Patent Description:
Optical measurement systems may be used to measure various parameters or characteristics of a specimen (e.g., a device-under-test (DUT) or sample material or component). Generally, an optical measurement system directs incident light at the specimen, and the specimen may produce polarized or unpolarized reflected light, polarized or unpolarized transmitted light, and electrical signal (e.g., current and voltage) in response to the stimulus. The optical measurement system typically includes devices to detect and analyze the reflected light, transmitted light, and/or electrical signal to measure the desired parameters or characteristics of the specimen.

As an example, an optical measurement system for use in measuring the extrinsic quantum efficiency (EQE) of a specimen may include a light source (and other associated components) to generate and direct a defined incident light at the specimen. Such optical measurement system may also include a reference detector to detect a portion of the incident light, and an electrical detector to measure an electrical response (e.g., current or voltage) generated by the specimen in response to the stimuli. Such optical measurement system may include an analysis component to calculate the EQE of the specimen based on signals generated by the measurement system.

Similarly, as another example, an optical measurement system for use in measuring the intrinsic quantum efficiency (IQE) may include a light source (and other associated components) to generate and direct a defined incident light at the specimen. Such optical measurement system may further include a reference detector to detect a portion of the incident light, a specular reflectance detector to detect light reflected at an angle from the specimen, a diffusive reflectance detector to detect scattered light reflected by the specimen, and an electrical detector to detect an electrical response (e.g., current or voltage) generated by the specimen in response to the stimuli. Such optical measurement system may include an analysis component to calculate the IQE of the specimen based on signals generated by the measurement system.

Often, in the aforementioned optical measurement systems, significant noise may be present in the signals measured or generated by the detectors and specimen. In some cases, the noise is so prevalent that DC sampling the signals may not be possible or may result in erroneous detection. To combat noise, some optical measurement systems employ a dedicated lock-in amplifier to extract signals buried in noise. According to this technique, the intensity, frequency, or phase of the incident light is modulated at a frequency. The dedicated lock-in amplifier receives and mixes the detector signal with a signal with an established phase relationship with the modulation frequency (often referred to as coherent or heterodyne detection). The mixed signal is then passed through a filter to generate essentially the detector signal with reduced noise.

<CIT> describes a high-speed Quantum Efficiency (QE) measurement device that includes at least one device under test (DUT), at least one conditioned light source having at least one filtered LED with a less than <NUM> bandwidth, where a portion of the conditioned light source is monitored by light source monitoring elements having at least one collection optic and at least one photo detector. The high-speed QE measurement device further includes delivery optics disposed to direct the conditioned light source to the DUT, a controller that drives the conditioned light source in a time dependent operation, where a response by each DUT from the conditioned light source is uniquely identified, and at least one reflectance measurement assembly having at least one reflectance collection optic and at least one photo detector disposed to receive a portion of the conditioned light that is reflected from the DUT. Additionally, the high-speed QE measurement device has a time-resolved measurement device that includes a current measurement device or a voltage measurement device, or a current measurement device and a voltage measurement device, where the time-resolved measurement device is disposed to resolve a current or a voltage, or a current and a voltage generated in the DUT by each conditioned light source. The high-speed QE measurement device further includes a sufficiently programmed computer disposed to determine and output an internal QE value for each DUT according to an incident intensity of at least one wavelength of from the conditioned light source and the time-resolved measurement. <CIT> discloses an apparatus for measuring quantum efficiency (QE) of solar cells. The apparatus includes a light source including an array of light emitting diodes (LEDs). Since all the LEDs can be power-modulated simultaneously and the corresponding cell responses to each of the LEDS can be analyzed simultaneously, the QE spectrum measurement time is greatly shortened as compared to conventional methods. <CIT> describes a signal processing unit comprising a phase detection circuit which is contained in the signal processing circuit. Phase-sensitive detection for a photo-acoustic signal is carried out by using as a reference signal and a modulated signal which is fed from the current supply.

A drawback to such optical measurement systems is how task specific the dedicated lock-in amplifier are designed. This makes it difficult to re-configure the system and apply it towards measurements that do not require or cannot utilize lock-in functionality. An example would be in a system that is required to measure both the EQE and IΓaE of specimens that can or cannot respond to the frequency of modulation on the stimulating light source.

The invention relates to systems according to independent claims <NUM>, <NUM> and <NUM> for measuring properties of a specimen.

An aspect of the disclosure relates to a system that may be configured to measure one or more properties of a specimen, such as the extrinsic quantum efficiency (EIaE), internal quantum efficiency (IQE), or other properties of the specimen. The system is configured to sample, digitize, and coherently detect signals from the specimen measurement system such that one or more resulting measurements are based on the signals acquired at substantially the same time instance. This facilitates the simultaneous calculation and presentation of the one or more resulting measurements in a real-time manner.

In accordance with a first exemplary embodiment, the system comprises a modulation frequency source configured to generate a modulation frequency voltage; a modulated light source configured to generate a modulated light signal based on a modulation frequency voltage; a specimen measurement system configured to direct at least a portion of the modulated light signal incident upon a specimen for measurement of one or more properties of the specimen, wherein the specimen measurement system is configured to generate a plurality of measurement currents pursuant to the measurement of the one or more properties of the specimen; wherein the specimen measurement system, comprises a reference detector configured to generate a first current of the plurality of currents, the first current being related to an intensity of the incident light signal; a reflectance detector configured to generate a second current of the plurality of currents, the second current being related to an intensity of a light signal reflected by the specimen in response to the incident light signal; and a detector configured to generate a third current of the plurality of currents based on an electrical signal generated by the specimen in response to the incident light signal; a signal conditioner configured to generate a plurality of measurement voltages from the plurality of currents, respectively; a data acquisition circuit configured to: sample and digitize the plurality of measurement voltages to generate a plurality of measurement digital signals; receive the modulation frequency voltage from the modulation frequency source without the modulation frequency voltage being converted into optical domain; and sample and digitize the modulation frequency voltage to generate a reference digital signal, wherein the sampling of the measurement voltages and modulation frequency voltage are performed in a substantially simultaneous manner; and a computing device configured to perform software-based coherent detection of the measurement digital signals using the reference digital signal and.

