JP3760594B2 - Optical information reader - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information reading apparatus that irradiates a reading target such as a barcode and reads an image to be read from the reflected light, and in particular can read a reading target at a position away from a reading port. .
[0002]
[Prior art]
The reflected light of the light emitted from the light emitting means such as a light emitting diode to the barcode attached to the product is imaged on the light receiving means on which the light receiving elements are arranged, and the image of the barcode is formed by the light receiving means. Optical information reading devices that read are known.
[0003]
Usually, such an optical information reading device irradiates the barcode with light from the light emitting means through the reading port in a state where the reading port provided in the case of the optical information reading device is substantially in contact with the barcode. The light reflected from the bar code is guided into the case of the optical information reader from the same reading port, and is imaged on the light receiving means.
[0004]
In such an optical information reading apparatus, it is necessary to bring the optical information reading apparatus to a commodity to which a barcode is attached, and there is a problem that the reading operation is troublesome. In order to solve this problem, not only the barcode existing in the vicinity of the reading port of the optical information reading apparatus but also a bar code several tens of centimeters (for example, 30 to 50 cm) from the vicinity of the reading port is used as the light receiving means. A so-called large-depth optical information reading device that reads a barcode efficiently without performing an operation of bringing the optical information reading device close to a product for each reading by forming an image and reading the image is conceivable.
[0005]
However, the barcode irradiation lens is set so that the irradiation light from the light emitting means used in the normal barcode is emitted from the entire reading port. This is because when the barcode is almost in contact with the reading port, the case of the optical information reading device becomes a blind spot, making it difficult to see the barcode. This is to ensure that the light beam strikes the bar code even if is slightly shifted. However, when the barcode irradiation lens is set to spread the irradiation light so that it is irradiated from the entire reading port in this way, only extremely weak light reaches the position of the barcode far from the reading port, and It is not clear whether the code reading port is directed to the bar code to be read, and there is a possibility that reading may be mistaken.
[0006]
For this, the intensity of reflected light incident on the light receiving means is detected, and the amount of reflected light for the light receiving means to convert the video information into an electrical signal by controlling the exposure time of the light receiving means based on the detection result. It is considered to always stabilize. In this way, the optical information can be read without bringing the reading port into contact with the reading target, and the more the reading port is separated from the reading target, the larger the readable range of the optical information can be increased. Thus, a wide range of optical information can be read without being limited by the diameter of the reading port.
[0007]
By the way, as a cause of reducing the reading performance when the reading port is separated from the reading target, there is a problem related to the illuminance distribution as well as the above-described reduction in reflected light intensity. That is, as shown in FIG. 4A, no matter how flat the illuminance distribution of the irradiation light from the light emitting means is, the reflected light is reflected at the time when the reflected light forms an image on the light receiving element through the imaging lens. The amplitude of the waveform decreases as it goes to the periphery. This is the COS of the imaging lens ^Four This is due to the law and MTF identification.
[0008]
With respect to this point, conventionally, for example, the light emitting means has been designed so that the illuminance distribution of the irradiated light is brighter in the periphery than in the center. For example, assuming that four light emitting diodes are arranged as the light emitting means, both end sides of the reading port are made denser than the central portion, or the irradiation directions of the four light emitting diodes are inclined toward both end sides of the reading port. Thus, a device for increasing the brightness of the peripheral portion to be read is also considered.
[0009]
However, these can be handled only when a barcode to be read exists at a specific position. That is, the degree to which the amplitude of the reflected light waveform decreases toward the periphery changes as the distance between the reading port and the barcode changes. Therefore, even if the arrangement of the light emitting diodes and the light quantity are adjusted so that an appropriate illuminance distribution is obtained in a state where the distance between the reading port and the barcode is α, the distance between the reading port and the barcode is not sufficient when actually reading. If it changes to β, there is a possibility that an appropriate illuminance distribution may not be obtained in that state.
[0010]
Therefore, it is conceivable to store control data corresponding to the distance in advance as a method of executing control corresponding to the illuminance distribution that changes according to the distance between the reading port and the barcode. For example, when there is a sampling barcode at the reading port, the light amount control value for each light emitting diode when the imaging state at the light receiving means is appropriate in the width direction of the reading port, the distance α (> 0) from the reading port The light intensity control value when the sampling barcode is at the position, the light intensity control value when the sampling barcode is at a position β (> α) from the reading opening, and the distance from the reading opening. Light quantity control values are stored in correspondence with a plurality of sampling positions that are sequentially changed. In actual reading operation, the distance from the reading port to the barcode is measured by any method, and the light amount control value corresponding to the measured distance to the barcode is read and executed. is there.
[0011]
[Problems to be solved by the invention]
However, conventionally, a distance sensor has been used to measure the distance from the reading port to the barcode. For example, an active triangulation or pyroelectric infrared sensor can be used as the distance sensor, but in any case, a process such as irradiating light to the barcode is necessary. It is necessary to deploy a configuration for distance measurement separately from the configuration for reading image data from the computer. In particular, assuming a handy type barcode reader or the like, it is not preferable that a configuration related to a distance sensor be provided near the reading port because this leads to a complicated configuration and an increase in size.
