Time of flight camera system with a data channel

Abstract

A light speed camera system, with a camera module, which has a light speed photo sensor, preferably based on mixed photo detection, having at least one reception pixel, and with an illumination module which has an illumination light source, wherein the illumination module and the camera module each have a transmission circuit which is formed in such a way that a first signal as a differential signal and a second signal as a modulated basic voltage can be transmitted between the camera module and illumination module via a differential signal line is provided.

Claims

1. A time of flight (TOF) camera system, with a camera module which features a TOF photo sensor, on the basis of photonic mixing detection, with at least one reception pixel and with an illumination module which features an illumination light source, wherein: the illumination module and the camera module respectively feature a transmission circuit which is configured such that a first signal is transmitted as a differential signal and another signal as a modulated basic voltage between the camera module and the illumination module via at least one difference channel, the camera module and the illumination module are connected to each other via two difference channels, wherein both transmission circuits only exhibit galvanic separations at interfaces for both difference channels, and the interfaces do not feature a galvanic separation for modulation and demodulation of the modulated basic voltage, the transmission circuits are configured such that the basic voltage of both difference channels is modulated, and the transmission circuit on a receiver side of the TOF camera system is configured such that a difference of the basic voltages of both difference channels is demodulated as a signal.

2. The TOF camera system according to claim 1, wherein the interfaces for modulation and demodulation are connected via at least one resistance and/or an inductance with the difference channels.

3. A procedure to operate the TOF camera system according to claim 1, wherein the first signal is provided for a transmission of data signals via one of the difference channels as the differential signal, and the another signal by modulation of the basic voltage (U.sub.CM1, U.sub.CM2) of the one of the difference channels.

4. The procedure according to claim 3, wherein the first and a second differential signal are transmitted, and the another signal is a third signal that is transmitted by modulated of the basic voltage of both difference channels.

Description

BRIEF DESCRIPTION

(1) Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

(2) FIG. 1 the basic principle of a TOF camera according to the PMD principle;

(3) FIG. 2 an inventive TOF camera system;

(4) FIG. 3 data transmission by means of an additional data line;

(5) FIG. 4 an inventive data transmission;

(6) FIG. 5 a potential-free data transmission;

(7) FIG. 6 a schematic diagram of a differential signal;

(8) FIG. 7 a potential difference between two difference channels;

(9) FIG. 8 a modulation between two difference channels; and

(10) FIG. 9 a differential signal transmission between two difference channels.

DETAILED DESCRIPTION

(11) FIG. 1 shows a measuring situation for an optical distance measurement with a TOF camera, as it is known, for example, from DE 197 04 496.

(12) The TOF camera system 1 comprises a transmission unit and an illumination module 10, 100 with an illumination light source 12 and an associated beam shaping optics 15, as well as a receiver unit or TOF camera 20 with a receiver optics 25 and a TOF photo sensor 22. The TOF photo sensor 22 features at least one pixel, preferentially, however, a pixel array and is configured in particular as a PMD sensor. The receiver optics 25 typically consists of several optical elements to improve the imaging properties. The beam shaping optics 15 of the transmitter unit 10 is preferentially configured as a reflector. Diffractive elements or combinations of reflecting and diffracting elements, however, can be used.

(13) The measuring principle of this arrangement is essentially based on the fact that the runtime of the emitted and reflected light can be determined on the basis of the phase shift of the emitted and received light. For that purpose, the light source 12 and the TOF photo sensor 22 are impinged via a modulator 30 with a specific common modulation frequency with a first phase position a. The light source 12 sends an amplitude-modulated signal with the phase position a corresponding to the modulation frequency. In the shown case, this signal or the electromagnetic radiation is reflected by an object 40 and, as a result of the distance covered, correspondingly strikes in a phase-shifted manner with a second phase position b on the TOF photo sensor 22. In the TOF photo sensor 22, the signal of the first phase position a of the modulator 30 is mixed with the received signal which has the runtime-induced second phase position b, the phase shift or the object distance 1 being determined from the resulting signal.

(14) FIG. 2 shows a TOF camera system in which the transmitting unit 10 and the receiving unit 20 are arranged in separate modules, namely in an illumination module 100 and in a reception or camera module 300. In the shown example, the camera module 300 also features the modulator 30, which transmits its signal via a data transceiver 301 and via a transmission channel 200 to the data transceiver 101 of the illumination module 100, and then to the transmission unit 10. If a response of the illumination module 100 is not provided, the data transceiver 301 of the camera module 300 can also be configured as a simple transmitter, and the data transceiver 101 of the illumination module as a simple receiver.

(15) FIG. 3 shows an exemplary typical connection of the camera module 300 with the illumination module 100 via three data channels 201, 202, 401. The transmission circuit or the data transceiver 301 of the camera module 300 exhibits a first and a second data interface 303, 304 for differential signals and provides a third data interface 302 for additional signals, for example as a CAN bus. The transmission circuit or the data transceiver 101 of the illumination module 100 accordingly correspondingly features first and second data interfaces 103, 104 as well as a third interface 102 for the additional third data channel 401. The first and second difference channel 201, 202 are preferentially bundled via a common cable 200 for the transmission. The modulation for the illumination and camera module 300 are preferentially transmitted via the first difference channel 201 to the illumination module 100. A safety-relevant response, for example according to the ASIL-B standard, can transmit a return signal preferentially originating at the transmitting second data interface 104 via the second difference channel 202 to the second data interface 304 to the camera module 300. To transmit other operationally relevant data, in particular diagnostic data, an additional data line 401, which furthermore is guided via its own cable 400, is required. As a rule, the diagnostic data is not time-critical and can also be transmitted, if necessary, in a simple data protocol.

