Optical distance calculation device and method of extending measurable range

Abstract

An optical distance calculation device and a method of extending a measurable range are disclosed. The device includes a light source that emits rays selectively modulated at a first modulation frequency and a second modulation frequency. A photonic mixer unit generates and stores a plurality of electrical output signals that respectively correspond to phase offset values applied according to an indirect time-of-flight technique and with respect to the selected modulation frequencies. A signal processing circuit processes a first number of electrical output signals at the first modulation frequency to calculate a first measurement phase angle from a calculated first measurement vector, and processes a second number of electrical output signals at the second modulation frequency to calculate a second measurement phase angle from a calculated second measurement vector. A phase angle difference between the first and second measurement phase angles is then calculated, and a correction value is applied to the phase angle difference to produce an extended range phase angle for calculating a distance.

Description

TECHNICAL FIELD

[0001] The present invention relates to an optical distance calculation device of the type employing, for example, indirect time-of-flight measurement techniques. The present invention also relates to a method of extending the measurable range of the type employing, for example, indirect time-of-flight measurement techniques to measure the range. BACKGROUND

[0002] In so-called time-of-flight sensing systems and other systems, such as game console vision systems, it is known to employ an illumination source to illuminate the surrounding environment (sometimes referred to as the “scene”) within the field of view of the illumination source, and to process the rays reflected by the features of the scene. Such so-called LiDAR (Light Detection and Ranging) systems use an illumination source to illuminate the scene with rays, and a detection device (e.g. an array of photodiodes, some optical elements and a processing unit) to detect the rays reflected from objects in the scene. The rays reflected from the objects in the scene are received by the detection device and converted into electrical signals, which are then processed by the processing unit by applying time-of-flight (ToF) calculations in order to determine the distance of the objects from the detection device. Although different kinds of LiDAR systems are known based on different operating principles, such systems basically are illuminating the scene and detecting the reflected rays.

[0003] In this respect, the so-called “flash LiDAR” technique, which is a direct ToF ranging technique, employs a light source that emits pulses of rays that are subsequently reflected by the features of the scene and detected by a detector device. In such a technique, the measured time of the round trip to and back from the reflecting features is used directly to calculate the distance to the reflecting features. The pulses of rays incident on the detector device are sampled in the time domain at a very high sampling rate. Therefore, the signal path in the processing circuitry implementing such a technique requires high bandwidth of the signal and large silicon “real estate”, i.e. such implementations require a relatively large area on the silicon wafer, which in turn limits the number of channels that can be supported on the integrated circuit. Therefore, the actual number of channels that can be supported by such a flash LiDAR sensor is typically lower than 100. To overcome this limitation, a mechanical scanning system is required that implements moving parts.

[0004] Another known LiDAR system employs the so-called “indirect time-of-flight” (iToF) ranging technique. The iToF system emits a continuous wave ray signal, and reflections of the continuous wave ray signal are received by a detector device and analyzed. A number of samples (e.g. four samples) of the rays reflected from the features of the scene are taken, each sample being phase stepped by, for example, 90°. Using this illumination and sampling method, the phase angle between the illumination and the reflection can be determined, and the determined phase angle can be used to determine the distance to the reflecting features of the scene.

[0005] In iToF systems, high frequency signal processing (demodulation) occurs at the pixel level and thus the post-pixel signal bandwidth required to integrate a large number of pixels on the same chip is low. As a result, iToF systems can support a larger number of channels and thus a higher spatial resolution measurement compared to direct ToF systems. However, iToF systems have a limited range measurement capability. In this regard, to achieve low random range measurement errors, iToF systems require a high modulation frequency which in turn reduces the unambiguous range of distances that can be unambiguously measured. For example, a 100 MHz modulation frequency results in an approximate unambiguous measurement range of 1.5 m.

[0006] As explained above, iToF systems sample with respect to different applied phases. A typical iToF system comprises a buffer that stores the analog signals generated by the so-called photomixer device with respect to the m phases used for subsequent signal processing. A discrete Fourier transform unit computes the fundamental frequency of the complex signal stored by the buffer in terms of the in-phase and quadrature components of the signal. Using the values of the in-phase and quadrature components, the phase angle and amplitude of the complex signal can be estimated and the distance to the object can be solved using the estimated phase angle information.

[0007] However, such amplitude modulated continuous wave type systems suffer from an inherent depth ambiguity due to the fact that the detectable phase angle information is constrained by the modulation frequency of the illumination ray signal. In this regard, the period of the modulated illumination ray equals the full phase of 2π. As a result, a reflected object at a distance to the illumination source that results in a time of flight that exceeds the period of the modulated illumination signal still falls within the range of distances bounded by the period of the modulated illumination signal and thus within its modulation frequency. This effect is referred to as range aliasing. Objects located in the so-called "unambiguous range" defined by the period of the modulated illumination signal can be correctly detected, but objects that exceed the unambiguous range are aliased back into the unambiguous range and thus detected at the wrong distance. As mentioned above, the unambiguous measurable range (UR) of the system is determined by the modulation frequency of the illumination continuous wave ray signal:

[0008]

[0009] where c is the speed of light, f mod is the modulation frequency of the illumination continuous wave ray signal.

[0010] Accordingly, according to equation (1) above, the unambiguous measurable range can be increased by reducing the modulation frequency, thereby adjusting the unambiguous measurable range such that more objects in the scene can be detected. However, the accuracy of the measured range depends on the signal-to-noise ratio SNR Φ of the estimated phase angle. In this regard, the signal-to-noise ratio SNRΦ The ability of the system to resolve objects at a predetermined resolution is given by the expression:

[0011]

[0012] As can be seen from equation (2) above, if an increased resolution is required, the modulation frequency must be increased, but this conflicts with the desire to decrease the modulation frequency to increase the unambiguous measurable range. Therefore, it is desirable to de-alias measurements of object distances that fall outside the unambiguous measurable range of the system as a method of increasing the unambiguous measurable range without adversely affecting the signal-to-noise ratio.

[0013] “Analysis of errors in ToF Range Imaging With Dual-frequency Modulation” (Jongenelen et al., IEEE Transactions on Instrumentation and Measurement, vol. 60, no. 5, May 2011, pp. 1861-1868) proposes a technique that employs two modulation frequencies to de-alias distance measurements, which uses a multiplicative inverse to determine a pair of aliases associated with the two modulation frequencies respectively. However, this calculation requires a degree of processing power, which is not cost effective for this class of ToF systems.

[0014] DE-B3-102013214677 discloses an alternative de-aliasing technique that also employs two modulation frequencies, but calculates the difference between the two aliased distance estimates and then uses a look-up table to identify the correct alias with respect to a given modulation frequency selected.

[0015] US 10,024,966 discloses another de-aliasing technique that performs de-aliasing in the phase angle domain by calculating a weighted phase difference between two phase angles. Each phase angle used is pre-weighted by a respective predetermined weighting factor. However, like the other de-aliasing techniques described above, at least one multiplication operation must be performed, which is computationally expensive and increases the demand on the existing limited processing resources of a ToF system. SUMMARY

[0016] According to a first aspect of the present application, there is provided an optical distance calculation apparatus comprising: a light source configured to emit a ray in accordance with an indirect time-of-flight measurement technique, the light source being configured to selectively modulate the ray at a first modulation frequency and a second modulation frequency in accordance with a predetermined frequency selection scheme; a photonic mixer unit configured to generate and store a plurality of electrical output signals corresponding to respective phase offset values applied in accordance with the indirect time-of-flight measurement technique and in respect of the selected modulation frequencies; and a signal processing circuit configured to process a first number of the plurality of electrical output signals in respect of the first modulation frequency so as to calculate a first measurement vector and a first measurement phase angle from the first measurement vector, and to process a second number of the plurality of electrical output signals in respect of the second modulation frequency so as to calculate a second measurement vector and a second measurement phase angle from the second measurement vector; wherein the signal processing circuit is configured to calculate a phase angle difference between the first measurement phase angle and the second measurement phase angle, and to apply a correction value to the phase angle difference to produce an extended range phase angle; and the signal processing circuit is configured to use the extended range phase angle to calculate an un-aliased range.