[0012]
The present invention has been made in view of these problems. In a large-depth optical information reading apparatus capable of reading optical information from a reading object located at a position away from a reading port, reading is performed without a separate distance sensor. An object of the present invention is to provide an optical information reading apparatus capable of calculating a distance to a target.
[0013]
[Means for Solving the Problems and Effects of the Invention]
The optical information reader according to claim 1, which has been made to achieve the above object, reads the irradiation light from the light emitting means from the inside of the case to the reading object outside the case through the reading port of the case. An optical information reading device that forms an image of reflected light from an object on a light receiving means inside the case through the reading port and reads an image to be read by the light receiving means, and is disposed at a predetermined reference position. Reference image size storage means for storing the image size of the reference reading object in a state of being imaged on the light receiving means by reflected light from the reference reading object, and the reflected light from the reading object at an arbitrary position. An image size detecting means for detecting an image size of the object to be read in a state of being imaged on the light receiving means; and the reference reading stored in the reference image size storing means. A distance calculating unit that calculates a distance to the reading target at the arbitrary position based on the degree of enlargement or reduction of the image size of the reading target detected by the image size detecting unit with respect to the image size of the capturing target. Features.
[0014]
According to this optical reading apparatus, the reference image size storage means sets the image size of the reference reading object in a state where the image is formed on the light receiving means by the reflected light from the reference reading object arranged at the predetermined reference position. When the image size detecting unit detects the image size of the reading target in a state where the image size detecting unit forms an image on the light receiving unit by the reflected light from the reading target at an arbitrary position, the distance calculating unit stores the reference image size storing unit The distance to the reading target at an arbitrary position is calculated based on the degree of enlargement or reduction of the image size of the reading target detected by the image size detection unit with respect to the image size of the reference reading target stored in.
[0015]
The principle of this distance calculation will be described with reference to FIG. For example, when a barcode Bst, which is an example of a reading target, is arranged at the reading port of an optical reading device, the reflected light from the barcode Bst forms an image on an optical sensor 36 as a light receiving means via an imaging lens 34. To do. In this case, the image size Wst of the barcode Bst formed on the optical sensor 36 is stored as a reference image size. In the actual reading operation, for example, the barcode Bo imaged on the optical sensor 36 when the barcode Bo of the distance calculation target located at the distance L1 from the reading port is read is Wo (<Wst). Suppose that Assuming that the size W of the barcodes Bst and Bo themselves does not change, Wo <Wst is because the barcode Bo for distance calculation is separated from the reading port by the distance L1.
[0016]
In FIG. 9, if the distance from the reading port to the imaging lens 34 is L2, and the distance L3 from the imaging lens 34 to the optical sensor 36, the reference image size Wst uses the size W of the barcode itself. It is expressed as:
Wst = (L3 / L2) W
On the other hand, the image size Wo on the optical sensor 36 corresponding to the barcode Bo at a distance L1 from the reading port is similarly expressed by the following equation using W.
[0017]
Wo = {L3 / (L1 + L2)} W
Eliminating W from these two equations leads to the relationship L2 · Wst = (L1 + L2) Wo, and L1 is expressed by the following equation.
L1 = {(Wst / Wo) −1} L2
Since the distance L2 is a value unique to the apparatus, if Wst and Wo are known, the distance L1 from the reading port of the barcode Bo that is the distance calculation target can be calculated. In other words, the distance to the bar code can be obtained by using the original function of the apparatus for reading image data to be read such as a bar code without using a hardware configuration such as a distance sensor.
[0018]
Conventionally, a distance sensor has been used to measure the distance from the reading port to the barcode. However, since processing such as irradiating light to the barcode is necessary, reading of image data from the barcode is required. It was necessary to deploy a configuration for distance measurement separately from the configuration for the purpose. In particular, assuming a handy type barcode reader or the like, it is not preferable that a configuration related to a distance sensor be provided near the reading port because this leads to a complicated configuration and an increase in size. In this regard, in the case of this apparatus, it is a large-depth optical information reading apparatus that can read optical information from a reading object located at a position away from the reading port, and can be read even without a separate distance sensor. Is very advantageous.
[0019]
As described above, the distance is calculated using the degree of enlargement or reduction of the image size. As the image size, it is conceivable to use the representative width of the image to be read. As the representative width, for example, in the case of a barcode, the portion where the barcode symbol exists, that is, the distance from the start character to the stop character may be used as the representative width. Note that the reading target of this apparatus may be a one-dimensional code such as a barcode or a two-dimensional code. In the case of a two-dimensional code, two vertical and horizontal widths are detected. In that case, for example, a larger width may be used as a representative width.
[0020]
As can be seen from the above description, the reading target of this apparatus is limited to some extent. That is, as a premise for the above distance calculation, the image size of the “reference reading target” when the reference image size Wst is stored and the image size of the “reading target at the time of distance calculation” need to be the same. It is. Therefore, it is very effective in the case of a reading target that has the same standard and a constant size, such as a barcode attached to a mail.
