Fig 1 - uploaded by Pratyasha Sahani
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Concept of image capture and spectroscopy of an RGB filter integrated with a gradient thickness optical color filter.
Source publication
We propose a pixelized gradient thickness color filter as the compact and space-saving element for achieving simultaneous imaging and spectroscopy using a single image sensor. By replacing the RGB filter integrated in portable devices this can serve the novel purpose on the same platform, and hence makes the device versatile.
Contexts in source publication
Context 1
... this study, as an idea to achieve both image capture and spectroscopy simultaneously using a single image sensor, we have designed and fabricated a device consisting of the gradient thickness optical filter in pixel form. The concept of an RGB filter integrated with a gradient thickness optical color filter is picturized in Fig. 1. The proposed device can perform both the functions at the same time without significantly compromising the image capture function before the spectroscopy function is incorporated. In addition, the missing parts of the object information in the acquired image by the image sensor due to incorporation of the color filter is proposed to ...
Context 2
... proposed device is intended to be equipped with an image sensor (in a portable device) to operate as a spectroscopic module. In the device design, the pixel-wise thickness variation of cavity gap layer is considered to range from 75nm to 185nm (which is suitable to obtain the transmission wavelengths over ~ 400-700nm as observed from Fig.1). In fabrication, the structural parameters of the device are chosen to be compatible with the commercially available image sensor (Hamamatsu Photonics' S10420-1006-01). ...
Context 3
... of the pixels with better filter qualities are compiled in Fig. 5. We observe from Fig. 5 that the peak transmission wavelength of the pixelized filter shows transition in the wavelength range of ~ 450-700nm depending on the pixel position. The peak transmittance value is reduced to ~ 45% as compared to the actual value (~ 60% as obtained in Fig. 1) which could be due to the remaining photoresist on the pixelated filter surface. The presence of photoresist will increase light reflection/ absorption/ scattering from the filter surface and hence, reducing the transmission efficiency. Fig. 5 shows that some of the transmission spectra are associated with small spikes (noise-like ...
Citations
... T UNABLE Fabry-Pérot filters (FPFs) have emerged as versatile and indispensable components across a multitude of scientific and industrial fields, including astronomy, metrology, optical communications, nondestructive everyday analysis, medical diagnostics, and environmental monitoring [1], [2], [3], [4], [5], [6], [7], [8]. The advent of tunable FPFs driven by microelectromechanical techniques has significantly advanced the development of complementary metal oxide semiconductor (CMOS)-integrated lab-on-a-chip devices such as miniature spectrometers [9], [10], [11], [12], [13], [14], [15], [16] and hyperspectral imaging systems [17], [18], [19], [20]. ...
A tunable air-gap Fabry–Pérot filter consisting of distributed Bragg reflectors as cavity mirrors was developed to operate in the visible wavelength range. The wavelength tunability of the filter was achieved based on the piezo actuation mechanism. Four in-plane identical piezo actuators were employed to simultaneously achieve both wavelength tunability and cavity air-gap parallelism in the filter. Two pairs of piezo actuators positioned at crossed locations enabled independent control of cavity air-gap dimensions along orthogonal directions in the cavity plane. Optical transmission measurements were performed at different spatial positions on the cavity region to estimate the cavity air-gap dimensions. The initial maximum spectral separation among different spatial positions owing to the initial non-parallelism of the cavity air gap was estimated to be ∼28 nm. After achieving cavity air-gap parallelism via piezo actuation, the final maximum spectral separation was reduced to ∼3 nm. The proposed device configuration significantly improved the cavity air-gap parallelism by minimizing the maximum variation of the cavity air-gap dimension from an initial value of 535 nm to a final value of 18 nm, resulting in an improvement by a factor of ∼30. This device prototype can enable high-resolution and high-throughput spectral transmission with improved spatial uniformity across a large cavity area, showing great promise for advancing hyperspectral imaging systems.
