JP2751086B2 - Lens focal length adjustment method and barcode reading method using the same method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates relates to a barcode reading method <br/>, in bar code scanner, the distance between the bar code label to allow the reading of at all times the optimum conditions be how set About the method.

[0002]

2. Description of the Related Art Conventionally, a high-end camera has a built-in automatic focusing device, which measures a distance to a subject, a base line long parallax triangle and an image sharpness, and moves a lens based on the measured value. This automatically adjusts the focus.
For the lens movement, a motor drive system or an air drive system is adopted, and a motor or air actuator is actuated by a predetermined amount with a control value obtained based on a measured value to set a lens position. I have.

However, incorporating a motor or the like has the drawback that the weight increases and the mechanism becomes complicated, resulting in an increase in the size of the apparatus. Further, since the focus adjustment needs to be performed in a very short time, the driving speed of the motor and the air actuator, the inertia of the lens system, and the like must be taken into consideration, and many technical problems arise. As a result, the lens drive system can be made as small as possible
Piezoelectric elements are used to achieve high-speed focus adjustment.
To adjust the focal length of the soft lens by the deformation force of
Various formulas have been proposed (for example, JP-A-60-144703,
(Japanese Utility Model Application Laid-Open No. 56-110403, JP-A-1-140118).

[0004] On the other hand, a bar code scanner belonging to an optical device like a camera is also provided with an objective lens system for imaging, but there is no one having a function of adjusting the focal length. This is because, when reading with a barcode scanner, the operator often keeps the barcode seal surface and the scanner at a substantially constant distance at all times and reads the barcode. It is based on the premise that the bar / space width can be read within the depth of focus without adjustment.

However, in a handy type bar code scanner or the like, an operator does not always read at a fixed distance, and in an automatic sorting system of a transported article using a bar code or the like, the size of the transported article and the belt line are not always used. The distance between the barcode scanner and the barcode seal attached to the conveyed article may greatly vary depending on the mounting position in the above. As a result, light reflected from the barcode element forms an image on the light receiving element surface outside the range of the depth of focus, and reading errors or inability to read frequently occur due to the incomplete image formation.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention
Focus adjustment method combining piezoelectric element and soft lens
Focusing on high-speed responsiveness and high-precision, stable operation functions, this product was created with the aim of providing a method for effectively eliminating reading errors caused by image formation outside the depth of focus range found in conventional barcode scanners. Was done.

[0007]

According to a first aspect of the invention of the present application, Les
The bar code symbol is scanned by the
The reflected light from the vol surface is collected by the objective lens system to the photoelectric converter.
A bar code scanner for reading bar code information , the objective lens system is deformed by the urging force of a piezoelectric element.
With a soft lens interposed, the piezoelectric element
A selective setting voltage is applied to the electrodes provided to
A focal length adjusting means for adjusting the focal length of the objective lens system by deforming the lens, changing a voltage value applied to the piezoelectric element for each scanning in a barcode symbol scanning process for a plurality of initial times, Before every scan
A first procedure for detecting a difference value between the bar read signal and the space read signal obtained from the photoelectric conversion unit , and storing the detected value in association with the applied voltage value, and among the difference values stored in the first procedure, The second procedure to determine the maximum value of the, the third procedure of applying an applied voltage value corresponding to the maximum value determined in the second procedure to the piezoelectric element, and bar code symbol scanning after applying the voltage in the third procedure According to a barcode reading method, a fourth procedure for processing a signal obtained from the photoelectric conversion unit as a normal read signal is executed.

