{"id":22390,"date":"2025-08-13T17:50:10","date_gmt":"2025-08-13T15:50:10","guid":{"rendered":"https:\/\/www.heliotis.com\/research_c4\/"},"modified":"2026-01-12T18:12:54","modified_gmt":"2026-01-12T17:12:54","slug":"research_c4","status":"publish","type":"page","link":"https:\/\/www.heliotis.com\/en\/research_c4\/","title":{"rendered":"Research_C4"},"content":{"rendered":"\t\t
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1 Million
Lock-ins.
Simultaneously.<\/h1>\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\theliCam\u2122 C4 \/ C4M<\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Lock-in experiments \u2013 massively parallel<\/div>\t\t\t\t<\/div>\n\t\t\t\t
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From point measurement to Lock-in imaging<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
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Classic Lock-in amplifiers measure at a single point. In Lock-in imaging, on the other hand, the same demodulation is performed pixel by pixel \u2013 amplitude and phase for each pixel. This enables experiments that are difficult or impossible to perform with point measurements: spatially resolved phase information, fast mapping, and robust evaluations even with strong noise. <\/p>

In applications with challenging lighting conditions \u2013 be it a weak signal in strong noise or very strong background or interference light \u2013 conventional cameras reach their limits. Either saturation (clipping) occurs early, or the weak signal must be averaged for noise reduction, which slows down the process or even makes it impossible. In both cases, the useful signal is dominated by interference sources. However, if the useful signal can be modulated and thus separated from the interference signals, the heliCam\u2122 C4 continues to deliver high-quality images. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t

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Figure 1: A camera with pixel-level Lock-in technology can almost completely suppress specific sources of interference such as constant background or 1\/f noise.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Making weak signals visible \u2013 even in strong noise<\/div>\t\t\t\t<\/div>\n\t\t\t\t
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The Lock-in principle<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
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A Lock-in amplifier makes extremely weak signals visible, even when they are superimposed by noise and extraneous light. It compares the input signal s(t)<\/em> synchronously with a reference signal of the same frequency and phase (phase-sensitive detection). <\/p>

Brief operation:<\/strong>
1. Input:<\/em> s(t)<\/em> contains useful signal + noise + interference signals
2. Synchronous Multiplication:<\/em> with references cos(\u03c9t)<\/code> and sin(\u03c9t)<\/code> \u2192 two channels I<\/strong> (In-Phase) and Q<\/strong> (Quadrature).
3. Integration \/ Low-pass:<\/em> Averaging over the measurement time T<\/strong> reduces the noise bandwidth (ENBW \u2248 1\/(2T)) and suppresses components outside the reference frequency.<\/p>

Result:<\/strong>
\u2022 Amplitude: R<\/strong> = \u221a(I2<\/sup> + Q2<\/sup>)
\u2022 Phase: \u03c6<\/strong> = atan2(Q, I)
\u2022 Broadband noise and non-synchronous extraneous light are largely averaged out; the useful signal remains as a DC component.
\u2022 In practice, the Lock-in acts like a very narrow-band, phase-sensitive filter<\/strong>, the selectivity of which is determined by the integration time T<\/strong>.<\/p>

In Lock-in imaging<\/strong>, the same process is performed pixel by pixel<\/strong>: Each pixel provides I\/Q (or amplitude\/phase) \u2013 the basis for spatially resolved, phase-sensitive measurements under demanding lighting conditions.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t

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Figure 2: Highly noisy useful signal in the time domain (left) and frequency domain (right). Despite larger interference amplitudes, the useful signal can be successfully extracted and measured thanks to the Lock-in principle. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Signal processing directly on the image plane<\/h2>\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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The Lock-in pixel signal processing developed and patented by Heliotis is the core of all our products. In our proprietary CMOS image sensor, phase-sensitive demodulation is performed directly at each pixel, rather than in the downstream signal path. Each pixel performs a synchronous I\/Q measurement and outputs a 10-bit In-Phase (I) and a 10-bit Quadrature (Q) value (dual-phase demodulation). Amplitude and phase of the useful signal can be determined directly from I and Q \u2013 area-based, stable, and reproducible.<\/p>

This pixel-parallel demodulation suppresses constant background, 1\/f noise, and non-synchronous interference light already during acquisition, so that even very small, modulated signals become reliably visible \u2013 without long averaging times.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\"heliSensS4IQ3\"\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\tThe platform is available in two resolutions: heliCam\u2122 C4 (512 \u00d7 542 pixels) and the high-resolution heliCam\u2122 C4M (1024 \u00d7 1102 pixels). The C4 platform paves the way for massively parallel Lock-in imaging \u2013 the technological basis of our camera family. \t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Typical Applications<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
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The application areas in which Lock-in cameras are most frequently used can be roughly outlined as follows:<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t

