JPS5813943B2 - Hikari Sousasouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical scanning device, and more particularly to an optical scanning device for a bar code reader that is capable of obtaining timing pulses.

Recently, it has been proposed to calculate the sales price and manage inventory by displaying the necessary data about the item in a barcode on the item for sale, and then scanning this barcode with a barcode reader. There is.

Conventionally, this barcode reading device is equipped with an optical scanning device such as a laser scanner that scans a transparent window provided in the reading device with a thin light beam, and the light beam that comes out through the transparent window is applied to the article. At this time, a part of the diffusely reflected light from the barcode, which is a part of the extremely minute reflected light that enters the reading device through the transparent window, is absorbed by a photoelectron multiplier installed in the reading device, for example. A photoelectric conversion element such as a tube converts the signal into an electric signal, and a slicer shapes the electric signal into a pulse signal corresponding to the bar code, thereby reading the contents of the bar code.

On the other hand, since this reading device is usually used in a relatively bright environment, quite strong disturbance light from, for example, a fluorescent light enters the photoelectric conversion element through the transparent window, so that it does not correspond to the desired optical signal. A considerably large electrical signal caused by this disturbance light is superimposed on the weak electrical signal generated by the disturbance.

As a result, the photoelectric conversion element may reach saturation,
Alternatively, the slicer input may exceed the allowable dynamic range due to this disturbance light, making slicing impossible.

Furthermore, the intensity of the light beam changes over time due to a decrease in the output of the laser tube, deterioration of the photoelectric conversion element, and deterioration of reflection efficiency due to dust adhering to the reflection system, so this weak electrical signal is increasingly extracted. It has problems such as being difficult to use.

In order to solve these problems, there is a demand for removing the output electrical signal component caused by the disturbance light component and for correcting the system's change over time.

The present invention has been made in view of the above circumstances, and its purpose is to obtain a timing pulse that can remove the output electrical signal component caused by the disturbance light component and correct the temporal change of the system. The objective is to provide an optical scanning device that can

A feature of the present invention for achieving the above object is to move a light beam and a plurality of hologram plates relatively, to apply the light beam to a code portion of an object within a predetermined area, and to transmit the reflected light to a light receiving element. In the optical scanning device, a non-reflection area that does not reflect the light beam outside the predetermined area and a diffuse reflection plate that diffusely reflects the light beam are provided outside the predetermined area, and the diffuse reflection plate includes the plurality of light beams. Scanned by a specific hologram plate among the hologram plates, the light receiving element receives the reflected light from the code part of the object and the disturbance light during the reading period, receives only the disturbance light during the disturbance light measurement period, and calculates the gain. a shielding part that receives the diffusely reflected light and disturbance light from the diffusely reflecting plate during the adjustment period, the specific hologram plate is partitioned by a reflecting plate, and is adjacent to the specific hologram plate and prevents passage of the light beam; and a reflected light detector for receiving the reflected light from the reflecting plate, and an output of the reflected light detector to obtain a timing signal indicating a disturbance light measurement period and a gain adjustment period of the light receiving element. It is a scanning device.

The present invention will be explained in detail below with reference to the illustrated embodiments.

FIG. 1 shows a block diagram of a barcode reading device 10 to which the present invention is applied.

The reading device 10 includes an optical scanning device 20 provided in a housing (not shown), and the optical scanning device 20 scans a transparent window 1 provided in a part of the housing in a grid pattern with a light beam. For example, a barcode label (not shown) affixed to an object passing outside the window 1 is scanned with this light beam through the window 1.

A part of the reflected light corresponding to the barcode generated by optically scanning the barcode passes through the window 1 and enters the light receiving element in the device, in this example, the photomultiplier tube 11, where it is converted into an electrical signal S1. be done.

FIG. 2 shows the optical scanning device 20 in enlarged detail, and the optical scanning device 20 includes a laser tube 21 and a rotating plate 2.
2, and near the edge of the rotary plate 22 are annular hologram plates a1, a2, . . . an-2 and ac.
is arranged so that it can transmit light.

The light beam 23 from the laser tube 21 is directed to a rotating plate 22 which is rotated by a mirror 24 and a lens 25.
These hologram plates are fixedly applied toward predetermined points through which they pass.

By rotating the rotary plate 22, the hologram plates al to an-2 scan the light beam 23 from the lens 25 to scan the window 1 from the back side in a grid pattern as shown by dotted lines in the figure.

When the light beams 23 are scanned in this manner, at least one of the light beams can completely traverse a barcode (not shown).

A diffused reflection plate 2 is provided on the back side of the housing near the window 1, and this diffused reflection plate 2 is a hologram plate a.

It is designed to be optically scanned by a chisel.

The area near the window 1 and the diffused reflection plate 2 is painted black so that even if a light beam hits it, it will not be reflected.

On the rotary plate 22, there is a hologram a next to the hologram plate ao on the side in the rotation direction (direction of arrow A) of the rotary plate 22, that is, a hologram a in the drawing.

A shielding portion ab that blocks the passage of the light beam 23 is formed between and an-2.

