Relative Illumination Research Articles

Wide Field of View Under-Panel Optical Lens Design for Fingerprint Recognition of Smartphone.

Fingerprint recognition is a widely used biometric authentication method in LED-backlight smartphones. Due to the increasing demand for full-screen smartphones, under-display fingerprint recognition has become a popular trend. In this paper, we propose a design of an optical fingerprint recognition lens for under-display smartphones. The lens is composed of three plastic aspheric lenses, with an effective focal length (EFL) of 0.61 mm, a field of view (FOV) of 126°, and a total track length (TTL) of 2.54 mm. The image quality of the lens meets the target specifications, with MTF over 80% in the center FOV and over 70% in the 0.7 FOV, distortion less than 8% at an image height of 1.0 mm, and relative illumination (RI) greater than 25% at an image height of 1.0 mm. The lens also meets the current industry standards in terms of tolerance sensitivity and Monte Carlo analysis.

Optical lens optimization design and tolerance analysis for a depth camera

This paper describes a depth camera lens design composed of eight glass lenses, where the field of view is 100°, the focal length is 1.88 mm, and the F/# is 2. The lens design requires the lens to be fixed and the object distance to be fixed at −745.964 mm. The depth of focus ranges from −0.0047 mm to 0.0096 mm and can be obtained by selecting a spatial frequency of 60 lp/mm for the Through-focus MTF optimization design. The object distance ranges from negative infinity (-∞) to −250 mm (for the depth of field), the MTF is greater than 0.73 at 60 lp/mm, the lateral color difference is less than 1.58 μm, the optical distortion is less than 1%, and the relative illumination is greater than 64%. When conducting tolerance analysis, we select a spatial frequency requirement of tolerance MTF>0.3. At an object distance of −745.964 mm, the lens resolution can reach 80 lp/mm. The object distance is -∞, and the lens resolution is above 59 lp/mm. The object distance is −250 mm, and the lens resolution can reach over 43 lp/mm. In this work, the depth camera lens is designed to have an object distance shooting range of −6 m to −0.25 m. When the object distance is −6 m, the object depth resolution is 61 mm; while at the object distance of −0.25 m, the object depth resolution is 0.1045 mm.

3D hierarchical microcubic morphological composite and its application for Bi-functional Humidity/Pressure sensing in TENG architecture

Harnessing the power of contact electrification, triboelectric nanogenerators (TENGs) are a cutting-edge energy technology, where output performance is greatly influenced by the micro/nano scale architectures of triboelectric layers. We present a study on the development of TENG by introducing an advanced 3D hierarchical microcubic morphological structure prepared by simple solution casting method, employing a renewable material, lignin, in combination with eco-friendly polyvinyl alcohol (PVA) matrix. The strategic incorporation of epichlorohydrin (EPCH) as a crosslinker enhances thermal stability, and crosslinking within the lignin/PVA composite (LPC) film. A remarkable outcome of this integration is the emergence of a 3D hierarchical microcubic structure within the LPC film. This structure, with its intricate 3D arrangement, emerges as the cornerstone that underpins the development of LPC-TENGs devices distinguished by their simple fabrication process, elevated output performance, and multifaceted applications. The LPC-TENG, adorned with its unique 3D hierarchical microcubic architecture, establishes new standards in energy harvesting and sensing capabilities with a maximum output power density of 135.4 mWm−2, a short-circuit current of 6.44 μA, and a maximum output voltage of 65 V (5 times higher than PVA-based TENGs). Additionally, the LPC-TENG showed exceptional performance as a self-powered bifunctional sensing system, providing a steady output voltage range of 0–10 V across various humidity levels (20–90 % RH) and a wide usable pressure range (0–162 kPa) with a low detection limit of 1 kPa. We demonstrated the application of the LPC-TENG in energy harvesting from human walking, enabling simultaneous measurements of environmental relative humidity, pressure, and illumination of 27 commercial LEDs. The unique 3D hierarchical microcubic architecture offers an unparalleled foundation for accommodating overall performance and diverse sensing functionalities.

