GB2184275A

GB2184275A - Bar code reading wand

Info

Publication number: GB2184275A
Application number: GB08629633A
Authority: GB
Inventors: Andrew John Wilks
Original assignee: OMEGA ELECTRIC Ltd
Current assignee: OMEGA ELECTRIC Ltd
Priority date: 1985-12-11
Filing date: 1986-12-11
Publication date: 1987-06-17
Also published as: GB8629633D0; GB8530545D0

Abstract

A bar code reading wand 1 has an optical head 3 incorporating an optical emitter 6 (which may incorporate a light emitting diode) associated with a photo transistor which is responsive to signals from the emitter 6 which have been reflected from a surface, and received signals are analysed by optical processing electronics 2. The head 3 incorporates a spring 4 which can be compressed as the head is pressed against a surface so as to operate a switch 5 which allows power to be applied to the optical emitter 6 and the processing electronics 2. The spring 4 can be replaced by a resilient member and the switch 5 can be a membrane switch. In an alternative arrangement the proximity of the tip of the wand to a surface is detected by a capacitively operated detecting element. The application of power to the emitter 6 only when the wand is in an operational position conserves the battery power of portable units. <IMAGE>

Description

SPECIFICATION Improvements relating to bar code wands This invention relates to a bar code reading wand.

Such awand will have, for example, a light emitting diode associated with a photo transistor which will respond to light reflected by a surface from the diode. These signals are then fed to optical processing electronics which registers changes in signals as the wand is moved over a bar code.

When bar code reading wands are used with portable computers then the power used in the bar code actively becomes high with respect to the low power consumption possible with present day portable computers. Consequently the batteries present in such portable devices can run down relatively quickly due to the heavy power consumption of the optical emitter in particular.

According to the invention there is provided a bar code wand incorporating an optical emitter and a photo transistor and optical processing electronics for processing signals received by the transistor as reflections of light from the optical emitter, and including an activating device for enabling at least the optical emitteronly when the tip of thewand incorporating the emitter and transistor is brought into contact with or very close proximity to a surface.

Whilstthe photo transmitter and/orthe optical processing electronics could be permanently powered whilst the wand is being used, it is preferred that the activating device should also be responsible for activating the photo transmitter and/orthe optical processing electronics. Power consumption is very much reduced by this system since the optical emitter, which is a heavy power user compared with the rest ofthe electrical components, is only operative for short periods of timewhilsta bar code is read and notwhilstthe bar code wand is being carried around.

In one preferred arrangement the activating device includes a pressure responsive switch, which could be a membrane switch. Such a wand could be constructed so that a spring, resilient pad or other biasing means within the head of the wand biases parts ofthe head away from a switch activating position.

In an alternative arrangement the activating device incorporates a capacitively operated detecting elementatthetipofthe barcodewand.Thisformof activating device could incorporate a comparatorfor registering a change in capacitance ofthe detecting elementsoasto produce an enablingsignalfora predetermined length oftime.

If necessary or preferred the activating device could incorporateatimerforensuringthatthe optical emitter, and any associated circuitry, is enabled for a predetermined length oftime.

The activating device could be effective so as to enable the optical emitter either directly or by the generation of an output signal indicating that the wand is in active position so that the optical emitter is ableto come into operation. Forthe lattertype of operation the wand could be made fully operational by actuating a manual switch, for example, in addition to the operation of the activating device itself.

The invention may be performed in various ways and preferred embodiments thereof will now be described with reference to the accompanying drawings, in which Figure 1 shows a bar code wand of this invention which employs a pressure activated switch; Figure2 is a diagrammatic circuit drawing which shows in detail the electrical operation of the device of Figure 1 ; Figure 3 shows second embodiment of a bar code wand of this invention which employs a membrane switch; Figure4isthe blockcircuitdiagram of a signal processing circuit associated with the device of Figure 3; Figure5shows a third embodiment of a barcode wand ofthis invention which employs a capacitively operated detecting element; and Figure6istheblockcircuitdiagramforthe capacitive detection circuit of the device of Figure 5.