[0017] The signal processing circuit can be configured to apply the correction value in response to a comparison of respective aliasing parameters associated with the first modulation frequency and the second modulation frequency.

[0018] The signal processing circuit can be configured to compare the first modulation frequency and the second modulation frequency.

[0019] The apparatus can further comprise: a first unambiguous measurable range associated with the first measurement phase angle; and a second unambiguous measurable range associated with the second measurement phase angle; wherein the signal processing circuit can be configured to compare the first unambiguous measurable range and the second unambiguous measurable range.

[0020] The calculation of the correction value can depend on a result of the comparison of the respective aliasing parameters.

[0021] The signal processing circuit can be configured to detect a wrap of the phase angle difference by a comparison of the phase angle difference with a phase angle wrap threshold.

[0022] The signal processing circuit can be configured to quantize the first measured phase angle into a first n-bit value and the second measured phase angle into a second n-bit value; the first n-bit value and the second n-bit value can be in an n-bit space, the n-bit space representing an angle range between essentially 0 and essentially 2π in the n-bit space; and the signal processing circuit can be configured to simultaneously calculate the phase angle difference by performing a subtraction operation using the quantized first measured phase angle and the quantized second measured phase angle and apply a correction value to the phase angle difference.

[0023] The signal processing circuit can be configured to select either the first measured phase angle or the second measured phase angle as the minuend of the subtraction operation, depending on the value of the result of the comparison of the respective aliasing parameters.

[0024] The extended range phase angle may have a defined extended range associated with the extended range phase angle; and the signal processing circuit may be configured to use the extended range phase angle to calculate the distance by scaling the defined extended range using the extended range phase angle.

[0025] The signal processing circuit can be configured to convert the first measured phase angle, which has a first defined measurable range associated with the first measured phase angle, into a refined extended phase angle, which has an extended defined measurable range associated with the extended range phase angle.

[0026] The signal processing circuit can be configured to convert the first measured phase angle into a corresponding refined extended phase angle by multiplying and adding a translation of the compressed first measured phase angle, thereby expanding the compressed first measured phase angle.

[0027] The compression ratio used to compress the first measured phase angle can be a proportionality constant; and the signal processing circuit can be configured to calculate the proportionality constant by evaluating the ratio of the first defined measurable range to the extended defined measurable range.

[0028] The signal processing circuit can be configured to calculate the number of rollover repetitions of the first measured phase angle using the difference between the compressed first measured phase angle and the extended range phase angle; and the signal processing circuit can be configured to use the number of rollover repetitions to expand the compressed first measured phase angle.

[0029] The signal processing circuit can be configured to expand the first measured phase angle by adding a scaling translation value based on the number of roll repetitions and the highest angular range value scaled by the scaling constant.

[0030] The signal processing circuit can be configured to convert the first measured phase angle having a first defined measurable range associated with the first measured phase angle into a first refined extended phase angle having a first extended defined measurable range associated with the extended range phase angle; the signal processing circuit can also be configured to convert the second measured phase angle having a second defined measurable range associated with the second measured phase angle into a second refined extended phase angle having a second extended defined measurable range associated with the extended range phase angle; and the signal processing circuit can be configured to calculate the average value of the first refined extended phase angle and the second refined extended phase angle.

[0031] The signal processing circuit can be configured to convert the first measured phase angle and the second measured phase angle into corresponding first refined extended phase angle and second refined extended phase angle by multiplying and compressing the first measured phase angle and the second measured phase angle respectively, and by additively translating the compressed first measured phase angle and the compressed second measured phase angle respectively, thereby expanding the compressed first measured phase angle and the compressed second measured phase angle.

[0032] The signal processing circuit can be configured to sum the first and second measured phase angles before converting the summed first and second measured phase angles into refined extended phase angles having an extended definite measurable range associated with the extended range phase angles.

[0033] The signal processing circuit can be configured to convert the sum of the first measured phase angle and the second measured phase angle into a corresponding refined extended phase angle by multiplying the sum of the first measured phase angle and the second measured phase angle and adding and translating the compressed sum of the first measured phase angle and the second measured phase angle, thereby expanding the compressed sum of the first measured phase angle and the second measured phase angle.

[0034] The compression ratio used to compress the sum of the first and second measurement phase angles can be a proportionality constant; and the signal processing circuit can be configured to calculate the proportionality constant by calculating a combination of the sum of the first and second measurement phase angles to define the measurable range, and evaluating the ratio of the calculated combined defined measurable range to the extended defined measurable range.

[0035] According to a second aspect of the invention, a method for extending the measurable range of an optical distance calculation device is provided, the method comprising: a light source emitting a ray according to an indirect time-of-flight measurement technique, the light source selectively modulating the ray at a first modulation frequency and a second modulation frequency according to a predetermined frequency selection scheme; a photonic mixer unit generating and storing a plurality of electrical output signals, the plurality of electrical output signals respectively corresponding to a phase offset value applied according to the indirect time-of-flight measurement technique and with respect to a selected modulation frequency; and a signal processing circuit processing a first number of the plurality of electrical output signals with respect to the first modulation frequency to calculate a first measurement vector and a first measurement phase angle based on the first measurement vector, and processing a second number of the plurality of electrical output signals with respect to the second modulation frequency to calculate a second measurement vector and a second measurement phase angle based on the second measurement vector; wherein the signal processing circuit calculates a phase angle difference between the first measurement phase angle and the second measurement phase angle, and applies a correction value to the phase angle difference to generate an extended range phase angle; and the signal processing circuit uses the extended range phase angle to calculate an anti-aliasing range.

[0036] According to a third aspect of the invention, a method for extending the measurable range of an optical distance calculation device is provided, the method comprising: emitting a ray according to an indirect time-of-flight measurement technique; selectively modulating the ray at a first modulation frequency and a second modulation frequency according to a predetermined frequency selection scheme; generating and storing a plurality of electrical output signals, each of the plurality of electrical output signals corresponding to a phase offset value applied according to the indirect time-of-flight measurement technique and with respect to a selected modulation frequency; processing a first number of the plurality of electrical output signals with respect to the first modulation frequency to calculate a first measurement vector and a first measurement phase angle based on the first measurement vector; and processing a second number of the plurality of electrical output signals with respect to the second modulation frequency to calculate a second measurement vector and a second measurement phase angle based on the second measurement vector; calculating a phase angle difference between the first measurement phase angle and the second measurement phase angle, and applying a correction value to the phase angle difference to generate an extended range phase angle; and using the extended range phase angle to calculate an anti-aliasing range.

[0037] Therefore, it is possible to provide an apparatus and method for mitigating the limitations of detectable range attributable to aliasing effects inherent in indirect time-of-flight measurement techniques. In this regard, the apparatus and method enable the generation of phase angle measurements corresponding to a longer detection range. The method and apparatus can also be implemented using simple computational techniques, thus avoiding the time, cost, and energy losses associated with computationally intensive techniques. Furthermore, the apparatus and method achieve anti-aliasing without compromising the signal-to-noise ratio of the calculated phase angle. Attached Figure Description

[0038] Now, referring to the accompanying drawings, at least one embodiment of the invention will be described by way of example only, in which:

[0039] Figure 1 This is a schematic diagram of an optical distance calculation device constituting an embodiment of the present invention;

[0040] Figure 2 yes Figure 1 A schematic diagram of the dealiasing unit;

[0041] Figure 3 It is by Figure 1 and Figure 2 A flowchart of a method for extending the measurable range performed by a device and constituting another embodiment of the present invention;

[0042] Figure 4 It is under the condition of the first relative modulation frequency and in the case of... Figure 2 The image of the range of aliasing before the dealiasing unit is processed;

[0043] Figure 5 It is a graph of the phase angle difference and the corrected phase angle under the first relative modulation frequency condition;

