JPH0721298A - Focal point adjustment device and optical code reader using the same - Google Patents

Abstract

PURPOSE:To displace the condensing position of a light beam irradiated from a light source in accordance with a using conditions under a state set beforehand. CONSTITUTION:A drive control part 12 changes voltage data to be supplied to a drive circuit 11 by time series change set before-hand. The drive circuit 11 changes voltage to be impressed to a piezoelectric actuator 2 in accordance with the voltage data. The piezoelectric actuator 2 generates distortion corresponding to the impressed voltage, and by displacement in the optical axis direction of a lens due to this distortion, the condensing position of the light beam irradiated from the light source 9 is changed. Therefore, the condensing position of the light beam irradiated from the light source 9 changes in a time series manner in conformity with the changing pattern of the voltage data outputted from the drive control part 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus adjusting device which adjusts the focal position of a lens system by displacing the lens system in the optical axis direction, and an optical code such as a bar code is read using this focus adjusting device. The present invention relates to an optical code reader.

[0002]

2. Description of the Related Art An optical code reader, such as a bar code reader, which irradiates a detection target with a light beam that has passed through a lens system and receives the reflected light to read an optical code such as a bar code, It is necessary to adjust the focal position of the lens system so that the focus position of the light beam matches the detection target. In order to adjust the focal position of the lens system through which such a light beam passes, conventionally, an electromagnetic coil is provided in the magnetic circuit formed by the magnets arranged to face each other, and an electric current is passed through the electromagnetic coil to form an electromagnetic coil. There is one in which an electromagnetic coil is displaced in the optical axis direction by an electromagnetic force generated between a magnetic circuit and a lens is fixed to the electromagnetic coil. However, with such a configuration, there is a problem that the apparatus becomes large-sized and the cost increases, that adjustment work at the time of assembly is difficult, and the characteristics change due to heat generation and wear.

Therefore, the applicant previously filed Japanese Patent Application No. 4-1717.
In No. 07, an actuator that generates strain according to an applied voltage and a plate that converts the strain generated in the actuator into a displacement of the lens system in the optical axis direction are provided, and a voltage is applied to the actuator so that the lens system We have proposed a focus adjustment device that adjusts the focus position of the.
Further, in the focus adjustment device using this actuator, a method of feedback controlling the focus position of the optical system is also adjusted by adjusting the voltage applied to the actuator so that the S / N ratio of the reflected light detection unit is maximized. Disclosed.

[0004]

However, when the position from the position of the light source to the detection target changes discontinuously and relatively greatly for each detection target such as a bar code reader, the focus position is adjusted by feedback control. Depending on the situation, there is a problem that the condensing position of the light beam cannot be quickly matched with the detection target.

An object of the present invention is to detect the condensing position of a light beam emitted from a light source even when the distance from the light source to the detection object changes discontinuously and relatively greatly for each detection object. An object of the present invention is to provide a focus adjustment device which can be quickly matched to an object and is suitable for an optical code reading device such as a bar code reader.

[0006]

A focus adjusting device according to a first aspect of the present invention is provided with an actuator for generating a distortion according to a voltage applied from a driving means, and the distortion generated in the actuator is lens system. In the focus adjusting device for converting into displacement in the optical axis direction, a voltage storage means for storing a time-series change of the applied voltage to the actuator, and a drive for controlling the output voltage of the drive means based on the stored contents of the voltage storage means. And a control means.

The focus adjusting device according to the invention described in claim 2 includes a voltage change setting means for receiving setting inputs of the voltage value stored in the voltage storage means and the maintenance time of each voltage value.

In the focus adjusting device according to the invention described in claim 3, the voltage storage means stores time-series changes of a plurality of kinds of applied voltages, and the time-series changes of a plurality of kinds of applied voltages. Of these, selection means is provided for accepting a selection of time-series changes in the applied voltage to be validated.

An optical code reading device according to a fourth aspect of the present invention comprises the focus adjusting device according to the first, second or third aspect, and irradiates the detection target with the light beam that has passed through the lens system. It is designed to read an optical code.

In the optical code reader according to the present invention as defined in claim 5, counting means for counting the number of times the optical code is read at each voltage, and the storage means stores the result based on the counting result of the counting means. And a voltage changing means for changing the maintenance time of each voltage value.

An optical code reader according to a sixth aspect of the present invention is provided with change content erasing means for erasing the content of the change in the maintenance time of each voltage value by the voltage changing means.