The system also comprises a data acquisition circuit configured to sample and digitize the plurality of measurement voltages to generate a plurality of measurement digital signals, and sample and digitize the modulation frequency voltage to generate a reference digital signal. The sampling of the measurement voltages and modulation frequency voltage is performed in a substantially simultaneous manner. The simultaneous sampling ensures that the one or more resulting measurements, such as EQE and IΓaE, are based on the currents generated by the specimen measurement system generated at substantially the same time instance. The system comprises a computing device configured to perform software-based coherent detection of the measurement digital signals using the reference digital signal.

In accordance with one embodiment, the computing device may be configured to perform the coherent detection of the measurement digital signals by at least mixing the measurement digital signals with a mixing signal based on the reference digital signal to generate a plurality of respective mixed digital signals, and filtering the digital mixed signals to generate output digital signals. In accordance with another embodiment, the mixing signal may be related to a frequency harmonic of the reference digital signal. Additionally, the computing device may be configured to generate one or more indications of the one or more properties of the specimen based on the output digital signals. Such one or more indications may include the EQE, IΓaE, or other one or more properties of the specimen.

In accordance with the first embodiment, the specimen measurement system comprises a reference detector configured to generate a first current of the plurality of currents, the first current being related to an intensity of the incident light signal, and wherein a second current of the plurality of currents is generated by the specimen in response to the incident light signal. Alternatively, the specimen measurement system comprises a reference detector configured to generate a first current of the plurality of currents, the first current being related to an intensity of the incident light signal, a reflectance detector configured to generate a second current of the plurality of currents, the second current being related to the intensity of a light signal being reflected by the specimen in response to the incident light signal, and a detector configured to generate a third current of the plurality of currents based on an electrical signal generated by the specimen in response to the incident light signal.

In accordance with a second exemplary embodiment, the system comprises a light source configured to generate a distinct band of wavelength light signals being modulated based on respective distinct modulation frequency voltages; an optical combiner configured to generate a combined light signal based on the distinct band of wavelengths modulated light signals; and a specimen measurement system configured to direct at least a portion of the combined light signal incident upon a specimen for measurement of one or more properties of the specimen, wherein the specimen measurement system is configured to generate a plurality of measurement currents pursuant to the measurement of the one or more properties of the specimen.

In accordance with the second embodiment, the system comprises a signal conditioner configured to generate a plurality of measurement voltages from the plurality of currents, respectively. Further, the system comprises a data acquisition circuit configured to sample and digitize the plurality of measurement voltages to generate a plurality of measurement digital signals, and sample and digitize the plurality of modulation frequency voltages to generate a plurality of reference digital signals. The sampling of the measurement voltages and the modulation frequency voltages are performed in a substantially simultaneous manner. Additionally, the system comprises a computing device configured to perform software-based coherent detection of the measurement digital signals using the reference digital signals.

The computing device may be configured to perform the coherent detection of the measurement digital signals by mixing the measurement digital signals with mixing signals based on the reference digital signals to generate a plurality of mixed digital signals, and filtering the digital mixed signals to generate output digital signals. In one aspect, the mixing signals are related to frequency harmonics of the reference digital signals, respectively. In another aspect, the mixing signals are related to one or more beat frequencies each based on one or more selected pairs of the reference digital signals.

As per the first exemplary embodiment, the computing device is configured to generate one or more indications of the one or more properties of the specimen based on the output digital signals, such as EQE, IQE, or any other one or more properties of the specimen. As per the first exemplary embodiment, the specimen measurement system may be configured to include a reference detector, a reflectance detector, as well as other detectors, and configured to produce the current generated by the specimen in response to the incident light.

In accordance with a third exemplary embodiment, the system comprises a light source configured to generate a plurality of light signals modulated based on a plurality of distinct modulation frequency voltages, respectively; a specimen measurement system configured to direct portions of the plurality of light signals incident upon distinct regions of a specimen for measurement of one or more properties of the specimen, wherein the specimen measurement system is configured to generate a plurality of measurement currents pursuant to the measurement of the one or more properties of the specimen; and a signal conditioner configured to generate a plurality of measurement voltages from the plurality of measurement currents, respectively.

Additionally, in accordance with the third exemplary embodiment, the system comprises a data acquisition circuit configured to sample and digitize the plurality of measurement voltages to generate a plurality of measurement digital signals, and sample and digitize the plurality of modulation frequency voltages to generate a plurality of reference digital signals. The sampling of the measurement voltages and the modulation frequency voltages are performed in a substantially simultaneous manner. In addition, the system comprises a computing device configured to perform software-based coherent detection of the measurement digital signals using the reference digital signals. Other elements of the third embodiment may be configured substantially the same or similar to the second embodiment.

Other aspects, advantages and novel features of the disclosure will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

<FIG> illustrates a block diagram of an exemplary optical signal processing system <NUM> in accordance with an aspect of the disclosure. In summary, the optical signal processing system <NUM> comprises: a light source configured to generate an incident light at a selected wavelength and amplitude modulated at a particular frequency; a specimen measurement system configured to direct the incident light at a specimen and generate a plurality of signals for measuring one or more characteristics of the specimen; a signal conditioner to generate suitable voltages for acquisition based on the signals generated by the specimen measurement system; a data acquisition circuit to substantially perform simultaneous sampling and digitizing of the voltages from the signal conditioner; and a software-based (SW-based) computing device configured to perform coherent detection and analysis of the digitized signals.