[0044] Figure 6 It is under the condition of the first relative modulation frequency by Figure 2 A diagram of the dealiasing phase angle generated by the dealiasing unit;

[0045] Figure 7 It is under the condition of the second relative modulation frequency and in Figure 2 The graph of the range of aliasing before the dealiasing unit;

[0046] Figure 8 It is a graph of the phase angle difference and the corrected phase angle under the second relative modulation frequency condition;

[0047] Figure 9 It is under the condition of the second relative modulation frequency by Figure 2 A diagram of the dealiasing phase angle generated by the dealiasing unit;

[0048] Figure 10 This constitutes yet another embodiment of the present invention. Figure 2 A schematic diagram of the replacement dealiasing unit for the dealiasing unit;

[0049] Figure 11 It is by Figure 1 and Figure 10 A flowchart of another method for extending the measurable range, which is performed by the apparatus and constitutes a further embodiment of the present invention;

[0050] Figure 12 It is under the condition of the first relative modulation frequency and in the case of... Figure 10The alternative dealiasing unit processes the range of aliased images before processing;

[0051] Figure 13 It is under the condition of the first relative modulation frequency by Figure 10 The dealiasing phase angle diagram generated by the alternative dealiasing unit;

[0052] Figure 14 This is a schematic diagram of another optical distance calculation device constituting another embodiment of the present invention;

[0053] Figure 15 yes Figure 14 A schematic diagram of the phase angle refinement unit;

[0054] Figure 16 It is by Figure 14 and Figure 15 A flowchart of a method for extending the measurable range that is performed by a device and constitutes another embodiment of the present invention;

[0055] Figure 17 It is shown that under the first relative modulation frequency condition and in the case of... Figure 14 and Figure 15 The dealiasing unit and phase angle refinement unit of the device process the range aliasing map before processing;

[0056] Figure 18 It is under the condition of the first relative modulation frequency by Figure 14 The device generates a map of the dealiasing phase angles; and

[0057] Figure 19 Based on Figure 1 The extended range phase angle calculated by the device and by Figure 14 The diagram compares the error in the distance with the refined extended phase angle calculated by the device. Detailed Implementation

[0058] Throughout the following description, the same reference numerals will be used to identify the same parts.

[0059] refer to Figure 1The indirect time-of-flight distance calculation device 100 includes an electromagnetic radiation source (not shown), such as a laser diode (LD) or a light-emitting diode (LED). In this example, the electromagnetic radiation source is infrared radiation that is amplitude-modulated according to indirect time-of-flight measurement techniques to be emitted as a continuous-wave light signal. The detection and ranging module of the device 100 includes an optical receiver photonic mixer pixel device 102, which includes a photodiode 104 having an anode operatively coupled to ground potential and a cathode coupled to a first input of a photonic mixer 106, the output of which is coupled to an integrator 108. In this example, for the sake of brevity and clarity, a single photonic mixer pixel device 102 is described. However, those skilled in the art will understand that the detection and ranging module includes an array of photonic mixer pixel devices of the aforementioned type.

[0060] Phase signal generator 112 is configured to generate a continuous wave electrical signal. The phase offset of the continuous wave signal can be selected via control input 114, and the phase of the continuous wave signal can be selected from a set of phase offsets: [θ0, θ1, ..., θ m-1 The output of the phase signal generator 112 is coupled to the second input of the photonic mixer 106.

[0061] The output of integrator 108 is coupled to the input of digital Fourier transform (DFT) unit 110. DFT unit 110 is supported by signal processing circuitry (not shown) of device 100. In this respect, phase angle measurements are serially transmitted to DFT unit 110, thereby reducing the memory requirements for the detection and ranging modules. DFT unit 110 includes an internal buffer (not shown) to support the serial transmission of measurements from integrator 108. To support this arrangement, DFT unit 110 is operatively coupled to timing control unit 116 supported by signal processing circuitry to maintain synchronization of data processing.

[0062] The timing control unit 116 has a synchronization output 118 that is operatively coupled to the timing input 120 of the DFT unit 110. The control output 122 of the timing control unit 116 is coupled to the control input 114 of the phase signal generator 112.

[0063] DFT unit 110 has multiple digital in-phase (I) / quadrature (Q) outputs 126. In this example, DFT unit 110 includes b pairs of digital I / Q outputs corresponding to different harmonics of the measured signal. Since the output of integrator 108 is an accumulated charge, in this example, the output of integrator 108 needs to be converted to the digital domain in the analog domain. This can be achieved, for example, by employing a photon counter as integrator 108 or by providing an analog-to-digital converter before DFT unit 110.

[0064] A first pair of I / Q outputs of a plurality of digital I / Q outputs 126 related to the first harmonic of the received reflected light signal is coupled to a phase angle calculation unit, such as an arctangent unit 124 supported by signal processing circuitry. In this example, the arctangent unit 124 includes a frame buffer (not shown) that serially receives the calculated phase angle and provides the calculated phase angle pair at a first phase angle output 128 and a second phase angle output 130 of the arctangent unit 124, although it should be understood that in other examples the frame buffer may be decoupled from the arctangent unit 124. The first phase angle output 128 is coupled to a first phase angle input 132 of a range dealiasing unit 134, which is also supported by signal processing circuitry. The second phase angle output 130 is coupled to a second phase angle input 136 of the range dealiasing unit 134. The range dealiasing unit 134 also includes an explicit range comparison result input 138 and a threshold input 140. The range dealiasing unit 134 further includes an extended phase angle output 142.

[0065] Go to Figure 2 The range dealiasing unit 134 includes a first input selector 144 having a first input, a second input, and an output. The range dealiasing unit 134 also includes a second input selector 146, which similarly has a first input, a second input, and an output. The first input of the first input selector 144 is coupled to a first phase angle input 132 of the range dealiasing unit 134, and the second input of the first input selector 144 is coupled to a second phase angle input 136. The first input of the second input selector 146 is coupled to the second phase angle input 136, and the second input of the second input selector 146 is coupled to the first phase angle input 132. The first and second input selectors are coupled to a specific range comparison result input 138. The output of the first input selector 144 is coupled to a first positive input of the first summing unit 148, and the output of the second input selector 146 is coupled to a second negative input of the first summing unit 148. The output of the first summing unit 148 is coupled to a first input of the second summing unit 150. The output of the first summing unit 148 is also coupled to the first input of comparator 152. The second input of comparator 152 is coupled to the threshold input 140 of range dealiasing unit 134. The output of the comparator is coupled to the first input of the first multiplier unit 154, and the second input of the first multiplier unit 154 is coupled to a source (not shown) that provides a constant 2π output value. The output of the first multiplier unit 154 is coupled to the second input of the second summing unit 150, and the output of the second summing unit 150 is coupled to the extended phase angle output 142 of range dealiasing unit 134.

[0066] In operation (Figure 3 In step 200, the light source emits (in step 200) a continuous wave light signal illuminating the scene. In this example, the light source emits light signals in an alternating sequence: a first light signal at a first modulation frequency, followed by a second light signal at a second modulation frequency. The emission at the first and second modulation frequencies occurs on a time frame, and in this example, the duration of the time frame is shared equally. In this respect, the emission of the first light signal at the first modulation frequency occurs in the first half of the time frame, and the emission of the second light signal at the second modulation frequency occurs in the second half of the time frame. This alternating pattern of emitted modulation frequencies is repeated on subsequent time frames. The switching between modulation frequencies is controlled by the timing control unit 116.

[0067] For simplicity, at least one object in the scene will be referred to as the object below, which reflects light signals emitted at different modulation frequencies. In this regard, rays at the first modulation frequency and rays at the second modulation frequency are backscattered from the object in the scene, and some of these backscattered rays are received by the photon mixer pixel device 102 (step 202).

[0068] Phase signal generator 112 is synchronized with the timing of the transmission of the first and second optical signals, generating a first continuous wave electrical signal at a first modulation frequency and a second continuous wave electrical signal at a second modulation frequency. Again, timing control unit 116 controls the selection of the modulation frequency, but also cycles through the set of phase offsets applied to the first and second electrical signals. A synchronization signal is also applied to DFT unit 110 via synchronization output 118.