[0012]

In the invention described in claim 1, the time series change of the applied voltage to the actuator is stored in the voltage storage means, and the output voltage controlled based on the stored contents of the voltage storage means is the drive means. Applied to the actuator from. The actuator generates a strain corresponding to the applied voltage, and this strain is converted into a displacement of the lens system in the optical axis direction. Therefore, the position of the lens system in the optical axis direction, that is, the focal length changes in a time-series manner in a predetermined state.

According to the second aspect of the invention, the voltage value stored in the voltage storage means and the maintenance time of each voltage value can be set and input by the voltage change setting means.

Therefore, the time-series change state of the applied voltage to the actuator can be arbitrarily set, and the focal length of the lens system changes in time-series according to the contents of this setting.

In the invention described in claim 3, the voltage storage means stores a plurality of time-series changes of the applied voltage, and which time-series change is valid can be selected by the selection means. it can. Therefore, when there are a plurality of modes of changing the focal length of the lens system, the applied voltage can be changed in time series according to each mode.

According to a fourth aspect of the invention, when an optical code reader for reading an optical code such as a bar code irradiates a light beam on a detection target, the focal length of a lens system through which the light beam passes. Changes in time series in a predetermined state. Therefore, the condensing position of the light beam irradiated to the detection target whose distance from the light source changes irregularly changes in time series in a predetermined state.

In the invention described in claim 5, the number of readings of the optical code at each voltage is counted by the counting means, and the maintenance time of each voltage value stored in the storage means is changed based on the counting result. To be done. Therefore, the maintenance time of the voltage applied to the actuator is changed according to the frequency of appearance of the distance from the light source to the detection target, and the probability that the light beam is focused at the position of the detection target can be increased.

In the invention described in claim 6, the contents of change of the maintenance time of each voltage value by the voltage changing means are erased by the change content erasing means. Therefore, when the appearance state of the detection target changes, this can be dealt with in advance.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a focus adjusting device according to an embodiment of the present invention. The focus adjusting device 1 is configured by mounting a piezoelectric actuator 2 composed of a laminated piezoelectric element on a substrate 7 on which a light source 9 such as a light emitting diode or a semiconductor light emitting element is installed. A displacement magnifying plate 4 is adhered to the upper surface of the piezoelectric actuator 2, and a Fresnel lens 5 is formed on the upper surface of the displacement magnifying plate 4. In the substrate 7, the light source 9 is installed in the recess 8 in the central portion, and the light transmitting portion 3 is formed to penetrate the portion of the piezoelectric actuator 2 facing the recess 8.

Further, in the displacement magnifying plate 4, the Fresnel lens 5 is formed at a position facing the light source 9. In addition, a hemispherical recess 6 is formed on the lower surface of the displacement magnifying plate 4. As a result, the displacement magnifying plate 4 is thick in the peripheral portion and thin in the central portion. When the light source 9 is driven with the above configuration, the light beam emitted from the light source 9 passes through the transparent portion 3 of the piezoelectric actuator 2, passes through the center of the Fresnel lens 5, and
The light is focused on the focal position of the Fresnel lens 5.

FIG. 2 is a block diagram showing the configuration of the focus adjusting device. A drive circuit 1 is provided for the piezoelectric actuator 2.
A drive voltage is applied from 1. The voltage value of the drive voltage is determined by the voltage data supplied from the drive controller 12 to the drive circuit 11.

In the focus adjusting device 1 configured as described above, when a drive voltage is applied to the piezoelectric actuator 2 from the drive circuit 11, the piezoelectric actuator 2 expands in the X direction (longitudinal direction) to generate strain ε and Y. It contracts in the direction (lateral direction) to generate strain ε '. Piezoelectric actuator 2
A displacement magnifying plate 4 having a dome-shaped recess 6 is joined to the upper surface of the displacement magnifying plate 4, and the displacement magnifying plate 3 is bent and deformed so as to contract in the lateral direction due to lateral strain of the piezoelectric actuator 2. Displacement magnifying plate 4 due to this bending deformation
The central part of the lens is displaced upward together with the Fresnel lens 5, and this displacement extends the distance between the Fresnel lens 5 and the light source 9, and the focal length of the Fresnel lens 4 also increases accordingly.

In this way, the focal length of the Fresnel lens 5 changes depending on the deformation amount of the displacement magnifying plate 4, and the deformation amount of the displacement magnifying plate 4 is the lateral strain ε'of the piezoelectric actuator 2.
Depends on the size of. Since the magnitude of the lateral strain ε ′ in the piezoelectric actuator 2 changes depending on the magnitude of the drive voltage applied to the piezoelectric actuator 2, the focal length of the Fresnel lens 5 is controlled by controlling the drive voltage applied to the piezoelectric actuator 2 as a result. Can be changed to a desired value.