[0021]
In addition, when the reference image size Wst is stored, the “reference position” where the reference reading target is arranged may be a reading port, for example. Although an example was given in the above description of the prior art, since the illuminance distribution changes or the illuminance decreases as the reading target such as a barcode moves away from the reading port, the reading port is used as a reference. It is preferable to calculate the distance.
[0022]
By the way, as the control performed based on the distance calculated without using the distance sensor as described above, for example, light amount control for the light emitting means can be considered. For example, as shown in claim 6, the light amount control value for the light emitting unit when the imaging state of the light receiving unit when the reference reading target is used has an appropriate illuminance distribution in the width direction of the reading port is expressed as a reading port. Are stored in correspondence with a plurality of sampling positions in which the distance from is sequentially changed, a light amount control value corresponding to the distance to the reading target calculated by the distance calculating means is read, and light emission is performed based on the light amount control value The light quantity control for the means is performed.
[0023]
The case where the image forming state in the light receiving means is an ideal illuminance distribution is a state in which the illuminance distribution in the width direction of the reading port is uniform (the amplitude of the reflected light waveform is uniform). As described above, no matter how flat the illuminance distribution of the irradiation light from the light emitting means is, when the reflected light forms an image on the light receiving element through the imaging lens, the COS of the imaging lens. ^Four The amplitude of the reflected light waveform decreases as it goes to the periphery due to the law, MTF characteristics, or the like. Therefore, in order to make the illuminance distribution uniform at the time of image formation on the light receiving means, roughly speaking, the illuminance of the irradiated light that is brighter in the periphery than in the center when viewed in the width direction of the reading port It is necessary to control the light emitting means so that the distribution is obtained.
[0024]
However, simply setting the light emitting means so that the illuminance distribution of the irradiated light is brighter in the periphery than in the center, it is only possible to deal with a barcode to be read at a specific position. That is, the degree to which the amplitude of the reflected light waveform decreases toward the periphery changes as the distance between the reading port and the barcode changes. This is due to the characteristics of the optical system (such as diffraction and the degree of image blur) and the surrounding environment. Therefore, even if the arrangement of the light emitting diodes and the amount of light are adjusted so that an appropriate illuminance distribution is obtained when there is a distance from the reading port to the barcode, the distance between the reading port and the barcode is not If it changes, there is a possibility that the illuminance distribution is not appropriate in that state.
[0025]
Therefore, the light amount control value for the light emitting unit when the imaging state at the light receiving unit is appropriate in the width direction of the reading port when the reading port has a reading target for sampling, the distance α (> 0) from the reading port. The light amount control value when there is a reading target for sampling at a position, the light amount control value when there is a reading target for sampling at a position β (> α) from the reading port, and the distance from the reading port. Light quantity control values are stored in correspondence with a plurality of sampling positions that are sequentially changed.
[0026]
In the actual reading operation, the distance calculating unit measures the distance from the reading port to the reading target, and the control unit stores the light amount control value corresponding to the measured distance to the reading target as the control value storage unit. The light quantity control is performed on the light emitting means based on the light quantity control value. In an actual reading operation, it is assumed that the distance h from the reading port to the reading target is often not equal to the distances α and β at the sampling position. For example, 0 <h ≦ In the case of α, the light amount control value at α may be used, and when α <h ≦ β, the light amount control value at β may be used. Alternatively, the light amount control values at other distances may be obtained by interpolation using the light amount control values at the distances 0, α, and β.
[0027]
The light quantity control value stored in the control value storage means may be stored as a control value of the energy supplied to the light emitting means, or within a time zone in which the light receiving means is in a light receiving state. Alternatively, it may be stored as a control value of the light emission time of the light emitting means.
[0028]
In addition, when the exposure time control for the light receiving means is performed in addition to the light quantity control, the control value storage means has an appropriate amount of light received when the imaging state at the light receiving means is used when the reading target for sampling is used. The exposure time control value for the light receiving means when realized by the above may be stored corresponding to a plurality of sampling positions. In this way, the control unit reads the light amount control value and the exposure time control value corresponding to the distance to the reading target from the control value storage unit, performs light amount control on the light emitting unit based on the light amount control value, and performs exposure time control. The exposure time can be controlled based on the value.
[0029]
If the exposure time of the light receiving means is limited by the shutter, the control value storage means may store the control value for the time for opening the shutter as the exposure time control value.
Further, when the gain control for the amplifying unit is also performed for the light amount control and the exposure time control, the control value storage unit appropriately controls the output from the light receiving unit when the reference reading target is used. The amplification factor corresponding to a plurality of sampling positions is also stored, and the control unit reads the amplification factor corresponding to the calculated distance to the reading target from the control value storage unit and amplifies based on the amplification factor. What is necessary is just to comprise so that the gain control with respect to a means may be performed.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic configuration diagram of an optical information reading device 4 as an embodiment to which the above-described invention is applied.
In the present embodiment, the optical information reader 4 is configured as a so-called bar code reader handy terminal. FIG. 1 is a schematic cross-sectional view of the optical information reader 4, and FIG. 2 is a block diagram of its control system.
[0031]
The optical information reading device 4 includes a case 12, a reading unit 14, a data processing output unit 16, and a power supply unit 18.
