Detailed Action
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Rejections – 35 USC § 102
The following is a quotation of the appropriate paragraphs of 35 U.S.C. 102 that form
the basis for the rejections under this section made in this Office action:
A person shall be entitled to a patent unless –(a)(2) the claimed invention was described in a
patent issued under section 151, or in an application for patent published or deemed
published under section 122(b), in which the patent or application, as the case may be, names
another inventor and was effectively filed before the effective filing date of the claimed
invention.
1. Claims 1-3, 5-7, 9-12, 14-16, & 18-19 are rejected under 35 U.S.C. 102(a)(2) as being
unpatentable over Nicolaescu et al (US 20190391243 A1), hereinafter Nicolaescu.
2. Regarding Claims 1 & 19:
Nicolaescu teaches a photodetection device, ([0002]: The disclosure generally relates to photonic integrated circuits, such as for automotive lidar). Nicolaescu teaches a laser light source, ([0009]: An optical signal generation module produces laser light with defined spectral and power characteristics). Nicolaescu teaches two or more photodetectors including respective light-receiving elements, the light-receiving elements being disposed separated from one another, ([0103]: the first and second optical signals traveling in waveguides 206 and 207 are coupled out of the PIC through grating couplers 204 and 205 respectively. A schematic for an implementation of the PIC for 4 channels is shown in FIGS. 4A and 4B. Other examples may have more or fewer channels). See Figs. 4A & 4B. Nicolaescu teaches detecting, via the light-receiving elements, reflected light from a subject irradiated with the coherent light, ([0108]: The outbound first optical signal beam can be reflected off targets and a portion of the reflected signal beam can be collected by the lens 407 and focused on the detector array 408). Nicolaescu teaches a cross-correlation section that mixes two optical signals detected by any two photodetectors out of the two or more photodetectors and a heterodyne correlation section that mixes, with heterodyne mixing, one of the optical signals before mixing by the cross- correlation section and a reference signal obtained by dividing the coherent light from the laser light source, ([0014]: In an aspect, the disclosure can feature a photonic circuit for providing detection of a frequency and a phase of a light beam. The photonic circuit can include a plurality of grating couplers that can be configured to receive a portion of a free space light beam. The photonic circuit can also include a plurality of signal mixers, wherein an individual signal mixer can be configured to receive a portion of the free space light beam from a corresponding grating coupler and a local oscillator light beam, where the individual signal mixer can be configured, such as to provide a first output corresponding to a sum of the free space light beam field and the local oscillator light beam field and a second output corresponding to a difference between the free space light beam field and the local oscillator light beam field. The photonic circuit can also include a plurality of detector pairs each detector pair corresponding to a signal mixer and receiving the light beam from the two outputs of the signal mixer). Nicolaescu further teaches, ([0015]: In an aspect, the disclosure can feature a method for detecting a frequency and a phase of a light beam using a photonic integrated circuit. The method can include receiving a portion of a free space light beam using a grating coupler. The method can also include providing a local oscillator and the received portion of the free space light beam from the grating coupler to a signal mixer. The method can also include providing a first output corresponding to a sum of the free space light beam field and the local oscillator light beam field and a second output corresponding to a difference between the free space light beam field and the local oscillator light beam field. The method can also include providing the local oscillator to a plurality of signal mixers substantially simultaneously. The method can also include sequentially providing the local oscillator to a plurality of signal mixers. The method can also include converting the first output to a first electrical signal and the second output to a second electrical signal, and wherein a difference between the first electrical signal and the second electrical signal can be used to provide a detected signal having reduced noise. The method can also include providing a plurality of grating couplers wherein a grating period, duty cycle or two-dimensional topology of the plurality of grating couplers varies with position on a photonic circuit to accommodate different angles of incidence of received free space light. The method can also include coupling free space light corresponding to an mth diffraction order using the grating coupler and coupling free space light corresponding to an nth diffraction order using another grating coupler adjacent to the grating coupler. The method can also include receiving a corresponding portion of a free space light beam for a subset of the plurality of signal mixers and simultaneously processing electrical signals provided by the subset of the plurality of signal mixers. The method can also include detecting multiple beat frequencies or phases simultaneously or sequentially. The method can also include receiving free space light beams of different wavelengths simultaneously).