FIG. 3 is a block diagram showing the configuration of the drive control unit of the focus adjustment apparatus. The drive control unit 12 is a CPU
21 and a memory 22 is connected to the CPU 21. Further, a D / A converter 25 is connected to the CPU 21 via an interface 24, and the output of the D / A converter 25 is supplied to the drive circuit 11. The CPU 21 operates according to the program written in the memory 22 based on the clock pulse supplied from the clock 23. Further, the memory 22 stores preset time-series changes in the applied voltage to the piezoelectric actuator 2. FIG. 4 shows an example of a time series change of the applied voltage. In the example shown in the figure, the focal length f of the Fresnel lens 5 is 10 mm, 20 mm, 25 mm, 3
Voltage V (1 that realizes 0 mm and 40 mm respectively
0), V (20), V (25), V (30), V (4
0) is applied at a ratio of 1: 3: 3: 2: 1.

FIG. 5 is a flow chart showing the processing procedure of the control unit. The CPU 21 reads the voltage value to be applied to the piezoelectric actuator 2 from the time series change of the applied voltage stored in the memory 22 at the input timing of the clock pulse from the clock 23 (n1, n2), and reads the read voltage value. The voltage data is supplied to the D / A converter 25 (n3). The CPU 21 repeatedly executes the processes of n1 to n3 at the timing of the clock pulse to change the voltage applied to the piezoelectric actuator 2 in the state shown in FIG. As a result, the focal length of the Fresnel lens 5 of the focus adjusting device is 10 m during the time t.
m, then 20 mm for 3t, 25 mm for 3t, then 30 mm for 2t,
After that, it becomes 40 mm during t.

As described above, in this embodiment, the applied voltage to the piezoelectric actuator 2 is changed according to the time series change stored in the memory 22 in advance, and the focal length of the Fresnel lens 5 is changed accordingly. The condensing position of the light beam emitted from the light source changes in a predetermined state.

As a time-series change of the voltage applied from the drive circuit 11 to the piezoelectric actuator 2, the voltage value can be changed in any state other than the stepwise change shown in FIG. 4, for example, a sine wave. it can. In this case memory 2
In 2, a change in applied voltage over time can be stored by a relational expression between time and a voltage value.

FIG. 6 is a block diagram showing the structure of a control unit for explaining the focus adjusting device according to the invention described in claims 2 and 3. In addition to the configuration shown in FIG. 3, a key controller 32 is connected to the CPU 21 via an interface 31. The key controller 32 inputs the operation data of the voltage key 33a, the time key 33b and the setting key 33c to the CPU 21. CPU
Reference numeral 21 changes the time series change of the applied voltage to the piezoelectric actuator 2 stored in the memory 22 as voltage change data based on the operation contents of the voltage key 33a and the time key 33b.

As a result, the changing state of the focus position of the light beam of the light source 9 which passes through the Fresnel lens 5 can be arbitrarily changed.

Further, plural kinds of voltage change data are stored in a part of the memory 22 so that the voltage change data to be validated can be selected by operating the setting key 33c.
As a result, any of the plurality of voltage change data stored in the memory 22 can be selectively validated, and the light beam focusing position can be changed in a pattern according to the situation.

FIG. 7 is a diagram showing an example of the configuration of the optical code reading device according to the fourth aspect of the invention. The optical code reading device 41 includes a polygon mirror 42 for deflecting and scanning the light beam emitted from the focus adjusting device 1 and a light receiving element 45 for receiving the light beam reflected by a detection target 43 such as a bar code label. And a light reception signal processing unit 45 for processing the light reception signal of the light receiving element 45.

This optical code reading device 41 detects a light beam emitted from the light source 9 of the focus adjusting device 4 as a detection target 4.
By rotating the polygon mirror 42 in the optical path up to 3, the light beam of the light source 9 scans the bar code on the detection target 43, and based on the light reception signal of the light receiving element 44 that receives the reflected light on the detection target 43. The black part and the white part of the bar code are discriminated to decode the bar code.

At this time, since the voltage applied to the piezoelectric sensor 2 in the focus adjusting device 1 changes in time series in a preset pattern, the position at which the light emitted from the light source 9 is focused also changes in accordance with this pattern. . Generally, in bar code readers used in stores, the distance from the light source to the bar code changes for each product, and even in the readable area of the bar code reader,
There are a range in which the appearance frequency of the barcode is high and a range in which the appearance frequency is low. For example, the distance from the light source 9 is 10 to 40 mm
When the barcode can be read in the range of
When the frequency of appearance of the bar code is high in the range of 20 to 30 mm from the light source 9, the light beam emitted from the light source 9 is changed by changing the applied voltage to the piezoelectric actuator 2 as shown in FIG. The probability of condensing light in the vicinity of the barcode can be increased, and the reading accuracy of the barcode can be increased.