[0008] A second invention is a bar code synth using laser light.
The bol is scanned and the reflected light from the barcode symbol surface is
The lens system focuses the light on the photoelectric converter and reads the barcode information.
In the bar code scanner, the objective lens system is used.
Softlens that can be deformed by the urging force of the piezoelectric element
To set the electrodes provided on the piezoelectric element selectively.
By applying a voltage to deform the soft lens,
Ri is provided the focal distance adjusting means for adjusting the focal length of the objective lens system, a bar code symbol scanning process over the initial several times by changing the voltage applied to the piezoelectric element in each time of scanning, each time the scan detects a read signal value of Kwai et Ttozon obtained from the photoelectric conversion unit, a first procedure for storing in correspondence with the detected value to the applied voltage value,
A second procedure for finding the maximum value among the detection values stored in the first procedure, a third procedure for applying an applied voltage value corresponding to the maximum value found in the second procedure to the piezoelectric element, and a third procedure. The photoelectric conversion is performed by scanning a barcode symbol after applying a voltage.
A barcode reading method, characterized by executing a fourth procedure of processing a signal obtained from the section as a normal read signal. And the first and second inventions
The soft urging force of the piezoelectric element in the focal length adjusting means
As a method of deforming the lens, the end face side of the hollow cylinder
Formed a number of notch slits from the
Peripheral edge of soft lens on inner peripheral side of comb-shaped part of electronic element molded body
And select the electrodes on the front and back of each beam in the comb.
Applying a set voltage to bend each beam of the comb
It is desirable to adopt a method that deforms soft lenses
Good.

[0009]

[0010]

[0011]

[Action]

Regarding the first invention: When a voltage is applied to a piezoelectric element, a deformation corresponding to the voltage value is caused. The deformation amount is very small but very stable with respect to the voltage value, a strong force can be supplied to the load, and the deformation response speed is extremely fast. Therefore, when the soft lens is deformed by the deformation urging force, the focal length of the objective lens system including the soft lens can be quickly changed with high accuracy, and the focal length can be changed by selectively setting the voltage value. It can be adjusted freely.

Here, as the soft lens, a soft convex / concave lens made entirely of a transparent resin, or a lens formed by enclosing a transparent liquid having a relatively high refractive index in a transparent resin film and molding it into a lens shape can be used. The objective lens system includes a soft lens and a biconvex lens or a combination of the soft lens and a biconcave lens / biconvex lens, and the focal length of the objective lens system changes due to the bending of the soft lens.

[0013]

By the way, generally, in the reading of the bar code is scanned a number of times the bar code symbol at a scan rate of approximately per 100 to 700 times, ensure that the data obtained in each scan is being read at a predetermined accuracy And process the data. Also, from an optical point of view, when the relative difference between the bar and space read signals is maximized, the focal length of the objective lens system is optimized, and the reflected light of the bar code symbol is reflected on the light receiving element surface. Is the clearest image. In the present invention, the initial multiple scans in the multiple scans are used for focus adjustment. In the first procedure, the barcode symbol is read by changing the voltage value applied to the piezoelectric element for each scan in the initial multiple scanning steps and sequentially changing the focal length of the objective lens system. Thereby, the correspondence between the applied voltage value and the relative difference between the bar and space read signals is obtained for each scan, and this is stored. In the second procedure, the maximum value of the difference values obtained for each of the scans is obtained, and the corresponding applied voltage (the voltage value in the optimal imaging state) is set. Then, in a third procedure, the set voltage value is applied to the piezoelectric element, and in a fourth procedure, a signal obtained by barcode symbol scanning after the application of the set voltage is captured and processed. Therefore, the scanning signal processed in the fourth procedure is a scanning signal read in the optimal image forming state.

[0015] The second invention; Utilizing Kwai et Ttozon in a bar code label, can be regarded as the optimum state of the focal length when the read signal of the same zone has the maximum value. In the present invention, sets handle, the first invention and the applied voltage by the same procedure of the read signal of Kwai et Ttozon just before reading the bar code symbol as a reference value. Therefore, in order but will be similar to the first invention in the fourth procedure can process the signal read by the optimum imaging state, to control the reference value only the maximum value of the read signal of Kauai et Ttozon This invention Quick control becomes possible. Soshi
And a focal length adjusting means according to the first and second inventions.
Then, as described above, the soft lens is
Holding by the molded element, and
To bend each beam of the comb,
Or flex outward to compress or stretch around the soft lens
You. As a result, the soft
The curvature of the front and back of the soft lens changes, causing optical distortion.
Focus of objective lens system including soft lens without causing
The distance can be adjusted.

