WO2000057347A1

WO2000057347A1 - Optical data reader with cableless infrared link

Info

Publication number: WO2000057347A1
Application number: PCT/US2000/007366
Authority: WO
Inventors: Shane P. Cooper; Chay K. La
Original assignee: Psc Scanning, Inc.
Priority date: 1999-03-19
Filing date: 2000-03-16
Publication date: 2000-09-28

Abstract

A cableless infrared optical data reading system, including a hand held optical reader (10) with a plurality of infrared LED's (15) which transmits data read from a bar code (20) to a remote infrared receiver (30) that is attached to an external data processor (35). The plurality of LED's (15) are disposed in a pattern which allows substantially omni-directional orientation of the optical reader (10), while maintaining a reasonably clear signal path to the remote infrared receiver (30). The infrared receiver (30) receives data transmitted by the optical reader (10), and sends a demodulated signal to the data processor (130) at the appropriate voltage levels.

Description

i i C_. 1 L L C. A L L Q. N

OPTICAL DATA READER WITH CABLELESS INFRARED LINK

BACKGROUND OF THE INVENTION The field of the present invention generally relates to optical systems for data reading. More particularly, the field of the present invention relates to a cordless optical data reading system having an improved wireless communication link between an optical reader and a separate receiving device.

Optical reading systems are widely used to read data, in the form of bar codes or other encoded symbols, printed on various objects. Typically, these systems employ an optical reader that illuminates a bar code (for example) and detects light reflected from the bars and spaces of the code. In a common system, an optical beam of light produced by a laser diode is used to scan the bar code symbol. The bars of the code absorb light, while the spaces of the code reflect light. The resulting pattern of reflected light is detected by circuitry within the optical reader. The reflected light is commonly detected by a photocell, photodiode, CCD array, or CMOS array sensor.

After the bar code is read by the optical reader, the detected signal is usually subject to filtering, amplification, digitization and decoding. In addition, the detected signal may be transmitted to data processing equipment located within the optical reader, or to a separate device such as a personal computer. In conventional systems where the signal is conveyed to a separate device, the optical reader is connected to the external data processor by means of cables. However, bulky cables limit the mobility of the optical reader, and take up additional space.

To provide greater mobility to the user, several wireless optical readers have been proposed. In such wireless optical reading systems, data is generally transmitted from the optical reader to an external data processor via a wireless communication link. Some of these systems employ radio frequency (RF) equipment for enabling wireless operation. However, RF optical reading systems are prone to electromagnetic interference from other electrical devices. Furthermore, RF equipment can be bulky and relatively expensive. Other wireless optical reading systems rely on infrared (IR) transmitters and receivers. One such example is found in U.S. Patent No. 4,418,277, issued to Tremmel et al., which describes a portable wand reader, that transmits a coded infrared signal to a stationary receiving/transmitting unit coupled to a data processor. However, in the system described in that patent, a number of stationary receiving/transmitting units are needed in order to operate the data reader within a large region. As a result, the mobility of the optical reader may be limited by the number of stationary receiving/transmitting units employed, and by the need for a clear communication path between the stationary receiving/transmitting units and the transmitting/receiving units on the optical reader. Furthermore, the use of multiple stationary receiving/transmitting units can be expensive and requires ample mounting space.

SUMMARY OF THE INVENTION The present invention relates in one aspect to a cableless infrared optical data reading system with an improved wireless communication link between a hand held optical reader and a separate receiving terminal. In one embodiment, a battery powered, hand held optical reader uses infrared light emitting diodes (LED's) to transmit data to the receiving terminal. The infrared LED's are preferably mounted around the trunk of the optical reader handle in such a way as to provide substantially omni-directional coverage, allowing the optical reader to be rotated or tilted at any orientation with respect to the stationary receiver without substantially impeding the IR communication link therewith. An exemplary embodiment in this regard includes four infrared LED's positioned circumferentially around the base of the optical reader handle. The receiving unit includes an IR receiver, which receives the data transmitted by the infrared LED's on the optical reader, demodulates the received signal, and sends the demodulated signal, at the appropriate voltage levels, to a host such as a personal computer. In addition to an IR receiver, the receiving unit may also include transmitter circuitry, which can send a modulated signal from the personal computer to the optical reader, thereby enabling two- way communication between the optical reader and the personal computer.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 A is a diagrammatic side view of a hand held optical reader and a remote ER receiver, attached to a personal computer, according to an embodiment of the present invention; Fig. IB is a diagrammatic bottom cross-sectional view of an embodiment of the optical reader shown in Fig. 1 A.

Fig. 1C is a side view of the optical reader handle shown in Figs. 1 A and IB;

Fig. 2 is a block diagram of an embodiment of a bar code scanning system; Fig. 3 is an electrical schematic of an IR transmitter according to an embodiment as described herein; and

Fig. 4 is an electrical schematic of an IR receiver according to an embodiment as described herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments will now be described with reference to the drawings. For simplicity of description, any element numeral in one figure will represent the same element if used in any other figure.

