JP4107237B2 - Method for identifying boundary position of optical information reader - Google Patents

Description

  The present invention relates to a boundary position specifying method of an optical information reading apparatus for specifying a boundary position between a bright pattern and a dark pattern in order to read optical information composed of a light and dark pattern obtained by combining a plurality of bright patterns and dark patterns having different widths. .

In this type of optical information reader, in order to read information contained in an information code such as a one-dimensional code or a two-dimensional code, the widths of the bright pattern and the dark pattern constituting the information code are detected. By detecting the widths of these bright and dark patterns, the information code can be read and decoded almost accurately. As a method for specifying the boundary position in this way, for example, there is a method disclosed in Patent Document 1. According to this method, the boundary position between the bright pattern and the dark pattern of the barcode can be specified by calculating the primary differential value and the secondary differential value of the analog barcode signal. In addition, although not directly related to the present invention, the document shown in Patent Document 2 is also known.
JP 2001-357347 A JP 2000-18920 A

  If the optical focal position deviation is within a predetermined reference range, the boundary position can be specified almost accurately by detecting the primary differential value or the secondary differential value (see FIG. 9A). When the optical focus position deviates from the reference, so-called defocusing occurs, and there is almost no difference between the maximum value and the minimum value of the primary differential value between sensor pixels as shown in FIG. 9B. Many zero-cross points are detected in the secondary differential value as compared with the actual light-dark pattern, and the boundary position cannot be specified.

  Further, in such an optical information reading apparatus, particularly when the distance to the reading object is adjusted to a position closer to the focal position, for example, a space (bright pattern) or a bar (dark pattern) constituting a barcode. The number of pixels of the optical sensor assigned to is increased, and accordingly, there is no difference in the amount of change in the primary differential value. Therefore, the zero cross point cannot be accurately detected, and the boundary position cannot be specified. Moreover, the position of the zero cross point may change greatly due to the influence of noise or the like.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical system that can detect a boundary position substantially accurately even if the optical focal position deviates from a reference. Another object of the present invention is to provide a method for specifying the boundary position of an information reading device.

  According to the first aspect of the invention, one continuous maximum value and one minimum value are detected for the luminance level in the boundary position assumed range setting process, and the boundary value is set as the boundary position assumed range. In the target range setting process, A target range for specifying the boundary position is set for the luminance level before and after the assumed boundary position range, and at least one or more front poles at the front and rear of the assumed boundary position range within the target range of the luminance level in the extreme value setting process Set the value and the back extremum for specifying the boundary position, and in the calculation process, the front extremum and the rear extremum set in the process of setting the extremum, and the maximum value and the minimum value between successive extreme values Before and after the boundary position assumption range calculated in the calculation process in the boundary position identification process. Since the position where the boundary position assumption range is divided by the ratio of local amplitudes is specified as the boundary position, even if the optical focus position deviates from the reference when specifying the boundary position, the boundary position is substantially accurate. Can be detected.

According to the second aspect of the present invention, in the calculation process, the local amplitude is calculated from the side close to the boundary position assumption range before and after the boundary position assumption range. Since the boundary position is specified based on the local amplitude, the boundary position can be detected with higher accuracy.
According to the third aspect of the present invention, in the calculation process, a plurality of local amplitudes are calculated before and after the boundary position assumption range from the side close to the boundary position assumption range, and in the boundary position specification process, the calculation is performed in the calculation process. In order to identify the position where the boundary position assumed range is divided by the ratio of the average values of the plurality of local amplitudes before and after being determined as the boundary position, a wide range of local amplitudes deeply related to the identification of the boundary position are used. The boundary position can be specified, and the boundary position can be detected with higher accuracy.

According to the fourth aspect of the present invention, in the focal position deviation presence / absence determination process, the presence / absence of the focal position deviation is determined, and in order to perform the above-described invention on the condition that the focal position deviation is determined, Can be identified efficiently.
According to the fifth aspect of the invention, the primary differential value is calculated for the luminance level of the light receiving process in the primary differential calculation process, and the primary differential value calculated in the primary differential calculation process in the focus position deviation presence / absence determination process. Whether or not there is a focal position deviation is determined because it is determined that there is a focal position deviation on the condition that the maximum value of is not more than the first predetermined value or the minimum value of the primary differential value is not less than the second predetermined value. Judgment can be made easily.