3. Regarding Claim 19:
Nicolaescu teaches a signal processor that calculates distance information regarding the subject on a basis of a difference frequency component caused by a cross-correlation signal from the cross-correlation section and the reference signal, ([0142]: FIG. 16 illustrates an example of an optical 3D imaging camera system 1650. An optical signal generation source can produce laser light with defined spectral and power characteristics. The light can be transmitted via optical fiber or through free space propagation to a photonic integrated circuit 1651. The 3D imaging camera system illustrated in FIG. 16 can include a photonic integrated circuit (PIC) 1651, which can perform a plurality of passive and active optical functions to create one or multiple signals with tailored amplitude, phase and spectral characteristics, direct the optical beam towards a target and detect the return signal on an array of sensors. In an example, the PIC 1651 can include a transmitter module 1701 a steering module 1702 and a receiver module 1703 as illustrated in FIG. 17. A functional block containing electrical drivers for the transmitter, steering and receiver blocks, as well as synchronization circuitry 1704 can be integrated on the chip or be separate from the chip. An outbound optical signal with tailored amplitude, phase and spectral characteristics can be generated by the optical signal generation source and the transmitter module 1701, and directed towards a target by steering module 1702 which can be part of the PIC 1700. The optical signal can be converted into an electrical signal by the array of sensors which are part of the receiver module 1703 of the PIC 1700. The plurality of electrical signals generated by receiver module 1703 can be processed by the electronic signal processing module which in an example can include an image signal processor 1652. By analyzing the plurality of electrical signals generated by PIC 1651, information about the location, velocity and reflectivity of targets can be quantified. A plurality of analyses can be performed on the signals generated by image signal processor 1652 with the help of software to create a pointcloud containing velocity, distance and reflectivity information about the surrounding environment).
4. Regarding Claim 2:
Nicolaescu teaches the heterodyne correlation section mixes, with the heterodyne mixing, an optical signal detected by each of the two or more photodetectors and the reference signal, and the cross-correlation section mixes any two optical signals after the heterodyne mixing by the heterodyne correlation section.
See Claim 1.
5. Regarding Claim 3:
Nicolaescu teaches the reflected light is different in frequency from the reference signal, ([0004]: Two alternative approaches are typically used to measure the coordinates of a remote target and create a 3D image of an object or environment: one based on time of flight measurements of a short pulse or pulse succession emitted by a laser converted to a 3D map, and the second based on a continuous wave laser transmitter which can be phase or frequency modulated, and the distance-correlated phase or frequency shift in the target scattered signal with respect to the original signal can be measured).
6. Regarding Claim 5:
Nicolaescu teaches a frequency difference between the reflected light and the reference signal is 10 GHz or less, ([0217]: Other frequency ranges for the intermediate frequency such as 1-10 GHz may be chosen and chirp may range from 100 MHz to 50 GHz).
7. Regarding Claim 6:
Nicolaescu teaches a balanced detector that converts the optical signals after the mixing by the cross-correlation section into an electric signal, wherein each of the two or more photodetectors is provided on a silicon substrate and includes a grating antenna in which the reflected light from free space enters, and the grating antenna and the balanced detector are coupled with each other via an optical waveguide, ([0117]: Each cell 600 includes two grating couplers 601, one 1×2 3 dB MMI coupler 602, two 2×2 MMI couplers 603, and 4 waveguide detectors 604. The second signal can be guided through waveguide 605 to the input of the 1×2 MMI coupler 602 and split equally by the coupler. The output of the 1×2 coupler 602 can be collected by waveguides 607 and can be input into one of the input ports of the 2×2 MMI coupler 603. The scattered first signal received by the detector can be coupled into the PIC though the grating couplers 601 and guided to the other input of the 2×2 MMI coupler 603 through waveguide 606. The 2×2 MMI coupler 603 serves to mix the scattered from the target first signal and the second signal into the two output waveguides of the 2×2 MMI coupler. The output of the 2×2 couplers can be guided into waveguide detectors 604 one on each output of the 2×2 MMIs 603 as shown in FIG. 7. In a coherent detection technique, the use of two detectors in a balanced detection configuration eliminates the dc component and therefore maximizes the signal photocurrent.).