Therefore, the photomultiplier tube 11 has hologram plates a1 to an-2.
a reading period Tr during which the reflected light of the light beam scanned by is incident along with external light; a disturbance light measurement period To during which the light beam is blocked by the shielding part ab and only external light is incident; and a hologram. a.

Thus, three periods are obtained for each rotation of the rotary plate 22, including a gain adjustment period Tg in which the diffused reflection plate 2 is scanned and the reflected light from the diffused reflection plate is incident together with external light.

In order to obtain the timing pulses that identify these three periods, the back side of the rotary plate 22, i.e. the laser tube 21
On the side, as shown in Fig. 3, there are holograms al, a2,...
......The area between an-2 and ao and the part of the shielding part ab is painted black by applying black paint, etc., and the part between the hologram a1 and the shielding part ab and the part between the hologram ac and the shielding part ab is Reflection means 26.2 for reflecting the light beam 23 by applying white paint or attaching a reflector plate, etc.
7 is provided.

Therefore, when the light beam 23 is applied to the rotating plate while rotating the rotating plate, the light beam 23 passes through the hologram plate,
Shielding part ab and hologram plate al, a2...an-2
The light beam is absorbed in the black areas between the two, and therefore no reflected light by the light beam 23 is generated on the back side of the rotary plate 22.

However, reflected light from the light beam 23 occurs in the reflection regions rl and r2 where the reflection means 26 and 27 at both ends of the shielding part ab are present.

This reflected light is converted into an electrical signal by a reflected light detector 28 consisting of a photoelectric conversion element such as a phototransistor, which is placed on the back side of the rotary plate 22 near the lens 24 so that the light beam 23 and external light do not enter. is converted to

Therefore, as shown in FIG. 4a, the timing signal S2 from the detector 28 is transmitted to the reflection area
It has pulses P1 and P2 corresponding to l and r2, respectively, and from this it is possible to know in which period the optical scanning device is in.

Returning to FIG. 1, the apparatus 10 includes a disturbance light removing device 30 for extracting an electrical signal component corresponding to the light reflected by the bar code from the signal S1 from the photomultiplier tube 11; , and a variable attenuator 60 that attenuates the output signal S4 from the amplifier 40 to a predetermined level and inputs it to the slicer 50.

The timing signal S2 is input to a timing pulse generator 12, and this generator 12 generates a gate signal S, which is generated within a period To, and a gate signal S6, which is generated within a period Tg.

These gate signals are, for example, each pulse P1, P2, respectively.
This can easily be obtained by a single pulse generator, which is controlled to rise triggered by a pulse and fall after a predetermined period of time.

Gate signals S5 and S6 are input to gate 31 and AND circuits 61 and 62, respectively.

The disturbance light removing device 30 includes a gate 31, a capacitor 32, and an inverting amplifier 33, which are closed only when a gate signal S is input.
a sampling hold circuit 34 consisting of; and an adder 3;
It consists of 5.

Then, the magnitude of the signal S1 containing only the component due to the disturbance light obtained in the period To is determined by the capacitor 32 and the gate 31.
The disturbance light voltage Ec charged in the capacitor 32 is inverted in polarity by an inverting amplifier, and added to the signal S1 obtained during periods Tg and Tr to calculate the electricity due to the disturbance light in this signal S1. This removes signal components.

The variable attenuator 60 includes resistors R1 to R8 and transistor Q1.
It includes an attenuation circuit 63 constituted by Q4 to Q4, a reversible counter 64 for controlling the amount of attenuation of this attenuation circuit 63, and a comparator 65.

Here, reference symbols A1 and A2 indicate buffer amplifiers.The outputs of the AND circuits 62 and 61 are connected to the addition terminal 64a and the subtraction terminal 64b of the reversible counter 64, respectively. A predetermined clock pulse CPL is inputted from a clock pulse oscillator 66 to each of the input terminals 1 and 1.

Further, a gate signal S6 from a timing pulse generator is input to each second input, and an output signal from a comparator 65 is input directly and via an inverter 67 to each third input.

The comparator 65 compares the output voltage v1 of the attenuation circuit 63 with the reference voltage V
.

is input, and the difference between both voltages and their magnitude relationship are judged and the result is output. When v1 is higher, "0" is output, and when v1 is lower, "1" is output. Output.

Therefore, when "1" is applied to each second input of the AND gates 61 and 62 during the period Tg, the reversible counter 64 drives the transistors Q1 to Q4 with the output of the output terminals 64c to 64f of the comparator 65. performs an addition or subtraction operation and V.

The attenuation amount is set so that −■.

Next, the operation of this reading device 10 will be described.

When the rotating plate 22 rotates and the light beam 23 is scanned by the hologram plate an-2 of the rotating plate 22, the light beam 2
3 hits the reflection region r1 and a reflected light is generated, and the reflected light detector 28 detects a pulse P1.

This pulse P1 is input to the timing pulse generator 12, and a gate signal S5 is applied to the gate 31.

Therefore, the gate 31 is closed and the value of the signal S1 from the photomultiplier tube 11 is sampled and held in the sampling and holding circuit 34.

