JPS5831477A - Reader of optical information - Google Patents

Abstract

PURPOSE:To prevent a erroneous read caused by time aging, in photoelectric converting efficiency, by comparing the magnitude of a signal of a storing circuit corresponding to a photoelectric converting element, and an output signal of the photoelectric converting element, so that binary information is outputted. CONSTITUTION:A photoelectric converting circuit 1 irradiates light to a recording medium 9, photodetects its reflected ray, and outputs an analog signal A corresponding to the photodetecting quantity. Also, this circuit 1 is provided with a light source for irradiating a light beam to the recording medium 9, and a photodetector for photodetecting the reflected ray from the recording medium 9. In this example, this photodetector is an image sensor which has arranged N pieces of photoelectric converting elements in one row, and this image sensor is driven by a clock signal B1 inputted from a controlling circuit 8, and serially outputs the analog signal A converted by each photoelectric converting element. This analog signal A is supplied to the second comparing circuit 7 mentioned in the latter part, also is converted to a digital signal in an A/D converting circuit 2, and after that, is supplied to the first comparing circuit 3 and a selecting circuit 4, too.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an apparatus for reading optical information such as characters or barcodes by utilizing the difference in light reflectance between the underlying portion of the medium and the information portion. Regarding.

Conventional devices of this type irradiate light onto the medium, receive the reflected light with a photoelectric converter, compare the output signal of the photoelectric converter with a reference value in a comparison circuit, and determine whether the medium is the underlying portion. It is converted into binary information that specifies whether it is an information part.

However, since conventional devices use the reference value of the comparison circuit as the absolute value of analog data, they are sensitive to changes in the light intensity and distribution of the light source, changes in the reflectance of the base, changes in the characteristics of the photoelectric conversion element, etc. This often resulted in misreading or unreadability, and it was also troublesome to adjust the optical system and electric circuit system.

It is an object of the present invention to provide a reading device in which there is no risk of misreading even if the light intensity reflectance, the characteristics of the photoelectric conversion factor, etc. change or are non-uniform, and the optical system and electric circuit system can be easily adjusted. purpose.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on an embodiment of a character reading device shown in the drawings.

In the figure, 1 is a photoelectric conversion circuit that irradiates the recording medium 9 with light, receives the reflected light, and outputs an analog signal according to the amount of received light, and includes a light source that irradiates the recording medium 9 with light and an apparatus medium. It is equipped with a light receiver that receives the reflected light from 9. In this example, this light receiver is an image sensor in which N photoelectric conversion elements are arranged at once, and this image sensor is driven by a clock signal BIK inputted from the control circuit 8, and the image sensor is Analog signal A)jl-
Add one to the cereal. This analog signal A is supplied to a second comparison circuit 7, which will be described later, and is also supplied to a 19th comparison circuit 3 and a selection circuit 4 after being converted into a digital signal in an A/D conversion circuit 2.

The A/D conversion circuit 2 converts the analog signal A input from the photoelectric conversion circuit 1 into binary data every time the clock signal B is input from the control circuit 8.

The first comparison circuit 3 is a circuit that compares the output signal of the A/D conversion circuit 2 and the output signal of the storage circuit 5, and determines which signal is larger (or smaller). The two specified magnitude designating signals C are sent from the control circuit 8 to the clock signal 8. is outputted to the selection circuit 4 every time it is input.

Such a comparison circuit 3 includes, for example, a magnitude comparison circuit that determines whether one binary data is larger or smaller than the other binary data, and outputs a binary signal according to the determination result. A determination circuit can be used.

The selection circuit 4 is a circuit that selects the larger signal among the output signals of the A/D conversion circuit 2 and the storage circuit 5 based on the output signal CK of the comparison circuit 3, and receives the selected signal from the control circuit 8 as a clock. Each time the signal B is input, it is output to the memory circuit 5. Such a selection circuit can be constructed of, for example, a group of 3-man AND gates having the same number as the number of bits of the output signal of the A/D conversion circuit 2, and a group of 3-man power inhibiting gates having the same number.

In this example, the memory circuit 5 is composed of a plurality of shift registers that individually correspond to bits of the output signal of the A/D conversion circuit 2. Each shift register has the same number of shift sections as the number of bits N of the image sensor of the photoelectric conversion circuit 1,
and the output signal of the selection circuit 4 is input to the data input terminal,
A clock signal B of the control circuit 8 is input as a shift pulse, and data is shifted every time this clock signal B is input. The output signal of the memory circuit 5 is not only supplied to the comparison circuit 3 and the selection circuit 4, but also converted into an analog signal DK in synchronization with the clock signal input from the control circuit 8 in the D/A conversion circuit 6. Thereafter, the signal is also supplied to the second comparison circuit 7. This memory circuit 5 is initially reset at the start of reading.

The second comparison circuit T receives a binary signal from the control circuit 8 from the clock signal 8. This is a circuit that outputs every time it is input, and the analog signal is used as the reference voltage [
input. The analog signal 0 is voltage-divided into 1, for example 80-, by a resistor or the like at the input of the comparator circuit 7. Such a comparison circuit T can be constructed of, for example, an arithmetic amplification circuit and an AND gate.

