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• The application of DMD in two techniques of phase and amplitude modulation were summarized. • Three wavefront shaping techniques were summarized. • Four typical methods for improving the signal-to-noise ratio in PAWS were summarized. • Four methods that push the boundaries of the acoustical limit in PAWS were summarized. In recent years, wavefront shaping technology has made it possible to refocus scattered photons through turbid media. The utilization of photoacoustic signal as feedback for wavefront shaping offers non-invasive and deep-penetrating advantages, making it increasingly attractive in the field of biomedical research. However, due to the short decorrelation time of scattered light in living biological tissues, demonstrating the technique in vivo remains challenging. Digital Micromirror Devices (DMD) with their various modulation modes and high refresh rates hold great potential in addressing this challenge and have been widely employed in Photoacoustic Guided Wavefront Shaping (PAWS) applications. This paper presents the fundamental principles of using photoacoustic signal as feedback to guide wavefront shaping and highlights the advantages of PAWS in biological tissue imaging. Furthermore, a comparative analysis of three commonly used spatial light modulators in PAWS is provided, along with an overview of the three main techniques employed in wavefront shaping. Additionally, methods for improving the signal-to-noise ratio and imaging resolution in PAWS are summarized, followed by a discussion on potential future directions for this field. [ABSTRACT FROM AUTHOR]

• An innovative quaternary hybrid light modulation (QHLM) based projection display is proposed. • A quaternary spatial light modulator is constructed by illuminating two parallel digital micro-mirror devices (DMDs) with different light intensities. • The quaternary digit-plane decomposition and the pixel-level alignment of two DMDs are realized. • The prototype is designed and implemented to verify that the QHLM can achieve 16-bit projection at 220 fps. Conventional spatial light modulators (SLM) can only be used for projecting 8-bit or 10-bit images at normal frame rate. Therefore, commercial high dynamic range (HDR) displays typically focus on boosting the contrast while neglecting to raise the bit-depth. Existing methods for high bit-depth display generally rely on stacking two SLMs to modulate the outgoing beam twice, namely multiplicative modulation, resulting in many troubles such as low optical efficiency, difficulty in pixel-level alignment, and complex image rendering algorithm. In this paper, an innovative quaternary hybrid light modulation (QHLM) based projection display is proposed and realized. By illuminating two parallel digital micro-mirror devices (DMDs) with different light intensities, the quaternary digit-planes (QDs) with four gray levels are able to be modulated rapidly. Aiming at this ability, the quaternary pulse width modulation (QPWM) is incorporated with the quaternary light-intensity modulation (QLM) to fundamentally improve the modulation efficiency compared to the binary light modulation mode. Furthermore, the quaternary digit-plane decomposition (QDD) based image splitting algorithm is adopted to split a high bit-depth image into two images that drive two DMDs respectively. The prototype is designed and built to verify the feasibility of the QHLM based projection display. The experimental results demonstrate that the prototype can project 16-bit images at 220 fps. Through additive modulation of two DMDs in parallel, the QHLM entirely avoids the drawbacks of multiplicative modulation. As a completely different technology, the QHLM has a great potential for HDR projection applications. [ABSTRACT FROM AUTHOR]

Spatial light modulators (SLMs) are versatile devices used for optical studies. These instruments have a wide area of application in photonics. Additionally, SLMs have potential utility in different applications, such as biomedical applications, laser based surgery for precise cutting and as optical tweezers to separate cells in a petri container. However, the high cost of SLM devices prevents their widespread use in many areas, including industrial areas and scientific research laboratories. This paper demonstrates how to design a digital light processor (DLP) based low-cost SLM and describes how to obtain structured electromagnetic waves with the designed SLM. Therefore, this research was undertaken to design and produce a low-cost SLM device for optical applications. For this purpose, two prerequisites had to be fulfilled, the first was to use suitable components of a projection device with DLP-based digital micro-mirror device (DMD), and the second was to eliminate unnecessary SLM components from the system. Finally, holographic images reflected on the SLM screen were created by using Mathematica software program to change the amplitude and phase of the electromagnetic waves in order to obtain the structured electromagnetic waves. [ABSTRACT FROM AUTHOR]

