JP2894060B2 - Optical information reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information reading apparatus for reading optical information such as a bar code using an image sensor such as a CCD.

[0002]

2. Description of the Related Art Conventionally, various information reading apparatuses for reading optical information such as bar codes have been proposed. FIG. 6 shows a configuration example of a non-contact type bar code reading device using a CCD sensor as an example of a conventional device.
Shown in

In a bar code reader 1 shown in FIG. 6, an image of a bar code 2 is formed on a CCD sensor 4 by a lens 3. The CCD sensor 4 outputs an electric signal according to the intensity of the light of the bar code 2 formed. This C
The output signal of the CD sensor 4 is amplified by the amplifier circuit 5 and then input to the binarization circuit 6. The binarization circuit 6
The input signal is converted into a digital signal corresponding to the bar of bar code 2. This digital signal is input to an electronic control unit 10 composed of a microcomputer. First, the counter unit 7 counts the width of the signal corresponding to the bar and digitizes it. The decoding unit 8 decodes the digitized data from a combination of a wide bar, a narrow bar, and each space. The result of this decoding process is output to the outside via the external terminal 9.

[0004]

Here, in the above-mentioned conventional device, since the CCD sensor can have only a finite number of pixels, the length of the readable bar code and the minimum width of the bar are in conflict with each other. Was. That is, for example, when the pixels of the CCD sensor are densely arranged, a narrower bar can be read, but the range that can be read at a time is reduced.

Although this problem can be solved to some extent by using a CCD sensor having a large number of pixels, the CCD sensor having a large number of pixels has a disadvantage that it is expensive. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is possible to precisely read an external image to be read and obtain a sufficient reading range without using an image sensor including a CCD sensor having a large number of pixels. It is an object of the present invention to provide an optical information reading device capable of performing the following.

[0006]

To achieve the above object, an optical information reading apparatus according to the present invention has a plurality of pixels, an image sensor for picking up an external image, and an external image on the image sensor. Optical means for imaging
Position change detecting means for detecting a relative position change between the image sensor and an external image based on video data obtained from the image sensor; and a distance between adjacent pixels of the image sensor by the position change detecting means. When a position change shorter than the detected position is detected, the image data obtained from the image sensor is superimposed on the image data at the original position according to the change position, and the image data is superimposed by the image data processing circuit. Signal processing means for restoring information contained in the external image captured by the image sensor based on the video data obtained.

[0007]

With the above arrangement, an external image is captured by the image sensor, and a relative position change between the image sensor and the external image is detected based on the video data. When the position change is shorter than the distance between adjacent pixels of the image sensor, the image data obtained from the image sensor is superimposed on the image data at the original position according to the change position.

Therefore, the video data obtained by the superposition increases the apparent number of sample points, so that a finer external image can be obtained than the video data, and the information contained in the external image can be accurately restored. can do. At this time, the reading range of the image sensor is not sacrificed, and a sufficient reading range can be secured.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view for explaining the configuration of one embodiment of the present invention.

As shown in FIG. 1, the optical information reading apparatus according to the present embodiment is a portable information reading apparatus in which various parts are integrated into a main body case 201 having a holding portion for a user to hold. Is configured as
The holding unit is provided with a trigger switch 217, and when the user operates the trigger switch 217, the reading operation of the external image (bar code) is started. The body case 201 has an opening 202 for taking in an image of an object such as a barcode label on which a barcode is printed. Around the opening 202, a light emitting element 215 for irradiating an object is provided.

Inside the main body case 201, there is provided an image sensor 204 for capturing an external image, the light receiving surface of which is arranged toward the opening 202. The image sensor 204 is a publicly-known image sensor including a two-dimensional CCD area sensor (hereinafter, 2D sensor). 2D from opening 202
On the optical path to the sensor 204, an external image is
A lens 203 for forming an image is provided on the lens 04. The lens 203 is configured as a single lens or a lens group including a plurality of lenses as necessary. An analog video signal output from the 2D sensor 204 is input to a signal processing operation circuit formed on a circuit board 214, and performs a decoding process on a barcode read by various signal processing and operations.