(16) To avoid additional cabling expenses without having to lose relevant data, a design according to FIG. 4 is recommended. The transmission of the modulation to the illumination module 100 as well as the corresponding response still occurs, as in FIG. 3, via the first and second difference channel 201, 202. The diagnostic data, on the other hand, is not transmitted via a separate cable, but via the already available difference channels 201, 202, by modulating a corresponding data information. In the shown example, it is provided to transmit the diagnostic data from the illumination module 100 in the direction of the camera module 300. To that end, the data is transmitted from the third data interface 102 to the first and second modulation unit 105, 106 for correspondingly modulating the first and second difference channels 201, 202. On the receiver side, the signal is demodulated in the camera module 300 via a first and second demodulator 305, 306 and is provided to the third interface 302 for further processing. Depending on the intended use, this modulation channel can also be configured as a forward and reverse channel or bi-directionally.

(17) The inventive solution now offers different arrangement options. The solution shown in FIG. 4 is essentially characterized by a differential signal modulated onto both data channels between the first and second data channel 201, 202. This additional data flow can be assessed by evaluating the potential differences between both data channels. In another embodiment, the basic potential is evaluated in relation to the reference or ground potential. In a design shown in FIG. 4, this facilitates a data transmission in four data channels.

(18) FIG. 5 shows a preferred embodiment, which, in contrast to the example shown in FIG. 4, provides a galvanic separation 80 before the interfaces 103 and 104 of the illumination module 100. The galvanic separation 80 is, in particular, configured as a transformer, but can also be configured as a capacitive, or optionally also as an optical transmitter, or in general as a transducer. Such a potential-free transmission permits a greater freedom during the modulation of a third signal onto both difference channels 201, 202. For example the modulation can occur in voltage ranges, or at amplitudes which lie outside the allowed “common mode” of the LVDS drivers. Transverse currents between the camera and the illumination modules 300, 100 can in addition also be prevented.

(19) During the transmission of the third signal, the modulation occurs as a signal difference between the first and second difference channel 201, 202. In the simplest case, this can occur as a simple amplitude demodulation, but also other types of modulation can be transmitted. In particular, the third signal can also be transmitted as a differential signal.

(20) The interfaces 102 or 302 can advantageously be configured for modulation or demodulation without a galvanic separation. In order to prevent transverse currents, both or one of both interfaces 102 and 302 can be connected via a resistance or a resistance network with the respective LVDS line or channel 201, 202. Likewise, a connection can also occur via inductances or corresponding networks.

(21) FIG. 6 schematically shows a time profile of an LVDS signal. The differential signal U.sub.D hereby varies around a basic potential and common mode signal U.sub.CM of 1.2 volts by +/−100 mV. The high signal thus lies at 1.3 volts and the low signal at 1.1 volt. Since, for the evaluation of the LVDS signal only the difference U.sub.D of both signals is used, it is basically immaterial at what level the basic potential U.sub.CM is located. The modulation of the basic potential U.sub.CM thus basically leaves the differential signal U.sub.D uninfluenced. What is important is that both line pairs of a difference channel 201, 202 are synchronously allocated with a potential off-set or potential modulation.

(22) FIG. 7 shows a preferred inventive procedure, in which both difference channels 201, 202 are controlled in a potential-free manner according to FIG. 5, wherein on the potential-free segment, the basic potential or the common mode voltage U.sub.CM1,2 are individually adjustable on each difference channel 201, 202. The information can thus to be transmitted via the modulation of the voltage difference U.sub.DCM1,2 between both difference channels 201, 202.

(23) FIG. 8 shows a simplified option, according to which the basic potential U.sub.CM2 of the second difference channel 202 is kept constant, and basically only the first basic potential U.sub.CM1 is modulated. For the sake of overview, the LVDS profile of both channels 201, 202 is not shown. The transmitted information is to be extracted from the time profile of the voltage difference U.sub.DCM1,2 between both channels 201, 202. During a transmission of the signal via coils or condensers, a DC-free signal code, for example a Manchester code, is to be preferred.

(24) As already mentioned, the information can be transmitted in various types of modulation, in particular, a transmission as a differential signal, especially as an LVDS is also possible, as shown, for example, in FIG. 9.

LIST OF REFERENCE NUMERALS

(25) 1 TOF camera system 10 Transmission unit 12 Illumination source 15 Beam shaping optic 20 Receiver unit, TOF camera 22 TOF photo sensor 25 Receiver optics 80 Galvanic separation 100 Illumination module 101 Data transceiver or transmission circuit of the illumination module 102 Third interface for additional 3.sup.rd data channel 103 First data interface for differential signals 104 Second data interface for differential signals (optional) 105 First modulation unit onto the 1.sup.st difference channel 106 Second modulation unit onto the 2.sup.nd difference channel 200 Transmission channel—cable for modulation 201 First difference channel 202 Second difference channel (optional) 300 Receiver module, camera module 301 Data transceiver or transmission circuit of the receiver module 302 Third interface for additional third data channel 303 First data interface for differential signals 304 Second data interface for differential signals 305 First demodulator for the first difference channel 306 Second demodulator for the second difference channel 400 Transmission channel—cable for diagnostic data 401 Third data channel