JP2732911B2 - Article detection method - Google Patents

Description

Detailed Description of the Invention [Table of Contents] Overview Industrial application field Conventional technology (Fig. 8) Problems to be solved by the invention Means for solving the problem (Fig. 1) Action Embodiment (a) One Description of Embodiment (FIG. 2) (b) Description of Operation of One Embodiment (FIGS. 3 to 7) (c) Description of Another Embodiment Effect of the Invention [Outline] Detection from Light Emitting Unit to Detection Space With regard to an article detection method that emits light, receives light reflected from the detection space at the light receiving unit, and detects the article from a change in the amount of light, it does not require a high power supply and can detect articles even when the intensity of disturbance light is strong. For the purpose of being able to do, a light emitting unit that emits detection light to the detection space, a light receiving unit that receives reflected light from the detection space, and multiple sensitivities can be selected,
A photoelectric conversion unit that photoelectrically converts the amount of light received by the light receiving unit with a selected sensitivity, an A / D conversion unit that A / D converts a reflected light intensity output of the photoelectric conversion unit, and has a plurality of reference voltages, A reference voltage generator that supplies a predetermined reference voltage to the A / D converter in accordance with the selection, and a controller that detects a change in the amount of light from an output of the A / D converter and detects an article. Before detecting the article, the control unit detects the output value of the A / D conversion unit, and selectively controls the sensitivity of the photoelectric conversion unit and the reference voltage of the A / D conversion unit according to the output.

[Industrial applications]

The present invention relates to an article detection method in which detection light is emitted from a light emitting unit to a detection space, reflected light from the detection space is received by a light receiving unit, and an article is detected from a change in light amount.

The bar-coded article enters the reading space,
Stationary barcode readers for reading barcodes of articles are widely used.

In such a barcode reader, constantly emitting the light scanning pattern to the reading space shortens the life of the light source and increases power consumption.

Therefore, the bar code reader has an article detection unit (device)
The optical scanning pattern is emitted when it is detected that the article has entered the reading space.

It is desired that such an article detection device can appropriately detect an article even when the intensity of disturbance light is high.

[Conventional technology]

 FIG. 8 is an explanatory diagram of the prior art.

As shown in FIG. 8 (A), the bar code reader BCR
Is fixed to a desk or the like, has an article detection unit ASU and a barcode reading unit SCR, emits detection light to a predetermined article detection space in the article detection unit ASU, and detects entry of an article from reflected light, The barcode reading unit SCR generates an optical scanning pattern,
The light is emitted to the reading space, receives the reflected light from the bar code of the article, analyzes the light, and reads the bar code.

As shown in FIG. 8 (B), the conventional article detection method is as follows.
The light emitting unit 1 is pulse-modulated by the driving unit 1a to emit pulse-modulated detection light.

The light receiving unit 2 receives the reflected light, performs photoelectric conversion in the photoelectric conversion unit 2a, outputs the reflected light intensity, and converts the reflected light intensity into a digital value in the A / D conversion unit 10, and then the light amount (intensity) of the digital reflected light intensity The light amount change detection unit 6 detects the article from the change.

[Problems to be solved by the invention]

By the way, in such article detection, if the intensity of disturbance light is high, the light receiving system is saturated, and it becomes impossible to detect an article by a change in light amount.

In order to detect an article even when the intensity of the disturbance light is high, conventionally, the power supply voltage has been increased so as to enlarge the operation area of the photoelectric conversion unit 2a.

However, in the prior art, a high power supply for the photoelectric conversion unit 2a must be provided in addition to a low power supply for driving other low-power components, and there is a problem that the device becomes expensive.

Therefore, an object of the present invention is to provide an article detection method capable of detecting an article even when the intensity of disturbance light is strong, without providing a high power supply.

[Means for solving the problem]

 FIG. 1 is a diagram illustrating the principle of the present invention.