Digital micro-mirror devices (DMDs) have been deployed in many optical applications. As compared to spatial light modulators (SLMs), they are characterized by their much faster refresh rates (full-frame refresh rates up to 32 kHz for binary patterns) compared to 120 Hz for most liquid crystal SLMs. DMDs however can only display binary, unipolar patterns and utilize temporal modulation to represent with excellent accuracy multiple gray-levels in display applications. We used the built-in time domain dynamic range representation of the DMD to project 8-bit complex-fields. With this method, we demonstrated 8-bit complex field modulation with a frame time of 38.4 ms (around 0.15 s for the entire complex-field). We performed phase conjugation by compensating the distortions incurred due to propagation through free-space and a scattering medium. For faster modulation speed, an electro-optic modulator was used in synchronization with the DMD in an amplitude modulation mode to create grayscale patterns with frame rate ~ 833 Hz with display time of only 1.2 ms instead of 38.4 ms for time multiplexing gaining a speed up by a factor of 32. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PEGMA brushes with arbitrary complex structures were fabricated via DMD-modulated Photo-ATRP reaction. • The growth of patterned PEGMA brushes could be regulated by adjusting the DMD light modulation parameter. • A functional surface with hydrophilic contrast was created. • The good selective BSA protein adsorption ability of the PEGMA brushes patterned surface allow the protein patterns with customized geometric feature were achieved. In the present work, programmable light pattern produced by digital micro-mirror device (DMD) spatial light modulator was employed to initiate the atom transfer radial polymerization (ATRP) for fabricating the patterned polymer brushes on the silicon substrate surface. Results from a series of characterization methods such as optical microscopy, 3D optical surface profiler, and X-ray photoelectron spectroscopy proved the poly (ethylene glycol) methyl acrylate (PEGMA) brushes with complex structures were successfully generated. The thickness of PEGMA brushes could be regulated by adjusting the DMD light modulation parameter including pattern size, gray value and exposure time. The contact angle measurements showed the PEGMA brushes could improve the hydrophilicity property of substrate surface. The antifouling property of the patterned surfaces with different shapes were tested, and the results indicated that the PEGMA brushes could effectively resist the adhesion of bovine serum albumin (BSA) protein, leading to the selective arrangement of protein. The reported method for generating the polymer brush patterns shows great potential for the manipulation of surface property in facilitating a range amount of applications from anti-biofouling coating, interface lubrication to biomimetic and smart surfaces. [ABSTRACT FROM AUTHOR]

• Digital micromirror device functions as both spatial and spectral modulator. • The experimental spectral resolution is 3.73 nm over the visible spectrum. • Real-time spectral video with a frame-rate up to 10Hz with compressive sampling. • With the potential to be easily extended to both ultraviolet and infrared. Spectral imaging technique, which retrieves both spatial and spectral information of a scene or an object, is an important tool in applications such as food inspection, vegetation monitoring and geographic remote sensing. Most spectral imaging systems have a complex system architecture, in which different components are used for different functions, limiting the efficiency of information retrieval. Here, we propose a hyperspectral imaging system with a simple architecture, where a multiplexing digital micromirror device functions both as a spatial light modulator for spatial imaging and a diffractive grating for spectral measuring simultaneously. The proof-of-principle system contains a group of lenses, a digital micromirror device and a one-dimensional detector array, and is capable of performing 128 × 128 pixel resolution hyperspectral imaging over the visible spectrum with an experimental 3.73 nm spectral resolution. Furthermore, by using a compressive sampling strategy, continuous real-time spectral video is performed with a frame-rate up to 10 Hz. The concise architecture of the proposed system, with the potential to be easily extended to both ultraviolet and infrared, offers an alternative scheme to manufacture low-cost, compact, hyperspectral imagers. [ABSTRACT FROM AUTHOR]

In this contribution, we present a high-speed, multiplex, grating spectrometer based on a spectral coding approach that is founded on principles of compressive sensing. The spectrometer employs a single-pixel InGaAs detector to measure the signals encoded by an amplitude spatial light modulator (digital micromirror device, DMD). This approach leads to a speed advantage and multiplex sensitivity advantage atypical for standard dispersive systems. Exploiting the 18.2 kHz pattern rate of the DMD, we demonstrated 4.2 ms acquisition times for full spectra with a bandwidth of 450 nm (5250–4300 cm−1; 1.9–2.33 µm). Due to the programmability of the DMD, spectral regions of interest can be chosen freely, thus reducing acquisition times further, down to the sub-millisecond regime. The adjustable resolving power of the system accessed by means of computer simulations is discussed, quantified for different measurement modes, and verified by comparison with a state-of-the-art Fourier-transform infrared spectrometer. We show measurements of characteristic polymer absorption bands in different operation regimes of the spectrometer. The theoretical multiplex advantage of 8 was experimentally verified by comparison of the noise behavior of the spectral coding approach and a standard line-scan approach. [ABSTRACT FROM AUTHOR]