DE102004059604A1 - Optoelectronic detector for marks on contrast model, has transmitter and receiver forming distance sensor element and also linkage of detected distance value and amplitude value for elimination of disturbing signal portions - Google Patents

Abstract

Optoelectronic detector (1) has transmitter (4) and receiver (6) which form distance sensor element, which works according to phase measuring principle. A linkage of detected distance value and amplitude value of the transmitting signals of the receiver takes place, for the elimination of disturbing signal portions, during the contrast model detection in the evaluating processor unit (8).

Description

The The invention relates to an optoelectronic device according to the preamble of claim 1.

such Optoelectronic devices are designed in particular as bar code readers, by means of which brands designed as barcodes can be detected. to Detection of the barcodes become the transmitted light rays emitted by the transmitter by means of a deflection unit periodically within a scanning range distracted. The reflected light rays reflected at the bar code is according to the light and dark bar elements of the barcode formed contrast patterns impressed an amplitude modulation, which for detecting the barcode in the evaluation unit of the optoelectronic Device is evaluated.

The Amplitude modulation of the received signal consists of a Sequence of edges, which in the evaluation unit for decoding the Barcodes is evaluated. The barcode itself is on items like Packages and the like printed. By the possibly high-contrast Surroundings of the barcode, which when scanning with the transmitted light beams is detected by the optoelectronic device, arise while every sampling period, that is while a scan within which the transmitted light rays sweep the scanning area, further edges in the received signal, in addition to the edges of the received signal, which are caused by the contrast pattern of the barcode occur.

The additional Flanks in the received signals make error-free decoding difficult the barcodes considerably.

Of the Invention is based on the object, an optoelectronic device of the aforementioned type so that with this as possible low constructive effort a safe detection of brands feasible is.

to solution This object, the features of claim 1 are provided. advantageous embodiments and appropriate training The invention are described in the subclaims.

The Optoelectronic device according to the invention is used to detect contrast marks and brands has a transmitting light beam emitting transmitter, a receiving light beams receiving recipient and a deflection unit for periodic deflection or transmitted light rays within a scanning range. In addition, the optoelectronic device according to the invention an evaluation unit, in which for decoding the marks the amplitude of the received light beams impressed by the contrast pattern amplitude modulation be evaluated. The transmitter and the receiver form according to the phase measurement principle working distance sensor element. For the elimination of interference signal components In contrast pattern detection, a link is made in the evaluation unit determined distance values and amplitude values of the received signals Recipient.

There the transmitter and the receiver the optoelectronic invention Device in addition form a distance sensor element, in addition to the mark detection also distance information about detected objects are recovered. According to the invention this distance information with the amplitude values of the received signals linked in the evaluation unit, to noise components, in particular Flanks in the received signals that are not detected by one Brand come to eliminate.

Especially Advantageously, the elimination of interference signals is such that of the received signals detected within one scan, ie within one sampling period only those received signals used for further evaluation that come from objects in a given distance range, and which are within a predetermined amplitude range.

By this combined evaluation of distance and amplitude information can Signals that are not from a given reading range are efficient be hidden. Also can Signal components of particularly strong and weakly light-reflecting Objects are to be eliminated. Because the reflectivities of surfaces are known to be detected brands, so signal components, the come from environments of the brand, be eliminated safely.

With the optoelectronic device according to the invention, the number of edges to be evaluated is thus considerably reduced in the course of the received signals, which considerably simplifies the evaluation in the evaluation unit for decoding a mark. Apart from the fact that the detection reliability according to the invention increases the detection of marks, the reduction of the edges to be evaluated also reduces the computing time required for decoding the marks in the evaluation unit. Thus, the evaluation can be designed in the form of inexpensive microcontrollers, whereby the Manufacturing costs of the optoelectronic device can be kept low.

to execution the distance measurements is the transmitted light beams by means of a modulator one Amplitude modulation with a given modulation frequency impressed. Through the light-time experience those who are reflected by an object Receive light beams a phase shift of the modulation frequency. To determine the distance then the phase shift of the modulation frequency between transmitted light beams and received light beams, wherein for this purpose a suitable phase detector is provided.

