JP3244045B2 - Optical scanner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser scanner which scans a symbol such as a bar code with a laser beam and optically reads the symbol such as a bar code by receiving reflected light.

[0002]

2. Description of the Related Art Some handy scanners that optically read symbols such as bar codes use light emitting diodes (hereinafter, referred to as LEDs) and laser light as light sources. L
Since a handy scanner using an ED as a light source irradiates a bar code with light generated by an LED and receives the reflected light, the bar code cannot be read unless the scanner body is brought close to the bar code by about 50 mm.

On the other hand, a handy scanner using a laser beam as a light source (hereinafter referred to as a laser scanner) scans a bar code with a highly directional laser beam generated by a laser oscillation section and receives the reflected light. You can read barcodes even when you are away, making it easier to aim for barcodes.

A conventional laser scanner will be described with reference to the drawings. FIG. 9 is a diagram showing a configuration of a conventional laser scanner. As shown in FIG. 10, the conventional laser scanner includes a laser oscillating unit 22, a reflecting mirror 25 for scanning a bar code with laser light, a reflecting mirror mounting shaft 26 for mounting the reflecting mirror 25, and a motor for driving the reflecting mirror 25. 27, a rotation speed detection unit 29 for detecting the rotation speed of the reflection mirror 25, a motor control unit 28 for controlling the motor 27 based on the rotation speed of the reflection mirror, and a light receiving unit 23 for receiving light reflected from the bar code. And a decoding unit 24 that decodes a signal from the light receiving unit 23 and reads a barcode. The operation of a conventional laser scanner is
The reflection mirror 25 is driven by a motor 27 so that the laser light generated by the laser oscillation unit 22 scans the bar code. The laser light reflected by the bar code is received by the light receiving unit 23 and the signal received by the decoding unit 24. Decoding and reading barcodes.

[0005] By the way, it is desirable to rotate the reflection mirror at a constant speed in order to improve the reading performance of the bar code, so it is necessary to detect the rotation speed of the reflection mirror. When a polygon mirror is used as the reflection mirror, means for detecting a rotational speed is disclosed in Japanese Patent Publication No. 5-35472 and Japanese Patent Laid-Open Publication No. 3-26285. In the case where the reflection mirror is driven to vibrate periodically. Japanese Patent Application Laid-Open No. 8-129601 discloses the means. In JP-A-8-129601, one coil is arranged on each side of a reflecting mirror having a permanent magnet mounted on the back side, and a driving pulse is periodically applied to the coil, so that the reflecting mirror is periodically rotated. Vibrating.

[0006]

However, when the reflecting mirror is vibrated periodically, immediately after the drive pulse is applied, the rotating direction of the reflecting mirror changes because the rotating direction of the reflecting mirror is reduced, and the bar code cannot be displayed. Since it becomes difficult to read, it is necessary to detect and control the rotation speed.However, if only the rotation speed of the reflection mirror is detected, it is not possible to know at which position the reflection mirror receives the drive pulse and the bar Scanning angle of the reflection mirror that can read the code (hereinafter, the effective scanning angle of the reflection mirror)
However, there is a problem that it cannot be designed.

The present invention solves the above problems,
An object of the present invention is to provide a laser scanner which clarifies an effective scanning angle of a reflection mirror and drives the reflection mirror at a constant rotation speed.

[0008]

[0009]

According to a first aspect of the present invention, a bar code or the like is scanned by reflecting a light beam emitted from a light beam irradiating portion with a rotating reflector. In a scanner for receiving the reflected light by a light receiving unit and decoding by a decoding unit, a position detecting means using a photo interrupter for detecting the position of the reflector and a signal from the position detecting means are analyzed. A signal analysis unit, a drive pulse generation unit that generates a drive pulse for driving the reflector, a drive pulse analysis unit that analyzes the rotational speed of the reflector from the drive pulse, and a reflector from the drive pulse analysis unit. A pulse width determination unit that determines the pulse width of the next drive pulse so that the rotation speed of the reflector becomes constant, the reflector is mounted on a U-shaped mounting shaft, and one end face is bent. And a mirror, which is constituted of the other end face as a photo-interrupter.

According to a second aspect of the present invention, there is provided a timer for measuring a first time after a drive pulse is generated, and when the first time drive pulse is not generated, the drive pulse generator is driven. This is to generate a pulse.