As shown in FIG. 1, the present invention provides a light emitting section 1 for emitting detection light to a detection space, a light receiving section 2 for receiving light reflected from the detection space, and a plurality of sensitivities. A photoelectric conversion unit 2a that photoelectrically converts the amount of received light with a selected sensitivity, and an A / D conversion unit that A / D converts the reflected light intensity output of the photoelectric conversion unit 2a
A reference voltage generator 5 having a plurality of reference voltages and supplying a predetermined reference voltage to the A / D converter 10 according to selection;
A control unit 6 for detecting a change in the amount of light from the output of the A / D conversion unit 10 to detect an article;
Detects the output value of the A / D converter 10 and selectively controls the sensitivity of the photoelectric converter 2a and the reference voltage of the A / D converter 10 according to the output.

[Action]

In the present invention, a photoelectric conversion unit 2a capable of selecting a plurality of sensitivities and a reference voltage generating unit 5 capable of selecting a plurality of reference voltages are provided.
Before the article is detected by the controller 6, the A / D converter 1
By monitoring the output of 0, the sensitivity and the reference voltage are selected, and the dynamic range is expanded without using a high power supply.

For this reason, if the intensity of the disturbance light is high, the photoelectric conversion unit 2a is switched to the low sensitivity side and the A / D conversion unit 10 is switched to the low reference voltage side to control the dynamic range of the photoelectric conversion unit 2a.

〔Example〕

 (A) Description of Configuration of One Embodiment FIG. 2 is a block diagram of one embodiment of the present invention.

In the figure, the same components as those shown in FIGS. 1 and 8 are indicated by the same symbols.

The photoelectric conversion portion 2a, the amplifier AMP is connected to the composed light receiving portion 2 with the photodiode, the gain resistor r _1, r ₂ of the amplifier AMP, connect the gain resistor r _2, and an analog switch AS1 for cutting a, it is possible to select the gain (sensitivity) to the high / low at the connection / disconnection gain resistor r ₂ by the analog switch AS1.

Reference numeral 3 denotes a high-pass filter that cuts a DC (low frequency) component of the output of the photoelectric conversion unit 2a. Reference numeral 4 denotes an AC amplifying unit that amplifies the output of the high-pass filter 3 by AC and outputs an AC output (FIG. 3). Reference).

Reference numeral 7a denotes a maximum value sample-hold circuit, which converts the maximum value of the AC output of the AC amplifier 4 into a sample-hold signal CTL1−
A sample-and-hold circuit 7b for sampling and holding by DLY is a minimum value sample-and-hold circuit for sampling and holding the minimum value of the AC output by a sample-and-hold signal CTL2-DLY.

8 is a differential amplifier, which is a maximum value sample hold circuit
The output of 7a is subtracted from the output of the minimum value sample-hold circuit 7b and amplified to generate a differential amplified output. 9 is a sample-and-hold unit, and the differential output of the differential amplifier 8 is converted by a sample-and-hold signal CTL3. The sample / hold 10 is the above-mentioned A / D (analog / digital) converter, which converts the sample-and-hold signal into a digital value. The reference voltage generator 5 is the above-mentioned reference voltage generator. The voltage Vref ₁ and the low reference voltage Vref ₂ are generated and switched by the analog switches AS4 and AS5.
Output to

AS2 and AS3 are analog switches, respectively, and control signals CT
Controlled by L9, analog switch AS2 is connected to inverter I
Opened by the control signal CTL9 inverted by V, the photoelectric conversion unit 2
The output of a is given directly to the A / D converter 10 and the analog switch AS
Reference numeral 3 denotes a circuit which is opened by the control signal CTL9 and inputs the output of the sample hold circuit 9 to the A / D converter 10.

The control section (light quantity change detection section) 6 is configured as follows.