The simultaneous sampling and coherent detection of the signals allow the SW-based computing device to more accurately generate one or more measurements of the specimen in real-time. This is because the one or more measurements depend on a plurality of signals generated at substantially the same time. In other words, inaccuracy or noise due to time differences in the acquisition of the signals is minimized. Additionally, because a plurality of measurements depend on different sets of signals generated from the specimen measurement system, the simultaneous sampling and coherent detection ensures that different measurements are based on signals acquired at substantially the same time. Further, such different measurements may be accurately displayed simultaneously in real-time.

More specifically, the optical signal processing system <NUM> comprises a modulated light source <NUM>, a modulation frequency source <NUM>, a wavelength selector <NUM>, a specimen measurement system <NUM>, a signal conditioning circuit <NUM>, a data acquisition circuit <NUM>, and a SW-based computing device <NUM>.

The modulated light source <NUM> generates a modulated light with a defined range or bandwidth (bw) of wavelengths λbwf. Examples of modulated light source may include lasers, diodes, and other types of light sources. The modulated light source <NUM> generates the modulated light λbwf based on a modulation signal or voltage Vmf, which cycles with a defined frequency (f). The modulation frequency source <NUM> generates the modulation signal or voltage Vmf for the modulated light source <NUM>. The wavelength selector <NUM> generates a modulated light with a selected wavelength λsf from the modulated light λbwf, wherein the selected wavelength λsf has a narrower band than the modulated light λbwf. The wavelength selector <NUM> may comprise a monochromator, filter, or other device capable of selecting a more narrowband wavelength within the wavelength range of the modulated light λbwf.

The specimen measurement system <NUM> is configured to direct the selected modulated light λsf incident upon a specimen for measurement of one or more properties or characteristics of the specimen. In accordance with the measurement, the specimen measurement system <NUM> generates a plurality of electrical signals, such as currents I<NUM> to IN.

For example, if the specimen measurement system <NUM> is configured to measure the extrinsic quantum efficiency (EQE) of a specimen, the specimen measurement system <NUM> may generate a current I<NUM> related to the power level of the incident light λsf upon the specimen, and a current I<NUM> generated by the specimen in response to the incident light λsf. If the specimen measurement system <NUM> is configured to measure the intrinsic quantum efficiency (IQE) of a specimen, the specimen measurement system <NUM> may generate a current I<NUM> related to the power level of the incident light λsf upon the specimen, a current I<NUM> related to a power level of specular light reflected by the specimen, a current I<NUM> related to a power level of diffusive light reflected by the specimen, and a current I4 generated by the specimen in response to the incident light λsf. It shall be understood that the specimen measurement system <NUM> may be configured to measure both EQE and IΓaE, as well as perform other measurements on the specimen.

The signal conditioning circuit <NUM> performs transimpedance amplification and signal conditioning of the currents I<NUM> to IN to generate voltages V<NUM> to VN suitable for sampling and digitizing by the data acquisition circuit <NUM>. For example, the signal conditioning circuit <NUM> may perform the transimpedance amplification with a positive gain to generate the voltages V<NUM> to VN at suitable levels, and apply filtering and/or other processing to reduce noise.

As previously discussed the data acquisition circuit <NUM> samples and digitizes the voltages V<NUM> to VN from the signal conditioning circuit <NUM> to generate digital signals D<NUM> to DN, respectively. Additionally, the data acquisition circuit <NUM> samples and digitizes the modulation voltage Vmf from the modulation frequency source <NUM> to generate digital signal Dmf. So that the coherent detection and any measurements performed by the SW-based computing device are based on the currents I<NUM> to IN derived at substantially the same time, the data acquisition circuit <NUM> is configured to simultaneously sample the voltages V<NUM> to VN and the modulation voltage Vmf.

The SW-based computing device <NUM> receives the digital signals D<NUM> to DN and Dmf by way of any suitable digital interface, such as a Universal Serial Bus (USB) interface, Peripheral Component Interface (PCI), and others. The SW-based computing device may be any type of computing device, such as a desktop computer, laptop, smart phone, tablet-type computer, and others. As discussed in more detail herein, the SW-based computing device <NUM> performs software-based coherent detection (also known as heterodyne or lock-in amplifier detection) to generate, potentially less-noisy, digital output signals related to the intensity or power level of the currents I<NUM> to IN generated at substantially the same time instance. The SW-based computing device <NUM> performs the coherent detection of the digital signals D<NUM> to D<NUM> in a manner that the resulting output signals are derived from the currents I<NUM> to I<NUM> at substantially the same time instance. This ensures time correlation for all the variables needed for the SW-based computing device <NUM> to derive the resulting one or more measurements (e.g., EQE and IQE) of the specimen.

Additionally, the SW-based computing device <NUM> may output the resulting one or more measurements, as well as the data derived from the specimen measurement system <NUM> and other associated data, to a user interface, such as a display, speakers, etc., to provide a user information related to the one or more measurements. Via the user interface, as in the case of input devices such as a keyboard, mouse, microphones, etc., the SW-based computing device <NUM> may receive instructions from a user as to how to perform the one or more measurements and how the information is provided to the user via the user interface. In this regards, the SW-based computing device <NUM> may send control signals to any of the elements of the system <NUM> to configure the system in accordance with the user's inputs.

<FIG> illustrates a block diagram of yet another exemplary optical signal processing system <NUM> in accordance with another aspect of the disclosure. The optical signal processing system <NUM> is a variation of the optical signal processing system <NUM> previously discussed, and includes many of the same elements as noted by the same reference numbers. The system <NUM> differs from system <NUM> in that the modulation signal or voltage Vmf is generated internally within the data acquisition circuit <NUM>, and not by an external modulation frequency source <NUM> as in system <NUM>. Otherwise, the operation of the optical signal processing system <NUM> is substantially the same as optical signal processing system <NUM> previously discussed in detail.