A third aspect of the present invention provides a timer for measuring a second time after the power of the scanner is turned on, a timer for measuring a third time after generating a driving pulse, and an optical scanner power supply. An initial drive pulse generator for generating the drive pulse for the second time after the power is turned on, and the second time after the power of the optical scanner is turned on, the cycle of the drive pulse signal is the third time Things.

According to a fourth aspect of the present invention, a hole is formed in the reflector mounting portion of the reflector mounting shaft to reduce the inertia of the reflector mounting shaft.

[0013]

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Since a driving pulse having a pulse width determined when a reflector reaches a certain position is generated, the effective scanning angle of the reflector can be clarified, and the driving pulse is determined by the rotation speed of the reflector. Is determined, the reflector can be driven at a rotational speed close to constant. Further, the portions used for detecting the positions of the reflector and the photointerrupter are balanced with each other about the rotation axis of the motor, so that the reflection mirror can be driven smoothly.

In addition, since the driving pulse is generated by the driving pulse generator when the driving pulse is not generated for the first time, the reflecting mirror is temporarily stopped by touching some obstacle or the rotation speed becomes extremely slow. Can also be restarted.

Further, since a drive pulse whose cycle is the third time is generated for the second time after the optical scanner power is turned on, a drive pulse for initial driving of the reflector can be generated. Thus, the reflector can be quickly shifted to the steady state.

In addition, since the inertia of the reflecting mirror mounting shaft is reduced, the reflector can be driven with less current consumption.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an external view of a reflection mirror driving portion according to an embodiment of the present invention. In FIG.
The reflection mirror mounting shaft 9 has a well-balanced structure that rotates about the rotation axis of the motor 10, so that the reflection mirror 8 can be driven smoothly, and the reflection mirror is mounted on one end surface, and the photo interrupter 1 is mounted on the other end surface. Used for position detection in. FIG. 2 is a diagram showing a positional relationship between the photo interrupter 1 and the reflection mirror 8 according to the embodiment of the present invention. As shown in FIG. 2, when the reflection mirror 8 is at a position within an angle α from the center of the photointerrupter 1, a signal from the photointerrupter 1 (hereinafter referred to as a “photo signal”) is an L signal and is at a position equal to or more than the angle α. When the photo signal is an H signal, the motor 10 acts to move the reflection mirror 8 to the position X1 when a drive pulse is applied to the A phase (hereinafter referred to as left scanning), and the reflection mirror when applied to the B phase. Assume that a force for moving the position 8 to the position Y1 acts (hereinafter, right scanning), and the motor 10 operates as a stepping motor. FIG. 3 is a view showing the structure of the reflecting mirror mounting shaft 9 in the present embodiment. Since a hole is formed in a portion where the reflecting mirror 8 is mounted, the inertia of the mirror mounting shaft 9 is reduced, and reflection is performed with less current consumption. The mirror 8 can be driven, and when the reflection mirror 8 is mounted on the reflection mirror mounting shaft 9 with an ultraviolet-curable adhesive or the like, light such as ultraviolet rays can be easily applied.

FIG. 4 is a block diagram showing a schematic configuration of a circuit for driving a laser scanner according to an embodiment of the present invention. In FIG. 4, since the operations of the conventional laser oscillating unit 22, light receiving unit 23, and decoding unit 24 shown in FIG. 10 are the same, a block diagram thereof is omitted, and only the driving part of the reflection mirror is shown. In FIG. 4, a reflecting mirror 8 for reflecting a laser beam, a reflecting mirror mounting shaft 9 for mounting the reflecting mirror 8, a photo interrupter 1 for detecting the position of the reflecting mirror 8, and a photo interrupter 1
And a drive pulse generator for generating a drive pulse for driving the reflection mirror 8 when the photo interrupter signal analyzer 2 detects the rise of the signal of the photo interrupter 1. 4 and a reflection mirror 8 from the driving pulse.
A drive pulse analysis unit 11 for analyzing the rotation speed of the motor, a pulse width determination unit 12 for determining the pulse width of the next drive pulse so that the rotation speed of the reflection mirror 8 is constant from the drive pulse analysis unit 11, A pulse separation unit 13 for separating a drive pulse into each phase of the motor 10 is provided. A first timer 3 for measuring a first time t1 after the generation of the drive pulse, and a laser scanner power supply 15 are turned on. A second timer 5 for measuring during a certain second time t2, an initial drive pulse generator 6 for generating the drive pulse for t2 after the laser scanner power supply 15 is turned on, and an initial drive pulse generator 6 A third timer 7 for measuring a third time t3 after the drive pulse is generated in
A switching unit 1 for switching between a pulse generator 6 and an initial drive pulse generator 6
4 is provided. The timing of driving pulse generation will be described. Here, it is assumed that a driving pulse is applied to the motor 10 when the output of the driving pulse generating unit 4 is an H signal. FIG. 5 is a circuit diagram showing an example of a partial circuit of the photo interrupter signal analyzer 2 and the drive pulse generator 4 according to one embodiment of the present invention. As shown in FIG. 5, when the drive pulse is not applied, that is, when the output of the inverter 33 is the L signal and the photo signal rises from the L signal to the H signal, the H signal to the D terminal of the flip-flop 30 is latched. Since ^* Q becomes an L signal and the diode 31 conducts, the capacitor 32 is discharged and the output of the inverter 33 becomes an H signal. Since the drive pulse generator 4 generates a drive pulse in synchronization with the rise of the photo signal, the drive pulse is generated when the drive pulse is rotated to the position Y for right scanning and to the position X for left scanning.