[0069] The first ray backscattered from the object and incident on the photonic mixer pixel device 102 at a first modulation frequency is demodulated by applying the first electrical signal generated by the phase signal generator 112 to the photonic mixer 106 (step 204). The phase shift of the first electrical signal cycles through the set of phase shifts mentioned above, and the digital representation of the charge is stored in the integrator 108, and thus a measurement is made with respect to each phase shift.

[0070] After the photonic mixer 106 receives the first ray, the second ray, backscattered from the object and incident on the photonic mixer pixel device 102, is demodulated by applying a second electrical signal generated by the phase signal generator 112 to the photonic mixer 106 (step 204). The phase shift of the second electrical signal cycles through the set of phase shifts mentioned above, and the digital representation of the charge is stored in the integrator 108, and thus a measurement is made with respect to each phase shift.

[0071] Therefore, for each modulation frequency, the measurements of the received first ray and the received second ray comprise a set of phase offset measurements, which are then received in series by the DFT unit 110 and converted into a pair of I / Q outputs constituting an I / Q vector V (step 204), representing the phase angle of the analog electrical measurements with respect to the fundamental frequency of the received first ray and the subsequently received second ray. In this regard, the integrator 108 provides a plurality of phase-separated amplitude measurement outputs in series, each representing a cumulative charge level with respect to the applied phase offset value of the photonic mixer pixel device 102. For each frame cycle, the DFT unit 110 calculates first and second intermediate I and Q values ​​for the received phase-separated amplitude measurements in series with respect to the received first ray or the received second ray, respectively, which are accumulated over the frame (measurement) cycle to generate corresponding first and second I and Q value results. Operation of this arrangement involves iteratively calculating a respective vector using the DFT unit 110 with respect to each associated incoming phase angle measurement. DFT unit 110 can also generate additional I / Q vectors about the harmonics of the charge measured by integrator 108.

[0072] After the electrical measurement signal is converted to the frequency domain, the DFT unit 110 provides the I and Q values ​​of the fundamental frequency for the received first ray and the subsequently received second ray at its output. In this example, a synchronization signal ensures that the fundamental frequency I / Q output of the current measurement frame of the DFT unit 110 is synchronously received by the arctangent unit 124. Then, according to the indirect time-of-flight measurement technique, the arctangent unit 124 (step 206) calculates a first angle of vector V1 for the received first ray based on the fundamental frequency I and Q values, and then calculates a second angle of vector V2 for the received second ray based on the fundamental frequency I and Q values. This first angle constitutes the first extracted (measured) calculated phase angle in the complex plane. This second angle constitutes the second extracted (measured) phase angle calculated in the complex plane. The first extracted phase angle Second extraction phase angle The outputs are provided as the first phase angle output 128 and the second phase angle output 130, respectively.

[0073] The first extracted phase angle Second extraction phase angle The range dealiasing unit 134 receives the data in order to calculate the extended (range) phase angle. The calculated extended phase angle can then be used to calculate the dealiasing range using the known relationship between the phase angle, defined range, and distance. Extended phase angle The calculation method is shown below.

[0074] As shown Figure 4 below, the first extraction phase angle and the second extraction phase angle resolve different maximum ranges. The first extraction phase angle has a first aliasing point 300, and the second extraction phase angle has a second aliasing point 302. For a given photon mixer pixel device, the difference between the phase angles is as follows.

[0075]

[0076] Where UR1 is the first unambiguous range with respect to the first extraction phase angle and UR2 is the second unambiguous range with respect to the second extraction phase angle d is the distance to the object being measured, and k1 and k2 are integer values representing the respective amounts of aliasing. The first unambiguous range UR1 and the second unambiguous range UR2 constitute the respective aliasing parameters used later in this article. Rearranging equation (3) gives the following expression.

[0077]

[0078] As can be seen from equation (4), the phase angle difference is close to zero at the boundaries of the new, extended, unambiguous range UR ext :

[0079]

[0080] According to equation (5), assuming that the phase angle difference is between -2π and +2π, because each of the first extraction phase angle and the second extraction phase angle is within 0 to 2π. Additionally, assume that the phase angle difference is monotonically related to the distance d within the extended unambiguous range UR ext .

[0081] According to equation (5) above, there are two use cases: and Therefore, according to the relationship between the modulation frequency and the unambiguous range (equation (1)), these two use cases can also be represented by the unambiguous ranges: UR1 < UR2, and UR1 > UR2. As used above, it should also be understood that the modulation frequency also constitutes an aliasing parameter.

[0082] Figures 4 to 6 [[IDID=60]]Regarding the first use case, where UR1 is less than UR2. Referring to Figure 5 , the phase angle difference In expanding the definite scope of UR ext The value increases with the increase of distance d, and Δk in equation (4) tracks the first extracted phase angle. Second extraction phase angle The difference lies in the wrapping state. Therefore, Δk repeats or toggles its integer value depending on whether both or only one of the extracted phase angles has been wrapped. In this example, Δk is in units (positive), although in other examples where the amplitude of the highest modulation frequency is more than twice the amplitude of the lowest modulation frequency used, the amplitude of Δk can be greater than units. Figure 4 It can be seen that the first extracted phase angle Second extraction phase angle Previously rolled up. Now, refer to it again. Figure 5 The first extracted phase angle It has already been folded, but the second extracted phase angle There is no roll-up yet, phase angle difference The shift is -2π. As a result, using this information about the -2π shift, the phase angle is extended. The calculation is as follows:

[0083]

[0084] Therefore, by correcting the angle Applied to the calculated phase angle difference To calculate the extended phase angle Among them, the correction angle for:

[0085]

[0086] Now, let's take the second use case where UR1 is greater than UR2. Figures 7 to 9 Phase angle difference In expanding the definite scope of UR ext The value increases with the increase of d, and Δk in equation (4) again tracks the first extracted phase angle. Second extraction phase angle The difference in the cascading state. Therefore, Δk repeats or toggles its integer value depending on whether both or only one of the extracted phase angles has cascaded. In this example, Δk is in units (negative), although in other examples where the amplitude of the highest modulation frequency is more than twice the amplitude of the lowest modulation frequency used, the amplitude of Δk can be greater than units. However, according to Figure 7 It can be seen that the second extracted phase angle Now, in the first extraction phase angle... Previously rolled up. Now, refer to it again. Figure 8 The second extracted phase angle It has already been folded, but the first extracted phase angle There is no roll-up yet, phase angle difference The shift is +2π. As a result, using this information about the +2π shift, the phase angle is extended. The calculation is as follows:

[0087]

[0088] Therefore, by correcting the angle again Applied to the calculated phase angle difference negative value To calculate the extended phase angle Among them, the correction angle for:

[0089]

[0090] In both use cases, the rollover point can be easily identified by comparison with zero. However, as a precaution against the noisy implementation of the extracted phase angle calculated therein, a decision threshold can be used instead. The phase angle overlap threshold is determined, and the decision threshold depends on the relative amplitudes of the first and second modulation frequencies. Set to an appropriate value slightly above or slightly below zero to facilitate reliable identification of the folding of the extracted phase angle.

[0091] Return to reference Figure 4 And specifically refer to Figure 2 The first extracted phase angle is generated by the arctangent unit 124. Second extraction phase angle Subsequently, the first extracted phase angle is received at the first phase angle input 132 and the second phase angle input 136 of the range dealiasing unit 134, respectively. Second extraction phase angle Of course, due to the alternating nature of the modulation frequencies of the emitted optical signal and the first and second electrical signals, the first extracted phase angle... Second extraction phase angle It is generated serially, so the first extraction phase angle Second extraction phase angle One of them is buffered by arctangent unit 124 until the first extracted phase angle. Second extraction phase angle Both are received for processing.