The distribution of the distance from the light source 9 to the bar code varies depending on the operator who performs the reading process. Therefore, by applying the focus adjusting device 1 according to the second aspect of the present invention to the optical code reading device 41, when the operator handling the bar code reader is changed, the focus is stored in the memory 22 accordingly. The bar code reading probability can be increased by changing the relationship between the applied voltage and time.

Further, by applying the focus adjusting apparatus 1 according to the invention described in claim 3, the time series change of the applied voltage of the pattern according to the appearance frequency of the bar code is stored for each of the plurality of operators. This has the advantage that even if the operator who handles the bar code reader is repeatedly replaced, it is possible to quickly realize the change pattern of the light beam focusing position according to the operator.

The present invention can also be implemented in a two-axis optical scanner that does not use a polygon mirror.

FIG. 8 is a block diagram of a control unit of a focus adjusting device applied to the optical code reading device according to the fifth and sixth aspects of the invention. ROM 52 and RAM
The CPU 51 provided with 53 operates based on the clock pulse input from the clock 54. The D / A converter 5 is connected to the CPU 51 via the interfaces 55 to 57.
8, the reset key 59 and the received light signal processing unit are connected. The D / A converter 58 converts the voltage data output from the CPU 51 into an analog signal and supplies the analog signal to the drive circuit 11. The reset key 59 is a RAM for the CPU 51
It is operated when erasing stored data in 53 described later. A signal indicating that the barcode data has been successfully read is input from the received light signal processing unit via the interface 57.

FIG. 9 is a memory map of the main part of the RAM which constitutes the above control part. RAM 53 memory area M
A1 and MA2 are assigned to the counter i and the timer T, respectively. The counter i is a memory area MB1 to MB1 which constitutes a time series change of the applied voltage.
Any of the voltage data V (1) to V (h) stored in h is sequentially specified. This voltage data V (1) -V
(H) is sequentially applied to the piezoelectric actuator 2 according to the contents of the counter i, and forms a pattern of a time series change of the applied voltage for one time.

In the memory areas MC1 to MCh, count data C (1) of the number of times the read signal is input in each voltage data.
~ C (h) is stored. Further, the memory areas MD1 to MD1
MDh is time data t for maintaining each voltage data.
(1) to t (h) are stored.

Each of the time data t (1) to t (h) is sequentially assigned to the timer T as a time for maintaining each of the applied voltages V (1) to V (h).

FIG. 10 is a flow chart showing the processing procedure of the control unit. The CPU 51 first sets the content of the counter i for specifying the applied voltage to 1 and sets the timer T
The time data t (i) specified by the contents of the counter i is set to (n11, n12). In this state, the input of a clock pulse from the clock 54 is awaited (n1
3) When the clock pulse is input, the pulse period ck of the clock pulse is subtracted from the content of the timer T (n1
4). At the same time, the voltage data V (i) specified by the content of the counter i is read from the RAM 53, and D
It is output to the / A converter 58 (n15).

Next, the CPU 51 determines whether or not the read signal is input from the received light signal processing unit (n16), and when the read signal is input from the received light signal processing unit, the counter C (i is specified by the counter i. ) Is incremented (n17). CPU11 is this counter C
It is determined whether or not the content of (i) has reached the constant value k (n18), and when the content of the counter C (i) has reached the constant value k, this is cleared (n19) and the counter i is set. After confirming that the content of the specified time data t (i) is less than or equal to the maximum value tmax of the set time (n2
0), the time data t (i) is lengthened by a predetermined time α (n21).

The CPU 51 repeatedly executes the processing of n13 to n21 until the content of the timer T becomes 0 (n2).
2). When the content of the timer T becomes 0, the counter i
Is incremented (n23), and it is determined whether or not the content of the counter i exceeds the set number h of voltage data (n24). When the content of the counter i is less than the set number h of voltage data, the process returns to n12, and when the content of the counter i exceeds the set number h of voltage data, the process returns to n11 and sets the content of the counter i to 1. .

That is, the CPU 51 sets n1 for each of the set voltage data V (1) to V (h).
The processing of 2 to n22 is executed. Further, the CPU 51 uses n1
If the read signal is not input at 6, the counter C (i) is equal to the constant value k at n18, and the time data t (i) is at or above the maximum value tmax of the set time at n20. , Go directly to n22.

