JPH0634255B2 - Optical reader - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical reading device for optically reading a bar code, characters, or the like by a hand scanner.

(B) Background technology Optical readers are used to read barcodes and characters. Irradiate the object with strong light, recognize reflected light or transmitted light with an image sensor, decompose this for each pixel,
Perform appropriate processing to fix barcodes, characters, etc.

Barcodes and characters are printed in black in the white background that becomes a black background, but since the positions are not known in advance, enter information for the parts without barcodes or characters and process them. It is about to do. This is wasteful both in terms of time and processing power.

When scanning barcodes and characters with a hand scanner, it is possible for humans to operate, so it is possible to select only the area in which information is written and scan.

However, even then, since there is nothing to specify regarding the position where the bar code or the character to be read exists, the reader continues to input meaningless information and process information in the entire scanned area. This also causes errors due to dirt and stains.

Therefore, the present inventor has realized that it is sufficient to preliminarily attach the work or the key line to the bar code or the character and determine the reading range within the arm or above the key line. . This has the following advantages.

(1) Since the information to be captured is in the frame or on the key line, only the minimum necessary information can be input, and there is no waste.

(2) The correct reading rate can be increased by incorporating the relations such as the relative position and direction with respect to the work and the key line in the algorithm for recognizing the barcode and the character.

You can expect benefits such as.

In order to do so, it is necessary to easily distinguish the information to be read such as a bar code and a character from the work and the key line that specify the described position.

To do this, for example, the following configuration may be considered.

The letters and barcodes are printed in black color, and the lines and key lines are lighter. Print in tones such as red, blue, and yellow. Two
Individual image sensors are used. The center wavelengths of incident light of the image sensors are made different so that one image sensor can read a character or the like and the other image sensor can read a wax or the like.

However, the mechanism using two image sensors would have the following drawbacks.

(1) With a simple reader such as a hand scanner,
The image sensor accounts for a large proportion of the component cost. Therefore, using two image sensors is problematic in terms of cost.

(2) Two image sensors must simultaneously give information to corresponding pixels at the same location. This alignment is difficult.

For this reason, using two image sensors is not the best solution.

(C) Object of the invention The present invention is directed to a character, a bar code, etc. from an object including a character, a bar code, etc. It is an object of the present invention to realize an optical reading device capable of distinguishing between and reading at a relatively low cost and for a person who does not require a high degree of adjustment.

Especially, it provides an effective method when the sensitivity of the sensor to the wax is high.

(D) Characters, frames, and photoelectric conversion element output objects for blank paper are characters, bar codes (called letters, etc.) on blank paper,
, And Waku, Kei line (which is called Waku, etc.). Characters and the like are printed in black, and have a strong contrast with white paper. Waku etc. should be printed in a lighter color.

In this way, when a strong illumination light is applied, the reflected light intensity should have three levels when the reflected light is monitored. The reflection from the white paper is the strongest, the reflection from the black character is almost nonexistent, and the reflection from the light colored wax is in the middle.

FIG. 1 is an explanatory diagram illustrating the photoelectric conversion element output for characters, frames, and blank sheets. XX ′ is the moving direction of the hand scanner, that is, the reading direction.

In the object O, it is assumed that a dark character A and a light frame B are printed on a white paper C. The output on the line XX 'of the photoelectric conversion element is shown aligned with the object. Since the reflection in the white paper area C is the strongest, the reflected light intensity is the strongest. The reflection in the character area A is weakest. The reflection in the work area B is in the middle.

Therefore, the two thresholds E and F should be given to distinguish the letter A, the frame B, and the blank sheet C.

The lower threshold value E is used to discriminate the character from the armpit, and has an intermediate value between the reflected light intensities of the both.

The upper threshold F is for discriminating between blank and blank.

When the output of the photoelectric conversion element is X, it means that the character is X <E, the character is E <X <F, and the blank is F <X.

Thus, the output X of the photoelectric conversion element should be ternary.

However, when the color of the wax is red or a color with a strong reflection in the infrared region, the reflection from the wax B is strong and the white paper C
It is almost the same as the reflection from.

In FIG. 2, which depends on the sensitivity distribution of the photoelectric conversion element, the solid line is a graph showing the sensitivity distribution of a general photoelectric conversion element. Generally, a photoelectric conversion element has peak sensitivity to near infrared light having a wavelength of 700 to 900 nm.