A reading unit 14 is disposed inside the front part of the case 12, and a rear part of the case 12 forms a gripping part 20 for an operator to hold with a hand. A reading port 22 that is long in the left and right sides (perpendicular to the paper surface in FIG. 1), that is, long in the width direction, is provided at the lower part of the front portion of the case 12, and a dustproof plate 24 is disposed at the back of the reading port 22. The reading port 22 is closed. This prevents dust from entering the case 12 through the reading port 22. The dust-proof plate 24 can pass at least red light as reading light described below.
[0032]
The reading unit 14 includes an illumination red light emitting diode 26 (corresponding to a light emitting unit), a light emission driving circuit 28, a barcode irradiation lens 30, a reflecting mirror 32, an imaging lens unit 34, and an optical sensor 36 (corresponding to a light receiving unit). It has. When the illumination red light emitting diode 26 emits light by the light emission drive circuit 28, the red light passes through the dust-proof plate 24 and irradiates the barcode 8 outside the case 12. In FIG. 1, the bar arrangement direction of the barcode 8 and the width direction of the reading port 22 are matched, and the barcode 8 is substantially in contact with the reading port 22 as shown by the solid line in FIG. The case where the barcode 8 is irradiated is shown. Of course, as shown by a broken line in FIG. 1, the reading may be performed with the reading opening away from the barcode 8.
[0033]
The red light reflected by the barcode 8 enters the case 12 again from the dust-proof plate 24, is reflected by the reflecting mirror 32, and enters the imaging lens unit 34 incorporating a longitudinally long aperture (not shown). The image of the barcode 8 is displayed on the optical sensor 36 in which the light receiving elements are linearly arranged in a line, and the arrangement direction of each bar and the light reception of the optical sensor 36 through a vertically long aperture and a plurality of imaging lenses. An image is formed in the same direction as the arrangement direction of the elements. The optical sensor 36 that photoelectrically converts and reads the image of the barcode 8 outputs it to the data processing output unit 16 side as an electrical signal representing the pattern of the image.
[0034]
Note that the longitudinal aperture incorporated in the imaging lens unit 34 is disposed closer to the reading port 22 than the imaging lens, and the barcode 8 is in a state where the longitudinal direction thereof coincides with the longitudinal direction of the bar of the barcode 8. Is set to read. In addition, the imaging system including the reflecting mirror 32 and the imaging lens unit 34 has a barcode 8 at least at the position of the reading port 22 and a position several tens of centimeters (for example, 30 to 50 cm) away from the position of the reading port 22. Is configured as a deep imaging system.
[0035]
The optical sensor 36 uses a document reading image pickup device of a facsimile apparatus in which light receiving elements are arranged in a line and the aspect ratio of each light receiving element is approximately “1”.
The data processing output unit 16 in the case 12 includes an amplifier circuit 41, a memory 42 (corresponding to a reference image size storage unit and a control value storage unit), a binarization circuit 43, a microcomputer 44 (control unit) on a substrate 38. And an output circuit 46 to a main unit such as a register or a host computer. When the reading data of the barcode 8 is input from the reading unit 14 via the amplifier circuit 41 and the binarization circuit 43, the data processing output unit 16 decodes the data by the processing of the microcomputer 44. The information represented by the barcode 8 is obtained, and the information is temporarily stored in the memory 42. Next, the information stored in the memory 42 is transmitted to the main unit as a serial signal by the output circuit 46. In the present embodiment, wired communication is used, but wireless communication using light or radio waves may be used.
[0036]
In addition, a buzzer device 48 is provided at a position where the reading unit 14 is accommodated at a position that does not affect the optical path, and the buzzer device 48 is sounded when the microcomputer 8 successfully decodes the barcode 8. ing.
The power supply unit 18 houses a battery 18a as a power supply.
[0037]
The microcomputer 44 includes a known CPU, ROM, RAM, I / O, and the like, and executes necessary processing as the data processing output unit 16 described above.
Here, an optical arrangement state is schematically shown in FIG. The illumination red light-emitting diode 26 described in FIG. 1 is actually composed of four illumination red light-emitting diodes 26a, 26b, 26c, and 26d as shown in FIG. The barcode 8 existing outside the case 12 is irradiated from the reading port 22 through the optical lens 30.
[0038]
The red light emitting diodes 26a, 26b, 26c, and 26d for illumination are arranged side by side in the width direction of the reading port, but the both ends of the reading port 22 are denser than the central portion. This is because the illumination light from the red light emitting diodes 26a, 26b, 26c, and 26d for illumination increases the illuminance at the peripheral portion rather than the central portion on the barcode 8 to be read. As shown in FIG. 3 (b), the illumination direction of the illumination red light emitting diodes 26a, 26b, 26c, and 26d is inclined toward both ends of the reading port 22 to increase the illuminance at the peripheral portion of the reading target. It is possible to devise such a technique.
[0039]
As described above, the illumination light from the red light emitting diodes 26a, 26b, 26c, and 26d for illumination increases the illuminance at the peripheral portion rather than the central portion on the barcode 8 to be read. No matter how flat, the COS of the imaging lens unit 34 is reflected when the reflected light forms an image on the optical sensor 36 through the imaging lens unit 34. ^Four This is to cope with the decrease in the amplitude of the reflected light waveform as it goes to the periphery as shown in FIG.