[0092] In this regard, once the first extracted phase angle is received Second extraction phase angle Both receive a control signal indicating whether the first defined range UR1 is less than the second defined range UR2. For the sake of simplicity and clarity, the evaluation of this inequality is not described herein. However, those skilled in the art will understand that in this example, another functional module of the signal processing circuitry of the detection and ranging module of device 100 performs such an evaluation and provides the control signal.

[0093] In response to the control signal, the first input selector 144 and the second input selector 146 are actuated to select the first extraction phase angle. Connect to the positive input of the first summing unit 148 and extract the second phase angle. Connect to the negative input of the first summing unit 148, or extract the first phase angle. Connect to the negative input of the first summing unit 148 and extract the second phase angle. It is connected to the positive input of the first summing unit 148. Therefore, the correction angle can be seen in this respect. The correction method depends on the aliasing parameters mentioned above used to generate the control signal. Compared to The comparison result of UR1 relative to UR2.

[0094] Then, according to the appropriate use case described above, depending on the evaluation of the explicit range inequality described above, the first summing unit 148 performs a subtraction of the first extracted phase angle and the second extracted phase angle. In this regard, a control signal is used to select the minuend of the subtraction operation performed by the first summing unit 148, the selection being based on the comparison result of the aliasing parameters mentioned above. Therefore, according to the relevant use case determined by evaluating whether UR1 is less than UR2, the first summing unit 148 generates the difference between the phase angles. (Step 208). Then, the comparator 152 converts the calculated phase angle difference... With the decision threshold Compare in order to identify (step 210) the phase angle difference. Has the folding point been reached? If the phase angle difference... At or beyond the fold point, a phase angle difference is required. Add 2π. To achieve this, comparator 152 depends on the phase angle difference. Is it less than the decision threshold? To provide a binary output of logic 0 or logic 1. In phase angle difference Less than the decision threshold If the comparator generates a logic 1 at its output, then comparator 152 generates a logic 0; otherwise, comparator 152 generates a logic 0. Multiplier unit 154 multiplies the output of comparator 152 by 2π at its second input. The multiplication result of multiplier unit 154 is passed to second summing unit 150. If the comparator generates a logic 1, the output of multiplier unit 154 is 2π (step 212); otherwise, the output is 0 (step 214). Thus, depending on the phase angle difference... In the first use case scenario, it is less than the decision threshold. Or greater than or equal to the judgment threshold 2π is selectively added to the phase angle difference. (Step 216). Second summing unit 150° phase angle difference Add 2π or 0 to produce an extended phase angle The extended phase angle is output at the extended phase angle output 142 (step 218). The extended (dealiasing) phase angle is calculated using the range dealiasing unit 134. Device 100 then uses the phase angle (in this example, the extended phase angle). The known relationship between the range and distance is explicitly defined to calculate the dealiasing distance to the object, and therefore the extended phase angle is used. For extended phase angle The corresponding expansion is scaled according to the specified range.

[0095] Repeat the above steps (steps 202 to 218) until distance measurement is no longer needed.

[0096] Due to the first phase angle Second phase angle The range is between 0 and 2π, so in another example, the range of the phase angle can be mapped to have 0 and 2π. n The values ​​between -1 and -1 are represented by n-bit binary words, and therefore by n-bit binary words. As a result of this mapping, the phase angle difference... The calculation is modulo 2π arithmetic, therefore the correction angle in the previous example does not need to be applied. Thus, the phase angle is extended. The calculation simplifies to:

[0097]

[0098] refer to Figure 10 The first phase angle is generated by using the calculated I and Q values ​​obtained from the DFT unit 110 through the arctangent unit 124. Second phase angle To achieve extended phase angle The calculation uses a phase angle mapping of an n-bit binary word.

[0099] In this example, the range dealiasing unit 134 includes a first input selector 144 having a first input, a second input, and an output. The range dealiasing unit 134 also includes a second input selector 146, which similarly has a first input, a second input, and an output. The first input of the first input selector 144 is coupled to a first phase angle input 132 of the range dealiasing unit 134, and the second input of the first input selector 144 is coupled to a second phase angle input 136. The first input of the second input selector 146 is coupled to the second phase angle input 136, and the second input of the second input selector 146 is coupled to the first phase angle input 132. The first and second input selectors are coupled to a specific range comparison result input 138. The output of the first input selector 144 is coupled to a first positive input of a third digital summing unit 156, and the output of the second input selector 146 is coupled to a second negative input of the third digital summing unit 156. The output of the third summing unit 148 is coupled to the extended phase angle output 142 of the range dealiasing unit 134.

[0100] refer to Figure 11 , Figure 1 and Figure 10 The device operates as follows.

[0101] As described in the example above, the light source emits (step 300) a continuous wave light signal illuminating the scene. In this example, the light source emits light signals in an alternating sequence: a first light signal at a first modulation frequency, followed by a second light signal at a second modulation frequency.

[0102] At least one object in the scene reflects the emitted light signals at different modulation frequencies. In this respect, the rays at the first modulation frequency and the rays at the second modulation frequency are backscattered from the objects in the scene (step 302) and received by the photonic mixer device or unit 102 (step 302).

[0103] A phase-shifted electrical signal is applied in the manner described above. The first and second backscattered rays received by the photonic mixer device 102 are demodulated (step 304) and transmitted to the DFT unit 110, which calculates the I and Q values ​​of the fundamental frequencies of the received first ray and the subsequently received second ray. These I and Q values ​​are provided at the output of the DFT unit 110. Then, according to the indirect time-of-flight measurement technique, the arctangent unit 124 (step 306) calculates a first angle of the first vector V1 of the received first ray based on the fundamental frequencies I and Q values, and then calculates a second angle of the second vector V2 of the received second ray based on the fundamental frequencies I and Q values. This first angle constitutes the first extracted (measured) calculated phase angle in the complex plane. This second angle constitutes the second extracted (measured) phase angle calculated in the complex plane.

[0104] However, in this example, the arctangent unit 124 additionally calculates the first phase angle within the desired range of 0 to 2π. Second phase angle Represented as discrete n-bit numbers, that is, using a predetermined n-bit quantization space (e.g., an 8-bit quantization space) and providing them to numbers with... Figure 10 The architecture shown is a range dealiasing unit 134. In this example, instead of the phase angle difference calculated relative to a threshold, In order to determine whether angle correction is needed Simply calculate the phase angle difference Because of the first phase angle Second phase angle The cascading does not require correction because it uses the first quantization phase angle. Second quantization phase angle Subtraction inherently applies a correction angle.

[0095]

[0105] Thus, the first extracted phase angle is generated by the arctangent unit 124. Second extraction phase angle Subsequently, the first extracted phase angle is received at the first phase angle input 132 and the second phase angle input 136 of the range dealiasing unit 134, respectively. Second extraction phase angle Of course, due to the alternating modulation frequencies of the emitted optical signal and the first and second electrical signals, the first extracted phase angle... Second extraction phase angle It is generated serially, so the first extraction phase angle Second extraction phase angle One of them is buffered by arctangent unit 124 until the first extracted phase angle. Second extraction phase angle Both are received for processing.

[0106] In this regard, once the first extracted phase angle of the digitization is received... Second extraction phase angle Both receive a control signal indicating whether the first defined range UR1 is less than the second defined range UR2 in a manner similar to that described in the preceding example. Again, for the sake of simplicity and clarity, the evaluation of this inequality is not described herein.