FIG. 6 is a circuit diagram showing an example of a circuit for explaining the basic operation of the drive pulse analyzer 11 and the pulse width determiner 12 in the present embodiment. In FIG. 6, when a drive pulse is applied, the capacitor 18 is discharged, and when no drive pulse is applied, the capacitor 18 is discharged.
Is charged and the voltage of the capacitor 18 has a reference voltage V1
When the voltage has dropped to the point, the sign of the output of the comparator 20 is inverted, and the drive pulse generator 4 stops the drive pulse in synchronization with the inversion. In FIG. 2, the time during which the driving pulse is not applied is the time during which the driving pulse is applied to the B phase during the right scanning and the reflecting mirror 8 moves to the position Y, so that the rotation speed of the reflecting mirror 8 is high. When the rotation speed is low, the length is short. That is, when the rotation speed of the reflection mirror 8 is high, the charging time for the capacitor 18 is short, and when the rotation speed is low, the charging time is long.

Actually, in order to make the rotation speed of the reflection mirror 8 at the time of left scanning and the rotation speed at the time of right scanning constant, since the left scanning and the right scanning are controlled separately, they are not shown. There are a capacitor for the A layer and a capacitor for the B layer of the motor 10.

FIG. 7 is a diagram showing the operation of the driving portion of the reflection mirror in the present embodiment. FIG. 7 shows an operation when the switching unit 14 is connected to the drive pulse generation unit 4 and the rotation speed of the reflection mirror 8 in the left scan is faster than that in the right scan. In FIG. 7, since the charging time of the capacitor for the layer B is longer than the charging time of the capacitor for the layer A, the pulse width of the driving pulse applied to the layer B is longer than that of the layer A, and the reflection during right scanning Since the rotation speed of the mirror 8 increases and the rotation speed during left scanning decreases, the difference between the rotation speed during left scanning and the rotation speed during right scanning decreases.

FIG. 8 is a diagram showing the operation of the reflection mirror driving section when the rotation speed of the reflection mirror in this embodiment is extremely low. The timer 3 starts when a drive pulse is generated. In FIG. 8, when a drive pulse is applied to the motor 10 and the next drive pulse is not applied after a lapse of time t1, the timer 3 generates a signal, whereby the drive pulse generator 4 generates the drive pulse. generate. Thus, even when the reflecting mirror 8 is extremely slowed down or stopped by touching an obstacle or the like, the reflecting mirror 8 can return to the normal state. Since the cycle t of the drive pulse corresponds to the scan rate of the laser scanner, it is necessary to set t1 to a larger value.

FIG. 9 is a diagram showing the operation of the reflection mirror driving portion when the power is turned on to the laser scanner in the present embodiment. The timer 5 starts when the laser scanner power supply 15 is turned on. In FIG. 4, a timer 7
The switching unit 14 is connected to the initial drive pulse generator 6 until the timer 5 counts the time t2, and then connected to the drive pulse generator 4. In FIG. 7, after a time t3 elapses after the initial drive pulse is applied to the motor 10, the timer 7 generates a signal, whereby the initial drive pulse generator 6 generates the initial drive pulse. Since the time t3 can be set to a value smaller than the time t,
Since the drive pulse can be generated in a short cycle, the state can be quickly shifted to the steady state.