A monitor screen 21 on which various information can be displayed by a dot matrix is provided above the holding portion of the main body case 201.
6 is provided obliquely to the oblique information. The monitor screen 216 is configured to display information obtained by decoding the read barcode and an image captured by the 2D sensor 204. In addition, a power supply 20 for supplying power to the above-described units is housed inside the holding unit of the main body case 201.

FIG. 2 is a block diagram showing the configuration of the signal processing operation circuit. In FIG. 2, when a bar code is irradiated by the light emitting element 215, the reflected light forms an image on the 2D sensor by the lens 203. 2D sensor 20
4 outputs an analog video signal corresponding to the image formation state of the bar code, and the signal is input to the amplifier circuit 205.
The amplification circuit 205 amplifies the input analog video signal to a required signal level. The amplified signal is input to the signal processing circuit 206 and is converted into a digital signal. The signal processing circuit 206 also performs processes such as removal of unnecessary signal components and signal enhancement.

The digital signal converted by the signal processing circuit 206 is input to a motion vector detection circuit 207, and a motion vector is detected based on the input digital signal. That is, the relative deviation (position change) from the barcode image due to the minute vibration caused by holding the information reading device is detected. The motion vector detection circuit 207 obtains a change component in each of the horizontal pixel direction (H) and the vertical pixel direction (V) of the 2D sensor 204 as a motion vector.

Since the motion vector detection circuit 207 is required to detect a position change shorter than the distance between adjacent pixels, the gradient method is used in the present embodiment. This gradient method calculates the amount of motion from the spatial density gradient and the density change between images (see Horn.
BKP and Schunck B .: 'Determining optical flow
', Artif. Intell., 17, pp. 185-203 (1981). ). In the gradient method, there is a possibility that a large error occurs in the flow calculated near the edge of a bar having high contrast. In this case, by providing a means for temporarily shifting the focal length between the lens 203 and the 2D sensor 204 and a means for reducing the amount of light emitted from the light emitting element 215, the contrast of the barcode can be reduced, and the motion vector detection Detection errors can be reduced.

Alternatively, an LPF (low-pass filter) having a variable cutoff frequency is provided in the signal processing circuit 206, and the cutoff frequency is set low at the time of bar code irradiation, and the light receiving signal is made dull to lower the contrast of the bar. By setting the cutoff frequency high so as not to affect the light receiving signal, the same effect as described above can be obtained.

According to the above method, the motion vector detecting circuit 2
The change amount signal in the H and V directions detected by 07 is input to the determination circuit 219. The determination circuit 219 determines whether or not the amount of change in the H and V directions detected by the motion vector detection circuit 207 has reached a predetermined change amount set in advance. When the determination circuit 219 determines that a predetermined amount of change has occurred, the 2D sensor 20
4 stores the digital signal of the barcode image captured by the storage circuit 208. The storage location in the storage circuit 208 is determined by the address control circuit 2 in accordance with the amount of change in the H and V directions detected by the motion vector detection circuit 207.
09 determines the storage address. As a method of this determination, for example, when it is desired to double the resolution of the 2D sensor 204 in the H direction, the storage address of the data in the H direction in the storage circuit 208 is first classified into an odd address and an even address. Then, the first data obtained from the 2D sensor at the original position is stored at an odd address, and thereafter, when a change amount in the H direction corresponding to half the distance between adjacent pixels of the 2D sensor 204 is detected. The second data obtained from the 2D sensor 204 is stored at an even address.

As a result, the first data and the second data of the 2D sensor 204 correspond to different points of the bar code to be read, and each point is a distance between pixels of the 2D sensor 204 in the H direction. Are in a positional relationship having a displacement of half of Therefore, if two data are overlapped so as to sandwich the second data on the first data as in the method of determining the storage address of the storage circuit 208 described above, the apparent number of sample points can be doubled. As a result, the resolution of the 2D sensor 204 in the H direction is doubled. Note that the resolution can be improved in the V direction of the 2D sensor 204 by the same method as described above.