[0107] In response to the control signal, the first input selector 144 and the second input selector 146 are actuated to select the first extraction phase angle. Connect to the positive input of the third digital summing unit 156 and extract the second phase angle. Connect to the negative input of the third summing unit 156, or extract the first phase angle. Connect to the negative input of the third summing unit 156 and extract the second phase angle. The positive input is connected to the third summing unit 156. Then, depending on the evaluation of the explicit range inequality described above, the third summing unit 156 performs a subtraction of the first extracted phase angle and the second extracted phase angle (step 310). In this regard, a control signal is used to select the minuend of the subtraction operation performed by the third summing unit 156, the selection being based on the comparison result of the aliasing parameters mentioned above. Therefore, according to the relevant use case determined by evaluating whether UR1 is less than UR2, the third summing unit 156 generates the difference between the phase angles. Then, the calculated phase angle difference Used as extended dealiasing phase angle The extended dealiasing phase angle is output at the extended phase angle output 142 (step 312). The extended (dealiasing) phase angle is calculated using the range dealiasing unit 134. The signal processing circuit of device 100 then uses the phase angle (in this example, the extended phase angle). The known relationship between the range and distance is explicitly defined to calculate the dealiasing distance to the object, and therefore, the extended phase angle is used. For extended phase angle The corresponding expansion is scaled according to the specified range.

[0108] Repeat the above steps (steps 300 to 312) until distance measurement is no longer needed.

[0109] Go to Figure 12In the case where UR1 is less than UR2, from the first phase angle Subtract the second phase angle get Figure 13 Dealiasing extended phase angle

[0110] In another example ( Figure 14 In this process, by using scaling techniques, the noise contribution from phase angle measurements performed using two different modulation frequencies can be averaged. This is achieved by extracting the first phase angle... Second extraction phase angle One of them is transformed into a refined extended phase angle. This is achieved by extracting the first phase angle. Second extraction phase angle Each has a first defined range UR1 and a second defined range UR2 associated with it, and the refined extended phase angle With associated extended explicit range UR ext For example, for the first extracted phase angle Second extraction phase angle The selected extracted phase angles are multiplied and compressed, then unwrapped and decompressed.

[0111] In this regard, the selection and expansion of the UR scope are clearly defined. ext One of the associated first defined range UR1 and second defined range UR2 l In order to calculate the refined phase angle This refines the phase angle Track the selected explicit range UR in terms of rollover and scaling. l and extended explicit range UR ext The relationship between the phase angles. It also has the same extended phase angle calculated in the example above. Same gradient. Refine phase angle. The refined phase angle is calculated as follows. This constitutes the extraction of phase angle from the first Second extraction phase angle The compressed version of the extracted phase angle is selected.

[0112]

[0113] in From the first phase angle Second phase angle Selected phase angle ( Figure 17), and corresponds to one of the first defined range UR1 and the second defined range UR2. S is the scaling factor constituting the compression ratio, which is the proportionality constant in the above equation (11) and is defined by the following ratio.

[0114]

[0115] For example, and refer to Figure 18 Select the first defined range UR1 and the first extracted phase angle. The refined phase angle, as indicated above, is still obtained through rollover. (In fact, it should be understood that if the second explicit range UR2 and the second extracted phase angle are selected...) A similar refinement of the phase angle will also occur. The convolution, but following the second extraction phase angle (The rollup). Therefore, it is necessary to adjust the refined phase angle as follows: In order to obtain a refined extended phase angle

[0116]

[0117] U is defined as follows.

[0118]

[0119] Where nint is the function that rounds the evaluation result within the square brackets to the nearest integer value, and produces U, where U is the refined phase angle. The number of stacked replicas, U, constitutes the selected extraction phase angle corresponding to the received rays scattered by the object. The number of rollover repetitions. This method is used to remove the extended phase angle. The noise contribution is reduced, while the selected extraction phase angle is adjusted by a scaling factor S. The noise contribution is scaled.

[0120] Although an explicit range is used to calculate the scaling factor S in the example above, the scaling factor S can alternatively be calculated by evaluating the quotient of the difference between the first modulation frequency and the second modulation frequency and the selected modulation frequency.

[0121] refer to Figure 14 In order to achieve the above technology, Figure 1The device 100 is configured such that, in addition to the range dealiasing unit 134, the signal processing circuitry also supports a phase angle refinement unit 158. The phase angle refinement unit 158 ​​includes a first phase angle input 160 and a second phase angle input 162. Similar to the range dealiasing unit 134, the first phase angle input 160 of the phase angle refinement unit 158 ​​is coupled to the first phase angle output 128 of the arctangent unit 124, and the second phase angle input 162 of the phase angle refinement unit 158 ​​is coupled to the second phase angle output 130 of the arctangent unit 124. The phase angle refinement unit 158 ​​also includes a scaling factor input 164 and an extended phase angle input 166, which is coupled to the extended phase angle output 142 of the range dealiasing unit 134. The phase angle refinement unit 158 ​​further includes a modulation frequency index input 168 and a refined extended phase angle output 170.

[0122] Go to Figure 15 The phase angle refinement unit 158 ​​includes a third input selector 172 having a first input, a second input, and an output. The third selector 172 is also operatively coupled to a modulation frequency exponent input 168. The first input of the third input selector 172 is coupled to a first phase angle input 160, and the second input of the third input selector 172 is coupled to a second phase angle input 162. The output of the third input selector 172 is coupled to a first input of a second multiplier unit 174, and the second input of the second multiplier unit 174 is coupled to a scaling factor input 164. The output of the second multiplier unit 174 is coupled to a first input of a fourth summing unit 176, and the output of the fourth summing unit 176 is coupled to a refined extended phase angle output 170. The output of the second multiplier unit 174 is also coupled to a negative input of a fifth summing unit 178, which functions as a subtractor. The positive input of the fifth summing unit 178 is coupled to an extended phase angle input 166. The output of the fifth summing unit 178 is coupled to the first input of the third multiplier unit 180, the second input of which is coupled to a source (not shown) that provides a constant 1 / (2πS) output value. The output of the third multiplier unit 180 is operatively coupled to the nearest integer calculation unit 182, the output of which is coupled to the input of the fourth multiplier unit 184. The second input of the fourth multiplier unit 184 is coupled to another source (not shown) that provides a constant 2πS output value. The output of the fourth multiplier unit 184 is coupled to the second input of the fourth summing unit 176.

[0123] In operation ( Figure 16 In the above text, regarding... Figure 1 One of the related previous examples describes the calculation of the extended phase angle. However, in this example, the first extracted phase angle is used. Second extraction phase angle One of them and the extended phase angle calculated by the range dealiasing unit 134. So that according to equation (11) to equation (14) and Figures 17 to 19 To calculate the refined extended phase angle In this respect, the phase angle refinement unit 158 ​​receives (step 400) the first extracted phase angle from the arctangent unit 124. Second extraction phase angle and receive the extended phase angle from the range dealiasing unit 134. As further described in detail below, the phase angle refinement unit 158 ​​also receives the first phase angle. Second phase angle The identifier for one of the choices. This choice is a specific range of URs associated with it. l The implicit choice. Although not shown, Figure 1 The signal processing circuit is configured to select (step 402) the specified range UR l and extracting phase angle And according to equation (12), the extended phase angle is used. The corresponding extended scope UR ext Calculate (step 404) the scaling factor S and store it for later use. Subsequently, for the subsequent extended phase angle... Instead of repeatedly calculating, the scaling factor S is simply retrieved from storage, so in this example, step 404 is typically performed only once.