At this time, the light beam 23 is blocked by the shielding part ab of the rotating plate 22, so the charging voltage E of the capacitor 32 is
c has a size corresponding to the intensity of only the disturbance light.

The rotary plate 22 further rotates and the light beam 23 reaches the reflection area r2.
, the gate 31 opens again for the next period T.

This sampling value will continue to be held until

When the light q beam 23 hits the reflection region r2, a pulse P2 is obtained, and as already mentioned, the gate signal S
6 is applied to the AND circuits 61 and 620 second human power.

At the time when the gate signal S6 is generated, the light beam 23
is hologram a.

Therefore, the disturbance light and the diffusely reflected light from the diffuse reflection plate 2 enter the photomultiplier tube 11 at this time.

This diffusely reflected light is set to be approximately equal to the average value of the amount of reflected light from the barcode in normal operation.

A signal S1 corresponding to these two lights is input to an adder 35 for a period T.

Since an electrical signal approximately corresponding to the magnitude of the diffusely reflected light, which is obtained by subtracting the magnitude of the disturbance light measured in , is output, the signal S3 can be abbreviated as the signal obtained when only the diffusely reflected light is input. It is extracted as a signal of magnitude.

The signal S3 is amplified by the amplifier 40 and attenuated by the attenuation circuit 63.
It is attenuated by , and taken out with a magnitude of v1.

As already mentioned, V1 is V at this time.

If it is not equal to , the signal S6 is applied, so the reversible counter is activated and the attenuation amount of the attenuation circuit is set so that v1 is equal to V0.

This reference voltage V.

is set in consideration of the input tolerance of the slicer 50.

Next, when the light beam 23 is scanned by the holograms a1 to an-2, the gate signal S6 becomes "0", so the counting operation of the reversible counter 64 is stopped, and the attenuation amount of the attenuation circuit 63 is set to the optimum value. Continue to hold it.

Therefore, even if the reflected light from the barcode obtained by the light beam scanned by the holograms a1 to an-2 enters together with the disturbance light, the disturbance light removing device 30 photoelectron-multiplies only the reflected light from the barcode. A signal substantially the same as the voltage signal obtained when light enters the tube can be extracted, and this signal can be input to the slicer at an appropriate magnitude by means of the variable attenuator 60.

This series of operations is repeated every time the rotary plate 22 rotates once, so the operation can extremely quickly follow changes in ambient light.

Further, since the gain of the entire system of the reading device 10 is automatically gain controlled by the variable attenuator 60, the factor of unstable operation due to changes over time is removed, and therefore the device can be operated stably for a long period of time.

In the above embodiment, the period T is a calibration period.

Although the period and Tg are provided once for each rotation of the rotary plate 22, it goes without saying that these periods may be provided correspondingly for each hologram plate.

Further, in the above embodiment, an example was shown in which a hologram plate was used to scan the light beam 23, but it goes without saying that an ordinary lens may be used instead of the hologram plate.

According to the present invention, as described above, a desired timing pulse can be extracted with the configuration of the reflection means provided on the rotary plate of the optical scanning device and the reflected light detector, so that it is different from the conventional optical scanning device. The present invention can be easily applied to extract a timing pulse corresponding to a desired timing, and this timing pulse can be used to remove the influence of ambient light, automatically correct system gain due to changes over time, or rotate a rotating plate. It is possible to provide an optical scanning device that has advantages such as being able to monitor numbers.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is an enlarged perspective view of the main parts of the optical system shown in Fig. 1, Fig. 3 is a partially enlarged back view of the rotating plate, and Figs. 4 a to C are FIG. 3 is a signal waveform diagram for explaining operation. In the drawing, 1 is a window, 2 is a diffused reflection plate, 10 is a barcode reader, 11 is a photomultiplier tube, 12 is a timing pulse generator, 20 is an optical scanning device, 21 is a laser tube, 22 is a rotating plate, and 23 is a rotating plate. a light beam, 26.27 a reflecting means, 28 a reflected light detector, aIHa2s"""""a
H-2'aC is a hologram plate, S1 is an input electric signal, S
2 is a timing signal, and S5 and S6 are gate signals.

Claims (1)

[Scope of Claims] 1. A light beam and a plurality of hologram plates are moved relatively, the light beam is applied to a code portion of an object within a predetermined area, and the reflected light is received via a light receiving element, In an optical scanning device that performs code identification of an object, a non-reflection area that does not reflect the light beam and a diffuse reflection plate that diffusely reflects the light beam are provided outside the predetermined area, and the diffuse reflection plate identifies one of the plurality of hologram plates. The light receiving element receives reflected light and disturbance light from the code section of the object during the reading period, receives only disturbance light during the disturbance light measurement period, and receives the disturbance light from the diffused reflection plate during the gain adjustment period. the specific hologram plate is partitioned by a reflecting plate, and a shielding portion for preventing passage of the light beam is provided adjacent to the specific hologram plate, An optical scanning device comprising: a reflected light detector that receives reflected light from a plate; and a timing signal indicating a disturbance light measurement period and a gain adjustment period of the light receiving element is obtained from the output of the reflected light detector. .