Also, depending on the situation of minute vibration (camera shake) caused by holding the information device, the 2D sensor 204 may not change to the originally expected position. In this case, the determination circuit 219 performs a process such as rounding off the change amount and determines that there is a change or no change. If it is determined that there is a change, it is determined that the predetermined change amount has been reached. Good. Further, the judgment circuit 219
Is constantly monitoring the output of the motion vector detection circuit 207, and when the motion vector detection circuit 207 detects a change amount greater than the distance between pixels, the position change is not due to camera shake, It is determined that it has been moved. In that case, the address control circuit 20
9 to prohibit the storage of data in the storage circuit 218.

The following method may be employed as a method of storing data in the storage circuit 208.

[0021]

(Equation 1) Gn (k, l) = Fn ([k / L], [l / L]) k, l = 1,2,3─LN Fn (i, j); (n = 1, ─, M i, j = 0,1, ─, N−1) where Fn (i, j) is an image signal having a different amount of change obtained every time the 2D sensor 204 scans, and Δn, i Δn, j is a 2D sensor 204 In the H and V directions, Gn is an image obtained by enlarging each image L times, and H (k, l) is an image obtained by integrating Gn in consideration of the deviation.

When data is stored in the storage circuit 208 by such a method, it is not necessary to separate the storage area of the storage circuit 208. In that case, an adder may be provided between the signal processing circuit 206 and the storage circuit 208, and the added data may be stored in the storage circuit 208.

As described above, the storage circuit 208 stores data obtained by digitizing a barcode with a resolution higher than the number of pixels of the 2D sensor 204. For the data stored in the storage circuit 208, the binarization circuit 21
8, the barcode image is decoded by performing the same processing as the conventional technique shown in FIG. 5 by the counting section 210 and the decoding section 211. In the above-described embodiment, the case where the resolution in the H direction of the 2D sensor 204 is doubled has been described. However, in the case where a resolution of twice or more is obtained, the distance between pixels corresponds to the desired resolution. Divided and set, the set position and motion vector detection circuit 207
May be compared with each other.

The functions of each circuit described above can all be realized using a microcomputer. The control contents in that case are shown in the flowcharts of FIGS. 3, in step 401, an analog video signal output from the 2D sensor 204 is converted into a digital signal. In step 402, based on the converted digital signal, the amounts of change in the H and V directions are detected as motion vectors. At this time, as indicated by the dotted lines, in steps 408, 402, and 409, the light emission amount of the light emitting element 215 is first reduced, and then the motion vector is detected. After the detection of the motion vector, the light emission amount is increased to the original state. , It is possible to reduce the motion vector detection error as described above.

In step 403, the amounts of change in the H and V directions are respectively compared with the set amounts of change. Step 4
In step 04, when the amounts of change in the H direction and the V direction do not match the set amounts of change, determination is made as to whether or not there is a change by rounding or the like as described above. Step 405
Then, the storage address (address) of the memory is determined according to the amount of change detected in steps 403 and 404. In step 406, data is actually written to the memory according to the address determined in step 405.
In step 407, it is determined whether or not the barcode reading process has been completed. If the process has been completed, the process exits this routine.

FIG. 4 is a flowchart showing the decoding process of the bar code image. In step 411, the data written in the memory is fetched. In step 412, the captured data is digitally compared and output as binary data. To digitize digitally,
The comparison may be performed simply by setting a predetermined threshold level, or a tracking-type digital comparison may be performed. In this case, it can be constituted by a combination of the comparator means, the delay means and the simple bit shift means.

In step 413, the width of the binary data obtained in step 412 is counted. In step 414, the width of the data counted in step 413 is restored, and in step 415, the information included in the symbol from the combination of the wide bar, narrow bar and each space of the barcode is reproduced and output. Then, in step 416, it is determined whether or not all decoding processing has been completed. If the decoding processing has been completed, this routine is exited.

FIG. 5 shows a relative position change between the bar code and the 2D sensor 204 in a time series. The operation of the present embodiment when the resolution in the H direction is doubled will be specifically described with reference to FIG.