[0124] As the selected extraction phase angle The first extracted phase angle Or the second extracted phase angle The selection is applied to the modulation frequency exponential input 168, and the calculated scaling factor S is applied to the scaling factor input 164. As a result of the signal applied to the modulation frequency exponential input 168, the first extracted phase angle... Or the second extracted phase angle The scaling factor S, calculated and applied to the scaling factor input 164, is applied to the second input of the second multiplier unit 174, which is then applied to the first input of the second multiplier unit 174. Therefore, the selected extraction phase angle is... Multiply by (step 406) the scaling factor S to produce a refined phase angle according to equation (11). Subsequently, according to equation (14), the refined phase angle is used. To calculate (step 408) the number of stacked replicas U. In this regard, the fifth summing unit 178 (step 410) calculates from the extended phase angle. Subtract the calculated refined phase angle The result is multiplied by the third multiplier unit 180 by (step 412) 1 / (2πS). The result of this multiplication is then processed by the nearest integer calculation unit 182 (step 414) to calculate the integer value closest to the received value, thereby calculating the number of folded copies U. As described in equation (13), the number of folded copies U is then multiplied by the fourth multiplier unit 184 by (step 416) 2πS to produce a scaling translation value, which is then processed by the fourth summing unit 176 and the refined phase angle calculated by the second multiplier unit 174. Summation (step 418) is performed to produce a refined, extended phase angle after dealiasing. In this regard, the number of stacked replicas U is used in conjunction with the highest angular range value of scaling (2πS) to additionally refine the phase angle through translation. And thus expand the refined phase angle Although the expanded refined phase angle has the same properties as the refined phase angle The same gradient, but still concatenated as implied above. Then, at the refined extended phase angle output of 170°, a refined extended phase angle is provided (step 420). from Figure 19 As can be seen from this, the phase angle is refined and extended. Signal ratio of extended phase angle Lower signal noise. The refined extended phase angle is calculated by the phase angle refinement unit 158. Device 100 then uses the phase angle (in this example, for refining the extended phase angle). The known relationship between the range and distance is explicitly defined to calculate the dealiasing distance to the object, and therefore, a refined extended phase angle is used. For refined extended phase angle The corresponding expansion is scaled according to the specified range.

[0125] Repeat the above steps (steps 400 to 418) until distance measurement is no longer needed.

[0126] In another example, the mapping from the phase angle range to an n-bit binary value described above can be used to simplify the scaling operation performed by the second multiplier 174 into a bit shift operation.

[0127] In the above embodiments, based on the first extracted phase angle The first defined range UR1 associated with the second extracted phase angle is whether it is less than or greater than the first defined range UR1. The associated second defined range UR2, using the first extracted phase angle Or the second extracted phase angle One of them is used to calculate the refined extended phase angle. The dealiasing extension phase angle calculated in the above embodiments The SNR is much greater than the SNR measured for the phase angle of the low-frequency modulated signal. The use of lower-frequency modulated signals translates to a defined range over longer distances. From the extended defined range UR ext Refined extended phase angle within The limiting factor for fine-grained distance calculation from the signal is optical power. In another embodiment, this can be achieved by using the available extracted phase angle. Instead of choosing one over the other, improve the use of [the technology / method] regarding [the specific application / method]. Figures 14 to 16 The dealiasing extended phase angle obtained by the apparatus and method of the foregoing embodiments SNR.

[0128] In this embodiment, for Figure 15 The device was modified to make Figure 15 The phase angle refinement unit includes a first phase angle refinement circuit and a second phase angle refinement circuit. The first phase angle refinement circuit is similar to... Figure 15 The circuitry is modified, but the third input selector 172 is omitted, and the first phase angle input 160 is more directly coupled to the second multiplier unit 174. The second phase angle refinement circuit is a copy of the first phase angle refinement circuit, and the second phase angle input 162 is coupled to the corresponding second multiplier unit of the second phase angle refinement circuit. In this example, the extended phase angle input 166 is operatively coupled to the respective positive inputs of the fifth summing unit 178 of both the first and second phase angle refinement circuits. As a result of the above adjustments, the modified phase angle refinement unit includes a first refined extended phase angle output 170 with respect to the first phase angle refinement circuit and a second refined extended phase angle output with respect to the second phase angle refinement circuit. In this example, the first and second refined extended phase angle outputs are respectively coupled to the inputs of a further summing unit, the output of which is operatively coupled to the input of a divider that divides the input signal by two and provides the result of the division at the output of the divider. The output of the divider constitutes the combined extended phase angle. Output.

[0129] During operation, Figure 14 The signal processing circuit is configured to calculate the first extracted phase angle according to equation (12). The first scaling factor S1 and the second extracted phase angle The second scaling factor S2, instead of a single scaling factor S. (The above is relative to...) Figure 15The aforementioned method applies a first scaling factor S1 (i.e., 1 / (2πS1) and 2πS1) to the third multiplier unit 180 and the fourth multiplier unit 184 of the first phase angle refinement circuit, respectively. Similarly, a second scaling factor S2 (i.e., 1 / (2πS2) and 2πS2) is applied to the third multiplier unit and the fourth multiplier unit of the second phase angle refinement circuit, respectively, in a similar manner. The first phase angle refinement circuit and the second phase angle refinement circuit are configured to... Figure 15 and Figure 16 The operation is similar to that described above, but uses the first scaling factor S1 and the second scaling factor S2. This is in contrast to... Figure 15 and Figure 16 In a similar manner, the first phase angle refinement circuit and the second phase angle refinement circuit respectively generate the first extended phase angle. Second extended phase angle It achieves averaging through a combination of further summing units and dividers to produce the combined extended phase angle mentioned above. The further summing unit is coupled to the first refined extended phase angle output and the second refined extended phase angle output, respectively. The apparatus and method of this embodiment benefit from both improved measurement resolution and an approximately 30% improvement in SNR compared to a single frequency measurement.

[0130] As described above relative to the foregoing example, bit shifting operations can be used instead of the third and fourth multiplier units of the first and second phase angle refinement circuits to achieve scaling performed by the first scaling factor S1 and the second scaling factor S2.

[0131] In yet another embodiment, fewer hardware components are used than in the foregoing embodiments, instead of replicating... Figure 15 The phase angle refinement circuit makes the phase angle refinement unit include a first phase angle refinement circuit and a second phase angle refinement circuit. Figure 15 The phase angle refinement circuit is modified as follows.

[0132] Given Figure 15 The phase angle refinement circuit includes a first phase angle input 160 and a second phase angle input 162 coupled to a second multiplier unit 174 via a third input selector 172. In this embodiment, the third input selector 172 is replaced by a phase angle summing unit having inputs operably coupled to the first phase angle input 160 and the second phase angle input 162 and an output operably coupled to the second multiplier unit 174.

[0133] During operation, the phase angle is not extracted first. Second extraction phase angle Instead of choosing between one of them, the phase angle summing unit extracts the first phase angle. Second extraction phase angle Summation, and the result relative to the modified phase angle refinement circuit. Figure 15 and Figure 16 The summed phase angles are processed in a manner similar to that of the selected extracted phase angles. Processing is performed. However, the scaling factor used is based on the first extracted phase angle. Second extraction phase angle The corresponding scaling factors for the first defined range UR1 and the second defined range UR2. In this regard, the combined defined range UR is calculated. C :

[0134]

[0135] Where c is the speed of light, f mod1 and f mod2 This is the modulation frequency of the lighting signal. Then, this combination is used to define the range UR. C To calculate the scaling factor:

[0136]

[0137] Extended phase angle generated by phase angle refinement circuit It is de-aliased, and as the system is located in the extended explicit range UR ext The distances between objects within the range change monotonically. The apparatus and method of this embodiment benefit from both improved measurement resolution and an approximately 30% increase in SNR compared to single-frequency measurements.

[0138] As in the scenario described in the previous embodiment, scaling performed by the scaling factor S can be achieved using bit shifting operations instead of the third multiplier unit 180 and the fourth multiplier unit 184, which employ phase angle refinement circuitry.

[0139] Those skilled in the art should understand that the above implementations are merely examples of various implementations conceivable within the scope of the appended claims. In fact, it should be understood that, for example, it is unnecessary to apply the same amount of phase offset to each of the first electrical signal at the first modulation frequency and the second electrical signal at the second modulation frequency, and the amount of phase offset applied to the first electrical signal may differ from the amount of phase offset applied to the second electrical signal. In fact, even if the same or different amounts of phase offset are applied to the first and second electrical signals, the phase offset values ​​need not be the same, or, in the case of different amounts of phase offset, the phase offset values ​​need not overlap. In other implementations, the phase offsets do not need to be applied in the cyclically increasing order described herein, and completely different application orders of phase offsets may be used with respect to each of the first and second electrical signals individually or both.