11a is a first register, which is used for A / D conversion with the sample signal CTL4.
11b is a second register, which samples and captures the output of the conversion unit 10, and outputs the A / D conversion unit 10b with a sample signal CTL5.
12a is a first delay unit, which emits light emission drive pulses CTL1 from the CPU 14 described later.
12b is a second delay unit that delays the inverted signal CTL2 of the light emission drive pulse CTL1 from the CPU 14 and outputs a sample / hold signal CTL2-DLY. , 13 are A / D converters which convert the threshold value Vth for detecting an article from the voltage dividing circuit into a digital value and output it to the CPU 14, and 14 is a CPU (central processing unit) which emits light. Drive pulse CTL1, its inverted signal CTL2, sample hold signal CTL3, sample signal CTL
4, CTL5, select signals CTL6, CTL7, CTL8, CTL9
It reads the contents of the / D converter 10, monitors the disturbance light, reads the contents of the registers 11a and 11b, calculates the change in the amount of reflected light, and detects the entry / ejection of the article by the processing of FIG. It is.

(B) Description of the operation of one embodiment FIG. 3 is an explanatory diagram of the light receiving output creation operation of one embodiment of the present invention,
FIG. 4 is a flowchart of an article detection process according to an embodiment of the present invention, and FIG.
FIG. 6 is an explanatory diagram of the article detection operation, FIG. 6 is a flowchart of the external light sample processing, and FIG. 7 is an explanatory diagram of the external light sample operation.

 First, the light receiving operation of FIG. 2 will be described with reference to FIG.

The CPU 14 outputs a light emission drive pulse CTL1, and causes the light emitting unit (LED) 1 to emit a pulse modulated light from the drive unit 1a.

The modulated reflected light is received by the light receiving unit 2, converted into an electric signal by the photoelectric conversion unit 2 a, the DC component is cut by the high-pass filter 3, AC-amplified by the AC amplifying unit 4, and becomes an AC output.

The light emission drive pulse CTL1 is delayed by the first delay section 12a to generate a sample hold signal CTL1-DLY.

The sample hold signal CTL1-DLY is synchronized with the emitted light, and is generated so as to be generated at the time when the reflected light by the emitted light becomes maximum.

Similarly, the inverted signal CTL2 of the light emission drive pulse given from the CPU 14 is delayed by the second delay unit 12b to create a sample hold signal CTL2-DLY.

This sample-and-hold signal CTL2-DLY is
Synchronized with 2 and created to occur at a time when reflected light is at a minimum.

Therefore, the maximum value sample hold unit 7a holds the maximum value of the AC output by the sample hold signal CTL1-DLY and outputs a hold output, and the minimum value sample hold unit 7b outputs the AC output by the sample hold signal CTL2-DLY. Holds the minimum value and outputs the hold output.

The differential amplifier 8 takes the difference between the two hold outputs, amplifies the output, and outputs a differential amplified output.

Therefore, the differential amplified output is the peak to pe of the AC signal.
Since ak is detected, the signal detection accuracy can be improved without deteriorating the S / N ratio, and an accurate reflected light intensity can be obtained.

The differential amplified output is sampled and held by the sample and hold unit 9 and outputs a sample and hold output.
The data is converted into a digital value by the conversion unit 10 and output to the registers 11a and 11b.

The operation of detecting an article using the reflected light intensity thus obtained will be described with reference to FIGS.

Incidentally, CPU 14 creates a the approach detection threshold Vth ₁ and a discharge detection threshold Vth _2, based on a threshold value of the A / D change unit 13, and both the threshold Vth _1, Vth ₂ , The number of entry samples C1,
Stores the number C2 of discharge samples.

The CPU 14 first initializes each unit.

Next, the CPU 14 resets the number C1 of M2 samples to “0”, performs external light sampling processing described later with reference to FIG. 6, and selects the sensitivity of the photoelectric detection unit 2a and the reference voltage of the A / D conversion unit 10. I do.

Further, the CPU 14 starts the output of the light emission drive pulse CTL1, turns on the light emitting unit 1 in a pulsed manner, and then gives a sample instruction (referred to as M1 sample) M1 (CTL4) to the register 11a.
The output of the A / D converter 10 is taken into the register 11a.

Next, the CPU 14 gives a sample instruction (referred to as M2 sample) M2 (CTL5) to the register 11b, and takes the output of the A / D converter 10 into the register 11b.