Figs. 1A, IB and 1C illustrate an example of a preferred battery powered, hand held optical reader 10. The optical reader 10 includes a head portion 12, a handle portion 14, and a base 13. The optical reader 10 may contain a light source, a detector, an optical lens and signal processing circuitry, not shown in Fig. 1 A, but all of which are well known in the art, for scanning an encoded symbol 20 (such as a bar code symbol), including one- dimensional, two-dimensional or stacked bar codes, or error-resilient codes such as PDF417. The optical reader 10 also preferably includes several or more surface-mounted infrared LED's 15, which send infrared signals to a remote IR receiver 30, thereby establishing a wireless communication link. Two infrared LED's 15a and 15b are visible in Figs. 1 A and lC. The IR receiver 30 filters and demodulates the signal sent by the infrared LED's 15, converts the received signal from Transistor Transistor Logic (TTL) voltage levels to RS232 voltage levels, and sends the converted signal to the communication port 37 of an attached personal computer 35.

As shown in the bottom and side views, respectively, of Figs. IB and 1C, the placement of four LED's 15a-d in a radial pattern, about the base 13 of the handle portion 14 provides, a near omni-directional line-of-sight or signal path with respect to the IR receiver 30. In other words, regardless of which way the optical reader 10 is rotated, turned, tilted or otherwise oriented, a reasonably clear signal path between the infrared LED's 15a-d and the stationary IR receiver 30 will still be provided. Tests have shown that the optical reader 10 as configured in Fig. IB provides a relatively clear signal path when oriented in virtually any direction. Even when obstructions are interposed, such as tables or fixtures, the four LED's 15a-d are positioned in a manner that facilitates the transmission of infrared signals, which bounce off the surfaces of the obstructions, and are received as reflected signals by the IR receiver 30.

The base 13 of the handle portion 14 is square, having the four infrared LED's 15a-d disposed at the corners (see Fig. IB). Only two of the infrared LED's 15a and 15b are visible in Figs. 1A and lC. In alternative embodiments, more or fewer than four infrared LED's 15 may be used. However, it is preferred that there are a sufficient number of LED's 15, with appropriate positioning, disposed in such a way as to provide a near omni-directional line-of-sight, so that a relatively clear signal path is provided at most any orientation of the optical reader 10 with respect to the stationary IR receiver 30.

Fig. 2 is a block diagram of various elements of a preferred optical reading system in which the optical reader of Fig. 1 A may be employed. However, the actual components of the optical reading system depends on a variety of preferences and trade-offs which are well understood and may be made by those skilled in the art. Thus, embodiments of the invention may have additional or fewer components, or different or altered components to those shown in Fig. 2.

As shown in Fig. 2, light reflected from an encoded symbol 20 (such as a bar code) passes through an optical lens 100 to a detector 110, which is connected to a control circuit 120. The detector 110 may be comprised of a photocell, photodiode, CCD array, or CMOS array sensor for example. The detected signal is passed through an analog processor 130, which filters the signal. The filtered signal is sent to a digitizer 140, where it is converted from an analog to a digital signal. The digital signal then passes through an edge detector 150 and is converted to data bytes 180, typically corresponding to measurements of features (e.g. bars and spaces) of the encoded symbol 20. The signal may be stored in a buffer or memory 160, before being accessed by a decoder 170, or otherwise further processed.

Some or all of the components described in Fig. 2 may be contained in the optical reader 10 itself. The location of the IR communication link with respect to the elements shown in Fig. 2 primarily depends on convenience for the designing engineer. In a preferred embodiment, at least the lens 100, detector 110, control circuit 120, and analog processor 130 are contained within the optical reader 10. It is preferable for a digital signal rather than an analog signal to be transmitted, because a digital signal is less susceptible to noise interference. Therefore, in a preferred optical reading system, one or more of the digitizer 140, edge detector 150, memory 160, and decoder 170 are also contained within the optical reader 10, with the remaining components (if any) being contained downstream of the IR receiver 30, or their functions may alternately be performed by the personal computer 35.

Fig. 3 is an electrical schematic of an IR transmitter 200 according to a preferred embodiment as described herein. The general purpose of the transmitter circuitry is to transmit a digital signal from a source, such as the decoder 170 located within the optical reader 10, to the remote IR receiver 30 (see Fig. 1 A). The IR transmitter 200 preferably receives transmitted data in the form of an ASCII digital signal sent from the decoder 170. The transmitted signal is connected to the base of NPN transistor 1200 and an input of NAND gate 1220. The other input of NAND gate 1220 is connected to a timer 1240 (such as an LM555 Timer), which sends a 40 KHz square wave signal with a 50% duty cycle. Accordingly, when the signal transmitted from the decoder 170 presents a logic low, no transmission can occur through NAND gate 1220. The output from NAND gate 1220 is applied to the base of NPN transistors 1250 and 1260. Each transistor is connected to a pair of infrared LED's 15, which receive power from a battery source 1229 of suitable rating (e.g. 9 volts).