[0040]
However, these can be dealt with only when a barcode to be read exists at a specific position. That is, the degree to which the amplitude of the reflected light waveform decreases toward the periphery changes as the distance between the reading port 22 and the barcode 8 changes. Therefore, for example, as shown by the broken line in FIG. 1, even if the adjustment is performed with reference to the case where the barcode 8 is irradiated with the barcode 8 substantially in contact with the reading port 22 as indicated by the solid line in FIG. In the state where the reading port 22 is separated from the barcode 8, it becomes inappropriate. For this reason, in a state where the reading port 22 is separated from the barcode 8, it is necessary to obtain an appropriate illuminance distribution of illumination light corresponding to the distance.
[0041]
In view of this point, in the present embodiment, the light emission drive circuit 28 is configured so that the amount of light of each of the illumination red light emitting diodes 26a, 26b, 26c, and 26d can be controlled. The light emission drive circuit 28 is, for example, as shown in FIG. 5. Here, a limiting resistor R is provided between the illumination red light emitting diode 26a (26b, 26c, 26d) and the power source Vcc, and the illumination red light emission. A transistor TR is connected to the low potential side of the diode 26a (26b, 26c, 26d). These limiting resistor R and transistor TR correspond to the light emission drive circuit 28. When the illumination red light emitting diode 26a (26b, 26c, 26d) emits light, the microcomputer 44 outputs a light emission signal P to the transistor TR, whereby a current is supplied to the illumination red light emitting diode 26a (26b, 26c, 26d). Flows and emits light.
[0042]
In the light quantity control of each of the illumination red light emitting diodes 26a, 26b, 26c, and 26d, for example, if the light quantities of the four illumination red light emitting diodes 26a, 26b, 26c, and 26d are made equal, the reflected light from the barcode 8 forms an image. If the output V1 at the peripheral portion is smaller than the output V2 at the central portion in the region D, for example, the light quantity of the two red light emitting diodes 26a and 26d for illumination at both ends is set to the two central illumination outputs. The control is such that the output V3 at the peripheral portion is substantially the same as the output V4 at the central portion, as shown in FIG. 4B, larger than the red light emitting diodes 26b and 26c. In this case, if the exposure time of the light receiving element in the optical sensor 36 is T1 shown in FIG. 6A, the central portion of the barcode 8 in FIG. 4 is illuminated within the exposure time T1, for example. The two red light emitting diodes 26b, 26c for lighting are turned on for the lighting time T2 shown in FIG. 6B and then turned off. In this way, in the light receiving element in the optical sensor 36, the light receiving element corresponding to the peripheral part can accumulate light longer than the light receiving element corresponding to the central part by the time T1-T2, so this lighting time T2 As shown in FIG. 4B, it is possible to make the output V3 at the peripheral portion approximately the same as the output V4 at the central portion.
[0043]
Further, if the output from the optical sensor 36 is too small, the binarization circuit 43 does not appropriately binarize, and as a result, the information on the barcode 8 cannot be read properly. Control is performed to increase the exposure time T1. When this exposure time T1 is lengthened, the light receiving time of the light receiving element of the optical sensor 36 is lengthened, and the amount of accumulated charge is increased accordingly, so that the output level from the optical sensor 36 is generally increased. As described above, within the predetermined exposure time T1, the two illumination red light emitting diodes 26b and 26c for illuminating the central portion of the barcode 8 are lit for the lighting time T2 shown in FIG. 6B. Therefore, if the exposure time T1 is increased, the lighting time T2 is also increased at the same rate.
[0044]
These controls are executed based on control values stored in the memory 42. Specifically, the red light emitting diodes 26a, 26b, 26c, and 26d for illumination when the imaging state of the optical sensor 36 when the reading target for sampling is an appropriate illuminance distribution in the width direction of the reading port 22 are described. A plurality of sampling positions in which the distance L from the reading port 22 is sequentially changed for the light amount control value (lighting time T2 in this case) and the exposure time T1 when the output level from the optical sensor 36 is an appropriate value. In the actual reading operation, the lighting time T2 corresponding to the distance from the reading port 22 to the barcode 8 is read from the memory 42, and control based on the control value is performed. .
[0045]
Therefore, in order to execute such control, it is necessary to obtain the distance from the reading port 22 to the barcode 8 during the actual reading operation. In the present embodiment, the distance is measured by a distance sensor or the like. Instead, the calculation is performed using image data read based on the reflected light from the barcode 8 that is the actual reading target.
[0046]
Although the principle of this distance calculation has been described with reference to FIG. 9, it will be described again based on the configuration of the present embodiment. In the optical information reading device 4 of the present embodiment, as shown in FIG. 7, the distance from the reading port 22 to the imaging lens unit 34 is L2, and the distance from the imaging lens unit 34 to the optical sensor 36 is L3. These values are known. The distance L1 from the reading port 22 to the barcode 8 is calculated.