8. Regarding Claim 7:
Nicolaescu teaches each of the two or more photodetectors includes an optical lens function that allows a large effective detection area, ([0115]: Once each of the first optical signals hit a target location as controlled by the corresponding beam steering unit 401, a portion of the signal scattered from a target can be collected by lens 407 and focused on the Pixel array 503 of the receiver PIC 408. A grating coupler 601 couples the return light into the planar circuit).
9. Regarding Claim 9:
Nicolaescu teaches each of the cross-correlation section and the heterodyne correlation section includes an optical path length adjustment function section that adjusts a phase difference of the optical signals or the reference signal, ([0011]: In an aspect, the disclosure can feature a method for providing a frequency chirped light beam. The method can include using a continuous wave light source, such as to provide a light beam. The method can also include coupling the light beam to a planar waveguide and dividing the light beam into a first portion and a second portion. The method can also include modulating the first portion of the divided light beam in-phase. The method can also include modulating the second portion of the divided light beam in-quadrature. The method can also include combining the modulated first portion of the divided light beam and the modulated second portion of the divided light beam to form a frequency chirped light beam. The method can also include providing a phase shift of the combined light beam, such as to adjust a phase of the frequency chirped light beam).
10. Regarding Claim 10:
Nicolaescu teaches each of the two or more photodetectors is provided on a silicon substrate, ([0009]: In an example, the transmitter and receiver PICs are implemented using a Silicon Photonics platform). Nicolaescu teaches the laser light source comprises a coherent laser light source that emits light in a single mode of SWIR wavelength region of 1.1 pm or more and 2.0 pm or less. ([0144]: In an example, the optical signal generation source can include a DFB or DBR laser, having a single transverse mode and a single longitudinal mode. In one example, the optical signal generation source can have a narrow linewidth corresponding to a long coherence length. In an example, the linewidth of the laser can be less than 250 KHz corresponding to a coherence length in excess of 400m. In another example lasers with linewidths in the range from 10 KHz to 10 MHz can be used). Nicolaescu further teaches, ([0010]: A wavelength of the light beam can be in a range from about 1300 nm to 1600 nm).
11. Regarding Claim 11:
Nicolaescu teaches the laser light source comprises a wavelength swept laser light source configured to continuously change a wavelength of the coherent light, ([0010]: In an aspect, the disclosure can feature a semiconductor photonic circuit for providing a frequency chirped light beam). Nicolaescu further teaches, ([0148]: In an example, the frequency of the input optical signal in the I/Q modulator can be approximately 193.54 THz corresponding to 1550 nm wavelength and can be linearly shifted between 193.54 THz+1 GHz and 193.54 THz+11 GHz during a ramp length of 10 microseconds. Other ramp lengths such as 100 ns to 1000 ms can be used, as well as other optical signal wavelengths and frequency chirps such as from 1 MHz to 200 GHz can be used. The width of the frequency modulation can be chosen depending on the desired system resolution and accuracy).
12. Regarding Claim 12:
Nicolaescu teaches a balanced detector that converts the optical signals after the mixing by the cross-correlation section into an electric signal, wherein the balanced detector performs current detection on a difference frequency component caused by a cross-correlation signal and the reference signal, the cross-correlation signal being generated by mixing in the cross-correlation section, ([0117]: Each cell 600 includes two grating couplers 601, one 1×2 3 dB MMI coupler 602, two 2×2 MMI couplers 603, and 4 waveguide detectors 604. The second signal can be guided through waveguide 605 to the input of the 1×2 MMI coupler 602 and split equally by the coupler. The output of the 1×2 coupler 602 can be collected by waveguides 607 and can be input into one of the input ports of the 2×2 MMI coupler 603. The scattered first signal received by the detector can be coupled into the PIC though the grating couplers 601 and guided to the other input of the 2×2 MMI coupler 603 through waveguide 606. The 2×2 MMI coupler 603 serves to mix the scattered from the target first signal and the second signal into the two output waveguides of the 2×2 MMI coupler. The output of the 2×2 couplers can be guided into waveguide detectors 604 one on each output of the 2×2 MMIs 603 as shown in FIG. 7. In a coherent detection technique, the use of two detectors in a balanced detection configuration eliminates the dc component and therefore maximizes the signal photocurrent).