[0140] In the above example, the alternating generation of the first and second electrical signals includes a complete set of phase offsets applied to each of the first and second electrical signals before the generation of subsequent electrical signals in the alternation pattern. However, those skilled in the art will understand that multiple alternations between the first and second electrical signals during a time frame can be employed for a shorter duration, and only some of the complete set of each phase value can be applied during that shorter duration. In such an implementation, the remaining phase offset values ​​are applied to one or more subsequent generations of the first and second electrical signals, thereby effectively interleaving the first and second electrical signals and their respective applied set of phase angles. For example, the following patterns can be employed: f1 / p1, f1 / p2, f2 / p1, f2 / p2, f1 / p3, f1 / p4, f2 / p3, f4 / p4, f1 / p1, f1 / p2… Of course, other phase offset and / or frequency selection schemes can be employed.

[0141] In the example above, when generating the first extracted phase angle Second extraction phase angle The two then generate the dealiasing extended phase angle. This is one possible implementation, in which device 100 calculates the dealiasing extended phase angle. Previously waiting to generate a new first extracted phase angle Second extraction phase angle However, in another example, when extracting a new phase angle At that time, the newly extracted phase angle can be... The previously extracted phase angle With the newly extracted phase angle Used together to calculate the next dealiasing extended phase angle.

[0142] It should be recognized that, unless otherwise explicitly stated, references to “rays” herein are intended as references to optical ranges relating to the electromagnetic spectrum, such as between about 350 nm and about 2000 nm, such as between about 550 nm and about 1400 nm, or between about 600 nm and about 1000 nm.

Claims

1. An optical distance calculation device, the device comprising: A light source configured to emit rays according to an indirect time-of-flight measurement technique, the light source being configured to selectively modulate the rays at a first modulation frequency and a second modulation frequency according to a predetermined frequency selection scheme; A photonic mixer unit is configured to generate and store a plurality of electrical output signals, the plurality of electrical output signals corresponding to phase offset values ​​applied according to the indirect time-of-flight measurement technique and with respect to a selected modulation frequency; as well as A signal processing circuit configured to process a first number of the plurality of electrical output signals with respect to a first modulation frequency in order to calculate a first measurement vector and calculate a first measurement phase angle based on the first measurement vector, and to process a second number of the plurality of electrical output signals with respect to a second modulation frequency in order to calculate a second measurement vector and calculate a second measurement phase angle based on the second measurement vector; in The signal processing circuit is configured to calculate the phase angle difference between the first measured phase angle and the second measured phase angle, and apply a correction value to the phase angle difference to generate an extended range phase angle. and The signal processing circuit is configured to use the extended range phase angle to calculate the dealiasing range, wherein The signal processing circuit is configured to convert a first measured phase angle having a first defined measurable range associated with the first measured phase angle into a refined extended phase angle having an extended defined measurable range associated with the extended range phase angle by multiplying and multiplying and shifting the compressed first measured phase angle to expand the compressed first measured phase angle. The multiplicative compression of the first measured phase angle is defined by the following equation: Where S is the compression ratio used to compress the first measured phase angle and is a proportionality constant. 1 represents the first measured phase angle, and fine This represents the first measured phase angle of the compression; and The signal processing circuit is configured to calculate the scaling constant by evaluating the ratio of the first defined measurable range to the extended defined measurable range; and The signal processing circuit is configured to calculate the number of convolutional repetitions of the first measured phase angle using the difference between the compressed first measured phase angle and the extended range phase angle; and The signal processing circuit is configured to use the number of rollover repetitions to unroll the compressed first measured phase angle. The number of repetitions of the stack is defined by the following formula: Where nint represents the function that rounds to the nearest integer value of the evaluation result, and ext This represents the extended range phase angle, and The signal processing circuit is configured to expand the first measured phase angle by adding a scaling translation value based on the number of rollover repetitions and the highest angular range value scaled by the scaling constant, as defined by the following formula: in, ext_fine This represents the refined extended phase angle.

2. The apparatus as claimed in claim 1, characterized in that, The signal processing circuit is configured to apply the correction value in response to a comparison of respective aliasing parameters associated with the first modulation frequency and the second modulation frequency.

3. The apparatus as described in claim 2, characterized in that, The signal processing circuit is configured to compare the first modulation frequency and the second modulation frequency.

4. The apparatus of claim 2, further comprising: A first clearly defined measurable range, which is associated with the first measured phase angle; as well as The second clearly defined measurable range is associated with the second measured phase angle; in The signal processing circuit is configured to compare the first defined measurable range and the second defined measurable range.

5. The apparatus as described in claim 2, characterized in that, The calculation of the correction value depends on the result of the comparison of the respective aliasing parameters.

6. The apparatus as claimed in any one of the preceding claims, characterized in that, The signal processing circuit is configured to detect the folding of the phase angle difference by comparing the phase angle difference with a phase angle folding threshold.

7. The apparatus according to any one of claims 1-5, characterized in that, The signal processing circuit is configured to quantize the first measured phase angle into a first n-bit value and the second measured phase angle into a second n-bit value, the first n-bit value and the second n-bit value residing in an n-bit space, the n-bit space representing an angle range substantially between 0 and substantially 2π in the n-bit space; and The signal processing circuit is configured to simultaneously calculate the phase angle difference by performing a subtraction operation using a quantized first measured phase angle and a quantized second measured phase angle, and to apply the correction value to the phase angle difference.

8. The apparatus of claim 7, wherein when subordinate to claim 2, is characterized in that, The signal processing circuit is configured to select either the first measured phase angle or the second measured phase angle as the minuend of the subtraction operation, depending on the value of the result of the comparison of the respective aliasing parameters.

9. The apparatus as described in any one of claims 1-5, characterized in that, The extended range phase angle has a defined extended range associated with the extended range phase angle; and The signal processing circuit is configured to use the extended range phase angle to calculate the distance by scaling the defined extended range using the extended range phase angle.

10. A method for extending the measurable range of an optical distance calculation device, the method comprising: The light source emits rays according to indirect time-of-flight measurement technology, and the light source selectively modulates the rays at a first modulation frequency and a second modulation frequency according to a predetermined frequency selection scheme; The photonic mixer unit generates and stores multiple electrical output signals, each corresponding to a phase offset value applied according to the indirect time-of-flight measurement technique and with respect to a selected modulation frequency. as well as The signal processing circuit processes the plurality of electrical output signals with respect to a first number of the first modulation frequency in order to calculate a first measurement vector and a first measurement phase angle based on the first measurement vector, and processes the plurality of electrical output signals with respect to a second number of the second modulation frequency in order to calculate a second measurement vector and a second measurement phase angle based on the second measurement vector; in The signal processing circuit calculates the phase angle difference between the first measured phase angle and the second measured phase angle, and applies a correction value to the phase angle difference to generate an extended range phase angle; and The signal processing circuit uses the extended range phase angle to calculate the dealiasing range, wherein The signal processing circuit is configured to convert a first measured phase angle having a first defined measurable range associated with the first measured phase angle into a refined extended phase angle having an extended defined measurable range associated with the extended range phase angle by multiplying and multiplying and shifting the compressed first measured phase angle to expand the compressed first measured phase angle. The multiplicative compression of the first measured phase angle is defined by the following equation: Where S is the compression ratio used to compress the first measured phase angle and is a proportionality constant. 1 represents the first measured phase angle, and fine This represents the first measured phase angle of the compression; and The signal processing circuit is configured to calculate the scaling constant by evaluating the ratio of the first defined measurable range to the extended defined measurable range; and The signal processing circuit is configured to calculate the number of convolutional repetitions of the first measured phase angle using the difference between the compressed first measured phase angle and the extended range phase angle; and The signal processing circuit is configured to use the number of rollover repetitions to unroll the compressed first measured phase angle. The number of repetitions of the stack is defined by the following formula: Where nint represents the function that rounds to the nearest integer value of the evaluation result, and ext This represents the extended range phase angle, and The signal processing circuit is configured to expand the first measured phase angle by adding a scaling translation value based on the number of rollover repetitions and the highest angular range value scaled by the scaling constant, as defined by the following formula: in, ext_fine This represents the refined extended phase angle.

Images