Note that the clock signal supplied from the control circuit 8 to each circuit is delayed by the amount of data delay in the electric circuit system.

In this device, the photoelectric conversion circuit 1 and the brass medium unit 9 are arranged in the arrangement direction (Y direction) of each photoelectric conversion element of the image sensor.
Clock signals B1-8 are sent from the control circuit 8 to each circuit +1;
．． Output. By doing so, after the memory circuit 5 is initial reset, the signals of each bit of the image sensor in the photoelectric conversion circuit 1 (an analog signal proportional to the amount of received light) are sequentially output in synchronization with the clock signal B1. ,A/
The D conversion circuit 2 converts it into a digital signal.

Among these digital signals, if the detection section on the arrangement medium s is white, each shift register of the storage circuit 5 will receive the same number of bits as the number of bits of the image sensor. , and since it has been initial reset, it is stored in the storage circuit 5.

That is, since the amount of light reflected from the storage medium 9 is larger in the white part than in the black part, the output signal of the image sensor is larger in the white part than in the black part. [The first comparison circuit 3 outputs the signal C indicating that the output signal of the A/D conversion circuit 2 is large, and the selection circuit 4 outputs the signal C indicating that the output signal of the A/D conversion circuit 2 is large.
The output signal of the /D conversion circuit 2 is outputted to the storage circuit 5, and the resulting A/D converted digital signal, which is the output signal of the previous E'1 image sensor, is stored in the storage circuit 5 at the same time as the bits of the image sensor. Stored sequentially.

The signal stored in the memory circuit 5 in this way is outputted to the first comparator circuit 3 in synchronization with the next analog output from the image sensor in the order of bits. It is used as a reference value for comparing the magnitude with the digital signal corresponding to the next analog signal, and is also supplied to the second comparison circuit 7 via the %D/mu conversion circuit 6. It is used as a reference value for comparing the next analog signal.

As a result of the comparison in the comparison circuit 3, if the output signal of the A/D conversion circuit 2 is large, this output signal is stored in the memory circuit 115, and since the analog signal ^ is large, the output signal is stored in the memory circuit 115. Binary information to specify @1” (or 10”)
) is output from the second comparator circuit 7, and if it is the opposite, the output signal of the memory circuit 5 is stored again on the memory surface msK, and binary information specifying that the analog signal A is small.
0'' (or @1'') is output from the second comparison circuit 7.

In this way, the larger signal of the output signal of the MU/D conversion circuit 2 and the output signal of the storage circuit 5 is stored in the storage circuit 5 in synchronization with the output signal of the photoelectric conversion circuit 1. The maximum value of the signal is stored corresponding to the bit of the image sensor.

Binary information '1'', ' output from the second comparison circuit 167
"0" is a signal specifying whether the detected portion on the storage medium 9 is white or black, and is sequentially superimposed in the bit order of the image sensor.

Note that the present invention can be applied not only to a character reading device but also to a reading device using 11 photoelectric conversion elements, such as a barcode reading device. In this case, the memory circuit 5
In this case, one shift register may be provided corresponding to one photoelectric conversion element. Further, the storage circuit 5 may store small data.

As described above, the present invention provides a memory circuit corresponding to a photoelectric conversion element, compares the magnitude of a signal in this memory circuit with an output signal of the photoelectric conversion element, and sends a large or small signal to the memory circuit. At the same time, the system outputs binary information indicating which one is larger, so by clearing the memory circuit every time a reading operation is performed, even if the circuit constant is fixed, the above-mentioned There are no reading errors even if circuit constants, light intensity, and photoelectric conversion efficiency change over time, there are no reading errors due to differences in the substrate of the placement medium, and multiple photoelectric conversion elements are installed like character reading devices. In the case of such a device, by providing a storage section for each photoelectric conversion element, it is possible to prevent mistaking even if there are changes in conversion efficiency, amount of received light (distribution of light amount), etc. between the photoelectric conversion elements. Even if the photoelectric conversion element is replaced, there is no need to adjust the circuit constants, and maintenance is easy. Even if information is continuously read on a recording medium with a different background color, the information is memorized every time the information is read. Clearing the circuit has the advantage of preventing reading errors.

[Brief explanation of the drawing]

The figure is a block diagram showing an example of an electric circuit of a character reading device. 1: Photoelectric conversion circuit, 2: A/D conversion circuit, 3.1=
Comparison circuit, 4: Selection circuit, 5: Memory circuit, 6: D/MU conversion circuit, 8: Control circuit, 9: Arrangement medium. Patent applicant Nippon Signal Co., Ltd.

Claims (1)

[Claims] a photoelectric conversion element that receives reflected light from a medium on which information is placed and outputs an analog signal proportional to the amount of received light; an A/D conversion circuit that converts the analog signal into a digital signal; a storage circuit; a first comparison circuit that compares the magnitude of the signal with the signal stored in the storage circuit;
a selection circuit that selects a larger or smaller signal from the digital signal and the signal and outputs it to the storage circuit based on the output signal of the comparison circuit; and a selection circuit that converts the signal stored in the storage circuit into an analog signal. a second D/A converter circuit to be replaced, and a second device that compares the output signal of the D/A converter circuit with the analog signal and outputs binary information specifying whether one is larger or smaller; An optical information reading device having a comparison circuit.