a light receiving surface of the light receiving sensor;
the imaging lens is formed to enable a maximum angle of incident light rays imaged on the light receiving sensor to be larger than a maximum angle of emitted light rays imaged on the light receiving sensor; and
the second polarizing unit is arranged between the imaging lens and the light receiving sensor.
4. An optical information reader, comprising:
a lighting unit configured to emit illumination light to an information code;
a first polarizing unit arranged on a light-exit side of the illumination unit;
a light receiving unit configured to receive light reflected from the information code;
a second polarizing unit arranged on a light-reception side of the light receiving unit; and
a reading unit configured to read the information code based on light reception results at the light receiving unit, wherein
the first polarizing unit is configured to as a switchable polarizing unit which is switchable to either one of a state where the illumination light is polarized in a first polarization direction and a state where the illumination light is polarized in a second polarization direction, and
the second polarizing unit is configured to polarize the reflection light to the second polarization direction.
5. The optical information reader of claim 1 , wherein the switchable polarizing unit is configured to include a liquid crystal member and a polarizing plate.
6. The optical information reader of claim 5 , wherein
the liquid crystal member is provided with a liquid crystal layer and a pair of one pair of alignment films opposed to each other via the liquid crystal layer and configured to have rubbing directions which are mutually different by 90 degrees, and
the alignment films are arrange such that the rubbing directions thereof are oblique to one of outer edges of the light receive surface of the light receiving unit.
7. The optical information reader of claim 5 , wherein
the liquid crystal member is provided with a liquid crystal layer containing a spacer,
the liquid crystal layer is formed such that a content rate of the spacer in a region acting as a light receiving range of the light receiving unit is lower than a content rate of the spacer in a region which is different from the light receiving range.
8. The optical information reader of claim 1 , wherein
the optical information reader comprises
a control unit configured to control switching operations of the switchable polarizing unit; and
a detecting unit configured to detect completion of the switching operations of the switchable polarizing unit,
wherein the light receiving unit is configured to start exposure thereof depending on results detected by the detecting unit, after completion of the switching operations of the switchable polarizing unit.
9. The optical information reader of claim 8 , wherein
the optical information reader comprises a storage unit into which data of the images captured from the light receiving unit are stored in sequence,
wherein the reading unit is configured to perform a decoding process for decoding and reading the information code from the captured images, every time the captured images are stored in the storage unit.
10. The optical information reader of claim 8 , wherein
the control unit is configured to perform a switchover between the polarization states of the switchable polarizing unit according to a predetermined switching frequency.
11. The optical information reader of claim 8 , wherein
the optical information reader comprises a setting unit configured to set the switching frequency for the switchable polarizing unit based on results of comparison made between i) decoded results of the reading unit related to the images captured from the light receiving unit in one of the polarization states switched over by the switchable polarizing unit and ii) decoded results of the reading unit related to the images captured from the light receiving unit in the other of the polarization states switched over by the switchable polarizing unit,
wherein the control unit is configured to perform the switchover in the switchable polarizing unit according to the switching frequency which has been set by the setting unit.
12. The optical information reader of claim 11 , wherein
the setting unit is configured to set the switching frequency at the switchable polarizing unit and exposure conditions for the light receiving unit, according to results of comparison made between i) results decoded by the reading unit which are obtained every time the exposure conditions are changed in one of the polarization states at the switchable polarization unit and ii) results decoded by the reading unit which are obtained every time the exposure conditions are changed in the other of the polarization states at the switchable polarization unit.
13. The optical information reader of claim 1 , wherein
the illumination unit comprises a light source which emits the illumination light and a condensing element which condenses the illumination light emitted by the light source, and
the first polarizing unit is arranged between the light source and the condensing element.
14. The optical information reader of claim 2 , wherein
the light receiving unit is provided with a light receiving sensor and an imaging lens which forms an image on a light receiving surface of the light receiving sensor;
the imaging lens is formed to enable a maximum angle of incident light rays imaged on the light receiving sensor to be larger than a maximum angle of emitted light rays imaged on the light receiving sensor; and
the second polarizing unit is arranged between the imaging lens and the light receiving sensor.
15. The optical information reader of claim 4 , wherein the switchable polarizing unit is configured to include a liquid crystal member and a polarizing plate.
16. The optical information reader of claim 15 , wherein
the liquid crystal member is provided with a liquid crystal layer and a pair of one pair of alignment films opposed to each other via the liquid crystal layer and configured to have rubbing directions which are mutually different by 90 degrees, and
the alignment films are arrange such that the rubbing directions thereof are oblique to one of outer edges of the light receive surface of the light receiving unit.
17. The optical information reader of claim 16 , wherein
the liquid crystal member is provided with a liquid crystal layer containing a spacer,
the liquid crystal layer is formed such that a content rate of the spacer in a region acting as a light receiving range of the light receiving unit is lower than a content rate of the spacer in a region which is different from the light receiving range.
18. The optical information reader of claim 4 , wherein
the optical information reader comprises
a control unit configured to control switching operations of the switchable polarizing unit; and
a detecting unit configured to detect completion of the switching operations of the switchable polarizing unit,
wherein the light receiving unit is configured to start exposure thereof depending on results detected by the detecting unit, after completion of the switching operations of the switchable polarizing unit.
19. The optical information reader of claim 18 , wherein
the optical information reader comprises a storage unit into which data of the images captured from the light receiving unit are stored in sequence,
wherein the reading unit is configured to perform a decoding process for decoding and reading the information code from the captured images, every time the captured images are stored in the storage unit.
20. The optical information reader of claim 4 , wherein
the illumination unit comprises a light source which emits the illumination light and a condensing element which condenses the illumination light emitted by the light source, and
the first polarizing unit is arranged between the light source and the condensing element.