Dynamic Range Mode Research Articles

Novel sensor developments for photon science at the MPG semiconductor laboratory

The world of photon science experiences significant advancements since the advent of synchrotron light sources with unprecedented brilliance, intensity and pulse repetition rates, with large implications on the detectors used for instrumentation. Here, an overview about the work on this field carried out at the semiconductor laboratory of the Max-Planck-Society (MPG HLL) is given. Main challenges are high dynamic range to resolve faint features at the fringes of scatter images as well as structures in bright peaks, and high bandwidth to fully exploit the fast timing capability of the source. A newly developed device to improve the signal-to-noise-ratio (SNR) at high bandwidths is the so-called MARTHA (Monolithic Array of Reach-Through Avalanche Photodiodes) structure, which integrates an array of APDs on a monolithic substrate. The reach-through architecture assures near 100% fill factor and allows implementing a thin entrance window with optimized quantum efficiency for low energy X-rays. The structures operate in proportional mode with adjustable gain, and can serve as a drop-in replacement for PAD detectors in hybrid pixel systems. A more sophisticated solution for low to medium frame rate applications with high contrast requirement are pnCCDs with high dynamic range in the pixel area featuring DEPFET based readout nodes with non-linear amplification (NLA). The high dynamic range mode has been demonstrated for pnCCD devices with a pixel size down to 75 μm2. Framerates of up to 1 kHz are possible for a 1 Megapixel detector. Small size prototypes of these structures have recently been manufactured. Modified DEPFET structures with build-in non-linear amplification are also used to implement active pixel detectors optimized for high dynamic range. Successfully prototyped for the DSSC sensors (DEPFET Sensor with Signal Compression) at the XFEL, these structures are increasingly being used in applications requiring high contrast and intensity, e.g., TEM imaging. Charge handling capability and output characteristics can be tailored to the requirements, as well as pixel geometry and size. The large intrinsic gain of the DEPFET provides excellent SNR even at fast timing. Pixels can be read with a speed of 100 ns, the resulting frame rate depends on the degree of readout parallelization.

Method for Evaluation of Linearity of Image Sensors in High Dynamic Range Mode

Image sensors in cameras that are used for outdoor imaging, such as for automotive applications, are typically operated in high dynamic range (HDR) mode. Photo-response linearity is a key performance indicator of image sensors. Existing procedures for evaluation of image sensor linearity are based on exposure variation. They are efficient when image sensors are operated in the basic mode, which has a limited dynamic range, however, they are difficult or impractical to implement with image sensors in HDR mode. This work presents a method to evaluate linearity of image sensors in HDR mode. The method uses an indirect approach, which is based on the relative response between color channels in color cameras. It is independent of the HDR mechanism and the actual photoresponse ratios between color channels; it can be applied to monochrome cameras with attenuation filters. We demonstrate the method with a camera module that includes a color image sensor that is activated in HDR mode with the recommended configuration file and with a file that was modified to produce a non-linear HDR response. Raw image data were collected with test targets in a controlled lab environment, and outdoors in a representative HDR scene. The data were used to calculate signal and noise properties to construct signal-to-noise ratio and relative channel response curves, and to evaluate color properties. Analysis of the relative response curves show that the proposed method is highly sensitive to deviation from linearity and that it correlates well with color artifacts.

Simultaneous measurement of aqueous redox-sensitive elements and their species across the soil-water interface

The redox-sensitive elements, such as iron, manganese, sulfur, phosphorus, and arsenic, shift their speciation every millimeter (mm) across the soil-water interface in the flooded soil environments. Monitoring of element speciation at this high-resolution (HR) within the SWI is still difficult. The key challenge lies in obtaining sufficient porewater samples at specific locations along the soil gradient for downstream analysis. Here with an optimized inductively coupled plasma mass spectrometry (ICP-MS) method and a HR porewater sampler, we demonstrate mm-scale element profiles mapping across the SWI in paddy soils. High-concentrations of iron and manganese (> 10 mg/L) were measured by ICP-MS in an extended dynamic range mode to avoid signal overflow. The iron profile along the SWI generated by the ICP-MS method showed no significant difference (p < 0.05) compared to that measured independently using a colorimetric method. Furthermore, four arsenic (arsenite, arsenate, monomethylarsonic and dimethylarsinic acid), two phosphorus (phosphite and phosphate) and two sulfur (sulfide and sulfate) species were separated in 10 min by ion chromatography -ICP-MS with the NH4HCO3 mobile phase. We verified the technique using paddy soils collected from the field, and present the mm-scale profiles of iron, manganese, and arsenic, phosphorus, sulfur species (relative standard deviation < 8%). The technique developed in this study will significantly promote the measurement throughput in limited samples (e.g. 100 μL) collected by HR samplers, which would greatly facilitate redox-sensitive elements biogeochemical cycling in saturated soils.