13. Regarding Claim 14:
Nicolaescu teaches each of the two or more photodetectors is provided on a silicon substrate, and on the silicon substrate, see Claim 6. Nicolaescu teaches on the silicon substrate, a first optical waveguide that guides the reflected light and a second optical waveguide that guides the reference signal are stacked at positions different from each other in a stacking direction, ([0160]: Local oscillator light can be coupled in waveguide 3101 from waveguide 3103 situated in the same layer as the other elements of the pixel structure 3000 and connected to the local oscillator distribution network such as 3309. A small fraction of light can be evanescently coupled from waveguide 3101 in the waveguides 3102 below through a vertical coupler for each pixel in the row as shown in FIG. 32. Waveguide 3101 can be above the waveguides 3102 and the evanescent coupling between the two waveguides can occur in a vertical plane. The vertical coupler architecture can allow for very precise control of the thickness of the oxide layer separating the two waveguides and together with the variation of the spatial overlap of the two waveguides or length of the coupler can allow for precise light distribution to each pixel).
14. Regarding Claim 15:
Nicolaescu teaches each of the first optical waveguide and the second optical waveguide mainly includes single crystal silicon or silicon nitride, ([0026]: The semiconductor photonic circuit can include silicon nitride. The semiconductor photonic circuit can include silicon). Nicolaescu teaches a flattening layer is provided between the first optical waveguide and the second optical waveguide on the silicon substrate, the flattening layer mainly including a silicone oxide film having a thickness of 100 nm or more and 1000 nm or less, ([0193]: In an example, the transmitter PIC may be implemented in silicon on insulator with the top silicon layer being 220 nm or 480 nm thick, buried oxide layer 2 micron thick, though other substrates such as top Si layers in the range from 500 nm to 10 microns and buried oxide layers in the range of 0.5-3 microns may be used).
15. Regarding Claim 16:
Nicolaescu teaches the photodetection device includes, as the two or more photodetectors, three or more photodetectors, and in the cross-correlation section, a sum of phase differences of three or more cross-correlation signals obtained from three or more pairs formed by combining any two of the three or more photodetectors is configured to be in a relation of closure phase, ([0014]: The photonic circuit can also include a plurality of signal mixers, wherein an individual signal mixer can be configured to receive a portion of the free space light beam from a corresponding grating coupler and a local oscillator light beam, where the individual signal mixer can be configured, such as to provide a first output corresponding to a sum of the free space light beam field and the local oscillator light beam field and a second output corresponding to a difference between the free space light beam field and the local oscillator light beam field. The photonic circuit can also include a plurality of detector pairs each detector pair corresponding to a signal mixer and receiving the light beam from the two outputs of the signal mixer. The plurality of grating couplers and the plurality of signal mixers can be divided into N groups, with each of the N groups having M grating couplers and M signal mixers. A local oscillator signal can be supplied to each of the plurality of signal mixers substantially simultaneously. A local oscillator signal can be sequentially supplied to each of the plurality of signal mixers. The photonic circuit can also include a first detection arm for converting the first output to a first electrical signal and a second detection arm for converting the second output to a second electrical signal. A difference between the first electrical signal and the second electrical signal can be used to provide a detected signal having reduced noise).