The carried out in this way Distance measurement requires a very small amount constructive effort. It is essential that the modulation frequency to carry out the distance measurement outside the frequency range of the amplitude modulations, which is the Receiving light beams are impressed by the contrast pattern of the brands. In this way, both measurements are without mutual interference feasible.

In a particularly advantageous embodiment of the invention for reinforcement the received signals a non-linear amplifier with a preferred logarithmic Characteristic used. The non-linear amplifier has a limiter output and a rectifier output. The pending at the limiter output Output signals are modulated with the modulation frequency and included the for the distance measurement necessary distance information. Because the amplitudes the output signals are limited, these no longer contain the information about the contrast pattern of the sampled mark.

Vice versa are rectified and then logarithmically amplified Receive signals in the non-linear amplifier generates video signals and over output the rectifier output, which is an amplitude variation caused by the contrast pattern of the detected mark is conditional. The rectifier function is the modulation eliminated with the modulation frequency from the video signal, so that this only the code information of the detected brand, however no longer contains the distance information.

Consequently can by separate evaluation of the output signals at the limiter output and the video signals at the rectifier output the distance information and code information of the brand separately and independently of each other be evaluated.

In a particularly advantageous embodiment of the invention not just the receive signals in a receive nonlinear amplifier strengthened. Rather, the output signals of the modulator, the Modulation of the transmitted light rays serves, in a transmitter-side nonlinear amplifier strengthened which is preferably identical to the receiving-side non-linear amplifier.

Thereby be the phase detector on the Limiting outputs the transmitting and receiving side nonlinear amplifier both transmission signals and reception signals in the form of amplitude-limited, preferably rectangular output signals fed. This ensures that the signal at the output of the phase detector a linear dependence from the phase difference of the output signals of both non-linear Amplifier has, whereby a particularly accurate distance measurement is made possible.

Farther can Particularly advantageous signals at the rectifier outputs of transmit and receive amplifier of a differential stage supplied in which the difference between the two signals is formed. The thus formed signal difference is independent of any variations in the Transmission power of the transmitter, whereby the subsequent evaluation in the evaluation is considerably simplified.

In a particularly advantageous embodiment of the invention the transmit and receive nonlinear amplifiers and the phase detector part of an integrated circuit. This leads to a further reduction of the manufacturing costs of the optoelectronic invention Contraption.

In An advantageous development of the invention is a cyclic Reference measurement against a in the sampling area in a fixed predetermined Distance arranged reference object. With this reference measurement can Error in the distance measurements due to drifting and aging be eliminated from components.

In a further advantageous embodiment of the invention is in dependence the determined distance measurements an adjustment of the focus position of Transmitter, whereby an autofocus function in the optoelectronic device to the automatic Optimization of the current reading range is achieved.

The The invention will be explained below with reference to the drawings. It demonstrate:

1 : Block diagram of a first exemplary embodiment of an optoelectronic device.

2 : Timing
a) the received signals at the output of the receiver
b) the unfiltered video signals at the rectifier output of the non-linear amplifier of the optoelectronic device according to 1
c) the output signals at the limiter output of the non-linear amplifier of the optoelectronic device according to 1
d) the filtered video signals at the rectifier output of the non-linear amplifier of the optoelectronic device according to 1

3 :
a) Time course of the received signals upon detection of two barcodes at different distances to the optoelectronic device according to 1
b) Time course of the video signal at the rectifier output of the non-linear amplifier of the optoelectronic device according to 1 ,

4 : Block diagram of a second embodiment of an optoelectronic device.

1 shows a first embodiment of an optoelectronic device 1 for detecting contrasting marks. In the 1 Trademark shown is from a barcode 2 whose contrast pattern is formed in the form of an alternating sequence of dark and light line elements of predetermined width.