In the barcodewand 1 shown in Figure 1, optical processing electronics 2 is only activated when pressure is applied to the optical head 3 of the device and the resulting travel againsttheresistanceofa spring 4causes a switch 5to bemadeto enablethe application of powerto an optical emitter6 and the optical processing electronics 2. Referring to Figure 2, when pressure is applied to the tip ofthewand 1, the switch 5 is activated to supply voltage to a light emitting diode7anda phototransistor8together with the optical processing electronics 1.

With the bar code wand 11 of Figure 3,when pressure is applied tothetip of the wand a compressible spacer 12 of rubber allows a small travel of the head 3 within the body operating, albeit momentarily, a membrane switch 13,which in turn, via a timer 14, applies powertothe optical emitter6 and optical processing electronics 2. Referring to Figure 4,when pressure is applied to the tip of the wand 11 of Figure 3 the switch 13closes momentarilyandthevoltage l5goestoearth potential which initiates the monostabletimer 14 which in turn applies powertothe light emitting diode 7, photo transistor 8 and optical processing electronics as previously described, with reference to Figure 3.

When the bar code wand 16 of Figure 5 is bought closetoasurface l7achangein capacitanceoccurs between coupling plate surfaces 18. This change is detected by a capacitive detection processing circuit 19 and power is applied to the optical processing electronics 2 and the optical element 6 for a finite amount oftime sufficient to allow the operatorto scan the bar code. Referring to Figure 6 a sinusiodal oscillator 20 is coupled to a currentto voltage amplifier 21 via the capacitive electrodes 18 fitted to the tip of the bar code wand 16 of Figure 5.When the tip is in free space the value ofthecurrentwill be constant and determined by the sinusiodal applied voltage and the reactance of the capacitance betweentheelectrodes l8sincethecurrentto voltage amplifier 21 can be regarded as a 'virtual earth' input. The output ofthe amplifier21 isapplied to a precision full wave rectifier 22 whose output will be a D.C. voltage. In turn this output is applied to two averaging filters, a slow filter 23 and a fast filter 24.

When the wand 16 is brought close to a surface 17 a change in the effective capacitance ofthe electrodes 18will occur due to a change in the di-electric between them. Hence it can be seen that the fast averaging filter 24 will produce a change while the slow averaging filter 23 will not. The outputs of 23 and 24 are applied to a difference amplifier 25 so that a change atthe output of amplifier 25 is fed to change detector 26. An output pulse fro the detector 26 is used to activate a monostabletimer 27 which in turn energises the optical element 6 and the optical processing electronics 2 of the bar code wand as previously described.

Claims

1. Abarcodewand incorporating an optical emitter and a photo transistor and optical processing electronics for processing signals received by the transistor as reflections of light from the optical emitter, and including an activating device for enabling at leastthe optical emitter only when the tip of the wand incorporating the emitter and transistor is brought into contact with or very close proximity to a surface.

2. Abarcodewand according to claim 1,wherein the activating device is responsible for activating also the photo transmitter and/or the optical processing electronics.

3. Abarcodewand accordingtoclaim 1 orclaim 2, wherein the activating device includes a pressure responsive switch.

4. A bar code wand according to claim 3, wherein the switch is a membrane switch.

5. A bar code wand according to claim 3 or claim 4, wherein a spring, resilient pad or other biasing means within the head of the wand biases parts of the head away from a switch activating position.

6. Abarcodewand according to claim 1 orclaim 2, wherein the activating device incorporates a capacitively operated detecting element at the tip of the barcodewand.

7. A bar code wand according to claim 6, wherein the activating device incorporates a comparatorfor registering a change in capacitance of the detecting elementsoasto produce an enabling signal fora predetermined length oftime.

8. Abarcodewand according to any one of claims 1 to 7, wherein the activating device incorporates a timerfor ensuring that the optical emitter, and any associated circuitry, is enabled for a predetermined length oftime.

9. A bar code wand according to any one of claims 1 to 8, wherein the activating device is effective to enablethe optical emitter either directly or bythe generation of an output signal indicating thatthe wand is in active position so thatthe optical emitter is able to come into operation.

10. Abarcodewandsubstantiallyasherein described with reference to any of the embodiments shown in the accompanying drawings.