16. Regarding Claim 18:
Nicolaescu teaches a signal processor that calculates distance information regarding the subject on a basis of a difference frequency component, ([0142]: The plurality of electrical signals generated by receiver module 1703 can be processed by the electronic signal processing module which in an example can include an image signal processor 1652. By analyzing the plurality of electrical signals generated by PIC 1651, information about the location, velocity and reflectivity of targets can be quantified. A plurality of analyses can be performed on the signals generated by image signal processor 1652 with the help of software to create a pointcloud containing velocity, distance and reflectivity information about the surrounding environment). Nicolaescu further teaches, ([0155]: In an example, the basic cell of the coherent receiver is shown in FIG. 30A. The weak return probe signal from the target can couple through the grating coupler 3001 in the plane of the chip and can be combined with a strong local oscillator in waveguide 3002 in the 2×2 multiplexer 3003. At the output of each of the 2×2 multiplexer 3003, are two waveguide detectors 3004 which can detect an optical signal at a frequency equal to the difference between the local oscillator and the return). Nicolaescu teaches caused by a cross-correlation signal from the cross-correlation section and the reference signal, See Claim 12. Nicolaescu teaches the laser light source outputs, as the coherent light, laser light with a waveform chirped by wavelength conversion in a time direction, ([0184]: In another example shown in FIG. 43, a plurality of second optical chirped signals from the output of the I/Q modulators 4304 are sent to a plurality of 1×N optical switches 4307, with each I/Q modulator output serving as input for one 1×N switch. Each switch can perform the switching of the optical signal between the N grating couplers which can be part of the array of grating couplers 4308. In an example 4 I/Q modulators can be used to provide the chirped optical signal for 4 arrays of 16 gratings each. In an example a plurality of first optical signals can be directed from the output of the I/Q modulators 4304 through waveguides 4306 to the receiver block to provide local oscillator signal). Nicolaescu further teaches, ([0186]: A plurality of first chirped optical signals can be directed towards the receiver block 4509 to provide a local oscillator for the receiver array. A plurality of second chirped optical signals are directed towards the steering block which in an example can include a digital reconfigurable grating array).
Claim Rejections – 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness
rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not
identically disclosed as set forth in section 102, if the differences between the claimed invention and the
prior art are such that the claimed invention as a whole would have been obvious before the effective filing
date of the claimed invention to a person having ordinary skill in the art to which the claimed invention
pertains. Patentability shall not be negated by the manner in which the invention was made.
17. Claim 8 is rejected under 35 U.S.C. 103 as being unpatentable over Nicolaescu et al (US 20190391243 A1), hereinafter Nicolaescu, in view of Dromey et al (“Reflecting and refracting optics in the condensing element of a two-beam interferometer”), hereinafter Dromey.
18. Regarding Claim 8:
Nicolaescu teaches each of the two or more photodetectors includes an optical lens function that allows a large effective detection area, See Claim 7.
Nicolaescu does not teach each of the two or more photodetectors includes an optical condensing mirror function that allows a large effective detection area.
However, Dromey teaches an interferometer employing either a reflective condenser or a refractive condenser to collect light onto a detector, ([Fig. 1]: Shows a comparison between a reflective and a refractive condenser).
It would have been obvious for one of ordinary skill in the art at the time of filing to modify Nicolaescu with Dromey to include a condensing mirror instead of a refractive condenser since these are known equivalents used for the same purpose, see MPEP 2144.06 II (Substituting Equivalents Known For The Same Purpose). In addition, it would have been obvious for one of ordinary skill in the art at the time of filing to modify Nicolaescu with Dromey to include a condensing mirror instead of a refractive condenser since, it is the same field of endeavor and results would have been predictable. One of ordinary skill in the art at the time of filing would have been motivated to modify Nicolaescu with Dromey since, using reflective optics eliminates chromatic aberrations and allows for the use of custom, highly efficient, reflective coatings across broad wavelength ranges. Depending on the coatings chosen these can also allow for light in an undesirable wavelength range to pass through the reflective condenser, rather than being reflected onto the detector, further reducing unwanted light and increasing SNR.