Then, the CPU 14 stores the sample data M of the registers 11a and 11b.
1, M2 is read, (M1-M2) is calculated, and (M1-M2)
The absolute value of 2) | M1-M2 | look, entry detection threshold Vth ₁
Compare with

In step, by comparison, | M1-M2 |> Vth 1 not equal Judging, CPU 14 determines that it is not an article enters the detection, updates the M2 sample number C1 to (C1 + 1).

Then, the CPU 14 checks whether the updated M2 sample number C1 has reached the predetermined value X1. If C1 = X1, the process returns to the step. If C1 = X1, the process returns to the step.

On the other hand, in the step, | M1-M2 |>
When it is determined that the threshold value is Vth ₁ , the CPU 14 determines that article entry has been detected, and performs article presence processing.

For example, in the example of the above-described barcode reader, the barcode reading unit SCR is activated.

Next, the CPU 14 causes the register 11b to sample M2, and
The output of the D conversion unit 10 is taken into the register 11b.

Then, the CPU 14 reads the sample data M1 and M2 of the registers 11a and 11b, calculates (M1-M2), and further calculates (M1
−M2) and the absolute value | M1−M2 |
compared with the h _2.

In step, by comparison, | M1-M2 | unless <Vth _2, article determines that the reading space.

That is, since the sample value M1 of the register 11a is of the background level without the article, as in the step, unless the sample value M2 of the register 11b falls to that level, it is not detected that there is no article, and the threshold value is not detected. If Vth or more, it is determined that the article is still in the reading space.

Then, the CPU 14 updates the M2 count number C2 to (C2 + 1), and compares the updated M2 count number C2 with the planned number X2.

If the M2 count number C2 has not reached the planned number X2, the process returns to the step. If the M2 count number C2 has reached the planned number X2, it is determined that there is an article but it is in a state where it does not move, and there is no article in the step.

In step, the CPU 14 determines that if | M1−M2 | <Vth ₂ ,
It is determined that the sample value M2 of the register 11b has fallen to the background level, it is determined that there is no article, the M2 count number C2 is set to zero, and the process returns to the step.

In this way, as shown in FIG. 5, the register 4b is sampled at a shorter cycle than the register 4a, and the two registers 11a and 11b are sampled.
By taking the difference (M1-M2), a change in the background level of the register 11a can be detected.

Then, by converting the difference into an absolute value and comparing it with a threshold value, a change in the background level is not picked up as noise,
False detection can be avoided.

The cycle of the M1 sample is “X1” in the step when there is no article, and is constant. However, when an article is detected, the cycle becomes variable until the absence of the article in the step or “X2” in the step.

Further, in this embodiment, the entry and discharge of the article can be detected using the two threshold values Vth ₁ and Vth ₂ , which is convenient.

Further, if it is determined that there is an X2 article for a certain period of time, the article is processed assuming that the article does not move, so that the processing is not repeated until the article is useless.

Next, the external light sample will be described with reference to FIGS. 6 and 7. FIG.

First, the CPU 14 turns off the control signal CTL9, turns on the analog switch AS2, and turns off the analog switch AS3.

As a result, the A / D converter 10 is disconnected from the sample hold unit 9 and directly A / D converts the output of the photoelectric converter 2a.

At this time, since the light emitting unit 1 does not emit light, the A / D converter 1
0 means that the external light received by the light receiving unit 2 is directly subjected to A / D conversion.

Then, the CPU 14 turns on the control signal CTL6, and
Is turned off, and the analog switch AS of the reference voltage generator 5 is turned off.
4 on, analog switch AS5 off, high reference voltage
Vref ₁ is supplied to the A / D converter 10 as a reference voltage.

Further, the CPU 14 turns off the control signal CTL8, and
and turning off the analog switch AS1 of a, disconnect the gain resistor r _2, the gain of the amplifier AMP and a high gain.

In this state, CPU 14 is to sample the output value of the A / D converter 10 (the external light intensity), and compares the external light threshold Vth ₃ scheduled the sample value DC.