<FIG> illustrates a block diagram of an exemplary software-based coherent detection system implemented by the exemplary SW-based computing device <NUM> in accordance with another aspect of the disclosure. The system <NUM> comprises a SW-based phase lock loop (PLL) module <NUM>, a SW-based frequency/harmonic (F/H) tone generator module <NUM>, SW-based mixer modules <NUM>-<NUM> to <NUM>-N, SW-based filter modules <NUM>-<NUM> to <NUM>-N, and a SW-based processing module <NUM>. The SW-based processing module <NUM> may interface with a control interface <NUM> for sending and/or receiving signals, such as control signals and sensed parameters, to and from other elements of the optical signal processing system <NUM> or <NUM>. Additionally, the SW-based processing module <NUM> may interface with a user interface <NUM> for sending and/or receiving signals, such as measurement-related information and control signals, to and from a user of the optical signal processing system <NUM> or <NUM>.

The SW-based PLL module <NUM> is configured to generate a signal that is phase locked with the digital signal Dmf. Since the digital signal Dmf is derived from the modulation signal Vmf, the signal generated by the SW-based PLL module <NUM> is phase locked with the modulation signal Vmf. Based on a selected fundamental or harmonic command P, the SW-based F/H tone generator <NUM> may regenerate the fundamental signal Dmf in the case P is equal to one (<NUM>), or may generate a desired harmonic P*Dmf of the signal in the case P is an integer greater than one (<NUM>). The harmonic may be used to detect harmonic components of the modulation frequency in the digital signals D<NUM> to DN. Although not shown for simplicity sake, the output signal P*Dmf of the SW-based F/H tone generator <NUM> includes both the sine and cosine components for proper heterodyne detection at the SW-based mixer modules <NUM>-<NUM> to <NUM>-N.

As mentioned, the selected tone P*Dmf from the SW-based F/H tone generator <NUM> is applied to the SW-based mixer modules <NUM>-<NUM> to <NUM>-N. The digital signals D<NUM> to DN are also applied to the SW-based mixer modules <NUM>-<NUM> to <NUM>-N, respectively. The SW-based mixer modules <NUM>-<NUM> to <NUM>-N mixes the digital signals D<NUM> to DN with the selected tone P*Dmf to generate respective mixed signals. Each of the mixed signals includes a direct current (DC) carrier component and a sideband component. The sideband component may be associated with noise in the system <NUM> or <NUM>. The corresponding SW-based filters <NUM>-<NUM> to <NUM>-N substantially eliminate the sideband components of the mixed signals to generate output signals DO1 to DON, respectively. The output signals DO1 to DON are related to the power level or intensity of the signals or currents I<NUM> to IN generated by the specimen measurement system <NUM>.

The SW-based processing module <NUM> processes the output signals DO1 to DON in accordance with the one or more desired measurements of one or more characteristics of the specimen. For example, if the optical signal processing system <NUM> or <NUM> is configured to measure EQE and/or IQE, the SW-based processing system <NUM> generates parameters indicative of the EQE and/or IΓaE based on the output signals DO1 to DON. The SW-based processing module <NUM> may send the measurement information to the user interface <NUM> to provide a user such information, in a graphical or non-graphical manner.

<FIG> illustrates a block diagram of another exemplary optical signal processing system <NUM> in accordance with another aspect of the disclosure. In the previous exemplary embodiments, the systems <NUM> and <NUM> were configured to generate an incident light for the specimen, whereby the incident light is configured with a selected wavelength and modulated at a particular frequency. In contrast, the optical signal processing system <NUM> is configured to generate a combined incident light for the specimen, whereby the combined incident light is derived from a plurality of lights at different wavelengths and modulated with different frequencies.

More specifically, the optical signal processing system <NUM> comprises modulated light sources <NUM>-<NUM> to <NUM>-M, modulation frequency sources <NUM>-<NUM> to <NUM>-M, an optical combiner <NUM>, a specimen measurement system <NUM>, signal conditioning circuit <NUM>, a data acquisition circuit <NUM>, and a SW-based computing device <NUM>.

The modulated light sources <NUM>-<NUM> to <NUM>-M generate lights λsf1 to λsfM configured with different wavelengths and modulated at different frequencies, respectively. The modulated light sources <NUM>-<NUM> to <NUM>-M generate λsf1 to λsfM based on modulation signals or voltages Vmf1 to VmfM generated by the modulation frequency sources <NUM>-<NUM> to <NUM>-M, respectively. Alternatively, instead of the external modulation frequency sources <NUM>-<NUM> to <NUM>-M, the modulation signals or voltages Vmf1 to VmfM may be generated internally in the data acquisition circuit <NUM>, as per optical signal processing system <NUM>.

The optical combiner <NUM> receive the respective lights λsf1 to λsfM from the modulated light sources <NUM>-<NUM> to <NUM>-M, and combines them to generate a combined light λcb. As an example, the optical combiner <NUM> may be configured as a homogenizing rod/coupler or other type of optical signal combining device. The combined light λcb is provided to the specimen measurement system <NUM>, which directs it incident upon a specimen. As per the previous specimen measurement system <NUM>, the specimen measurement system <NUM> generates a plurality of electrical signals I<NUM> to IN associated with the one or more measurements being performed on the specimen. Similar to the previous embodiments, the specimen measurement system <NUM> may be configured to generate electrical signals I<NUM> to IN pursuant to an EQE and/or IΓaE measurement.

Similar to the previous embodiments, the signal conditioning circuit <NUM> performs transimpedance amplification of the currents I<NUM> to IN and associated signal conditioning to generate corresponding voltages V<NUM> to VN suitable for sampling and digitizing by the data acquisition circuit <NUM>.