Development of Dα band symmetrical visible optical diagnostic for boundary reconstruction on EAST tokamak

To investigate the potential of utilizing visible spectral imaging for controlling the plasma boundary shape during stable operation of plasma in future tokamak, a Dα band symmetric visible light diagnostic system was designed and implemented on the Experimental Advanced Superconducting Tokamak (EAST). This system leverages two symmetric optics for joint plasma imaging. The optical system exhibits a spatial resolution less than 2 mm at the poloidal cross-section, distortion within the field of view below 10%, and relative illumination of 91%. The high-quality images obtained enable clear observation of both the plasma boundary position and the characteristics of components within the vacuum vessel. Following system calibration and coordinate transformation, the image coordinate boundary features are mapped to the tokamak coordinate system. Utilizing this system, the plasma boundary was reconstructed, and the resulting representation showed alignment with the EFIT (Equilibrium Fitting) results. This underscores the system’s superior performance in boundary reconstruction applications and provides a diagnostic foundation for boundary shape control based on visible spectral imaging.

Optical Simulation Design of a Short Lens Length with a Curved Image Plane and Relative Illumination Analysis.

This study proposes a three-lens design with a short lens length and explores the curved imaging plane and performs a relative illumination analysis. There are two ways to reduce the lens length: shortening the back focal and lens group lengths. We derived the relevant parameter relationships of three lenses using the first-order geometric optics theory. The optical lens length can be controlled within 2 mm. The shorter the lens length, the larger the angle of the chief ray in the image space, resulting in an increase in the field curvature and astigmatism. Third-order Seidel aberrations can be effectively reduced by a curved image plane. We also derived the equations for relative illuminance, solid angle, surface transmittance, and internal transmittance for the short three-lens design. The optical lens design uses a curved image plane to shorten the distance from the off-axis beam image space to the image plane and reduce the incident angle of the chief ray on the image plane. The formula and design results verified by Code V software (version 11.2) show that both the solid angle and relative contrast of the lens can be increased. For the proposed three-lens design with a short lens length, the semi-field angle is 32°, F/# is 2.7, the effective focal length is 1.984 mm, the image plane area is 2.16 mm × 1.22 mm, and the curvature radius of the concave image plane is 3.726 mm. Moroever, the MTF (100 lp/mm) is larger than 52%, the lateral color aberration is less than 2.12 μm, the optical distortion is less than 2.00%, and the relative illumination is greater than 68%.

Catalyst Support Interactions of Highly Active Nife-LDH Towards the Implementation in Photoelectrochemical and Sea-Water Based Water Splitting Technologies

For the implementation in photoelectrochemical (PEC) and sea-water based water splitting devices it is of utmost importance to find stable substrates that do not degrade under application related potentials and illumination. While PEC devices incorporate an absorber that has to be protected from the harsh conditions in the electrolyte, the prevalence of Cl- ions in sea-water based water splitting devices leads to corrosion of most metallic substrates under application related potentials. Catalyst coated TiO2 substrates are therefore used as protection layers in PEC devices, while titanium porous transport layers show great stability in anionic exchange membrane sea-water splitting devices.In this study we investigated the interaction between state-of-the-art NiFe-LDH as a catalyst for the OER and titanium substrates. It was shown that the activity of NiFe-LDH on bare Ti/TiOx substrates was very poor. Through the incorporation of thin metal interlayers (Au, Ni) an increase in current density by two orders of magnitude could be observed. Through detailed XPS measurements before and after electrochemical activation of the electrodes we were able to show an improved transformation of the as prepared catalyst into the highly active (oxo)hydroxide phase for the gold and nickel sputtered titanium electrodes. An accelerated stress test performed on these electrodes showed a stable behavior for most electrode assemblies, with Nickel interlayers showing great promise for PEC devices. From our experiments we exclude a pure conductivity enhancement as possible explanation, but instead propose an additional change in the local atomic and electronic structure at the metal-support and metal-catalyst interfaces.