The optoelectronic device 1 has a transmitted light rays 3 emissive transmitter 4 and a receiving light beam 5 receiving recipient 6 on. Furthermore, a deflection unit 7 provided by means of which the transmitted light beams 3 be deflected periodically within a scanning range. The deflection unit 7 is formed in the present case by a rotating polygon mirror wheel, via which the transmitted light beams 3 and the received light beams 5 are guided. The one from the transmitted light rays 3 swept scan area extends in a plane and extends as in 1 represented over an angular range α.

The over the deflection unit 7 deflected transmitted light rays 3 be over the barcode 2 led and from this as receiving beams 5 to the recipient 6 reflected back. Due to the contrast pattern of the barcode 2 becomes the receiving light beams 5 imprinted an amplitude modulation, which is the code information of the barcode 2 contains and which in an evaluation unit 8th for decoding the barcode 2 is evaluated. The evaluation unit 8th is formed in the present case of a microcontroller.

The transmitter 4 and the receiver 6 do not serve solely for the detection of barcodes 2 , The transmitter 4 and the receiver 6 also form a working according to the phase measurement principle distance sensor element.

To carry out the distance measurements are from the transmitter 4 emitted transmitted light rays 3 by means of a modulator 9 with a modulation frequency f _M , which is in an oscillator 10 , in particular a sine wave oscillator, is generated, modulated.

Due to the finite light transit time, the phase of the received light rays reflected back from an object is 5 to the phase of the transmitted light beams modulated by f _M 3 postponed. To determine this phase difference is a phase detector 11 provided, which is preferably formed by a mixer.

Thus the distance measurement and the detection of the contrast patterns of the barcodes 2 can occur independently of each other, the modulation frequency f _{M is} outside the frequency range, in which the by the contrast pattern of the barcodes to be detected 2 Conditional amplitude modulations are. Preferably, the modulation frequency f _{M is selected to be} five to ten times higher than the frequencies of the amplitude modulations caused by the contrast patterns.

The at the output of the receiver 6 pending receive signals become a filter 12 supplied, which is formed in the present case of a band-pass filter whose center frequency corresponds to the modulation frequency f _M.

The received signals filtered in this way become a receiving-side non-linear amplifier 13 supplied with logarithmic characteristic. The nonlinear amplifier 13 has a limiter output 13a and a rectifier output 13b on.

At the limiter output 13a output signals are output, which are generated from the received signals in that their maximum amplitudes are limited to a predetermined value. The output signals are in the form of square wave _signals varying at the modulation frequency f _M. Due to the limitation of the amplitudes of the output signals, the amplitude modulations which are caused by the contrast pattern of the detected barcode are eliminated therein. Thus, the output signals at the limiter amplifier alone contain the distance information about the detected barcode 2 , At the rectifier output 13b Video signals are output. These video signals are obtained by rectification and subsequent logarithmic amplification of the Emp won catch signals. Due to the rectification, the video signals no longer vary with the modulation frequency f _M. Rather, the video signals alone contain an amplitude variation in the form of an envelope modulation, which contain the code information of the detected barcode.

To determine the distance, the output signals of the modulator 9 over a filter 14 , which in the present case is formed by a low-pass filter, the phase detector 11 fed. Likewise, the output signals are at the limiter output 13a the phase detector 11 fed. In the phase detector 11 is generated from these output signals, a signal which is proportional to the phase difference of the received light beams 5 towards the transmitted light emitted by the transmitter 3 is. The signal at the output of the phase detector 11 is about a filter 15 , which is preferably formed by a low-pass filter, in the evaluation unit 8th read. In the evaluation unit 8th the corresponding object distance is calculated from the phase difference.

The video signals at the rectifier output 13b of the nonlinear amplifier 13 be over another filter 16 , which is preferably designed as a low-pass filter, in the evaluation unit 8th read. Based on the video signals, the decoding is done with the transmitted light beams 3 scanned Barco's 2 , For this purpose, the flanks of the video signal, which are the transitions between the light and dark bar elements of the detected barcode 2 correspond in the evaluation unit 8th evaluated.