[0047]
As can be seen from FIG. 9, the width (reference image width) Wst of the image formed on the optical sensor 36 when the reference barcode Bst is arranged at the reading port 22 and the position at a distance L1 from the reading port 22. If the width of the image formed on the optical sensor 36 when a certain barcode Bo is read (distance calculation target image width) Wo is the same as the width W of both barcodes Bst and Bo itself, Wo <Wst. This is because the barcode Bo is separated from the reading port 22 by a distance L1.
[0048]
These two image widths Wst and Wo are expressed by the following equation using the width W of the barcode itself.
Wst = (L3 / L2) W
Wo = {L3 / (L1 + L2)} W
Eliminating W from these two equations leads to the relationship L2 · Wst = (L1 + L2) Wo, and L1 is expressed by the following equation.
[0049]
L1 = {(Wst / Wo) −1} L2
Since the distance L2 is a value unique to the apparatus, if Wst and Wo are known, the distance L1 from the reading port 22 to the barcode Bo can be calculated. That is, the distance to the bar code can be obtained by utilizing the original function of reading the image data of the bar code without using a hardware configuration such as a distance sensor.
[0050]
In the present embodiment, a sampling label as shown in FIG. 8 is used as the reference barcode Bst in FIG. The width W1 of the white bar and the width W2 of the black bar in this sampling label are configured at equal intervals of, for example, 1 mm or more where the influence of the characteristics of the optical system such as diffraction and the degree of image blur is small. In addition, a gap W smaller than the width of the reading port 22 is formed by two thick bars (in order to distinguish them from normal bars, it is preferably twice or more of W1 and W2).
[0051]
Next, processing for storing the above-described reference image width Wst and various control values will be described. This storage processing is performed at the time of factory shipment, for example. Since this is executed by the microcomputer 44, the process will be described with reference to the flowchart of FIG.
[0052]
When the process is started, it is first determined whether or not a sampling label (see FIG. 8) on which the reference barcode Bst (see FIG. 9) is printed is arranged in the reading port 22 (S110). For example, the operator who performs the initial setting may give an instruction by pressing an operation button (not shown). In this case, the setting is completed when the operation button is pressed (S110: YES), and the process proceeds to S120. To do.
[0053]
In S120, the reference image width Wst is calculated. This is because the output from the optical sensor 36 based on the reflected light from the reference bar code Bst is amplified by the amplifier circuit 41, the amplified signal is binarized by the binarizing circuit 43, and the binarized signal is converted into the binarized signal. This is carried out by taking in the microcomputer 44 and calculating the interval W between the thick bars (see FIG. 9) of the reference bar code Bst described above. The calculated interval W is the reference image width Wst of the reference barcode Bst imaged on the optical sensor 36.
[0054]
Then, the calculated reference image width Wst and known L2 and L3 are stored in the memory 42 (S130).
Thereafter, it is determined whether a sampling label (see FIG. 8) is arranged at a predetermined sampling position (S140). Similarly to the processing of S110 described above, for example, an operator who performs initial setting may give an instruction by pressing an operation button (not shown). In this case, setting is completed when the operation button is pressed ( (S140: YES), the process proceeds to S150. In S150, the exposure time T1 and the amplification factor corresponding to the sampling position are stored.
[0055]
First, with respect to the sampling position, the sampling position is appropriately set up to a predetermined maximum value max including the distance 0 from the reading port 22, that is, the case where the sampling label is arranged in the reading port 22, and the sampling label is set. May be sequentially moved and instructed to complete the setting with the above-described operation button or the like each time.
[0056]
In this case, for the exposure time T1 and the amplification factor, it is conceivable that values necessary at the sampling position are set in advance and given from the outside. Of course, an appropriate value may be selected by determining whether or not decoding can actually be performed while changing the control value as in a lighting time T2 to be described later, but here it is given from the outside for simplicity.
[0057]
Next, in S160, the lighting time T2 is controlled. As described above, the illumination red light emitting diodes 26a, 26b, 26c, and 26d are turned on for the lighting time T2 shown in FIG. 6B and then turned off within the exposure time T1 of the light receiving element in the optical sensor 36. Control is executed during reading. For example, two illumination red light emitting diodes 26b and 26c for illuminating the central portion of the barcode 8 are controlled to be turned off after being lit for a lighting time T2, and the illumination red light emitting diodes 26a and 26d at both ends are controlled. Since the light receiving element in the optical sensor 36 can accumulate light longer than the light receiving element corresponding to the central part by the time T1-T2, the light receiving element in the optical sensor 36 can accumulate light for a longer time. By adjusting T2, as shown in FIG. 4B, it is possible to make the output V3 at the peripheral portion substantially the same as the output V4 at the central portion.
[0058]
Therefore, in this S160, several candidates for the lighting time T2 are prepared for each of the lighting red light emitting diodes 26a, 26b, 26c, and 26d, and finally, a combination of these is set.
Since it is necessary to determine whether or not this setting is appropriate, it is determined whether or not decoding is possible in S170. Specifically, the illumination operation is performed at the exposure time T1, the amplification factor, and the set lighting time T2 described above, and an output from the optical sensor 36 based on the reflected light from the reference barcode Bst by the illumination is an amplification circuit. Amplified at 41, the amplified signal is binarized by the binarization circuit 43, the binarized signal is decoded by the microcomputer 44, and it is determined whether or not it has been properly decoded.
