Optical reading apparatus having a reading sensor of electronic scanning type

• US 4,538,060 A
• Filed: 05/31/1983
• Issued: 08/27/1985
• Est. Priority Date: 05/31/1982
• Status: Expired due to Term

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Sakai, Toshiyasu, Hara, Masahiro, Teraura, Nobuyuki
• Primary Examiner(s): Pitts, Harold I.
• Application Number:
  US06/499,406
• Time in Patent Office: 819 Days
• Field of Search: 235/462, 235/466, 235/472
• US Class Current: 235/462.28
• CPC Class Codes: G06K 7/10881 constructional details of hand-held scanners

Abstract

In an optical reading apparatus having a reading sensor for converting optically readable information into an electrical signal by electronically scanning an image of optical information, such as a bar code, a detector is provided to detect the intensity of light incident on an information label on which the information is provided. Data indicative of the light intensity is used to determine a subsequent scanning period in such a manner that the scanning period of the reading sensor is shortened when the light intensity increases or vice versa. Since the decrease in the scanning period results in lower output voltage from the reading sensor, undesirable saturation in circuitry following the reading sensor is effectively prevented, providing stable operation of the reading sensor, such as a bar code reader.

Claims

1. An optical reading apparatus for converting optically readable information into an electrical signal by means of a reading sensor of electronic scanning type, comprising:

first means for detecting the intensity of light incident on an information label on which said optically readable information is provided; and

second means responsive to said first means for controlling the scanning period of said reading sensor.

2. An optical reading apparatus as claimed in claim 1, wherein said first means comprises circuitry responsive to an output signal from said reading sensor.

3. An optical reading apparatus as claimed in claim 2, wherein said first means comprises a sample-and-hold circuit responsive to said output signal from said reading sensor;

a low pass filter responsive to an output signal from said sample-and-hold circuit; and

a peak detector responsive to said output signal from said low pass filter.

4. An optical reading apparatus as claimed in claim 3, wherein said sample-and-hold circuit comprises:

a first capacitor arranged to be cyclically charged with a voltage proportional to the output signal from said reading sensor;

an analog switch arranged to open and close in response to a clock pulse signal;

a second capacitor arranged such that the voltage across said first capacitor is intermittently transmitted thereto via said analog switch; and

a voltage follower responsive to the output voltage across said second capacitor.

5. An optical reading apparatus as claimed in claim 3, wherein said peak detector comprises:

a peak hold circuit having a diode and a capacitor; and

a buffer amplifier responsive to a voltage across said capacitor.

6. An optical reading apparatus as claimed in claim 2, further comprising:

an analog-to-digital converter responsive to said circuitry; and

a read-only memory the data of which is arranged to be selectively read out in accordance with digital data from said analog-to-digital converter.

7. An optical reading apparatus as claimed in claim 3, further comprising:

an analog-to-digital converter responsive to said peak detector; and

a read-only memory the data of which is arranged to be selectively read out in accordance with digital data from said analog-to-digital converter.

8. An optical reading apparatus as claimed in claim 6, wherein said second means comprises:

counter circuitry for counting the number of clock pulses; and

a digital comparator for comparing the data from said read-only memory with the count of said counter circuitry so as to produce a coincidence signal when the data are equal to each other.

9. An optical reading apparatus as claimed in claim 7, wherein said second means comprises:

counter circuitry for counting the number of clock pulses; and

a digital comparator for comparing the data from said read-only memory with the count of said counter circuitry so as to produce a coincidence signal when the data are equal to each other.

10. An optical reading apparatus as claimed in claim 8, wherein said analog-to-digital converter is arrannged to be controlled by the count of said counter circuitry and said coincidence signal.

11. An optical reading apparatus as claimed in claim 9, wherein said analog-to-digital converter is arranged to be controlled by the count of said counter circuitry and said coincidence signal.

12. An optical reading apparatus as claimed in claim 7, wherein said data prestored in said read-only memory is selected so as to satisfy the following equation;

space="preserve" listing-type="equation">ts.sub.N =K.sub.2 /V.sub.PN

wherein

ts_N is a scanning period of an N^th scanning;

K₂ is a constant;

V_PN is a peak voltage from said peak detector, resulted from the N^th scanning.

13. An optical reading apparatus as claimed in claim 1, wherein said reading sensor is installed in a hand-held casing.

14. An optical reading apparatus as claimed in claim 1, wherein said reading sensor is installed in a hand-held casing in which a light source is mounted to illuminate said information label.