During a scanning period, that is, during a scan, the transmitted light beams become 3 not just about the barcode to be captured 2 but also about the environment of the barcode 2 , This environment may be formed, for example, by a package or the like on which the barcode 2 is applied. Furthermore, further background objects may be during a scan with the transmitted light beams 3 be recorded.

The detection of such further objects optionally leads to further edges in the video signal. To eliminate these additional edges are at the evaluation 8th valid distance ranges and amplitude ranges of the video signal defined. Only if the distance and amplitude values currently determined within a scan lie within these validity ranges are the corresponding edges of the video signal used for further evaluation. Flanks of the video signal for which distance or amplitude values lying outside of the validity ranges are rejected, on the other hand. In this way, edges of the video signal can not be detected by a barcode to be detected 2 come, with high security be filtered out.

The 2a - 2d show the time profiles of the received signals and the output signals at the limiter output 13a and rectifier output 13b of the nonlinear amplifier 13 within a scan when detecting a barcode 2 , It shows 2a the timing of the received signals at the output of the receiver 6 , According to the transmission beams 3 impressed modulation frequency f _{M also} varies the received signal with this modulation frequency. By the reflection of the received light beams 5 at the barcode 2 is the receiving light beams 5 and thus impressed on the received signals an amplitude modulation in the form of an envelope modulation.

In each case, the regions of the received signal with a high amplitude originate from the detection of a bright bar element of the barcode 2 and the regions of low amplitude from the detection of a dark bar element of the bar code 2 ,

The 2 B shows the video signals at the rectifier output 13b of the nonlinear amplifier 13 , 2d shows the in the filter 16 filtered video signals. By rectification and subsequent logarithmic amplification of the received signals in the nonlinear amplifier 13 is eliminated in the video signals of varying with the modulation frequency f _M signal component. Accordingly, the video signal contains only the envelope modulation, the code information of the detected barcode 2 contains. This code information will be in the evaluation unit 8th evaluated for decoding the barcode.

2c shows the time course of the output signals at the limiter output 13a of the nonlinear amplifier 13 , By limiting the output signal to a constant maximum amplitude, the envelope modulation of the received signal containing the code information is eliminated in the output signals. The rectangular output signals varying with the modulation frequency f _M are with respect to that with the modulator 9 generated modulation of the transmitted light rays 3 phase. This phase shift as a measure of the distance of the barcode 2 the optoelectronic device 1 is in the phase detector 11 determined and in the evaluation unit 8th evaluated.

The 3a . 3b show the temporal courses of the received signal ( 3a ) and the filtered video signal ( 3b ) when detecting two identical barcodes 2 at different distances. The area marked I shows the signal components for the detection of the first barcode 2 in close proximity to the optoelectronic device 1 , The area labeled II shows the signal components for the Detection of the second barcode 2 in greater distance. Because the first barcode 2 at a closer distance to the optoelectronic device 1 is arranged, the signal amplitudes of the received signal in the area I are greater than in the area II. Since the barcodes 2 are formed identically, the ratios of the amplitudes for the detection of light and dark areas for both areas I and II are identical.

Because of this, the video signals ( 3b ) by the logarithmic amplification of the received signals in both regions I and Π the same signal value between maximum amplitude (corresponding to a bright bar element of a barcode 2 ) and minimum amplitude (corresponding to a dark bar of a barcode 2 ) on.

Due to the different distances of the barcodes 2 For example, the video signals in area I are shifted from the signals II only by a constant level.

By additionally performed distance measurement and comparison of the current distance values with a valid distance range, for example, the signal components in the region II can be eliminated, so that in the evaluation 8th only the area I of the video signal for decoding the first barcode 2 in the short distance to the optoelectronic device 1 is evaluated.