[0059]
If decoding is possible (S170: YES), the lighting time set in S160 is an appropriate value, and the lighting time T2 is stored in S180. If decoding is not possible (S170: NO), S160 is stored. Return to and set another combination.
[0060]
Thus, when the processing up to S180 is completed, as shown in the control value table in FIG. 11, the lighting red light emitting diodes 26a, 26b, 26c, and 26d are turned on corresponding to the distance L1 of a certain sampling position. Control values such as time T2, exposure time T1, and amplification factor are stored in the memory 42.
Then, in S190, it is determined whether or not the storage of the control values corresponding to all the sampling positions has been completed. If it has been completed (S190: YES), this process is terminated, but if not yet completed (S190: NO), the process returns to S140, and the control value storing process (S150 to S180) at another sampling position is executed.
[0061]
When the processing of FIG. 10 is completed, the control value table of FIG. 11 is set corresponding to the distances L1 of all sampling positions.
Next, distance calculation and data capture processing in an actual reading operation will be described with reference to the flowchart of FIG.
[0062]
When the process is started, first, a distance calculation target image width Wo is calculated (S210). This is because the amplification circuit 41 amplifies the output from the optical sensor 36 based on the reflected light from the barcode Bo for distance calculation, and the binarization circuit 43 binarizes the amplified signal. The computer 44 captures the digitized signal, and calculates the portion where the barcode symbol exists, that is, the distance from the start character to the stop character as the distance calculation target image width Wo.
[0063]
Then, using this distance calculation target image width Wo, a distance L1 from the reading port 22 of this distance calculation target barcode Bo is calculated (S220). As described above, the distance L1 can be expressed as L1 = {(Wst / Wo) −1} L2. Since the distance L2 is a fixed value stored in S130 of FIG. 10 and the reference image width Wst is also stored in S130 of FIG. 10, the distance calculation target image width Wo calculated in S210. Can be used to calculate the distance L1.
[0064]
In subsequent S230, the control value corresponding to the distance L1 calculated in S220 is read from the control value table (see FIG. 11) in the memory 42. In S240, illumination control is performed using the read control value. Perform data capture. That is, the illumination operation is performed with the lighting time T2 corresponding to each of the red light emitting diodes 26a, 26b, 26c, and 26d for illumination shown in the control value table of FIG. 11, the exposure time T1 in the optical sensor 36, and the amplification factor in the amplifier circuit 41. The amplification circuit 41 amplifies the output from the optical sensor 36 based on the reflected light, binarizes the amplified signal by the binarization circuit 43, and decodes the binarized signal by the microcomputer 44. Thus, a reading operation is performed.
[0065]
As described above, according to the optical information reading device 4 of the present embodiment, the reading port 22 is utilized by utilizing the original function of reading the image data of the barcode 8 without using a hardware configuration such as a distance sensor. To the bar code 8 can be obtained. Conventionally, a distance sensor has been used to measure the distance from the reading port 22 to the barcode 8, but since a process such as irradiating the barcode 8 with light rays is necessary, an image from the barcode 8 is used. It was necessary to deploy a configuration for distance measurement separately from the configuration for reading data. In particular, assuming a handy type barcode reader or the like, it is not preferable that a configuration related to the distance sensor be provided near the reading port 22 because this leads to a complicated configuration and an increase in size. In this respect, in the case of the present optical information reading device 4, it is a large depth optical information reading device that can read optical information from the barcode 8 located at a position away from the reading port 22, and has a separate distance sensor. This is very advantageous because the distance to the reading target can be calculated without the need.
[0066]
As can be understood from the above description, the reading target of the optical information reading device 4 is limited to some extent. That is, the above-described principle of distance calculation is based on the distance W between the thick bars (see FIG. 8) of the reference bar code Bst (see FIG. 9) and the distance calculation object, that is, the reading object when the reference image width Wst is stored. It is assumed that the width W of the barcode Bo (see FIG. 9) itself is the same. Therefore, it is very effective in the case of a reading target having the same standard and a constant size, such as a barcode 8 attached to a mail.
[0067]
As described above, the present invention is not limited to such an embodiment, and can be implemented in various forms without departing from the gist of the present invention.
The optical information reader 4 according to the above-described embodiment is a reader for the barcode 8, but the two-dimensional code can be similarly configured and produces the same effect.
[0068]
In the above embodiment, as the image size when the distance L1 is calculated using the degree of enlargement or reduction of the image size, a representative of the barcode image such as the reference image width Wst and the distance calculation target image width Wo. The width. This is because the reading target is a one-dimensional code called a barcode. For example, when a two-dimensional code is assumed as a reading target, two widths, a vertical width and a horizontal width, are detected. In some cases, for example, a contrivance such as setting the larger width as the representative width may be used.
[0069]
In addition, although the “reference position” where the reference bar code Bst is arranged when the reference image width Wst is stored is the reading port 22 in the above-described embodiment, it can be similarly realized even at another position. However, since the illuminance distribution changes or the illuminance decreases as the barcode 8 moves away from the reading port 22, it is preferable to calculate the distance from the reading port 22 as a reference.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an optical information reading apparatus as one embodiment.