According to the sixth aspect of the invention, the secondary differential value is calculated for the luminance level in the light receiving process in the secondary differential calculation process, and the secondary differential calculated in the secondary differential calculation process in the focus position deviation determination process. Since it is determined that there is a focal position deviation on the condition that the number of zero-crossing values is equal to or greater than a predetermined number, it is possible to easily determine whether there is a focal position deviation.
According to the seventh aspect of the present invention, the degree of defocus is determined based on the luminance level in the light receiving process in the defocus degree determination process, and the defocus degree determination process is performed in the second luminance level target range setting process. In order to set the target range for specifying the boundary position with respect to the luminance level before and after the boundary position assumed range according to the determined degree of the focal position deviation, the luminance of the local amplitude for specifying the boundary position according to the focal position deviation It becomes possible to set the target range of the level.

  According to the eighth aspect of the present invention, in the second luminance level target range setting process, when it is determined that the degree of the focal position deviation is large in the defocus degree determination process, the luminance level target range is set to be narrow. By reducing the number of local amplitudes required as the boundary position specifying target and determining that the degree of defocus is small in the defocus degree determination process, the target range of the luminance level is set wide. Since the number of local amplitudes required as the boundary position specifying target is increased, the target range of the luminance level of the local amplitude for boundary position specifying can be set according to the magnitude of the focal position shift.

  According to the ninth aspect of the present invention, in the second luminance level target range setting process, average values of local amplitudes are calculated for the front and rear sides of the target range for specifying the boundary position of the boundary position assumed range. If the difference between the average values of the local amplitudes is greater than or equal to the third predetermined value, the number of local amplitudes required as the boundary position specifying target is set to be small by setting the target range of the luminance level to be narrow, When the difference between the average values is less than the third predetermined value, the number of local amplitudes required as the boundary position specifying target is set large by setting the target range of the luminance level wide, so the front side and the rear side It is possible to set the number of local amplitudes that are the boundary position identification target according to the difference in the average value of the local amplitudes.

  According to the invention described in claim 10, in the second luminance level target range setting process, the maximum value and the minimum value of the local amplitude are calculated before and after the boundary position assumed range, and the maximum value and the minimum value of the local amplitude are calculated. When the difference is equal to or greater than the fourth predetermined value, the number of local amplitudes required as the boundary position specifying target is set to be small by setting the target range of the luminance level to be narrow, and the maximum value and the minimum value of the local amplitude are set. When the difference is less than the fourth predetermined value, the number of local amplitudes required as the boundary position specifying target is increased by setting the target range of the luminance level wide, so When the difference between the maximum value and the minimum value of the local amplitude is less than the fourth predetermined value, the number of local amplitudes required as the boundary position specifying target can be increased by setting the target range of the brightness level wide. Because the way, it becomes possible to set the number of local amplitude as a border location subject in accordance with the difference between the maximum value and the minimum value before and after the local amplitude of the boundary position expected range.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 2A shows a schematic electrical configuration block diagram of the optical information reading apparatus 1. The optical information reader 1 used in a POS system such as a supermarket cash register is also called a handy terminal, and optically reads a one-dimensional code such as a bar code or a two-dimensional code such as a QR code. It is configured to read. 2B and 2C show examples of a one-dimensional code and a two-dimensional code. FIG. 2B shows a bar code B, and FIG. 2C shows a QR code, which are also called an information code B. For example, in the case of the barcode shown in FIG. 2B, a white relatively bright rectangular space B1 (corresponding to a bright pattern) and a black relatively dark rectangular bar B2 (corresponding to a dark pattern) are present. The information code B is configured by being combined linearly. In the case of a two-dimensional code such as a QR code shown in FIG. 2C, rectangular white cells B1 (corresponding to a bright pattern) and black cells B2 (corresponding to a dark pattern) are combined in a matrix.

  In FIG. 2A schematically showing the electrical configuration of the optical information reader 1 for optically reading such an information code B, the optical information reader 1 is mainly composed of a control circuit 2. Has been. A memory 3, an operation unit 4, a display unit 5, and an external interface unit 6 are connected to the control circuit 2. The optical information reading device 1 is operated by being supplied with power from a built-in power supply circuit 7. For example, in the case of the handy type optical information reading apparatus 1, a battery is built in and a power supply voltage is supplied to the whole through the power supply circuit 7.

