JPS61265684A - Bar code reader - Google Patents

Abstract

PURPOSE:To simplify the constitution of a reader and to improve a reading ratio by detecting unnecessary weak signal among bar code analog signals and prohibiting a bar code black/white deciding circuit from making the unnecessary decision. CONSTITUTION:A laser scan beam making incident on a bar code label refects strongly and lightly the white bar and black one of the bar code, respectively. A photodetecting element 1 converts the reflected light beam into an electrical signal, and a pre-amplifier circuit 2 amplifies the electrical signal up to a necessary level. This bar code level signal is applied to a weak level detecting and deciding circuit 5 to detect the state where it is below a certain level (V). At this time a decision inhibiting signal (d) is generated, and is applied to a bar code black and white level deciding circuit 3. Then the inputted bar code analog signal is decided. When it is in the inhibition state, the bar code is decided at a white level unconditionally. The constitution of the reader is simplified and the reading ratio is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention scans a printed barcode attached to a product with a laser beam, and uses the reflected light to create a barcode. The present invention relates to a barcode reading device that reads information.

[Conventional technology]

FIG. 3 is a block diagram of a commonly used circuit in a barcode reading device that reads barcode labels.

In FIG. 3, (11 light receiving elements, (2) preamplifier circuits, +31 bar food level determination circuits, and In are bar code decoding circuits.

Next, the movement will be explained using FIGS. 3 and 4. The laser scanning beam incident on the barcode label is reflected strongly in the case of white bars and weakly in the case of black bars, depending on the black and white of the barcode. This reflected light is converted into an electrical signal by the light receiving element (11). (2) The barcode signal converted into an electrical signal by the light receiving element (11) is converted into an electrical signal by the barcode black and white level determination circuit described below. [3
This is a preamplifier that performs amplification to the level required for 1.

Figure 4(a) shows the barcode and laser scanning beam (
b) shows the barcode analog signal amplified by the preamplifier (2). This barcode analog signal is
By barcode black and white level judgment circuit (3)! Figure 4 (
Voltage comparison is performed at the voltage level shown by the broken line in b),
It is converted into a barcode digital signal. This barcode digital signal is shown in Figure 4 (cl).
4), it is decoded to see if it is a barcode, and it is determined whether it has been read correctly.

[Problem that the invention seeks to solve]

As shown in Figure 4(b), the barcode analog signal contains slight random noise (mainly amplifier noise,
In conventional barcode reading devices, as shown in Fig. 4(c), random noise is detected and converted into a random digital signal.
Unnecessary @8 is sent to the barcode decoding circuit (4), and due to the random nature of this signal, the barcode decoding circuit f41 fails to decode it, causing an unnecessary burden on the barcode decoding circuit (41). Therefore, there were drawbacks such as deterioration of reading performance.

The present invention aims to eliminate the drawbacks of the prior art as described above.

[Means for solving problems]

When the barcode analog signal is weak, the barcode reading device according to the present invention detects f'L and provides a weak level detection/determination prohibition circuit that prohibits the -code black/white level determination circuit from making any determination. This is how it was done.

[Effect]

The barcode reading device according to the present invention disables barcode black and white level determination when the barcode analog signal is weak as described above, thereby preventing complicated and high-performance reading operations, thereby making the device inexpensive and stable. Being disguised.

[Embodiments of the invention]

Hereinafter, a practical example of the present invention will be explained with reference to the drawings. ! F
In figure ll'1, fil i photodetector, [21r/
(4) is the barcode decoding circuit, (6) is the same as (3), the barcode analog signal from (2) is input, and (3) is the barcode decoding circuit. ) is a weak level detection judgment prohibition circuit that generates a judgment prohibition signal.

Next, the operation will be explained using the EGZ diagram in FIG. The laser scanning beam incident on the barcode label is reflected strongly in the case of white bars and weakly in the case of black bars, according to the black and white of the barcode. This reflected light is converted into an electrical signal by the light receiving element fi+. The barcode signal converted into an electrical signal is amplified by the preamplifier circuit (2) to a certain level necessary for the barcode black and white level determination circuit (3). Figure 2 (al) shows the barcode and laser scanning beam t-1 (b), and the barcode analog signal amplified by (2) at that time. When inputting, as shown in Figure 2 ('b), a state in which the barcode analog signal is below a certain level (V or less) is detected, and in this state, the judgment shown in Figure 2 (a) is made. Prohibit! i is generated and this judgment prohibition signal is input to the barcode black and white level judgment circuit (3).The barcode F black and white judgment circuit (3) is similar to the weak level detection judgment circuit (5) when the barcode analog signal is detected. However, the judgment is made at the voltage level shown by the broken line on day C in Figure 4!I2.
When the inhibit input signal from the weak level detection/judgment circuit (6) is in the inhibit state, it is unconditionally determined to be a white level and converted into a barcode digital signal as shown in FIG. 11!2 (e). The barcode signal converted into a digital signal is decoded by the barcode decoding circuit f41. As described above, by prohibiting unnecessary weak level judgments, unnecessary signals are not input to the barcode decoding circuit, and the decoding processing load is reduced, thereby improving reading performance. It becomes possible.

Further, in the above embodiments, a barcode reading device has been described, but the present invention can also be applied to information reading devices other than barcode reading devices, and the same effects as in the above embodiments can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, unnecessary weak signals (mainly amplifier noise in scanning other than barcodes) are detected in the barcode analog signal, and unnecessary weak signals are detected for the barcode black/white determination circuit. By providing a weak level detection judgment prohibition circuit that prohibits judgment, unnecessary input signals are not input to the barcode decoding circuit, so a complicated and high-performance barcode decoding circuit is not required, and the device becomes less expensive. This has the effect of providing a device with a high reading rate.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a barcode reading device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a barcode reading device according to an embodiment of the present invention. FIG. 3 is a block diagram of a conventional barcode reading device, and FIG. 4 is an explanatory diagram of the internal signals shown in FIG. 3. (!1... Light receiving element, (21... Preamplifier circuit, (
3... Barcode black and white level judgment circuit, (41...
Barcode decoding circuit, (5)...weak level detection judgment circuit. In the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A light receiving element that converts the scanning laser reflected light from the barcode label into an electrical signal, a preamplifier circuit that amplifies the signal from this light receiving element to a certain level of barcode analog signal, and a black/white determination of the barcode analog signal. a weak level detection judgment prohibition circuit that prohibits the judgment circuit from making judgments when this barcode analog signal is weak; and a judgment circuit that prohibits the judgment circuit from making judgments when the barcode analog signal is weak; and a decoding circuit for barcode signals judged by the judgment circuit and converted into digital signals. A barcode reading device comprising a barcode decoding circuit that performs processing.