Ultra-wide angle panoramic imaging system based on a multiplexed reflective surface.

We propose an ultra-wide angle panoramic imaging system based on a multiplexed reflective surface, which consists of a panoramic head unit (PHU) and the relay lens group. The multiplexed reflective surface is applied in the PHU to reflect light from glass and air for imaging, obtaining the front and rear view channels, respectively. With a field of view (FoV) of 360∘×(35∘-120∘) and an f-number of four, this system has good image quality and relative illumination in the FoV. In addition, it has loose tolerance requirements and a diameter ratio of 7.2, reducing the difficulty of manufacturing and assembly. This optical system architecture provides a promising solution for panoramic perception over a wider FoV.

A compact wide-angle DUV lens suitable for SO2 monitoring

We report the design and development of a compact wide-angle deep ultraviolet (DUV) lens suitable for sulfur dioxide (SO2) monitoring. The lens (focal length = 10 mm, F-number = 4, full field of view = 35°) is made of synthetic quartz (SiO2, SQ) glass, sapphire (Al2O3) crystal, and calcium fluoride (CaF2) crystal whose dimensions are optimized for 290–320 nm wavelengths. Compared to a conventional doublet lens with the same focal length, F-number, and full field of view, our design exhibits slight vignetting and peripheral astigmatism but with corrected chromatic aberrations, smaller focal shifts (127 µm), tighter spot sizes (19–24 µm), and better image resolution and contrast (modulation transfer function, MTF ≥ 0.4). The lens properties have also been confirmed experimentally with the fabrication and evaluation of an actual lens based on our design. The actual lens exhibits a barrel-type distortion of 3.3 %, relative illumination of 94–100 % at 0–5° field angles, and a tangential MTF performance curve similar to what are expected from the design. Our compact lens is shown to exhibit better properties than conventional lenses and promises better performance in wide-angle DUV imaging applications, especially for SO2 detection.

Влияние клена ясенелистного (Acer negundo L.) на естественное возобновление сосны обыкновенной в Барнаульском ленточном бору

The influence of ash-leaved maple (Acer negundo L.) on the natural regeneration of scots pine in the Barnaul ribbon forest in different types of forest growing conditions is considered. It was found that the ash-leaved maple forms a dense, closed undergrowth up to 10 m high in moist forest-growing conditions (A3), whereas in fresh forest-growing conditions (A2) it was noted only once. The closeness of the undergrowth of maple in the grass forest is 0,8…1,0 units, while the undergrowth with a predominance of local plant species (Siberian mountain ash, goat willow) in the grass forest has a closeness of no more than 0,5 units, in the fresh forest no higher than 0,2…0,4 units. The undergrowth of maple strongly obscures the components of the forest located under it: living ground cover and undergrowth. The shading of the living ground cover leads to its significant transformation, with a change in the floral composition and structure. Shading of the undergrowth leads to a complete absence of seedlings, self-seeding and the actual undergrowth of the common pine, interrupting the process of natural renewal. Using the obtained values of illumination under the canopy of the forest, it was found that in a grassy forest with a maple understory, the relative illumination is no more than 7,9 %, whereas in a grassy and fresh forest with an undergrowth of local species, 29,5…47,9 %. The density of pine undergrowth in a fresh forest with undergrowth of local species is 7,5…17,5 thousand units/ha, which is 3–7 times more than in a grass forest with undergrowth of local species. There is a close positive relationship between the relative illumination under the forest canopy and the density of undergrowth (r = 0,830). Ash-leaved maple acts as an aggressive undesirable breed, which limits the most important environmental factor — illumination, leading to the disappearance of pine undergrowth under the canopy of the forest.

Effects of temperature, relative humidity, and illumination on the entomological parameters of Aedes albopictus: an experimental study.