  The control circuit 2 is connected to an irradiation unit 9 made of a red light-emitting diode via an illumination drive circuit 8. When a trigger switch provided in the operation unit 4 is operated, the control circuit 2 performs irradiation control from the irradiation unit 9 toward the reading object A through the illumination driving circuit 8. When an information code B such as a one-dimensional code or a two-dimensional code is printed on the reading object A, the light irradiated to the reading object A is reflected by the light / dark pattern of the information code B, and the light is condensed. Light is received by the optical sensor 11 through the image means 10.

  The image forming means 10 is constituted by a lens, for example, and causes the optical sensor 11 to form an image of the light irradiated and reflected from the irradiation unit 9 onto the reading object A. The optical sensor 11 is also referred to as, for example, an area sensor, and includes, for example, light receiving elements such as CCDs arranged in a two-dimensional plane, and is read based on control performed by the control circuit 2 via the sensor driving circuit 13. The reflected light reflected by the object A is photoelectrically converted for each pixel of the light receiving element, and the serial pixel signal is given to the waveform shaping unit 12. The waveform shaping unit 12 amplifies the analog signal photoelectrically converted by the optical sensor 11 and converts the signal to a luminance level by analog-digital conversion. The waveform shaping unit 12 performs low-pass filter processing as necessary, and performs memory control by memory control performed by the control circuit 2. 3 is stored.

  The external interface unit 6 inputs and outputs data between the control circuit 2 and an external device (not shown). The control circuit 2 is constituted by, for example, a microcomputer, and controls the entire reading apparatus main body 1 having such a configuration based on a control program.

The operation of the above configuration will be described with reference to FIGS. In the description of this operation, an embodiment in which the information code B is applied to a barcode will be described.
In the optical information reading apparatus 1 having the above-described configuration, when reading a barcode B that is a combination of a plurality of spaces B1 and bars B2, the control circuit 2 scans the reading target A one-dimensionally and receives light by the optical sensor 11. The signal is taken in, and the luminance level A / D converted by the waveform shaping unit 12 as described above is sequentially stored in the memory 3.
FIG. 1 shows an example of the brightness level stored in the memory so as to correspond to the barcode B printed on the reading object A. In the barcode B in which the space B1 and the bar B2 having different widths are combined, the brightness level is relatively high in the space B1 portion, and the brightness level is relatively low in the bar B2 portion.

  As a result of the experiment in the conventional configuration, when the degree of focal position deviation is optically small and no optical defocusing occurs, the zero-cross point of the secondary differential value is the boundary between the space B1 and the bar B2. However, when the focal position shift is large and optical defocusing occurs, the waveform becomes linearly gradual. In particular, the second-order differential value of the luminance level is the luminance level. It is known that a lot of zero cross points are generated because the noise is inevitably buried in detecting the noise, and the boundary position cannot be determined even if the zero cross points are detected (FIG. 9B). )reference).

  Therefore, the control circuit 2 specifies the boundary position by performing the processing shown in the flowcharts of FIGS. That is, the control circuit 2 reads the luminance level stored in the memory 3 and first performs a process of calculating a primary differential value for this luminance level (step S1), and then performs a process of calculating a secondary differential value. (Step S2). Then, the control circuit 2 detects the extreme value (maximum value and minimum value) using the primary differential value for each scan (step S3). Thereafter, the control circuit 2 sequentially selects one continuous maximum value and one minimum value from the detected extreme values from the front, and the boundary position assumption range between the one maximum value and the one minimum value. Set as H (step S4).

  In the present embodiment, in order to show the main points of the present invention, an embodiment when the maximum value Pa1 and the minimum value Pb1 are selected and set as one continuous maximum value and one minimum value in FIG. 1 will be described. At this time, a boundary position from the space B1 to the bar B2 always exists between the one maximum value Pa1 and the one minimum value Pb1 (see the boundary position assumption range H). Thereafter, the control circuit 2 performs a process for determining whether or not there is a focal position shift (step S5).