In FIG. 5, the distance between a specific pixel P (i, j) of the 2D sensor 204 and an adjacent pixel P (i + 1, j) is τ.
It is. The time when the 2D sensor 204 is at t = t1 is set as the original position, and the pixel P (i, j) at this position is first determined.
Data is taken in. Next, at t = t2, the 2D sensor 204 is displaced to the right in the H direction, and its position change is τ.
/ 2 has been reached. Then, the pixel P at t = t2
The data of (i, j) is also fetched and superimposed on the data at t = t1. On the other hand, when t = t3, the change in the position of the 2D sensor 204 is greater than the pixel-to-pixel distance τ with respect to the original position. At this time, the capture of the data of the pixel P (i, j) is prohibited. . When t = t4, the position change of the 2D sensor 204 is within the pixel distance τ. At this position, whether or not the data of the pixel P (i, j) is fetched is determined as follows.
Other judgment factors, such as the processing result such as rounding off the displacement amount and whether data collection at this position has been completed, are taken into consideration.

Although only the position change in the H direction has been described here, the same effect can be obtained by the same operation for the position change in the V direction. In addition, 2
Even when the position of the D sensor 204 changes in the oblique direction, H
It goes without saying that the same processing can be performed by obtaining the amounts of change in the direction and the V direction.

Further, in the present invention, in order to increase the apparent number of sample points, it is only necessary to cause a slight shift in the relative positional relationship between the external image to be read and the information reading device. For this reason, in the above-described embodiment, the information reading device is configured to be portable, and the minute vibration during the portable use is used as a relative position change. However, the information reading device itself is fixed and the 2D sensor is used. An actuator may be provided to slightly vibrate the object 204, the object may be vibrated, or the object may be moved by a belt conveyor or the like.

[0032]

As described above, according to the optical information reading apparatus of the present invention, an external image is captured by the image sensor, and the relative position between the image sensor and the external image is determined based on the image data. A position change is detected. When the position change is shorter than the distance between adjacent pixels of the image sensor, the image data obtained from the image sensor is superimposed on the image data at the original position according to the change position.

Therefore, the image data obtained by the superimposition increases the apparent number of sample points. Therefore, it is possible to precisely read an external image to be read without using an image sensor such as a CCD sensor having a large number of pixels. Becomes possible. At this time, the reading range of the image sensor is not sacrificed, and a sufficient reading range can be secured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of an information reading device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a signal processing operation circuit according to the embodiment.

FIG. 3 is a flowchart illustrating a process of superimposing video data according to a relative position change between an external image and a sensor.

FIG. 4 is a flowchart illustrating a decoding process according to the embodiment.

FIG. 5 is an explanatory diagram illustrating the operation of the present embodiment.

FIG. 6 is a configuration diagram illustrating an example of a configuration of a conventional device.

[Explanation of symbols]

 201 body case 203 lens 204 2D sensor 213 power supply 214 circuit board 216 display unit 217 trigger switch

Claims (4)

(57) [Claims] An image sensor having a plurality of pixels for capturing an external image; an optical unit for forming an external image on the image sensor; and an image sensor based on video data obtained from the image sensor. Position change detection means for detecting a relative position change between the image sensor and the external image, and when a position change shorter than the distance between adjacent pixels of the image sensor is detected by the position change detection means,
Video data processing means for superimposing the video data obtained from the image sensor on the video data at the original position in accordance with the change position, and based on the video data superimposed by the video data processing circuit, An optical information reading device comprising: signal processing means for restoring information contained in a captured external image. 2. The optical information reading device according to claim 1, further comprising a main body case having a holding portion for holding the portable device, wherein each of the constituent elements is housed in the main body case. 2. The optical information reading apparatus according to claim 1, wherein the relative position change with respect to an external image utilizes minute vibration when the information reading apparatus is used in a portable manner. 3. A method according to claim 1, wherein the relative position change between the image sensor and the external image detected by the position change detecting means is caused by an intentional movement of a wearer or by a minute vibration during use of the wearer. 3. The image processing apparatus according to claim 2, further comprising: a judging means for judging, and a permission means for permitting the processing of the video data processing means only when it is judged that the vibration is small during portable use. Optical information reading device. 4. The optical information reading apparatus according to claim 1, further comprising a vibration generating means for causing the image sensor to vibrate minutely.