19. Claims 4 & 13 are rejected under 35 U.S.C. 103 as being unpatentable over Nicolaescu et al (US 20190391243 A1), hereinafter Nicolaescu, as applied to Claims 1 & 12, in view of Crouch et al (US 20160377724 A1), hereinafter Crouch.
20. Regarding Claim 4:
Nicolaescu teaches the photodetection device includes one or a plurality of functional blocks each including the any two photodetectors, the cross-correlation section, and the heterodyne correlation section. See Claim 1.
Nicolaescu does not teach each of the functional blocks includes a function of sampling a spatial frequency component determined depending on a relative positional relationship between respective photodetection elements of the any two photodetectors.
However, Crouch teaches, ([0046]: FIG. 1 is a block diagram that illustrates example operation of a high resolution 3D LADAR system, according to an embodiment. A chirped transmit source 110 produces transmitted light (Tx) 112 that flood illuminates a target 190 at some nominal range R, and the fast focal plane array (FPA) records the interference between the returned light (Rx) 192 and a reference beam chirp produced concurrently with the transmitted light Tx. The complex return field g.sub.0(x,y,t) 193 resulting from the heterodyne interference encodes the 3-D spatial information at various positions 130a through 130g, collectively referenced as positions 130, along a line of travel 121. The total synthetic aperture, d.sub.SA 123, provides enhanced resolution along the direction of platform motion along line of travel 121.).
It would have been obvious for one of ordinary skill in the art at the time of filing to modify Nicolaescu with Crouch to include each of the functional blocks includes a function of sampling a spatial frequency component determined depending on a relative positional relationship between respective photodetection elements of the any two photodetectors, since it is the same field of endeavor and results would have been predictable. One of ordinary skill in the art at the time of filing would have been motivated to modify Nicolaescu with Crouch, since such a configuration enables spatial heterodyne detection, provides non-redundant sampling, reduce or remove velocity and angle ambiguity, resulting from the measurement of both distance and velocity. In addition, the hardware requirements may be simplified.
21. Regarding Claim 13:
Nicolaescu does not teach a signal processor that performs aperture synthesis processing, the aperture synthesis processing including sampling, on a basis of the difference frequency component, a spatial frequency component corresponding to a relative positional relationship between the light- receiving elements in the any two photodetectors and converting the spatial frequency component into intensity distribution in real space by signal processing.
However, Crouch teaches, ([0062]: In step 431, multiple 3D field segments are synthesized using a processor. In some embodiments, the field segments have fewer than three dimensions, e.g., when a single detector or a 1D array of detectors is used. Any conventional registration and synthesizing methods may be used. As indicated above, in some embodiments, the segments being aperture synthesized are multiple subsets of pixels (regions of interest) of a digital camera. The no-physical motion aspect of the aperture synthesis is new). Crouch further teaches, ([0050]: Aperture synthesis depends on translation between the speckle field, that is, g0 the interference pattern of the backscattered light with the reference beam, and the receive aperture in the aperture plane, which in this depicted configuration is also the pupil place. A multitude of configurations achieve this effect. In the example analysis, the transceiver locations 130 are located and it is assumed that the transmitter moves with the fast FPA in a monostatic configuration (both transmitter and receivers moving together). However, this assumption is not required as bi-static (one is stationary and the other moving relative to the target) and multi-static (both moving relative to the target or several detectors or transmitters moving separately) configurations are also possible. The spatial relationship between transmitter and receiver does not have to be known to form imagery. However, knowledge of the spatial relationship can help in processing and interpreting the image. The synthetic aperture size, dSA 123, is shown and the enhanced cross-range resolution is nominally given by Equation 2). Crouch goes on to teach, ([0059]: In step 423, a complex waveform is received at the one or more detectors in the detector array at the fast frame rate. The complex waveform indicates both the amplitude and phase of the difference between the returned signal from the target and a reference signal based on the laser chirp, e.g., in heterodyne interference).