The data acquisition circuit <NUM> samples and digitizes the voltages V<NUM> to VN from the signal conditioning circuit <NUM> to generate digital signals D<NUM> to DN. The data acquisition circuit <NUM> also samples the modulation voltages Vmf1 to VmfM from the modulation frequency sources <NUM>-<NUM> to <NUM>-N to generate digital signals Dmf1 to DmfM, respectively. As per the previous embodiments, the data acquisition circuit <NUM> simultaneously samples and digitizes the voltages V<NUM> to VN and Vmf1 to VmfM so that the resulting measurement(s) generated by the SW-based computing device <NUM> are based on signals derived from the specimen at substantially the same time instance.

As per the previous embodiments, the SW-based computing device <NUM> receives the digital signals D<NUM> to DN and Dmf1 to DmfM via a digital interface (e.g., USB, PCI, etc). The SW-based computing device <NUM> performs coherent detection of the digital signals D<NUM> to DN using the modulation-based signals Dmf1 to DmfM to generate output digital signals indicative of the intensity or power level of the currents I<NUM> to IN from the specimen measurement system <NUM>. The SW-based computing device <NUM> performs the coherent detection of the digital signals D<NUM> to D<NUM> in a manner that the resulting output signals are derived from the currents I<NUM> to I<NUM> at substantially the same time instance. This ensures time correlation for all the variables needed for the SW-based computing device <NUM> to derive the resulting one or more measurements (e.g., EQE and IQE) of the specimen.

<FIG> illustrates a block diagram of yet another exemplary optical signal processing system <NUM> in accordance with another aspect of the disclosure. The optical signal processing system <NUM> is a variation of the optical signal processing system <NUM>, and includes many of the same elements as indicated by the same reference numbers. The optical signal processing system <NUM> differs from optical signal processing system <NUM> in that the modulated light sources <NUM>-<NUM> to <NUM>-M may generate light signals λsf1 to λsfM with substantially the same wavelength, but modulated with different frequencies.

Another difference is that the light signals λsf1 to λsfM are transmitted separately into the specimen measurement system <NUM>. The specimen measurement system <NUM> directs the light signals λsf1 to λsfM at different regions of a specimen. This may be done to perform spatial analysis of the specimen. The resulting currents I<NUM> to IN generated by the specimen measurement system <NUM> may each have contributions from the light signals λsf1 to λsfM. Using coherent detection, the SW-based computing device <NUM> is capable of separating the contributions for individual analysis thereof.

<FIG> illustrates a block diagram of another exemplary software-based coherent detection system implemented by the exemplary SW-based computing device <NUM> in accordance with another aspect of the disclosure. The SW-based computing device <NUM> comprises a plurality of SW-based PLL modules <NUM>-<NUM> to <NUM>-M, a plurality of F/H tone generator modules <NUM>-<NUM> to <NUM>-M, and a beat tone generator module <NUM>. Additionally, the SW-based computing device <NUM> further comprises a tone selector (mux) <NUM>, a plurality of SW-based coherent or lock-in amplifier sections <NUM>-<NUM>-N to <NUM>-M-N, and a SW-based processing module <NUM>. As per the previous embodiments, the SW based processing module <NUM> may interface with a control interface <NUM> for sending control signals and receiving sensed parameters, and may also interface with a user interface <NUM> for providing and receiving information to and from a user.

The SW-based PLL modules <NUM>-<NUM> to <NUM>-M generate signals phase locked with the digital signals Dmf1 to DmfM, respectively. The F/H tone generator modules <NUM>-<NUM> to <NUM>-M generate fundamental (P=<NUM>) or harmonics (P > <NUM>) signals P*Dmf1 to P*DmfM based on user selected parameter P, respectively. The beat tone generator module <NUM> generates a selected beat frequency signal Dmf1-Dmfj based on a selected pair i and j of the phase locked signals generated from the SW-based PLL modules <NUM>-<NUM> to <NUM>-M. The generated signals or tones P*Dmf1 to P*DmfM and Dmf1-Dmfj are provided to the tone selector module <NUM>. Based on a user select signal (SEL), the tone selector module <NUM> outputs selected tones T<NUM> to TM.

The SW-based coherent or lock-in amplifier sections <NUM>-<NUM>-N to <NUM>-M-N use the selected tones T1 to TM to generate coherently-detected output signals DO11 to DOMN, respectively. For instance, if the fundamental frequencies Dmf1 to DmfM are chosen for the selected tones T<NUM> to TM, then the output signals DO11-DO1N to DOM1-DOMN indicate the intensity or power level of the fundamental frequency components of the current signals I<NUM> to IN from the specimen measurement system <NUM>, respectively. If harmonic frequencies P*Dmf1 to P*DmfM (P><NUM>) are chosen for the selected tones T<NUM> to TM, then the output signals DO11-DO1M to DOM1-DOMN indicate the intensity or power level of the selected harmonic frequency components of the current signals I<NUM> to IN from the specimen measurement system <NUM>, respectively. Similarly, if a certain beat frequency is chosen for the selected tones T<NUM> to TM, then the output signals DO11-DO1N to DOM1-DOMN indicate the intensity or power level of the selected beat frequency component of the current signals I<NUM> to IN from the specimen measurement system <NUM>, respectively.

The SW-based processing module <NUM> processes the output signals DO11-DOIN to DOM1-DOMN in accordance with the one or more desired measurements of one or more characteristics of the specimen. For example, if the optical signal processing system <NUM> or <NUM> is configured to measure EQE and/or IQE, the SW-based processing system <NUM> generates parameters indicative of the EQE and/or IΓaE based on the output signals DO11-DO1N to DOM1-DOMN. The SW-based processing module <NUM> may send the measurement information to the user interface <NUM> to provide a user such information, in a graphical or non-graphical manner.

<FIG> illustrates a block diagram of another exemplary optical signal processing system <NUM> in accordance with another aspect of the disclosure. The optical signal processing system <NUM> is an exemplary implementation of optical signal processing system <NUM> previously discussed, with a specimen measurement system being configured to measure EQE and/or IQE.