If the wax is a reddish color or a color with strong infrared reflection. This is a characteristic often found in carbon-free printing inks. Such a reddish color reflected light distribution is shown by a broken line in FIG.

The peak of the distribution of reflected light of reddish color and the peak of the sensitivity of the photoelectric conversion element substantially match in the near infrared region. For this reason, the reddish color reflected light is particularly well felt by the photoelectric conversion element. The reflected light from the white paper is the maximum, but the reflected light from the reddish color expression becomes almost the same.

FIG. 3 shows the photoelectric conversion element output X of the same object as that of FIG. 1 in which the frame is printed in red.

The output of the blank area B and the blank area C are extremely close to each other,
By comparing with the upper threshold value F, it is difficult to discriminate between the blank B and the blank sheet C without any obvious error.

(E) Configuration of the invention In the output X of the photoelectric conversion element, the value C for a blank sheet and the value B for a frame are close to each other, and it is difficult to set the upper threshold value F between them.

Therefore, the lower threshold value E is divided into two and designated as α and β. Both are values at a level lower than the value B for wax. β is called a first threshold and α is called a bias value.

FIG. 5 is a graph showing an example of the photoelectric conversion element output X for white paper C, frame B, and character A.

The bias value α is subtracted from the element output X. FIG. 6 is a graph showing (X-α) on the vertical axis.

Although the horizontal axis represents time t, it may be considered as position coordinates because it scans blanks and characters on a blank sheet.

Next, the value of (X-α) is amplified. FIG. 7 is a graph showing the value of the output Y after amplification. If the amplification factor is a, then Y = a (X−a) (1). By doing so, the difference in output between the blank B and the blank sheet C is magnified a times, and separation is facilitated.

At this stage, Y output for Waku B and blank paper C is Yb,
Yc. Since this difference is a times the difference between B and C,
It becomes easy to set a new threshold value in between and to separate this. Therefore, the second threshold value γ is set so that Yb <γ <Yc (2). The Y output is divided into upper and lower parts by γ and binarized. This can easily be done with a comparator. Let Z be the binarized output.

Z = θ (Y-γ) (3). Here, θ (Y) is a step function that becomes 1 when Y is positive and 0 when Y is negative. In this way, Z = 1 for a blank sheet and Z = 0 for a character or frame.

On the other hand, the source output X in FIG. 5 is binarized by the first threshold β. This separates only the characters. The binarized output W is given by W = θ (X−β) (4). FIG. 9 is a graph of the binarized output W. W = 0 for letters, W for blank, Waku
= 1.

Comparing Z in FIG. 8 and W in FIG. 9 shows that the character is 0 and the blank paper is 1. However, about the waku, they are eating each other with Z = 0 and W = 1.

Therefore, the exclusive OR circuit is used to extract only the wax. Exclusive-OR gives an output 1 only when two inputs are different and gives an output 0 when the two inputs are the same. The output V of the exclusive OR is shown in FIG.

V = .Z + W. (5) In this way, since V = 1 for the wax and V = 0 for the character and the blank sheet, the position of the wax can be detected by this.

(F) Configuration of the reader FIG. 4 is a block diagram showing the configuration of the optical reader of the present invention.

Reference numeral 1 denotes a housing, which is slid on an object to be read 2 while moving the housing by hand. The housing 1 includes a light source 3, a photoelectric conversion element 4, an amplifier 5, a differential amplifier 6, binarization circuits 7 and 8, an exclusive OR circuit 9, and the like.

The light source 3 illuminates the reading object 2 with strong light. There are blank pages, frames, letters, etc., each with different reflectance. The reflected light is incident on the photoelectric conversion element 4 using a lens or the like,
Since a current signal (or voltage signal) proportional to the light intensity is obtained, it is amplified through the amplifier 5.

The differential amplifier circuit 6 multiplies the difference between the photoelectric conversion element output X and the bias value α by a and has an action corresponding to the equation (1).

The binarization circuit 8 compares the output Y of the differential amplifier circuit 6 with the threshold value γ and binarizes it, and has an action corresponding to the expression (3). Output Z is 1 for blank sheets and 0 for characters or frames
Is.