  FIG. 4 is a flowchart showing the determination processing operation for the presence / absence of the focal position deviation performed by the control circuit. In FIG. 4, the control circuit 2 indicates that the maximum value of the primary differential value of each luminance level within the assumed boundary position range H is not more than a first predetermined value, or the minimum value of the primary differential value is the first value. It is determined whether the value is equal to or greater than a predetermined value of 2 (step T1). The first predetermined value is set to a value different from the second predetermined value, and is set to be larger than the second predetermined value. At this time, if the condition of step T1 is satisfied, it is determined that there is a focal position shift. This is because when the luminance level of the pixel signal transitions from the bar B2 (dark pattern) to the space B1 (bright pattern), the degree of increase in the luminance level becomes the maximum. This is because the degree of increase decreases due to the effect of defocusing near the position, and the maximum value of the primary differential value does not exceed the first predetermined value. In addition, when the transition from the space B1 to the bar B2 is performed, the degree of decrease in the luminance level becomes the minimum value, but the minimum value of the primary differential value does not fall below the second predetermined value as described above. That is, the presence / absence of defocus can be efficiently determined by adding the condition of step T1 to the determination condition of defocus / presence as necessary.

  Further, the control circuit 2 determines whether or not the number of zero cross points of the secondary differential value of each luminance level within the boundary position assumed range H is equal to or greater than a predetermined number (step T2). In other words, considering the case where the luminance level is buried in noise, or the case where the pixel signal waveform is linear due to defocusing and there are many zero-cross points of secondary differential values due to resolution and noise during A / D conversion, the boundary position If it is assumed that it is difficult to determine the second derivative value by the second derivative value, whether or not a predetermined number or more of zero-cross points of the second derivative value has been detected is added to the determination condition of step T2. good. By adding this step T2 to the determination condition, it is possible to efficiently determine whether or not there is a focus position shift.

  The control circuit 2 determines that there is a focal position shift when any of the determination conditions of Steps T1 to T2 is satisfied (Step T3), and determines that there is no focal position shift if both are not satisfied (Step T4). ). At this time, referring back to FIG. 3, when the control circuit 2 determines that there is no focal position deviation (step S5: NO), for example, the primary differential value and the secondary differential value are used as shown in the background art. When the binarization process is performed (step S6), but it is determined that there is a focus position shift, the focus position shift degree determination process shown in FIG. 5A is performed. In the present embodiment, the control shown in FIG. 5A is performed. Instead, the following processing is performed as necessary even when the control circuit 2 determines that there is no focus position deviation. You may do it.

  First, target ranges H1 and H2 for specifying the boundary position of the initial luminance level are set (step U1: target range setting process). The reason why the target ranges H1 and H2 for specifying the boundary position of the brightness level are set is that the brightness level close to the front and rear of the assumed boundary position range H affects the boundary position specifying conditions. That is, the control circuit 2 sets predetermined initial target ranges H1 and H2 for position specification in front of and behind the assumed boundary position range H.

Thereafter, the control circuit 2 calculates the front extreme values Pa2 and Pa3 and the rear extreme values Pb2 and Pb3 before and after the assumed boundary position range H in the initial target ranges H1 and H2 of this luminance level (step U2), and the boundary Set for position identification (extreme value setting process). At this time, in FIG. 1, the following explanation will be made assuming that the front extreme values Pa2 to Pa3 and the rear extreme values Pb2 to Pb3 are calculated.
Thereafter, the control circuit 2 calculates local amplitudes a1 to a2 and b1 to b2 within the initial target ranges H1 and H2. The local amplitudes a1 to a2, b1 to b2 are absolute values of differences between successive extreme values for the front extreme values Pa2 to Pa3 and the rear extreme values Pb2 to Pb3 together with the one maximum value Pa1 and the one minimum value Pb1. In FIG. 1, local amplitudes a1 = | Pa1-Pa2 |, a2 = | Pa2-Pa3 | on the front side of the boundary position assumed range H are shown in FIG. The local amplitude b1 = | Pb1-Pb2 |, b2 = | Pb2-Pb3 | is shown, and the control circuit 2 calculates the local amplitudes a1 to a2 and b1 to b2. “|” Indicates a symbol of an absolute value.

Thereafter, the control circuit 2 performs a variation determination process of the local amplitudes a1 to a2 and b1 to b2 of the initial target ranges H1 and H2 of the luminance level shown in FIG. This determination process may be provided as necessary. There are a determination method based on the difference between the front and rear local amplitudes as a variation determination of the local amplitude, and a determination method based on the difference between the maximum value and the minimum value described in the embodiment described later. The latter will be described later. Here, the former will be described.
<Determination method based on difference between front and rear local amplitude>
Hereinafter, a variation determination method based on the difference between the front and rear local amplitudes will be described. Average values are calculated for a plurality of local amplitudes a1 to a2 on the front side and a plurality of local amplitudes b1 to b2 on the rear side of the assumed boundary position range H (step V1). That is, (a1 + a2) / 2 and (b1 + b2) / 2 are calculated. The average value of the plurality of local amplitudes may be weighted as necessary. If only one value is obtained for the initial luminance level target range, the average process is omitted. Anyway.