[0016]

【Example】

FIG. 1 shows a sectional view of a lens focal length adjusting mechanism in a barcode scanner provided with an objective lens and a control system circuit diagram thereof. In the same figure, reference numeral 1 denotes a piezoelectric element molded body, which has a hollow cylindrical shape having a fixing flange portion, and has a number of notch slits 2 formed at regular intervals from the front end surface thereof. The shape part 3 is comprised. Then, the notch slit 2 of the comb-shaped portion 3
Electrodes 5 and 6 on which copper foil is deposited are provided on the front and back surfaces of each beam 4 divided by. On the other hand, reference numeral 7 denotes a concave-convex soft lens made of a transparent resin, which is adhered to the inner peripheral surface on the tip side of each beam 4 formed in the piezoelectric element molded body 1 in a state where the peripheral edge thereof is fitted and grasped. I have. A rigid biconvex lens 8 is attached to the rear end opening side of the piezoelectric element molded body 1, and an objective lens system is configured by a combination of the soft lens 7 and the biconvex lens 8.

Further, in this bar code scanner, a half mirror 9 is provided behind the piezoelectric element molded body 1, and light incident through the objective lens system is transmitted through the half mirror 9 and a phototransistor is provided. The reflected light from the half mirror 9 is incident on the pin photodiode 11. The phototransistor 10 and the pin photodiode 11 are arranged so that the optical distance between their light receiving surface and the soft lens 7 is the same. Incidentally, the objective lens system may be provided with a monochromatic filter lens or the like in addition to the soft lens 7 and the biconvex lens 8, and in this case, the same optical distance is ensured.

The operation of the bar code scanner when reading a bar code will be described below with reference to the flowchart of FIG. First, when there is a reading start instruction from the operation unit 12, the laser beam scanning control unit 1
3 activates the laser light generator 14 to generate laser light, and activates the motor 15 to rotate the polygon mirror 15a. Here, the laser light is converged by the condenser lens 16, reflected by the polygon mirror 15a, further reflected by the plane mirror 17, and irradiated while scanning the surface of the bar code seal 18. Then, by the scanning of the laser beam, the reflected light reflected on the surface of the bar code seal 18 is incident on the objective lens system of the piezoelectric element molded body 1 which has been opposed to the bar code seal 18 in advance, and is condensed. The reflected light passes through the half mirror 9 and enters the phototransistor 10.

In this state, the data processing unit 20 operates based on the control program at the start of scanning, and the D / A converter 21
The voltage control circuit 22 causes the voltage V1 to be applied to the electrodes 5 and 6 of the piezoelectric element molded body 1 by the D / A-converted signal (S1, S1).
2). Then, the phototransistor 10 performs photoelectric conversion of the incident light in synchronization with one irradiation scan of the laser light, and outputs a read voltage to the light receiving circuit 23 (S3).
In this case, the light receiving circuit 23 amplifies the reading voltage and outputs the amplified reading voltage to the PP detection circuit 24 at the next stage. The output voltage becomes an analog waveform corresponding to the bar and space of the barcode symbol. That is, the output becomes smaller at the time of bar scanning and becomes larger at the time of space scanning.
This is output to the P detection circuit 24.

Here, the PP detection circuit 24 detects the peak-to-peak value (PP value) from the output waveform (S4). That is, the relative difference between the voltage value at the time of reading the space and the voltage value at the time of reading the bar is obtained. Then, the PP value is immediately converted to digital data by the A / D converter 25 and taken into the data processing unit 20, and the data processing unit 20 converts the value into the applied voltage data V1 (or the applied voltage sequence). Data) is saved in the internal memory (S5).

