JP4303826B2 - Scan motor control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling a scan motor used for reading information by optical scanning with a barcode reader or the like.
[0002]
[Prior art]
For example, a bar code reader is provided with a light projecting optical system for optically reading information described on a bar code label. In this light projecting optical system, a bar code reader is operated by a reciprocating vibration operation by a scan motor. The information is optically read by performing scanning scanning of the reading light onto the code label. That is, in this light projecting optical system, for example, as shown in FIG. 3, light from the semiconductor laser (LD) 102 is reflected and oscillated by a scan motor 101 in which a reflecting mirror 100 is fixed. Further, the reversing operation of the scan motor 101 is controlled by the drive circuit 103.
[0003]
By the way, in such a projection optical system, for example, the resistance value of the coil provided in the scan motor slightly changes due to seasonal temperature fluctuations, for example, in summer, the resistance value increases due to temperature rise, As a result, a phenomenon may occur in which the amount of current flowing in the coil is substantially reduced and the scan width of the motor is narrowed. In addition, a phenomenon in which the scan width varies depending on variations of individual scan motors.
[0004]
Therefore, for example, a control circuit for detecting the amount of current flowing through the coil and a voltage value and raising it to a predetermined value is provided, feedback control is performed, or a constant current circuit is provided to correct the scan width. I'm trying to prevent it. In addition, variations in individual scan motors are corrected using adjustment resistors or the like.
[0005]
[Problems to be solved by the invention]
However, in the projection optical system having such a configuration, the circuit becomes large in any case, which is a big problem for downsizing and cost reduction of the barcode reader.
[0006]
Therefore, in view of the above-described circumstances, the present invention is suitable for downsizing and cost reduction of a circuit, and an object of the present invention is to provide a scan motor control method capable of constantly maintaining a scan width. Is.
[0007]
[Means for Solving the Problems]
That is, the invention described in claim 1 is a method of controlling a scan motor used for reading information by optical scanning with a barcode reader or the like, and is reflected by a reflecting mirror fixed integrally with the scan motor. A position sensor is provided at the boundary position of the projection scanning area where the subsequent light is projected and scanned, and the current output time width to the scan motor is increased until the reflected light is incident / received on this position sensor, and the temperature increases or This is to correct the reduction in the vibration width of the scan motor due to the voltage drop.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In this embodiment, the same members as those described in the prior art are given the same reference numerals to avoid redundant description.
FIG. 1 shows a light projecting optical system to which a scan motor control method according to the present invention is applied. In this light projecting optical system, in addition to a scan motor 101 with a reflecting mirror 100 and a light source (semiconductor laser 102). , First and second position sensors 1 and 2, a control unit 3, and a drive circuit 4.
[0009]
The first and second position sensors 1 and 2 are respectively installed at positions that are left and right boundary portions when the reading light emitted from the light source 102 is projected with a desired scan width A, and in this embodiment, A photoelectric conversion element that outputs a predetermined electric signal to the control unit when reading light with a predetermined wavelength is incident is used.
[0010]
When the control unit 3 inputs signals output from the first and second position sensors 1 and 2, the control unit 3 outputs a predetermined control signal to the drive circuit 4, and the input is the first and second position sensors. The output is connected to the input of the drive circuit 4 while being connected to 1 and 2. In the control unit 3, the pulse widths to be output (ΔT1, ΔT2, ΔT3,...) Are output as shown in FIG. 2 until the signals from the first and second position sensors 1 and 2 are input. When the signals (α, β) from the position sensor are input, the output signal width is fixed there.
[0011]
When the control signal from the control unit 3 is input, the drive circuit 4 amplifies this signal and outputs it as a drive signal to the coil of the scan motor 101. In this embodiment, the pulse width of the control signal is increased. Accordingly, the drive signals to the coils (current output time widths ΔI1, ΔI2, ΔI3,...) Are increased.
[0012]
Therefore, according to this embodiment, for example, when the amount of current flowing through the coil of the scan motor decreases with an increase in indoor temperature (the same applies when the voltage decreases), the scan width decreases with this decrease. The reading light from 102 does not enter the first position sensor 1 and the second position sensor 2. As a result, since predetermined signals are not output from these position sensors, as shown in FIG. 2, a control signal having a gradually widened pulse width is output from the control unit 3.
[0013]
In this way, the current output time width per scan flowing to the coil of the scan motor 101 increases according to the spread of the pulse width, so the rotation angle (rotation time) of the scan motor 101 also increases, and the scan width A becomes smaller. Expand.
As a result, since the reading light reaches the first and second position sensors 1 and 2, a control signal fixed to the pulse width (ΔT4) at that time is output thereafter.
[0014]
As a result, even if the scan width A is reduced due to, for example, a seasonal temperature change (rise) or the like, the scan width A can be corrected and controlled so as not to become narrower than the set scan width.
[0015]
【The invention's effect】
As described above, according to the present invention, the position sensor is provided at the boundary position of the projection scanning area where the light reflected by the reflection mirror fixed integrally with the scan motor is projected and scanned. Since the current output time width to the scan motor is increased until the reflected light is incident / received, the reduction in the vibration width of the scan motor due to temperature increase or voltage decrease can be corrected. Therefore, it is possible to control the scan width uniformly without downsizing, and the handy-type bar code reader is suitable for downsizing and cost reduction. Further, by changing the position of the sensor, the scan width can be easily changed without changing or adjusting other components.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a light projection optical system to which a scan motor control method of the present invention is applied.
FIG. 2 is a time chart showing the operation of the present invention.
FIG. 3 is a schematic configuration diagram showing a conventional light projecting optical system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st position sensor 2 2nd position sensor 3 Control part 4 Drive circuit 100 Reflection mirror 101 Scan motor 102 Light source (semiconductor laser)
A Scan width

Claims (1)

A method for controlling a scan motor used for reading information by optical scanning with a barcode reader or the like,
A position sensor is provided at a boundary position of a light projection scanning area where light reflected by a reflection mirror fixed integrally with the scan motor is projected and scanned,
Increase the current output time width to the scan motor until the reflected light is incident / received on this position sensor,
A method for controlling a scan motor, comprising correcting a reduction in a vibration width of the scan motor accompanying an increase in temperature or a decrease in voltage.

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