73‐3: Invited Paper: Influences of Circadian Illuminances from Lighting and TV on the Human Locomotor Activity, Sleep Disorder, EEG, HRV, and Melatonin Secretion

To address the need for an accurate evaluation of circadian illuminance (CIL) that precisely characterizes the intensity of blue light emanated by displays and/or lighting and to investigate how the blue light affects the human body biology, we developed the circadian illuminometer and applied it to two comparative clinical studies. In terms of the CIL from lighting, all of the circadian rhythm of locomotor activity, sleep quality, and melatonin secretion were improved for 12 subjects under circadian lighting in comparison to normal lighting. In a comparative study of the effects of evening watching TVs in high dynamic range mode, i. e., using two different types of 65‐inch TVs (A and B) in the market, on an electroencephalography (EEG), heart rate variability (HRV), and melatonin secretion, B is found for 32 subjects to have a better health effect on the human body than A in perspective of visual fatigue, arousal, concentration, comfort, and sleep disorder. A also showed significant circadian disturbance, which are mainly caused by a higher CIL in A (54.28 blx) than in B (25.18 blx). Finally, our results show evidence that the effects of CIL on locomotor activity, sleep disorder, EEG, HRV, melatonin, and circadian rhythm can potentially play the role of a new performance metric for human‐centric displays/lighting.

Wide Dynamic Range CMOS Image Sensor with Adjustable Sensitivity Using Cascode MOSFET and Inverter

In this paper, a wide dynamic range complementary metal-oxide-semiconductor (CMOS) image sensor with the adjustable sensitivity by using cascode metal-oxide-semiconductor field-effect transistor (MOSFET) and inverter is proposed. The characteristics of the CMOS image sensor were analyzed through experimental results. The proposed active pixel sensor consists of eight transistors operated under various light intensity conditions. The cascode MOSFET is operated as the constant current source. The current generated from the cascode MOSFET varies with the light intensity. The proposed CMOS image sensor has wide dynamic range under the high illumination owing to logarithmic response to the light intensity. In the proposed active pixel sensor, a CMOS inverter is added. The role of the CMOS inverter is to determine either the conventional mode or the wide dynamic range mode. The cascode MOSFET let the current flow the current if the CMOS inverter is turned on. The number of pixels is 140 (H) × 180 (V) and the CMOS image sensor architecture is composed of a pixel array, multiplexer (MUX), shift registers, and biasing circuits. The sensor was fabricated using 0.35 μm 2-poly 4-metal CMOS standard process.

Optimization of instrument response and resolution of standard- and high-speed power compensation DSC

Normally, for Standard DSC, the PerkinElmer power-compensation setting is the low dynamic range mode (LDRM). In this mode, a noise filter is applied to decrease the noise-to-signal ratio, which concomitantly gives rise to a delay in time of the signal measured. In case the signal is expected to be of high intensity — experienced for instance at high scan rates using High Performance DSC (HPer DSC) — the noise filtering could be diminished by which the associated delay in time would be less, leading to a faster response of the instrument, also resulting in an improved resolution. In fact, such can be realized using the faster noise filter of the high dynamic range mode (HDRM) available for the Pyris 1 and Diamond DSCs, which DSCs are both equipped with the HyperDSCTM technique (HyperDSC being the commercial version of HPer DSC). The improvement in response is maximal for high rates like 100–500°C min−1 but even at low rates like 10°C min−1 it is still significant. Thus, taking advantage of HDRM, low-molar substances like indium and 4,4′-azoxyanisole show appreciable increasing height-to-width ratios for signals caused by crystallization, melting and the crystal liquid crystal transition respectively. Another advantage, the faster realization of steady state after the starting of the DSC, is of help in case of overlapping starting and transition signals during dynamic crystallization and melting, and during isothermal crystallization as elucidated for a HDPE. For 4,4′-azoxyanisole and for an ethylene-propylene copolymer having a broad melting range, it is shown that such faster response leads to a still better resolution with respect to temperature, even at high scan rates.