  Then, it is determined that the variation is large on condition that the difference between the average values of the local amplitudes before and after the assumed boundary position range H is equal to or larger than the third predetermined value (YES in step V2 in FIG. 5B). (Step V3) By narrowing the target range of the luminance level for specifying the boundary position (Steps U5 to U6 in FIG. 5A), the number of local amplitudes to be specified as the boundary position specifying target is reduced. That is, in FIG. 1, the target ranges H1 and H2 of the luminance level are set narrow so as to exclude the extreme values Pa3 and Pb3. In this way, the local amplitude targeted when the boundary position is specified in steps S8 to S9 of FIG. 3 to be described later after completion of the process of determining the degree of focal position deviation, for example, a1 = | Pa1-Pa2 |, b1 = It is assumed that only | Pb1-Pb2 |

  Conversely, it is determined that the variation is small on the condition that the difference between the average values of the local amplitudes before and after the assumed boundary position range H is equal to or larger than the third predetermined value (NO in step V2 in FIG. 5B) (step V4) By setting the target ranges H1 and H2 of the luminance level for specifying the boundary position widely (step U7 in FIG. 5A), a large number of local amplitudes to be specified as the boundary position specifying target is set. That is, in FIG. 1, extreme values Pa4 and Pb4 are added by setting the target ranges H1 and H2 of the luminance level wide. In this way, the local amplitude targeted when the boundary position is specified in steps S8 to S9 of FIG. 3 to be described later after the process of determining the degree of the focal position deviation is set to a3 together with a1 to a2 and b1 to b2, for example. = | Pa3-Pa4 |, b3 = | Pb3-Pb4 | are added, and the number of local amplitudes around the target boundary position assumption range H is set to a plurality (for example, 3).

  Thereafter, as shown in FIG. 3, the control circuit 2 calculates the targeted local amplitude around the boundary position assumed range H (step S <b> 8). In this case, when one local amplitude a1, b1 close to the boundary position assumed range H is set as the local amplitude before and behind the boundary position assumed range H, the control circuit 2 sets the front and rear The position where the boundary position assumed range H is divided by the ratio of local amplitudes is specified as the boundary position (step S9). That is, the control circuit 2 calculates a value of Cp that satisfies the relationship | Pa1-Cp |: | Cp-Pb1 | = a1: b1, and obtains a value close to Cp within the boundary position assumption range H. The level is searched, and the position of the luminance level that can take a value close to this Cp is specified as the boundary position C. This principle is illustrated in FIG. The boundary position C indicates that it is a position of a luminance level in which local amplitudes in front and rear of the assumed lifetime position range H are allocated to a1: b1. FIG. 6 is a diagram for explaining the principle, and it should be noted that the direction of the amplitude is different from that in FIG.

  When the control circuit 2 sets a plurality of local amplitudes a1 to a3 and b1 to b3 close to the assumed boundary position range H as the local amplitudes before and after the assumed boundary position range H in step S8 of FIG. Specifies the position obtained by dividing the boundary position assumption range H as the boundary position by the ratio of the average value of the local amplitudes a1 to a3 and the average value of the local amplitudes b1 to b3 close to the boundary position assumption range H (step S9). ).

  That is, the control circuit 2 calculates the value of Cp satisfying the relationship of | Pa1-Cp |: | Cp-Pb1 | = (a1 + a2 + a3) ÷ 3: (b1 + b2 + b3) ÷ 3 in steps S8 to S9 in FIG. Then, a brightness level that obtains a value close to Cp within the assumed boundary position range H is searched, and the position of the brightness level that can take a value close to Cp is specified as the boundary position C.

  After specifying the boundary position C in this way, binarization processing is performed so as to assign the bar B2 and the space B1 on the front side and the rear side with reference to the boundary position C (step S10). The result is stored in the memory 3. Then, the control circuit 2 returns to step S4 until the entire binarization is completed, and performs the binarization processing of the barcode B for all the boundary position assumed ranges H, and this binarization processing is performed for all the boundaries. If the process ends within the assumed position range H (step S11: YES), a decoding process is performed based on the binarized signal (step S12), and the decoding process ends.