If the sample value DC external light threshold Vth ₃ or more, it is determined that the ambient light is strong, CPU 14, as the dotted line in FIG. 7, a control signal CTL6 is turned off and then turned on the CTL7, reference voltage generator Turn off analog switch AS4 of 5, analog switch A
Turn on S5, apply the low reference voltage Vref ₂ as a reference voltage to the A / D conversion unit 10, turn on the control signal CTL8, turn on the analog switch AS1 of the photoelectric conversion unit 2a, connect the gain resistor r2, The gain of the amplifier AMP is set to a low gain.

If the sample value DC does not exceed the external light threshold Vth ₃ is a control signal CTL6,7,8 as it is, a high gain,
Set to high reference voltage.

Then, when the sample value DC does not exceed the external light threshold value or upon completion of the step, the CPU 14 turns on the control signal CTL9, turns off the analog switch AS2, turns on the analog switch AS3, and connects with the A / D conversion unit 10. The connection of the photoelectric conversion unit 2a is disconnected, and the photoelectric conversion unit 2a is connected to the sample hold unit 9, and the process returns.

In this way, the disturbance light is monitored before the article is detected,
When the intensity of the disturbance light is equal to or more than a predetermined value, the dynamic range is expanded by switching the photoelectric conversion unit 2a to a low gain (sensitivity) and switching the reference voltage of the A / D conversion unit 10 to a low voltage.

(C) Description of Another Embodiment In the above-described embodiment, the gain and the reference voltage are set in two steps. However, the gain and the reference voltage may be set in three or more steps, and the CPU may select the gain and the reference voltage in accordance with the external light intensity. .

Also, the light amount change detection unit has been described as being integrated with the control unit, but may be another unit, and a part of the calculation of the CPU may be configured by dedicated hardware.

Further, the application to a barcode reader has been described as an example, but the invention can be applied to other types.

Although the present invention has been described with reference to the embodiments, the present invention can be variously modified in accordance with the gist of the present invention, and these are not excluded from the present invention.

〔The invention's effect〕

As described above, according to the present invention, the disturbance light is monitored in advance and the sensitivity of the photoelectric conversion unit and the reference voltage of the A / D conversion unit are selected, so that the dynamic range can be increased without using a high power supply. This provides an effect that the article can be appropriately detected from the reflected light intensity even if the disturbance light intensity is high.

[Brief description of the drawings]

 FIG. 1 is a principle diagram of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. FIG. 5 is an explanatory diagram of an article detecting operation according to one embodiment of the present invention, FIG. 6 is a flowchart of an external light sample processing in FIG. 4, and FIG. FIG. 8 is an explanatory view of the prior art. In the figure, 1 ... light emitting section, 2 ... light receiving section, 2a ... photoelectric converting section, 5 ... reference voltage generating section, 6 ... control section, 10 ... A / D converting section.

Continued on the front page (72) Inventor Yoshihiro Oyama 2-16-20 Shimura, Itabashi-ku, Tokyo Copal Corporation (72) Inventor Tatsuo Sasaki 2-16-20 Shimura, Itabashi-ku, Tokyo Copal Corporation (72 ) Inventor Hiroaki Kawai 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-60-60576 (JP, A)

Claims (1)

(57) [Claims] A light emitting section for emitting detection light to a detection space.
And a light receiving unit (2) for receiving reflected light from the detection space; and a photoelectric conversion unit (2a) for selecting a plurality of sensitivities and photoelectrically converting the amount of light received by the light receiving unit (2) with the selected sensitivity. A / D for A / D converting the reflected light intensity output of the photoelectric conversion unit (2a)
A converter (10); a reference voltage generator (5) having a plurality of reference voltages and supplying a predetermined reference voltage to the A / D converter (10) according to selection;
And a control unit (6) for detecting a change in the amount of light from the output of the A / D conversion unit (10) to detect an article. The control unit (6) performs A / D conversion before the article is detected. Detecting an output value of the conversion unit (10) and selectively controlling the sensitivity of the photoelectric conversion unit (2a) and the reference voltage of the A / D conversion unit (10) according to the output value; method.