Fig. 4 is an electrical schematic of an IR receiving unit 300 according to a preferred embodiment as described herein. The general purpose of the circuitry depicted in Fig. 4 is to receive data transmitted by the infrared LED's 15, demodulate and filter the digital signal, and then send the extracted data to a personal computer 35 at the appropriate voltage levels. The IR receiver 30, of receiving unit 300, receives the signal transmitted by the IR transmitter 200. The IR receiver 30 preferably has a built-in demodulator and bandpass filter (not shown), and may be embodied, for example, as a GP1452X IR receiver manufactured by Sharp Electronics Corporation, Mahwah, New Jersey. The filtered signal 1 output from the IR receiver 30 is connected to a level shifter 1300, such as a MAX232 Converter, which converts TTL/CMOS voltage levels (0V to 5 V) of the demodulated and filtered signal 1 to RS232 voltage levels (-12V to +12V). The output 14 of the level shifter 1300 is connected to a serial output pin of a junction connector 1350, such as the Received Data (RX) input for the RS232 Com Port of a personal computer 35. In another aspect, a mechanism for supplying power to the IR receiver is provided. Two pins, for example, such as the Request To Send (RTS) and Data Terminal Ready (DTR) pins of the junction connector 1350 are each connected to a high conductance ultra fast diode 1400, which enables a voltage regulator 1450 to be powered by either the RTS DTR outputs of an the RS232 Com Port. If the signal from either the RTS output or the DTR output is high, then power is transmitted from the RS232 Com Port to the voltage regulator 1450, which converts the transmitted power to a suitable logic level (e.g. from 12V to 5V). The converted power is supplied from the voltage regulator 1500 to the IR receiver 30. Both the IR receiver 30 and the level shifter 1300 may draw power from the RS232 Com Port of a personal computer 35, without requiring an external power supply.

In an alternative embodiment, the IR receiving unit 300 may also contain transmitter circuitry enabling two-way communication between the optical reader 10 and the computer 35. For example, the IR receiving unit 300 may comprise IR transmission circuitry similar to that shown in Fig. 3, and the hand held optical reader 10 may comprise IR receiving circuitry similar to that shown in Fig. 4, but without the connections to the host computer 35.

Thus, while embodiments and applications of the present invention have been shown and described, it would be apparent to one skilled in the art that other modifications are possible without departing from the inventive concepts set forth herein.

Claims

CLAIMS What is claimed is:

1. A portable optical reader comprising: an optical reader housing, said optical reader housing comprising a handle and optical reading circuitry; and a plurality of infrared transmitters disposed upon said optical reader housing in a pattern allowing substantially omni-directional orientation of said optical reader, while maintaining a relatively clear signal path to a remote infrared receiver.

2. An optical reader according to Claim 1 further comprising: an optical lens; a detector; and an analog processor.

3. An optical reader according to Claim 1 further comprising a digitizer.

4. An optical reader according to Claim 1 further comprising an edge detector.

5. An optical reader according to Claim 1 further comprising a memory.

6. An optical reader according to Claim 1 further comprising a decoder.

7. An optical reader according to Claim 1 wherein the optical reader comprises a handheld scanner having a head portion, and wherein the plurality of infrared transmitters comprises four LED's circumferentially disposed about a bottom of the handle portion, evenly spaced about a perimeter thereof.

8. A portable optical reader comprising: an optical reader housing, said optical reader housing comprising a head portion and a handle portion; and a plurality of infrared transmitters constructed and arranged upon said handle portion of said optical reader housing in a pattern allowing substantially omni-directional orientation of said optical reader, while maintaining a relatively clear signal path to a remote infrared receiver.

9. An optical reader according to Claim 8 further comprising: an optical lens; a detector; and an analog processor.

10. An optical data reading system comprising an optical data reader and a remote infrared receiver, the optical data reader comprising an optical lens, a detector, an analog processor, and a plurality of infrared transmitters, disposed in a pattern allowing substantially omni-directional orientation of said optical reader, while maintaining a clear signal path to the remote infrared receiver; and the infrared receiver comprising a demodulator, a filter, and a voltage converter; wherein said infrared receiver is connectable to an external data processor.

11. An optical reading system according to Claim 10 wherein said infrared receiver includes a power regulator.

12. An optical reading system according to Claim 10 wherein said infrared receiver includes transmitting circuitry enabling two-way communication between said optical reader and said external data processor.

13. An optical reader according to Claim 10 wherein the optical data reader comprises a handheld scanner having a head portion and a handle portion and wherein the plurality of infrared transmitters comprises four LED's circumferentially disposed about a bottom of the handle portion, evenly spaced about a perimeter thereof.

14. A method of reading data with a portable optical reader, comprising the steps of: receiving light on a photodetector, and generating a photodetector output signal in response thereto, said photodetector being located on a portable optical reader; processing said photodetector output signal, thereby producing a processed photodetector signal; modulating said processed photodetector signal, thereby producing a modulated photodetector signal; and transmitting said modulated photodetector signal simultaneously from a plurality of infrared transmission sources in such a manner as to maintain a relatively clear signal path with stationary infrared receiver regardless of which way the portable optical reader is oriented.