In particular, the optical signal processing system <NUM> comprises a modulated light source <NUM>, a modulation frequency source <NUM>, a wavelength selector <NUM>, a light bias controller <NUM>, an electrical bias controller <NUM>, a specimen measurement system <NUM>, a signal conditioning circuit <NUM>, a data acquisition circuit <NUM>, a SW-based computing device <NUM>, and a user interface <NUM>. The specimen measurement system <NUM>, in turn, comprises a specular reflectance detector <NUM>, a beam splitter <NUM>, a diffusive device <NUM>, a specimen <NUM>, an X-Y stage <NUM>, a reference detector <NUM>, a diffusive reflectance detector <NUM>, and an optical transmission detector <NUM>.

The modulated light source <NUM> is configured to generate a modulated light signal having a defined range of wavelengths λbwf. The modulated light source <NUM> is configured to generate the light signal λbwf based on a modulation signal or voltage Vmf generated by the modulation frequency source <NUM>. The wavelength selector <NUM> is configured to generate a modulated light signal having a selected wavelength λsf based on the light signal λbwf from the modulated light source <NUM>, wherein the selected wavelength λsf has a narrower band than the modulated light λbwf. As previously discussed with reference to system <NUM>, the wavelength selector <NUM> may comprise a monochromator, filter or other devices.

With regard to the specimen measurement system <NUM>, the beam splitter <NUM> splits the light signal λsf into a reference signal and an incident signal. The reference signal is provided to the reference detector <NUM>. In response to the reference signal, the reference detector <NUM> generates a current I<NUM>. The current I<NUM> is related (e.g., proportional) to the intensity or power level of the light source λsf. The incident signal is directed to the specimen <NUM> by way of the diffusive device <NUM>. The diffusive device <NUM> may comprises an integration sphere or other type of diffusive device.

The specimen <NUM> may generate a current I<NUM> in response to the diffusive incident light. The current I<NUM> may be used to determine the EQE and IQE, as well as other properties of the specimen <NUM>. In some cases, some of the incident light may pass or transmit through the specimen <NUM>, which may be detected by optical transmission detector <NUM>. In response to the transmitted light, the optical transmission detector <NUM> generates a current I<NUM>. The current I<NUM> may be used to determine the EQE and IQE, as well as other properties of the specimen <NUM>.

Some of the incident light is reflected off of the specimen <NUM>. The reflected light is received by the diffusive device <NUM>. The diffusive device <NUM> includes a port for outputting the diffusive reflected light. A diffusive reflectance detector <NUM> generates a current I<NUM> in response to the diffusive reflected light from the diffusive device <NUM>. The current I<NUM> may be used to determine the EQE and IQE, as well as other properties of the specimen <NUM>. Additionally, some of the incident light reflected off of the specimen <NUM> at a normal angle, referred to herein as specular reflected light, passes through the diffusive device <NUM> and the beam splitter <NUM>, and is detected by the specular reflectance detector <NUM>. The specular reflectance detector <NUM> generates a current I<NUM> in response to the specular reflected light. The current I<NUM> may be used to determine the EQE and IQE, as well as other properties of the specimen <NUM>.

The X-Y stage <NUM> of the specimen measurement system <NUM> supports the specimen <NUM>, and facilitates the positioning of the specimen <NUM> either manually by a user or by way of an X-Y control signal generated by the SW-based computing device <NUM>. The X-Y stage <NUM> may further include a sensor for generating a signal indicative of the temperature of the specimen. The X-Y stage <NUM> may provide the temperature signal to the SW-based computing device <NUM> via a control line.

The light bias controller <NUM> of the optical signal processing system <NUM> may direct a controllable light at the specimen <NUM> in accordance with one or more measurements being made with regard to the specimen. In this regards, the SW-based computing device <NUM> generates a control signal for the light bias controller <NUM>. Additionally, the electrical bias controller <NUM> may bias the specimen <NUM> with a controllable bias signal (e.g., a bias voltage and/or current) in accordance with one or more measurements being made with regard to the specimen. In this regards, the SW-based computing device <NUM> generates a control signal for the electrical bias controller <NUM>.

As per the previous embodiments, the signal conditioning circuit <NUM> receives the currents I<NUM> to I<NUM> from the specimen measurement system <NUM> and generates therefrom respective voltages V<NUM> to V<NUM> suitable for sampling and digitizing by the data acquisition circuit <NUM>. As per the previous embodiments, the data acquisition circuit <NUM> samples and digitizes the voltages V<NUM> to V<NUM> and the modulation frequency voltage Vmf to generate digital signals D<NUM> to D<NUM> and Dmf, respectively. As per the previous embodiment, the data acquisition circuit <NUM> samples these voltages in a substantially simultaneous manner.

The SW-based computing device <NUM> performs the coherent detection of the digital signals D<NUM> to D<NUM> in a manner that the resulting output signals are derived from the currents I<NUM> to I<NUM> at substantially the same time instance. This ensures time correlation for all the variables needed for the SW-based computing device <NUM> to derive the EQE and IQE, as well as other properties of the specimen. As per the previous embodiments, the SW-based computing device <NUM> may provide and receive control-related signals to and from various elements of the optical signal processing system <NUM> per control lines indicated as alternate long- and-short-dashes. Additionally, the SW-based computing device <NUM> may provide and receive measurement-related information to and from a user via the user interface <NUM>.

<FIG> illustrates a block diagram of yet another exemplary optical signal processing system <NUM> in accordance with another aspect of the disclosure. The optical signal processing system <NUM> is an exemplary implementation of optical signal processing system <NUM> previously discussed, with a specimen measurement system being configured to measure EQE and/or IQE.