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Imaging in scattering media<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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A large part of research aims to capture optical images in turbid structures or, more generally, to focus light that interacts with a scattering medium.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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Interferometric 3D Imaging<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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In interferometric 3D imaging, both improvements to scanning white light interferometry and alternative measurement methods have been proposed.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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Quantitative Phase Imaging Methods<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Several research groups have proposed quantitative phase imaging methods to obtain label-free and high-contrast images of, for example, biological cells, which appear largely transparent in classical, absorption-based optical measurements.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Quantum Sensing<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Applications in quantum sensing are gaining increasing importance, particularly with regard to a widefield quantum diamond microscope for dynamic imaging of the smallest magnetic fields.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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Spectroscopy<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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Spectroscopic methods that detect the smallest and fastest periodic changes in the spectrum, caused by various mechanisms, have been repeatedly implemented with Lock-in cameras from Heliotis.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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Further Applications<\/p>\t\t\t\t<\/div>\n\t\t\t\t

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More information on the mentioned and other application examples of the Lock-in camera can be found in our collection of research publications.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

\n\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\tView Publications<\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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FAQs<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
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Lock-in cameras are a comparatively new but extremely powerful tool in research. They open up exciting possibilities for phase-sensitive imaging and high-precision experiments. <\/p>

Below you will find answers to some frequently asked questions.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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For which Signal Conditions is the Camera Particularly Well Suited? <\/div><\/span>\n\t\t\t\t\t\t\t\n\t\t\t<\/path><\/svg><\/span>\n\t\t\t<\/path><\/svg><\/span>\n\t\t<\/span>\n\n\t\t\t\t\t\t<\/summary>\n\t\t\t\t
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\n\t\t\t\t\t\t\t\t\tThe heliCam\u2122 is ideal for experiments with strong background noise or DC components. It effectively suppresses the background and narrowly filters out the modulated useful signal \u2013 even if the signal is orders of magnitude smaller than the background. \n\nIt is not optimal under extremely low-light conditions, as it has a high Full-Well Capacity (FWC) and therefore requires more light for optimal results.\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/details>\n\t\t\t\t\t\t
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Which Demodulation Frequencies are Supported? <\/div><\/span>\n\t\t\t\t\t\t\t\n\t\t\t<\/path><\/svg><\/span>\n\t\t\t<\/path><\/svg><\/span>\n\t\t<\/span>\n\n\t\t\t\t\t\t<\/summary>\n\t\t\t\t
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The heliCam\u2122 C4 with 542\u00d7512 Lock-in pixels demodulates signals in the range from 305 Hz to 134 kHz.<\/p>

The heliCam\u2122 C4M with 1024×1102 Lock-in pixels demodulates signals in the range from 305 Hz to 50 kHz.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/details>\n\t\t\t\t\t\t

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Is there Application Software? <\/div><\/span>\n\t\t\t\t\t\t\t\n\t\t\t<\/path><\/svg><\/span>\n\t\t\t<\/path><\/svg><\/span>\n\t\t<\/span>\n\n\t\t\t\t\t\t<\/summary>\n\t\t\t\t
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\n\t\t\t\t\t\t\t\t\tYes, the heliCam\u2122 is supplied with the heliViewer\u2122 application software \u2013 for camera configuration as well as for data acquisition, display, and export.\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/details>\n\t\t\t\t\t\t
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Is there an SDK for Python \/ Matlab? <\/div><\/span>\n\t\t\t\t\t\t\t\n\t\t\t<\/path><\/svg><\/span>\n\t\t\t<\/path><\/svg><\/span>\n\t\t<\/span>\n\n\t\t\t\t\t\t<\/summary>\n\t\t\t\t
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\n\t\t\t\t\t\t\t\t\tYes, an SDK is available for both Python and MATLAB\u00ae \u2013 including programming examples for both languages.\n\nAdditionally, other programming languages such as C++, C#, and Rust are also supported.\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/details>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t
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How Can I Learn more about this Camera? <\/div><\/span>\n\t\t\t\t\t\t\t\n\t\t\t<\/path><\/svg><\/span>\n\t\t\t<\/path><\/svg><\/span>\n\t\t<\/span>\n\n\t\t\t\t\t\t<\/summary>\n\t\t\t\t
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Further information can be found in our documentation<\/strong> and on the following pages:<\/p>\n\n