  The experimental results obtained by binarization at this time are shown in FIG. Compared with the binarization result obtained by using the secondary differential value or the primary differential value using the conventional technique or the like (refer to the binarization result by the conventional method), the corresponding light / dark pattern of the information code B A good result (see the binarization result according to the present embodiment) can be obtained so as to substantially match. The binarization result according to the present embodiment shown in FIG. 7 calculates one local amplitude Pa2 and Pb2 before and after the boundary position assumed range H, and | Pa1-Cp |: | Cp-Pb1 | = a1: b1 The experimental result which calculated the value of Cp which satisfy | fills this relationship, and specified the position of the boundary position C is shown.

  According to such an embodiment, the reflected light reflected by the barcode B is photoelectrically converted by the optical sensor 11, and this serial signal is A / D converted into a luminance level, and a certain maximum value Pa1 for this luminance level. And a boundary position assumed range H is calculated by calculating the minimum value Pb1, and one or more extreme values Pa2 to Pan and Pb2 to Pbn (n is a positive integer) are respectively set before and after the boundary position assumed range H. Positions set for calculation, calculated as local amplitudes a1 to am, b1 to bm (m is a positive integer) before and after the boundary position assumed range H, and divided by a ratio of average values of the front and rear local amplitudes Since the boundary position is specified, the boundary position can be detected almost accurately even if the focus position of the captured image is deviated. It will be able to top.

(Second Embodiment)
FIG. 8 shows an explanation of the second embodiment. The difference from the first embodiment resides in the local amplitude variation determination processing, and the target range of the luminance level that is the boundary position specifying target, that is, the boundary position. There is a method for setting the number of local amplitudes to be specified. Hereinafter, a different part from 1st Embodiment is demonstrated and description is abbreviate | omitted about another description.

That is, in FIG. 8, the control circuit 2 calculates the maximum value and the minimum value of the local amplitude of the initial target ranges H1 and H2 calculated for the front side and the rear side (step W1). That is, in FIG. 1, b2 = | Pb2-Pb3 | and a2 = | Pa2-Pa3 | in the initial target ranges H1 and H2 are calculated as the maximum value and the minimum value, respectively.
When the difference between the maximum value and the minimum value is equal to or greater than the fourth predetermined value (step W2: YES), the control circuit 2 determines that the variation is large (step W3), and the luminance level that is the boundary position specifying target Is set to be narrow (step U6 in FIG. 5A), so that the number of local amplitudes of the boundary position specifying target is set to be small. Conversely, if the condition of step W2 is not satisfied, it is determined that the variation is small (step W4), and the target range of the luminance level that is the boundary position specifying target is set wide (step U7 in FIG. 5A). Thus, the number of local amplitudes of the boundary position specification target is increased. Accordingly, it is possible to obtain substantially the same operational effects as those of the first embodiment.

(Other embodiments)
The present invention is not limited to the above embodiment, and for example, the following modifications or expansions are possible. Although the embodiment has been described in which the bar code is scanned and read one-dimensionally, the QR code may be read.

Correspondence diagram of light and dark pattern and luminance level showing the first embodiment of the present invention (A) is a block diagram showing an electrical configuration, (b) is a diagram showing an example of a one-dimensional code, and (c) is a diagram showing an example of a two-dimensional code. Flowchart showing information code decoding process (part 1) Flow chart showing decoding process of information code (Part 2) (A) and (b) are flowcharts showing information code decoding processing (parts 3 and 4). Explanatory diagram showing the principle of boundary position identification Figure comparing experimental results FIG. 5B equivalent view showing the second embodiment of the present invention (A) (b) is explanatory drawing of a prior art example

Explanation of symbols

In the drawings, reference numeral 1 denotes an optical information reader, and 2 denotes a control circuit.