Thereafter, in this bar code scanner, the above steps S2 to S5 are performed m times (for example, 20 times) while sequentially changing the voltage applied to the electrodes 5 and 6 of the piezoelectric element molded body 1.
It is repeatedly executed, and each time, the PP value corresponding to each applied voltage data Vi is saved in the built-in memory of the data processing unit 20 (S6, S7 → S2). The respective voltage values V1 to Vm applied in the above-described repetition procedure are due to the fact that those voltages are applied to the electrodes 5 and 6 and the beams 4 of the piezoelectric molded body 1 bend in the centrifugal direction or the centrifugal direction. It is set within the range in which the soft lens 7 can be deformed, and is applied while gradually increasing or decreasing in each repetition process of m times.

By the way, if the distance a between the surface of the bar code seal 18 and the objective lens system including the soft lens 7,
The relationship between the optical distance b between the objective lens system and the phototransistor 10 and the focal length f of the objective lens system is (1/1).
a) + (1 / b) = 1 / f = 2 · (n−1) · (1 /
If r) , the reflected light of the barcode symbol forms an image on the phototransistor 10 with the maximum illuminance difference between the bar and the space. Here, n is the refractive index of the lens when the objective lens system is assumed to be one lens, and r is the radius of curvature of the surface of the assumed lens.

Therefore, the data processing unit 20 immediately compares the m PP values saved in the built-in memory and obtains the maximum PP value among the m PP values when m scans have been completed ( S6 → S8). The applied voltage data saved corresponding to the maximum PP value is used to optimally set the focal length f of the objective lens system with respect to the distance a on the basis of the above equation (1). Is reflected at an optical distance b from the objective lens system.

Based on this principle, the data processing section 20 reads out the applied voltage data corresponding to the obtained maximum PP value and outputs it to the D / A converter 21. Is applied to the electrodes 5 and 6 of the piezoelectric element molded body 1 (S9). That is,
At the point in time when the scanning for m times is completed, the objective lens system is controlled such that the reflected light of the barcode symbol is incident on the light receiving surface of the phototransistor 10 in an optimally formed state. At this stage, if a procedure for further correcting the applied voltage value is provided in consideration of the fact that the piezoelectric element molded body 1 has a constant impedance, the optimum imaging state can be quickly realized. The above control process is performed at 100 to 70 per second.
Although it is executed in the scanning process of zero times, the data processing time is extremely short because the data can be saved and a simple comparison operation can be performed, and it can be sufficiently executed within the time of continuous continuous scanning.

When the focal length f of the objective lens system including the soft lens 7 is adjusted in this way, the data processing unit 20 sets the read ready mode, and sets the pin photodiode 11 and the A / D converter 26 to After the signal is turned ON, the read signal of the barcode symbol after the (m + 1) th scanning which is continuously scanned is transmitted from the pin photodiode 11 to the A.
Fetched into the data processing unit 20 via the / D converter 26,
The processed data is transmitted to the host computer (not shown) (S10). In this continuous scanning, since the optical distance between the objective lens system, the phototransistor 10 and the pin photodiode 11 is the same,
The reflected light of the bar / space of the bar code symbol clearly forms an image on the light receiving surface of the pin photodiode 11, and the bar without the reading error is always present regardless of the distance between the bar code scanner and the bar code seal. Code scanning can be performed. In other words, the range in which the barcode can be read by the barcode scanner is restricted by the relationship with the depth of focus of the objective lens system. However, according to this embodiment, the range can be significantly increased, Even if the distance between the bar code scanner and the bar code seal is set too small or too large, it is possible to always read accurately.

