Lock-in amplifier

About: Lock-in amplifier is a research topic. Over the lifetime, 521 publications have been published within this topic receiving 4455 citations.

Selective image extraction by synthesis of the coherence function using two-dimensional optical lock-in amplifier with microchannel spatial light modulator

Abstract: A novel optical information processing system by synthesis of the coherence function is built up to extract a two dimensional image from a three-dimensional object at a tenable depth with neither mechanical scanning nor digital calculation. In this system, a two-dimensional optical lock-in amplifier with the microchannel spatial light modulator is developed to detect selectively the coherence component, so that the limitation to the depth resolution introduced by the holographic detection which was used in our previous systems is overcome. Selective image extraction Is demonstrated successfully.

Low-voltage low-power integrated analog lock-in amplifier for gas sensor applications

Abstract: We propose a low-voltage (±1 V) low-power (3 mW) lock-in amplifier, fabricated in a standard CMOS technology (AMS 0.35 μm) with analog features and utilized for low-frequency gas sensor applications. The proposed lock-in architecture, which works at a fixed input signal frequency (77 Hz) with a very low input noise (only 34 nV/(sqrt(Hz)) @ 77 Hz), can be utilized to detect very small quantities of reagent gas, especially if combined with other techniques, as the sensor thermal modulation. The integrated solution has been fabricated on a single chip, requiring a reduced silicon area (about 5 mm 2 ). Experimental measurements have confirmed the capability of the proposed lock-in system to reveal very small signals, in particular, testing the whole system for gas detection, a resolution improvement by a factor valued about 50 allows to detect gas concentrations lower than 1 ppm.

Stabilization of electro-optic modulator bias voltage drift using a lock-in amplifier and a proportional-integral-derivative controller in a distributed Brillouin sensor system.

Abstract: In a distributed Brillouin sensor system, it is crucial to keep the pulse energy uniform for a constant signal-to-noise ratio. This means that the variable dc leakage (pulse base) for the electro-optic modulator (EOM) must be locked. We examine two different methods of locking the EOM bias voltage and look at the advantages and disadvantages of each locking method. It is found that the two locking methods, one based on a lock-in amplifier and the other using proportional-integral-derivative control, both have applications in which they excel at locking the pulse base.

Signal‐to‐noise ratio in lock‐in amplifier synchronous detection: A generalized communications systems approach with applications to frequency, time, and hybrid (rate window) photothermal measurements

Abstract: Detailed analytical models of signal‐to‐noise ratios (SNR) of the conventional frequency domain (FD) and time domain (TD) photothermal measurement methodologies are developed and compared to the rate‐window photothermal method, both theoretically and experimentally The conclusions of this study demonstrate that the lock‐in amplifier (LIA) rate‐window measurement mode in general, and the digital LIA mode, in particular, exhibits superior SNR to both the conventional frequency‐scanned LIA FD method and to the transient, time‐averaged TD method Between the pulse‐duration‐scanned and pulse‐repetition‐period scanned rate‐window methodologies, the former clearly exhibits superior SNR The theoretical conclusions are in agreement with experimental SNRs using the implementation of the foregoing measurement methodologies with simple infrared photothermal radiometric setups

Broadband digital lock-in amplifier techniques

Abstract: Using only commercially available equipment, we have developed simple digital lock‐in techniques that surpass the capabilities of analog lock‐in amplifiers. We describe both dual‐channel and single‐channel digital lock‐ins that are capable of measurement at any harmonic or subharmonic of the reference frequency. The best of these digital lock‐ins operates over a frequency range from dc to 400 kHz with lower phase noise and better flexibility, stability, and orthogonality than any analog lock‐in amplifier.