Claims (12)

Boundary position specification of an optical information reader that specifies a boundary position from the bright pattern to the dark pattern or the dark pattern to the bright pattern in order to read an information code composed of a bright pattern and a dark pattern obtained by combining a plurality of bright patterns and dark patterns In the method
A light receiving process for receiving light via the information code and photoelectrically converting it to a luminance level that changes with time;
A boundary position assumption range setting process for detecting one continuous maximum value and one minimum value for the luminance level, and setting a boundary position assumption range between the maximum value and one minimum value;
A target range setting process for setting a target range for specifying a boundary position for a luminance level in front and rear of the boundary position assumed range;
An extreme value setting process for setting at least one forward extreme value and a backward extreme value in front of and behind the assumed boundary position range within the target range of this luminance level for specifying the boundary position; and
Regarding the front extreme value and the rear extreme value set in this extreme value setting process, and the one maximum value and one minimum value, the difference between successive extreme values is set as the local amplitude before and after the boundary position assumption range, respectively. A calculation process to calculate,
An optical information comprising: a boundary position specifying step of specifying, as a boundary position, a position obtained by dividing the boundary position assumption range by a ratio of local amplitudes before and after the boundary position assumption range calculated in the calculation process; Method for identifying boundary position of reader. In the calculation process,
2. The boundary position specifying method for an optical information reading apparatus according to claim 1, wherein the local amplitude is calculated from the side close to the boundary position assumption range before and after the boundary position assumption range. In the calculation process,
A plurality of local amplitudes are respectively calculated from the side close to the boundary position assumption range before and after the boundary position assumption range,
In the boundary position specifying process,
The position obtained by dividing the boundary position assumption range is specified as a boundary position by a ratio of average values of a plurality of local amplitudes before and after calculated in the calculation process. A boundary position specifying method for an optical information reader. A focal position deviation presence / absence determination process for determining the presence / absence of a focal position deviation is provided,
4. A boundary position specifying method for an optical information reading apparatus, wherein the boundary position specifying method according to claim 1 is performed on the condition that it is determined that there is a focal position shift by this process. A first-order differential calculation process for calculating a first-order differential value for the luminance level of the light receiving process;
In the focal position shift presence / absence determination process,
There is a focus position deviation on condition that the maximum value of the primary differential value calculated in the primary differential calculation process is not more than a first predetermined value or the minimum value of the primary differential value is not less than a second predetermined value. The boundary position specifying method for an optical information reading device according to claim 4, wherein: A second derivative calculation process for calculating a second derivative value for the luminance level of the light receiving process;
In the focal position shift presence / absence determination process,
6. The optical information reading according to claim 4, wherein it is determined that there is a focal position deviation on condition that the number of second-order differential values calculated in the second-order differential calculation process is zero or more. A method for identifying the boundary position of a device. Defocus degree determination process for determining the degree of focus position shift based on the luminance level of the light receiving process,
A second luminance level target range setting process for setting a target range for boundary position specification with respect to the luminance level in front and rear of the boundary position assumed range according to the focus position shift determined in the defocus level determination process. A boundary position specifying method for an optical information reading device according to any one of claims 1 to 6, further comprising: In the second luminance level target range setting process,
When it is determined that the degree of the focal position deviation is large in the defocus degree determination process, the number of local amplitudes required as the boundary position identification target is reduced by setting the target range of the luminance level to be narrow,
When it is determined that the degree of the focal position deviation is small in the defocus degree judging process, the number of local amplitudes required as the boundary position specifying target is increased by setting the target range of the luminance level wide. 8. The method for specifying the boundary position of an optical information reader according to claim 7. In the second luminance level target range setting process,
Calculate the average value of the local amplitude before and after the target range for specifying the boundary position of the boundary position assumed range,
When the difference between the average values of the local amplitudes on the front side and the rear side is equal to or larger than the third predetermined value, the number of local amplitudes obtained as the boundary position specifying target is set by narrowing the target range of the luminance level. If the difference between the average values before and after the setting is less than the third predetermined value, the number of local amplitudes required as the boundary position specifying target is set larger by setting the target range of the luminance level wider. 9. The method for specifying a boundary position of an optical information reading apparatus according to claim 7 or 8, wherein: In the second luminance level target range setting process,
When the maximum value and the minimum value of the local amplitude are calculated before and after the boundary position assumption range, and the difference between the maximum value and the minimum value of the local amplitude is a fourth predetermined value or more, the target range of the luminance level If the difference between the maximum value and the minimum value of the local amplitude is less than the fourth predetermined value, the brightness level target is determined. 10. The boundary position specifying method for an optical information reader according to claim 7, wherein the number of local amplitudes required as the boundary position specifying target is increased by setting a wide range.   11. The light receiving process according to claim 1, wherein an analog signal obtained by receiving and photoelectrically converting an optical sensor through an information code is converted from analog to digital to obtain a luminance level. Boundary position specifying method for optical information reading apparatus. 12. The method according to claim 1, wherein the information code is a one-dimensional code or a two-dimensional code.

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