It would have been obvious for one of ordinary skill in the art at the time of filing to modify Nicolaescu with Crouch to include a signal processor that performs aperture synthesis processing, the aperture synthesis processing including sampling, on a basis of the difference frequency component, a spatial frequency component corresponding to a relative positional relationship between the light- receiving elements in the any two photodetectors and converting the spatial frequency component into intensity distribution in real space by signal processing, since it is the same field of endeavor and results would have been predictable. One of ordinary skill in the art at the time of filing would have been motivated to modify Nicolaescu with Crouch, since the aperture synthesis approach enables ultra-high spatial and angular resolution without needing a large physical lens. By processing the spatial frequency of the beat (difference) frequencies between photodetectors, it effectively synthesizes a massive virtual antenna, eliminating bulky hardware while dramatically improving object identification and tracking precision. In addition, such systems can simplify hardware requirements and the processor can filter out ambient background noise, atmospheric distortion, and interference from other LiDAR systems, improving the SNR.
22. Claim 17 is rejected under 35 U.S.C. 103 as being unpatentable over Nicolaescu et al (US 20190391243 A1), hereinafter Nicolaescu, as applied to Claim 1, in view of Lardin et al (US 20160377721 A1), hereinafter Lardin.
23. Regarding Claim 17:
Nicolaescu does not teach a signal processor that calculates Doppler velocity of the subject in a sight direction of the two or more photodetectors on a basis of wavelength shift information regarding the coherent light calculated on a basis of a difference frequency component caused by a cross-correlation signal from the cross-correlation section and the reference signal.
However, Lardin teaches, ([0069]: To one skilled in the art of circuit design, it is commonly known that there are a variety of techniques that can be used to determine the beat difference frequency within the filtered beat difference signal 161. For example, the filtered beat difference signal 161 could be sampled with an analog to digital converter (ADC) circuit and then processed in a digital signal processor (DSP) to perform a fast Fourier transform (FFT). Alternatively, the signal could be fed into a phased locked loop (PLL) architecture, wherein the control voltage on the internal voltage controlled oscillator is sampled as a measure of the frequency. Generally, the signal processing involved in mixing, filtering, and determining frequencies based on the electrical signals from the detectors will be referred to as the signal processing block 170). Lardin further teaches, ([0091]: In another embodiment, both the distance to the object and the object's radial velocity with respect to the laser source can be determined at the same time. Typically, the object's radial velocity is determined using two laser modulations, one with an increasing wavelength with time (i.e., up-chirp), and one with a decreasing wavelength with time (i.e., down chirp). Alternatively an up-chirp and a down-chirp can be combined into a single triangle wave. Due to the Doppler shift associated with the object's radial velocity, the beat frequencies that result from the increasing wavelength modulation and the decreasing wavelength modulation will differ. It is well known that the difference in beat frequencies are a measure of the radial velocity while the average of the beat frequencies are a measure of the distance to the target. By utilizing two lasers and two detectors, one laser-detector pair could be configured for the increasing wavelength modulation with time, while the other laser-detector pair could be configured for the decreasing wavelength modulation with time. By separating the center wavelengths of the two lasers and placing the appropriate filters over each detector, one could prevent the two subsystems from interacting, yet allow the subsystems to simultaneously measure the components that, when combined, determine both the distance and the radial velocity of the object).
It would have been obvious for one of ordinary skill in the art at the time of filing to modify Nicolaescu with Lardin to include a signal processor that calculates Doppler velocity of the subject in a sight direction of the two or more photodetectors on a basis of wavelength shift information regarding the coherent light calculated on a basis of a difference frequency component caused by a cross-correlation signal from the cross-correlation section and the reference signal, since it is the same field of endeavor and results would have been predictable. One of ordinary skill in the art at the time of filing would have been motivated to modify Nicolaescu with Lardin, since such a configuration eliminates the need for independent, computationally heavy Fast Fourier Transforms (FFTs) for each photodetector. By extracting the Doppler shift from a cross-correlation difference frequency, the system directly isolates true, line-of-sight target velocity with drastically reduced processing latency, lower sampling rates, and immunity to phase noise.
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's
disclosure.
US 20180364336 A1: Discloses Lidar systems using multiple detectors.
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/J.W.N./Examiner, Art Unit 3645
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