FIG. 2 is a block diagram of a control system of the optical information reading apparatus.
FIG. 3 is an explanatory diagram showing an arrangement of red light emitting diodes for illumination of the optical information reading device.
FIG. 4 is an explanatory diagram of a reflected light waveform imaged on an optical sensor.
FIG. 5 is a circuit diagram showing a luminance adjustment mechanism of a red light emitting diode for illumination of the optical information reader.
FIG. 6 is a time chart showing an exposure time T1 and a lighting time T2 of the illumination red light emitting diode in the optical sensor.
FIG. 7 is an explanatory diagram for illustrating a distance calculation principle.
FIG. 8 is an explanatory diagram of a sampling label.
FIG. 9 is an explanatory diagram for illustrating a distance calculation principle.
FIG. 10 is a flowchart showing processing for storing a reference image width Wst and various control values.
FIG. 11 is an explanatory diagram of a control value table.
FIG. 12 is a flowchart showing distance calculation and data capture processing in an actual reading operation.
[Explanation of symbols]
4 ... Optical information reader 8 ... Bar code 12 ... Case
14 ... Reading unit 16 ... Data processing output unit 18 ... Power supply unit
18a ... battery 20 ... grip 22 ... reading port
24 ... Dustproof plate
26 (26a, 26b, 26c, 26d) ... red light emitting diode for illumination
28 ... Light emission drive circuit 30 ... Barcode irradiation lens
32 ... Reflector 34 ... Imaging lens 36 ... Optical sensor
38 ... Substrate 41 ... Amplification circuit part 42 ... Memory
43 ... Binary circuit 44 ... Microcomputer 46 ... Output circuit
48 ... Buzzer device
Bst ... Standard barcode Bo ... Distance calculation target barcode
Wst: Reference image width Wo: Distance calculation target image width
L1: Distance from the reading port 22 to the distance calculation target barcode Bo
L2: Distance from the reading port 22 to the imaging lens unit 34
L3: Distance from the imaging lens unit 34 to the optical sensor 36

Claims (10)

Irradiation light from the light emitting means is irradiated from the inside of the case to the reading target outside the case through the reading opening of the case, thereby forming an image of reflected light from the reading target on the light receiving means inside the case via the reading opening. An optical information reader for reading an image to be read by the light receiving means,
Reference image size storage means for storing the image size of the reference reading object in a state of being imaged on the light receiving means by reflected light from a reference reading object arranged at a predetermined reference position;
Image size detection means for detecting the image size of the reading object in a state of being imaged on the light receiving means by reflected light from the reading object at an arbitrary position;
Based on the degree of enlargement or reduction of the image size of the reading target detected by the image size detection unit with respect to the image size of the reference reading target stored in the reference image size storage unit, the reading target at the arbitrary position is reached Distance calculating means for calculating the distance of;
An optical reading device comprising: The optical information reading apparatus according to claim 1, wherein the image size is a representative width of the image to be read. The predetermined reference position is the reading port;
The optical information reading apparatus according to claim 1, wherein the distance calculating unit is configured to calculate a distance from the reading port to the reading target at the arbitrary position. The optical information reading apparatus according to claim 1, wherein the reading target is a barcode. The optical information reading apparatus according to claim 1, wherein the reading target is a two-dimensional code. When the reference reading target is used, the light amount control value for the light emitting means when the imaging state of the light receiving means becomes an appropriate illuminance distribution in the width direction of the reading opening, and the distance from the reading opening are sequentially set. Control value storage means storing corresponding to a plurality of changed sampling positions;
Control means for reading out the light quantity control value corresponding to the distance to the reading target calculated by the distance calculating means from the control value storage means, and performing light quantity control on the light emitting means based on the light quantity control value;
The optical information reader according to claim 1, comprising: The optical information reading apparatus according to claim 6, wherein the light amount control value stored in the control value storage unit is a control value of energy supplied to the light emitting unit. The light quantity control value stored in the control value storage means is a control value of a light emission time of the light emitting means within a time zone in which the light receiving means is in a light receiving state. 7. The optical information reading device according to 6. The control value storage means also includes an exposure time control value for the light receiving means when the imaging state of the light receiving means when the reference reading target is used is realized with an appropriate amount of received light. Remembers corresponding to the position,
The control unit is also configured to read out the exposure time control value corresponding to the calculated distance to the reading target from the control value storage unit and perform exposure time control for the light receiving unit based on the exposure time control value. 9. The optical information reading apparatus according to claim 6, wherein the optical information reading apparatus is provided. Furthermore, an amplification means for increasing the amplification factor of the output waveform of the light receiving means is provided,
The control value storage means also stores an appropriate amplification factor in the amplification means for the output from the light receiving means when the reference reading target is used, corresponding to the plurality of sampling positions,
The control unit is also configured to read out the amplification factor corresponding to the calculated distance to the reading target from the control value storage unit and perform amplification factor control on the amplification unit based on the amplification factor. An optical information reader according to claim 6.

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