Although the effective scanning angle of the reflecting mirror in this embodiment is 2α, the effective scanning angle of the reflecting mirror 8 can be increased by increasing the width W of the reflecting mirror mounting shaft 9 in FIG.

[0026]

[0027]

The optical scanner according to the first aspect of the present invention comprises:
A drive pulse having a determined pulse width is generated when the reflector reaches a certain position, so that the effective scanning angle of the reflector can be clarified, and the pulse width of the drive pulse is determined by the rotation speed of the reflector. Therefore, the reflector can be driven at a rotational speed close to a constant. Further, the portions used for detecting the positions of the reflection mirror and the photo-interrupter are balanced with each other about the rotation axis of the motor, so that the reflection mirror can be driven smoothly.

In the optical scanner according to the second aspect of the present invention, when the driving pulse is not generated for the first time, the driving pulse is generated in the driving pulse generating section. Also, when the rotation speed becomes very slow, it can be restarted.

In the optical scanner according to the third aspect of the present invention, a drive pulse having a cycle equal to the third time is generated for a second time after the power of the optical scanner is turned on. In this case, a drive pulse can be generated, and the reflecting mirror can be quickly shifted to a steady state.

In the optical scanner according to the fourth aspect of the present invention, since the inertia of the reflection mirror mounting shaft is reduced, the reflector can be driven with less current consumption.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a reflection mirror driving unit of an optical scanner according to an embodiment of the present invention.

FIG. 2 is a top view showing a positional relationship between a photo interrupter and a reflection mirror according to one embodiment of the present invention.

FIG. 3 is an external perspective view showing the structure of a reflection mirror mounting shaft according to the embodiment of the present invention.

FIG. 4 is a block diagram showing a schematic configuration of a circuit for driving an optical scanner according to the embodiment of the present invention;

FIG. 5 is a circuit diagram showing an example of a partial circuit of a photointerrupter signal analyzer and a drive pulse generator according to an embodiment of the present invention.

FIG. 6 is a circuit diagram showing a circuit example of a drive pulse analysis unit and a pulse width determination unit according to an embodiment of the present invention.

FIG. 7 is a time chart illustrating a process up to the generation of a drive pulse in one embodiment of the present invention.

FIG. 8 is a time chart showing a drive pulse when the rotation speed of the reflection mirror is extremely low in one embodiment of the present invention.

FIG. 9 is a time chart for explaining a drive pulse when power is supplied to the optical scanner according to the embodiment of the present invention;

FIG. 10 is a block diagram showing a conventional optical scanner.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photo interrupter 2 photo interrupter signal analyzer 3 timer 4 drive pulse generator 5 timer 6 initial drive pulse generator 7 timer 8 reflective mirror 9 reflective mirror mounting shaft 10 motor 11 drive pulse analyzer 12 pulse width determiner 13 pulse separator 14 Switching unit 15 Laser scanner power supply

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-209586 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06K 7/10

Claims (4)

(57) [Claims] A scanner that scans a bar code or the like by reflecting a light beam emitted from a light beam irradiation unit with a rotating reflector, receives the reflected light at a light receiving unit, and decodes the reflected light at a decoding unit. In the photointerrupter for detecting the position of the reflector
, A signal analyzer for analyzing a signal from the position detector, a drive pulse generator for generating a drive pulse for driving the reflector, and rotation of the reflector from the drive pulse. A driving pulse analyzing unit for analyzing a speed, and a pulse width determining unit for determining a pulse width of a next driving pulse from the driving pulse analyzing unit so as to keep the rotation speed of the reflector constant, and Attached to the shaft
One end face is used as a reflection mirror, and the other end face is used as a photo interface.
Optical scanner characterized by being configured as a raptor.
Na. A timer for measuring a first time after a drive pulse is generated, wherein the drive pulse generator generates a drive pulse when the first time drive pulse is not generated. The optical scanner according to claim 1, wherein: 3. A second power supply after the scanner power is turned on.
, A timer for measuring a third time after generating a drive pulse, and an initial drive pulse generator for generating the second time drive pulse after the optical scanner power is turned on. 2. The optical scanner according to claim 1, wherein a period of the drive pulse signal is the third time during a second time after the power of the optical scanner is turned on. Wherein a hole in the reflector mounting portion of the reflector mounting shaft, the optical scanning according to claim 1, characterized in that to reduce the inertia of the reflector mounting shaft
Na.