In particular, the optical signal processing system <NUM> comprises modulated light sources <NUM>-<NUM> to <NUM>-<NUM>, modulation frequency sources <NUM>-<NUM> to <NUM>-<NUM>, an optical combiner <NUM>, a light bias controller <NUM>, an electrical bias controller <NUM>, a specimen measurement system <NUM>, a signal conditioning circuit <NUM>, a data acquisition circuit <NUM>, a SW-based computing device <NUM>, and a user interface <NUM>.

Modulated light sources <NUM>-<NUM> to <NUM>-<NUM> are configured to generate modulated light signals having distinct selected wavelengths λsf1, λsf2, and λsf3, and modulated with distinct frequencies based on modulation signals or voltages Vmf1, Vmf2 and Vmf3 generated by the modulation frequency sources <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>, respectively. The optical combiner <NUM> combines the modulated light signals λsf1, λsf2, and λsf3 to generate a combined light signal λcb. The specimen measurement system <NUM> uses the combined light signal λcb to generate an incident light for a specimen. The specimen measurement system <NUM> may be configured substantially the same or similar to specimen measurement system <NUM>, previously discussed in detail.

As per the previous embodiment, the specimen measurement system <NUM> generates currents I<NUM> to I<NUM>. The signal conditioner <NUM> performs transimpedance amplification and signal conditioning to convert the currents I<NUM> to I<NUM> into suitable voltages V<NUM> to V<NUM> for sampling and digitizing by the data acquisition circuit <NUM>. As per the previous embodiments, the data acquisition circuit <NUM> samples and digitizes the voltages V<NUM> to V<NUM> and the modulation voltages Vmf1 to Vmf3 to generate digital signals D<NUM> to D<NUM> and Dmf1 to Dmf3, respectively. The data acquisition circuit <NUM> samples and digitizes the signals in a substantially simultaneous manner.

As per SW-based computing device <NUM> previously discussed, the SW-based computing device <NUM> performs coherent detection of the digital signals D<NUM> to D<NUM> using modulation signals Dmf1 to Dmf3 to generate output digital signals. If, for example, the coherent detection uses the fundamental tones Dmf1 to Dmf3, the detected output signals indicate the intensity or power level of the fundamental frequency component of the currents I<NUM> to I<NUM> generated by the specimen measurement system <NUM>. If, for example, the coherent detection uses harmonics P*Dmf1 to P*Dmf3 (P><NUM>), the detected output signals indicate the intensity or power level of the corresponding harmonic frequency component of the currents I<NUM> to I<NUM> generated by the specimen measurement system <NUM>. If, for example, the coherent detection uses a selected beat frequency (Dmfi ± Dmfj)(i≠j, i=j={<NUM>,<NUM>,<NUM>}), the detected output signals indicate the intensity or power level of the corresponding beat frequency component of the currents I<NUM> to I<NUM> generated by the specimen measurement system <NUM>.

As per the previous embodiment, the light bias controller <NUM> of the optical signal processing system <NUM> directs controllable light at the specimen in accordance with one or more measurements being made with regard to the specimen. In this regards, the SW-based computing device <NUM> generates a control signal for the light bias controller <NUM>. The electrical bias controller <NUM> biases the specimen with a controllable bias signal (e.g., a bias voltage and/or current) in accordance with one or more measurements being made with regard to the specimen. In this regards, the SW-based computing device <NUM> generates a control signal for the electrical bias controller <NUM>.

<FIG> illustrates a block diagram of still another exemplary optical signal processing system <NUM> in accordance with another aspect of the disclosure. The optical signal processing system <NUM> is an exemplary implementation of the optical signal processing system <NUM> previously discussed, with a specimen measurement system being configured to measure EQE and/or IQE.

In particular, the optical signal processing system <NUM> comprises modulated light sources <NUM>-<NUM> to <NUM>-<NUM>, modulation frequency sources <NUM>-<NUM> to <NUM>-<NUM>, beam steering or programmable mask <NUM>, a light bias controller <NUM>, an electrical bias controller <NUM>, a specimen measurement system <NUM>, a signal conditioning circuit <NUM>, a data acquisition circuit <NUM>, a SW-based computing device <NUM>, and a user interface <NUM>.

Modulated light sources <NUM>-<NUM> to <NUM>-<NUM> are configured to generate modulated light signals λsf1, λsf2, and λsf3 having substantially the same wavelength, but modulated with distinct frequencies based on modulation signals or voltages Vmf1, Vmf2 and Vmf3 generated by the modulation frequency sources <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>, respectively. The beam steering / programmable mask <NUM> is configured to direct the modulated light signals λsf1, λsf2, and λsf3 to desired regions of a specimen. The specimen measurement system <NUM> uses the modulated light signals λsf1, λsf2, and λsf3 to generate incident light signals for a specimen for spatial analysis thereof. The specimen measurement system <NUM> may be configured substantially the same or similar to specimen measurement system <NUM>, previously discussed in detail.

As per the previous embodiments, the specimen measurement system <NUM> generates currents I<NUM> to I<NUM>. The signal conditioning circuit <NUM> performs transimpedance amplification and signal conditioning to convert the currents I<NUM> to I<NUM> into suitable voltages V<NUM> to V<NUM> for sampling and digitizing by the data acquisition circuit <NUM>. As per the previous embodiments, the data acquisition circuit <NUM> samples and digitizes the voltages V<NUM> to V<NUM> and the modulation voltages Vmf1 to Vmf3 to generate digital signals D<NUM> to D<NUM> and Dmf1 to Dmf3, respectively. The data acquisition circuit <NUM> samples the signals in a substantially simultaneous manner.