The binarization circuit 7 receives the amplified output X of the photoelectric conversion element and the first output.
It is a circuit that compares the threshold value β and binarizes it. Output W is (4)
Corresponds to what is given by the expression. W is 0 for letters,
It is 1 for blank paper and waku.

The exclusive OR circuit 9 calculates the exclusive OR of the outputs W and Z of the binarization circuits 7 and 8. Use an exclusive OR gate IC.

After all, the character information as the output of the binarization circuit 7 is output by W, and the vacuum information as the output of the exclusive OR circuit 9 is output by V.

(G) Effect (1) It is possible to recognize the character or bar code part and the work or key line part respectively.

Therefore, it is possible to limit the place where the character or the bar code exists to within the frame or just above the key line. Since the reading operation only needs to be performed on a limited area from the beginning, the reading operation is executed quickly. In addition, since correct stains and stains are not read, the correct reading rate is improved.

(2) Since the output of one sensor is ternary,
The optical configuration is simple. The device of the present invention can be realized by simply adding an electric processing system to the conventional hand scanner.

(3) Especially, red (or K-line) color or
When a general printing ink that does not contain carbon is used, it is effective for distinguishing the blank from the blank.

[Brief description of drawings]

FIG. 1 is a diagram showing an output appearing in a photoelectric conversion element in correspondence with an object to be printed, when a character, a stamp or the like is printed on a blank sheet and traced with a hand scanner. FIG. 2 is a graph showing the sensitivity distribution of the photoelectric conversion element and the distribution of reflected light of red-colored wax. FIG. 3 is a graph showing the output of the photoelectric conversion element when the sensitivity of the photoelectric conversion element to the vacuum is high. FIG. 4 is a block diagram showing the configuration of the optical reading apparatus of the present invention. FIG. 5 is a graph showing the output X of the photoelectric conversion element in correspondence with blank paper, blank, and characters. Although the horizontal axis is time t, it can be considered that this represents the position on the printed matter because the hand scanner is scanned. FIG. 6 is a graph showing the output after the operation (X-α). FIG. 7 is a graph showing the product of (X-α) amplified with an amplification factor α. The vertical axis is Y. This is equal to a (X-α).
γ is a threshold newly provided between Yc and Yb. FIG. 8 is a graph in which the Y value is binarized. The vertical axis is Z =
θ (Y−γ). FIG. 9 is a graph showing the output W obtained by binarizing the value of X with β. FIG. 10 is a graph of the exclusive OR V of Z and W. It is 1 for Waku and 0 for characters or blank paper. 1 ... Case 2 ... Object to be read 3 ... Light source 4 ... Photoelectric conversion element 5 ... Amplifier 6 ... Differential amplifier 7 ... Binarization circuit 8 ... Binarization circuit 9 ... Exclusive logic Sum circuit

Claims (1)

[Claims] 1. A hand scanner having a built-in light source 3, a lens and a photoelectric conversion element 4 is operated to write a character having a low reflectance on a white paper having a high reflectance, a symbol and a reflectance which is lower than that of a white paper. In an optical reading device that reads a wire or key line having a low reflectance close to that of a white paper, the output X of the photoelectric conversion element 4 is branched into two systems, and the output X to the first system is converted to a white paper, a paper, a paper A binarization circuit that compares a first threshold value β corresponding to an intermediate light level between the reflected light from the line and the reflected light from the character and binarizes the character and the blank paper, the wax, and the key line so as to distinguish them. 7 and the output X to the second system are input, and the bias value α, which is a constant value slightly lower than the level corresponding to the work and key lines, is subtracted from X and then amplified to correspond to the reflected light from the character. Signal that is saturated and that corresponds to a blank page. Signal is amplified to a level close to the upper limit of the dynamic range of the circuit, and the output of the differential amplifier circuit 6 is reflected light from a blank sheet and reflected light from a work line and a key line. The second threshold value γ corresponding to the intermediate light level of
It is composed of a binarizing circuit 8 for binarizing so as to distinguish it from a character and an exclusive OR circuit 9 for taking an exclusive OR of the outputs of the two binarizing circuits 7 and 8 to form parts such as characters and symbols. , Waku,
An optical reader characterized by recognizing parts such as a key line.