4 shows a second embodiment of the optoelectronic device 1 , The structure of the optoelectronic device 1 according to 4 corresponds substantially to the embodiment according to 1 , In contrast to the embodiment according to 1 has the optoelectronic device 1 according to 4 one to the modulator 9 and the filter 14 downstream transmit side nonlinear amplifier 17 on, the same with the receiving side non-linear amplifier 13 is trained. The two nonlinear amplifiers 13 . 17 and the phase detector 11 are components of an integrated circuit. The limiter output 17a the transmission side nonlinear amplifier 17 is as well as the limiter output 13a the receiving side nonlinear amplifier 13 on the phase detector 11 guided. Because with the sendesei non-linear amplifier 17 the output signals of the modulator 9 in rectangular output signals at the limiter output 17a be converted and accordingly also at the limiter output 13a the receiving side nonlinear amplifier 13 rectangular output signals arise, the signal varies at the output of the phase detector 11 linear with the phase shift between transmitted light beams 3 and receiving light beams 5 , whereby a particularly simple and accurate distance determination is made possible.

Another difference from the embodiment according to 1 exists in the optoelectronic device 1 in that the video signals at the rectifier output 13b the receiving side nonlinear amplifier 13 as well as the signals at the rectifier output 17b the transmitter-side non-linear amplification 17 a differential level 18 are fed. The signals at the output of the differential stage 18 be over the filter 16 the evaluation unit 8th fed. By difference formation in the differential stage 18 carry variations of the transmission power of the transmitter 4 not to a change of the code information containing signals at the output of the differential stage 18 ,

The embodiments according to 1 and 4 can be developed such that one of the filters 12 or 14 is formed by a tunable all-pass filter. By tuning the allpass filter, existing phase shifts within the electronics can be eliminated so that the input signals of the phase detector 11 essentially alone by the light transit time of the transmitted light beams 3 from the transmitter 4 to the barcode 2 and back to the receiver 6 have formed phase difference.

1

optoelectronic contraption

2

barcode

3

Transmitted light beams

4

transmitter

5

Receiving light rays

6

receiver

7

Deflector

8th

evaluation

9

modulator

10

oscillator

11

phase detector

12

filter

13

amplifier

13a

Limiter output

13b

Rectifier output

14

filter

15

filter

16

filter

17

amplifier

17a

Limiter output

17b

Rectifier output

18

differential stage

Claims (23)