In this embodiment, the input phototransistor 10 in the control process is interposed with the half mirror 9 interposed.
And a pin photodiode 11 for data input during the reading process are provided separately, but only the pin phototransistor (10) is provided as a light receiving element without interposing the half mirror 9, and the PP detection circuit 24 is provided. In the control process, P-
When the A / D converter 26 is set to the P detection mode and controlled to switch to the through mode in the data reading process,
The / D converter 25 can also be used in common, and the number of parts can be reduced. In this case, the attenuation of the amount of light incident on the light receiving element can be reduced.

Embodiment B: This embodiment also relates to a bar code scanner provided with an objective lens, and the lens focal length adjusting mechanism and its control system circuit have substantially the same configuration as that of the above-described embodiment A. I have. However, in this embodiment, different procedures for the focal length control of the objective lens system, in order to set the optimum voltage value based on the reflected light of the Kwai et Ttozon 18a of the bar code label 18, in FIG. 1 P- The P detection circuit 24 is a maximum voltage detection circuit.

Hereinafter, the operation when reading a barcode in this embodiment will be described with reference to the flowchart of FIG. The operation procedure of S11 to S17 is a procedure corresponding to S1 to S7 in the embodiment A. In the initial m scanning processes, the voltages sequentially changed to the electrodes 5 and 6 of the piezoelectric element molded body 1 each time are used. The same applies to reading the scanning signal from the output of the phototransistor 10 by applying the scanning signal. However, without the reference value P-P values by the bar code symbol entire scan as in the Example B In Example A, the reference value only photoelectric conversion output due to reflected light Kwai et Ttozon 18a.

[0029] That is, the maximum voltage detection circuit 24, every time each scanning process is a high voltage output by the reading of the Kwai et Ttozon 18a detects the maximum voltage value Qi, the data processing unit 20 is the maximum voltage of each the scan Data is transferred to electrodes 5 and 6
Is saved in the internal memory in accordance with the applied voltage data to the internal memory (S11 to S17).

Next, when the scanning for m times is completed, the saved m Qi values (i = 1 to m) are compared to find the maximum value Qmax (S18). And that Qm
applied voltage data saved corresponding to ax
The voltage is read out to the converter 21 and the voltage specified by the data is applied to the electrodes 5 and 6 of the piezoelectric element molded body 1 by the voltage control circuit 22 (S19).

Thereafter, as in the case of the embodiment A, the pin photodiode 11 and the A / D converter 26 are turned ON, and the (m + 1) th and subsequent bar code symbol read signals continuously scanned are output from the pin photodiode. A / D from 11
Although the data is taken into the data processing unit 20 via the converter 26 (S20), also in this case, the focal length f of the objective lens system is changed by the predetermined amount of bending of the soft lens 7 according to the following equation.
Thus, the reflected light of the bar / space of the bar code symbol is clearly imaged on the light receiving surface of the pin photodiode 11.

Further, in the embodiment B, because it covers only the maximum intensity of the reflected light Kwai et Ttozon 18a, detection and subsequent data processing of the maximum voltage becomes relatively easy, fast bar code with the scanning rate When applied to a scanner, it is possible to perform control with a margin.

[0033]

The invention of the present application has the following effects by having the above configuration. According to the first and second aspects of the present invention, there is provided a focusing device that combines a piezoelectric element and a soft lens.
Utilizes the high-speed responsiveness of the knotting method and high-precision stable operation
And applied to barcode scanner objective lens
By rationally configuring the focus adjustment control procedure,
Proper distance between barcode scanner and barcode seal
The bar code symbol reflected light
It is possible to form a clear image on the child and read
A bar code scanner that does not generate errors is realized.
In other words, a bar that can read barcode symbols
Increased allowable distance between code scanner and barcode seal
This eliminates the need for manual adjustment by the operator and improves operability.
Aim up. In particular, the invention of claim 2 provides a sorting system for conveyed articles.
Needs to read barcodes quickly like stems
Accurate and fast sorting by applying to the system
It dramatically improves the efficiency of the work. Claim 3
In the invention of the present invention, the deformation response speed to the applied voltage of the piezoelectric element is increased.
Faster and without optical distortion
Adjust the focal length of the objective lens system including the soft lens
Enables stable , high- speed , high-precision barcodes
Realize reading.