As per SW-based computing device <NUM> previously discussed, the SW-based computing device <NUM> performs coherent detection of the digital signals D<NUM> to D<NUM> using modulation signals Dmf1 to Dmf3 to generate detected output signals. If, for example, the coherent detection uses the fundamental tones Dmf1 to Dmf3, the detected output signals indicate the intensity or power level of the fundamental frequency component of the currents I<NUM> to I<NUM> generated by the specimen measurement system <NUM>. If, for example, the coherent detection uses harmonics P*Dmf1 to P*Dmf3 (P><NUM>), the detected output signals indicate the intensity or power level of the corresponding harmonic frequency component of the currents I<NUM> to I<NUM> generated by the specimen measurement system <NUM>. If, for example, the coherent detection uses a selected beat frequency (Dmfi ± Dmfj)(i≠j, i=j={<NUM>,<NUM>,<NUM>}), the detected output signals indicate the intensity or power level of the corresponding beat frequency component of the currents I<NUM> to I<NUM> generated by the specimen measurement system <NUM>.

The SW-based computing device <NUM> performs the coherent detection of the digital signals D<NUM> to D<NUM> in a manner that the resulting output signals are derived from the currents I<NUM> to I<NUM> at substantially the same time instance. This ensures time correlation for all the variables needed for the SW-based computing device <NUM> to derive the EQE and IQE, as well as other properties of the specimen. As per the previous embodiments, the SW-based computing device <NUM> may provide and receive control-related signals to and from various elements of the optical measurement system <NUM> per control lines indicated as alternate long-and-short-dashes. Additionally, the SW-based computing device <NUM> may provide and receive measurement-related information to and from a user via the user interface <NUM>.

As per the previous embodiment, the light bias controller <NUM> of the optical measurement system <NUM> directs controllable light at the specimen in accordance with one or more measurement being made with regard to the specimen. The SW-based computing device <NUM> generates a control signal for the light bias controller <NUM>. The electrical bias controller <NUM> biases the specimen with a controllable bias signal (e.g., a bias voltage and/or current) in accordance with one or more measurement being made with regard to the specimen. In this regards, the SW-based computing device <NUM> generates a control signal for the electrical bias controller <NUM>.

<FIG> illustrates a screen shot of an exemplary graphical user interface (GUI) <NUM> generated by an exemplary user interface in accordance with another aspect of the disclosure. The GUI <NUM> comprises a measurement display portion <NUM> configured to illustrate one or more selected measurements. In this example, the measurement display portion <NUM> depicts a graph of the EQE measurement in graph form. The x- or horizontal-axis represents wavelength, and the y- or vertical axis represents EQE. It shall be understood that the measurement display portion <NUM> may illustrate the one or more selected measurements in other formats, such as tabulated, pie charts, bar charts, and others. For instance, the display portion <NUM> may display the EQE, IQE, RS, and RD at the same time during a wavelength scan.

The GUI <NUM> further comprises a measurement selection portion <NUM> configured to allow a user to select one or more measurements for depiction in the measurement display portion <NUM>. For instance, in this example, the measurement selection portion <NUM> illustrates the EQE as being the selected measurement, as indicated by the juxtaposed checkmark. Additionally, in accordance with this example, the measurement selection portion <NUM> lists other available measurements, such as IQE, channels <NUM>-<NUM> (e.g., related to the various signals generated by a specimen measurement system described herein), spectral responsivity, signal from specular reflectance detector (RS), signal from diffusive reflectance detector (RS), and sum of signals from specular and diffusive reflectance detectors (RS+RD). It shall be understood that more or less different types of measurements may be available to a user via the measurement selection portion <NUM>.

The GUI <NUM> further comprises a graph labeling portion <NUM> with text boxes for allowing a user to label the x- and y- axes of the graph depicted in the measurement display portion <NUM>. Additionally, the GUI <NUM> comprises a legend area <NUM> for identifying the plot. This is useful when the graph depicts multiple plots. Also, the GUI <NUM> includes a drop-down box <NUM> to allow a user to select the display format for the one or more selected measurements, such as graph, tabulated, and others.

The GUI <NUM> also comprises a scan detail area <NUM> that provides information related to the current scan. The GUI <NUM> also includes a current session <NUM> indicating the data log files related to the current session. Using the load and remove soft buttons <NUM> and <NUM>, a user is able to load the data from a selected data log file, as well as remove a data log file. Further, the GUI <NUM> includes start and abort soft buttons <NUM> to allow a user to start a measurement scan and to abort a measurement scan. It shall be understood that GUI <NUM> is merely an example, and the GUI may be configured in many different manners.

Claim 1:
A system (<NUM>), comprising:
a modulation frequency source (<NUM>) configured to generate a modulation frequency voltage;
a modulated light source (<NUM>) configured to generate a modulated light signal based on the modulation frequency voltage;
a specimen measurement system (<NUM>) configured to direct at least a portion of the modulated light signal incident upon a specimen for measurement of one or more properties of the specimen, wherein the specimen measurement system (<NUM>) is configured to generate a plurality of measurement currents pursuant to the measurement of the one or more properties of the specimen, wherein the specimen measurement system (<NUM>) , comprises:
a reference detector (<NUM>) configured to generate a first current of the plurality of currents, the first current being related to an intensity of the incident light signal;
a reflectance detector (<NUM>) configured to generate a second current of the plurality of currents, the second current being related to an intensity of a light signal reflected by the specimen in response to the incident light signal; and
a detector configured to generate a third current of the plurality of currents based on an electrical signal generated by the specimen in response to the incident light signal;
a signal conditioner (<NUM>) configured to generate a plurality of measurement voltages from the plurality of currents, respectively;
a data acquisition circuit (<NUM>) configured to:
sample and digitize the plurality of measurement voltages to generate a plurality of measurement digital signals;
receive the modulation frequency voltage from the modulation frequency source (<NUM>) without the modulation frequency voltage being converted into optical domain; and
sample and digitize the modulation frequency voltage to generate a reference digital signal, wherein the sampling of the measurement voltages and modulation frequency voltage are performed in a substantially simultaneous manner; and
a computing device (<NUM>) configured to perform software-based coherent detection of the measurement digital signals using the reference digital signal.