Optoelectronic device ( 1 ) for detecting marks having contrast patterns, with a transmitted light beam ( 3 ) emitting transmitter ( 4 ), a received light beam ( 5 ) receiving recipients ( 6 ), a deflection unit for the periodic deflection of the transmitted light beams ( 3 inside half of a scanning range, and with an evaluation unit ( 8th ), in which the decoding of the marks which the received light beams ( 5 ) are evaluated by the contrast patterns impressed amplitude modulations, characterized in that the transmitter ( 4 ) and the recipient ( 6 ) also form a working according to the phase measurement principle distance sensor element, and that for the elimination of interference signal components in contrast pattern detection in the evaluation unit ( 8th ) a combination of determined distance values and amplitude values of the received signals of the receiver ( 6 ) he follows. Optoelectronic device ( 1 ) according to claim 1, characterized in that, during a sampling period in the receiver ( 6 ) registered received signals in the evaluation unit ( 8th ) are evaluated only those received signals that come from a lying in a predetermined distance range mark and whose amplitudes are within a predetermined amplitude range. Optoelectronic device ( 1 ) according to one of claims 1 or 2, characterized in that for carrying out distance measurements the transmitted light beams ( 3 ) by means of a modulator ( 9 ) Amplitu denmodulation with a predetermined modulation frequency f _{M is} impressed. Optoelectronic device ( 1 ) according to claim 3, characterized in that the modulation frequency f _M outside the frequency range of the received light beams ( 5 ) is due to the amplitude patterns of the marks impressed amplitude modulations. Optoelectronic device ( 1 ) according to claim 4, characterized in that the received signals at the output of the receiver ( 6 ) a receive-side non-linear amplifier ( 13 ) with a rectifier output ( 13b ) and a limiter output ( 13a ), wherein at the rectifier output ( 13b ) Video signals whose amplitude variation corresponds to the contrast pattern of the respectively detected mark, and wherein at the limiter output ( 13a ) Output signals containing distance information are pending. Optoelectronic device ( 1 ) according to claim 5, characterized in that the non-linear amplifier ( 13 ) has a logarithmic characteristic. Optoelectronic device ( 1 ) according to one of claims 5 or 6, characterized in that for determining the distance the output signals of the modulator ( 9 ) and at the limiter output ( 13a ) of the receiving-side non-linear amplifier ( 13 ) a phase detector ( 11 ). Optoelectronic device ( 1 ) according to claim 7, characterized in that the phase detector ( 11 ) is formed by a mixer. Optoelectronic device ( 1 ) according to one of claims 3 to 8, characterized in that the modulator ( 9 ) and the recipient ( 6 ) one filter each ( 12 . 14 ) is subordinate. Optoelectronic device ( 1 ) according to claim 9, characterized in that one of the filters ( 12 . 14 ) is formed by a tunable all-pass filter. Optoelectronic device ( 1 ) according to one of claims 5 to 10, characterized in that the output signals at the limiter output ( 13b ) of the receiving-side non-linear amplifier ( 13 ) via a filter ( 16 ) of the evaluation unit ( 8th ) are supplied. Optoelectronic device ( 1 ) according to one of claims 7 to 11, characterized in that the signals at the output of the phase detector ( 11 ) via a filter ( 15 ) of the evaluation unit ( 8th ) are supplied. Optoelectronic device ( 1 ) according to one of claims 12 or 13, characterized in that the filters ( 15 . 16 ) are each formed by a low-pass filter. Optoelectronic device ( 1 ) according to one of claims 9 to 13, characterized in that the filtered output signals of the modulator ( 9 ) a transmitter-side non-linear amplifier ( 17 ), which has a limiting output ( 17a ) and a rectifier output ( 17b ), are supplied. Optoelectronic device ( 1 ) according to claim 14, characterized in that the transmitter-side non-linear amplifier ( 17 ) and receiving nonlinear amplifiers ( 13 ) are formed identically. Optoelectronic device ( 1 ) according to one of claims 14 or 15, characterized in that the output signals of the limiter outputs ( 13a . 17a ) of the transmitting side and receiving side nonlinear amplifiers ( 13 . 17 ) the phase detector ( 11 ) are supplied. Optoelectronic device ( 1 ) according to claims 14 to 16, characterized in that the rectifier outputs ( 13b . 17b ) of the transmit and receive nonlinear amplifier ( 13 . 17 ) of a differential stage ( 18 ) are supplied. Optoelectronic device ( 1 ) to An Claim 17, characterized in that the signals at the output of the differential stage ( 18 ) via a filter ( 16 ) of the evaluation unit ( 8th ) are supplied. Optoelectronic device ( 1 ) according to claim 18, characterized in that the filter ( 16 ) is formed by a low-pass filter. Optoelectronic device ( 1 ) according to one of claims 14 to 19, characterized in that the transmitter and receiver non-linear amplifier ( 13 . 17 ) and the phase detector ( 11 ) Are components of an integrated circuit. Optoelectronic device ( 1 ) according to one of claims 1 to 20, characterized in that for the cyclical referencing of distance measurements made with the distance sensor reference measurements against a within the scanning range arranged at a predetermined distance reference object are performed. Optoelectronic device ( 1 ) according to one of claims 1 to 21, characterized in that, depending on the distance measurements made with the distance sensor element, an adjustment of the focus position of the transmitter ( 4 ) is feasible. Optoelectronic device ( 1 ) according to one of claims 1 to 22, characterized in that the marks of barcodes ( 2 ) are formed.