[0034]

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of a lens focal length adjusting mechanism in a barcode scanner according to an embodiment and a control system circuit thereof.

FIG. 2 is a flowchart illustrating an operation procedure when executing barcode reading according to the embodiment A;

FIG. 3 is a flowchart illustrating an operation procedure when executing barcode reading according to the embodiment B;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Piezoelectric element molded body 2 Notch slit 3 Comb part 4 Beam 5, 6 electrode 7 Soft lens 8 Biconvex lens 9 Half mirror 10 Phototransistor 11 Pin photodiode 12 Operation part 13 Laser light scanning control part 14 Laser light generation part 15 Motor 15a polygon mirror 16 the condenser lens 17 reflecting mirror 18 bar code label 18a Kwai et Ttozon 20 data processing section 21 D / A converter 22 the voltage control circuit 23 receiving circuit 24 P-P detection circuit or a maximum voltage detection circuit 25 and 26 A / D converter

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 7/04 G06K 7/015 G06K 7/10

Claims (3)

(57) [Claims] 1. A bar code symbol is scanned by a laser beam.
The reflected light from the bar code symbol surface
In a barcode scanner for reading barcode information by condensing light on a photoelectric conversion unit , a piezoelectric element is provided in the objective lens system.
Interposed with a soft lens that can be deformed by the
And apply a selective setting voltage to the electrodes provided on the piezoelectric element.
A focal length adjusting means for adjusting the focal length of the objective lens system by deforming the soft lens, and a voltage value applied to the piezoelectric element for each scanning in a plurality of initial barcode symbol scanning processes. A first procedure of detecting a difference value between a bar read signal and a space read signal obtained from the photoelectric conversion unit for each scan, and storing the detected value in association with an applied voltage value; A second procedure for finding the maximum value of the difference values stored in the procedure, a third procedure for applying an applied voltage value corresponding to the maximum value found in the second procedure to the piezoelectric element, and a voltage in the third procedure The photoelectric conversion is performed by scanning the barcode symbol after the application.
A fourth step of processing a signal obtained from the conversion unit as a normal read signal. 2. A bar code symbol is scanned by a laser beam.
The reflected light from the bar code symbol surface
In a barcode scanner for reading barcode information by condensing light on a photoelectric conversion unit , a piezoelectric element is provided in the objective lens system.
Interposed with a soft lens that can be deformed by the
And apply a selective setting voltage to the electrodes provided on the piezoelectric element.
A focal length adjusting means for adjusting the focal length of the objective lens system by deforming the soft lens, and a voltage value applied to the piezoelectric element for each scanning in a plurality of initial barcode symbol scanning processes. And the quiet obtained from the photoelectric conversion unit for each scan.
Detects a read signal values of d Ttozon, a second procedure for obtaining a first procedure for storing in correspondence with the detected value to the applied voltage value, the maximum value of the detected values stored in the first procedure,
A third step of applying an applied voltage value corresponding to the maximum value obtained in the second step to the piezoelectric element, and a signal obtained from the photoelectric conversion unit by barcode symbol scanning after applying a voltage in the third step. A bar code reading method, comprising: executing a fourth procedure of processing as a normal read signal. 3. The change of the piezoelectric element in the focal length adjusting means .
The method in which the soft lens is deformed by the biasing force is the peripheral part of the soft lens on the inner peripheral side of the comb-shaped part of the piezoelectric element formed by forming a number of notch slits from the end face side of the hollow cylinder and forming a comb-shaped part 3. A method in which a soft lens is deformed by applying a selective setting voltage to electrodes applied to the front and back surfaces of each beam of the comb portion to bend each beam of the comb portion. Barcode reading method.