Through the above processing, the CPU 51 causes the set voltage data V (1) to V (h) to be time data t (1) to t (h) stored in the memory areas MD1 to MDh, respectively. Each of which is maintained. During this time, the number of times the light reception signal processing unit has succeeded in reading is counted for each voltage data, and when the number of times of successful reading becomes a constant value k in any voltage data, the maintenance time of the voltage data is lengthened by a predetermined time α. This makes it possible to lengthen the duration of the voltage corresponding to the focal length at which the bar code appears frequently, and to change the condensing position of the light emitted from the light source according to the bar code appearance frequency.
The bar code reading probability and its accuracy can be increased.

The memory areas MA1 to MA1 of the RAM 53 are
As shown in FIG. 11, the stored contents of MBh are cleared by an interrupt process by operating the reset key 59. Thus, when the operator is replaced, a pattern can be automatically created according to the appearance state of the barcode by the new operator.

[0047]

According to the invention described in claim 1, the focal length of the lens can be changed based on a preset time series change, and the light source can be used without using complicated control such as feedback control. There is an advantage that the irradiated light beam can be condensed at a position that changes in time series.

According to the invention described in claim 2, it is possible to appropriately change the condensing position of the light beam of the light source in accordance with the use state.

According to the third aspect of the present invention, as the time-series change of the converging position of the light beam emitted from the light source, it is possible to appropriately select from a plurality of types suitable for the use condition. .

According to the invention described in claim 4, since the optical code can be read by changing the condensing position of the light beam emitted from the light source in a fixed pattern, the optical code such as a bar code can be read. By setting the time-series change of the applied voltage according to the appearance pattern of, it is possible to improve the reading probability and reading accuracy of the optical code.

According to the invention described in claim 5, the maintenance time of the converging position of the light beam emitted from the light source can be changed according to the appearance state of the optical code. It is possible to automatically set the time series change of the light collecting position according to the.

According to the invention described in claim 6, it is possible to eliminate the time-series change of the condensing position which is automatically set in accordance with the appearance state of the optical code, and it is possible to eliminate the optics relating to a new operator. The pattern according to the appearance state of the dynamic code can be automatically set again.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a focus adjustment device that is an embodiment of the present invention.

FIG. 2 is a block diagram of a focus adjustment device of the present invention.

FIG. 3 is a block diagram of a control unit of the focus adjustment apparatus according to the invention described in claim 1.

FIG. 4 is a diagram showing a time-series change of an applied voltage to an actuator stored in a memory included in the control unit.

FIG. 5 is a flowchart showing a processing procedure of the control unit.

FIG. 6 is a block diagram of a control unit of the focus adjusting apparatus according to the invention described in claims 2 and 3.

FIG. 7 is a diagram showing a configuration of an optical code reader according to claims 4 to 6.

FIG. 8 is a block diagram of a control unit of a focus adjustment device applied to the optical code reading device according to the fifth and sixth aspects of the invention.

FIG. 9 is a memory map of a main part of a memory of the control unit.

FIG. 10 is a flow chart showing a processing procedure of a control unit of the focus adjustment apparatus applied to the optical code reading apparatus according to the invention described in claim 5;

FIG. 11 is a flowchart showing a part of the processing procedure of the focus adjustment apparatus applied to the optical code reading apparatus according to the sixth aspect of the invention.

[Explanation of symbols]

 1-Focus adjusting device 2-Piezoelectric actuator 5-Fresnel lens 9-Light source 11-Drive circuit 22-Memory (voltage storage means)

Claims (6)

[Claims] 1. A focus adjusting device comprising an actuator that generates a distortion according to a voltage applied from a driving means, and converting the distortion generated in the actuator into a displacement of a lens system in an optical axis direction. Voltage storage means for storing the time-series change of, and drive control means for controlling the output voltage of the drive means based on the stored contents of the voltage storage means,
Focus adjustment device. 2. The focus adjusting apparatus according to claim 1, further comprising voltage change setting means for receiving setting inputs of a voltage value stored in said voltage storage means and a maintenance time of each voltage value. 3. The voltage storage means stores time-series changes of a plurality of kinds of applied voltages, wherein time-series changes of the applied voltage to be validated among time-series changes of the plurality of kinds of applied voltages. The focus adjustment device according to claim 1, further comprising a selection unit that receives a selection of a change. 4. An optical code reader comprising the focus adjusting device according to claim 1, 2 or 3, and irradiating a light beam that has passed through the lens system to a detection target to read an optical code. 5. Counting means for counting the number of times the optical code is read at each voltage, and voltage changing means for changing the maintenance time of each voltage value stored in said storage means based on the counting result of the counting means. The optical code reader according to claim 4, further comprising: 6. The optical code reader according to claim 5, further comprising change content erasing means for erasing the content of the change in the maintenance time of each voltage value by said voltage changing means.