Aedes albopictus (Diptera: Culicidae) is a mosquito from Asia that can transmit a variety of diseases. This paper aimed to explore the effects of temperature, relative humidity, and illumination on the entomological parameters related to the population growth of Aedes albopictus, and provide specific parameters for developing dynamic models of mosquito-borne infectious disease. We used artificial simulation lab experiments, and set 27 different meteorological conditions to observe and record mosquito's hatching time, emergence time, longevity of adult females, and oviposition amount. We then applied generalized additive model (GAM) and polynomial regression to formulate the effects of temperature, relative humidity, and illumination on the biological characteristics of Aedes albopictus. Our results showed that hatchability closely related to temperature and illumination. The immature stage and the survival time of adult female mosquitoes were associated with temperature and relative humidity. The oviposition rate related to temperature, relative humidity, and illumination. Under the control of relative humidity and illumination, ecological characteristics of mosquitoes such as hatching rate, transition rate, longevity, and oviposition rate had an inverted J shape with temperature, and the thresholds were 31.2°C, 32.1°C, 17.7°C, and 25.7°C, respectively. The parameter expressions of Aedes albopictus using meteorological factors as predictors under different stages were established. Meteorological factors especially temperature significantly influence the development of Aedes albopictus under different physiological stages. The established formulas of ecological parameters can provide important information for modeling mosquito-borne infectious diseases.

Relative illuminance improvement method of monocentric reflective mobile phone lens

Relative illuminance improvement method of monocentric reflective mobile phone lens

Indoor Air Factors Affecting the Growth of Microorganism in an Indonesian Gas Company’s Dormitory

Introduction: Mold may affect the Indoor Air Quality (IAQ) in workplace dormitories. This study aims to investigate indoor air factors that affect molds growth in a dormitory of an LNG Company in Indonesia. Several indoor air determinant factors, including relative humidity, general temperature, wet temperature, dry temperature, air velocity, illumination, particulate matter, and carbon dioxide concentration were assessed against the growth of microorganism colonies. Methods: This study was a cross-sectional study using a 2 (two)-stage Andersen sampler based on NIOSH 0800 Bioaerosol Sampling Method for Indoor Air Quality for viable bioaerosol sampling. Bioaerosol samples were collected from 50 indoor, corridor, and outdoor sampling points. The total colony count for bioaerosols (TCC) was then determined (CFU/m3). Ten indoor air quality parameters, i.e., relative humidity, general temperature, wet temperature, dry temperature, air velocity, illumination, particulate matter, and carbon dioxide concentration, were measured. Results: The average mold colony concentration in the dormitory rooms was higher (703.1 CFU/m3) than the maximum standard issued by the Ministry of Health of the Republic of Indonesia (< 700 CFU/m3) while the relative humidity was very high (84.4% RH on average), with a direct relation between the humidity and the mold colony concentration. A significant correlation was also identified between mold colony concentration, wet temperature, and CO2 concentration. Conclusion: Significant correlations between bioaerosols, relative humidity, wet temperature, and indoor CO2 concentration indicate insufficient ventilation and poor indoor air quality in the dormitory.

Cost-Effective Design of a Miniaturized Zoom Lens for a Capsule Endoscope.

This paper presents a miniaturized design of a 2× zoom lens for application to a one-megapixel image sensor in a capsule endoscope. The zoom lens is composed of four lenses, including three plastic aspheric lenses and one glass spherical lens, and adopts a three-lens group design. This capsule endoscope is mainly for observation of the small intestine, which has a radius of about 12.5 mm. The height of the object is thus set to 12.5 mm. The object surface is designed to be curved surface with a radius of curvature of 15 mm. The focal length of the zoom lens ranges from 1.064 mm to 2.039 mm, and the full angle of view ranges from 60° to 143°, the f-number is F/2.8-F/3.5, the zoom lens is 11.6 mm in length, and the maximum effective diameter of the zoom lens is 6 mm. The zoom lens design is divided into six segments, corresponding to the different magnifications from Zoom 1 to Zoom 6. The magnification ratios are -0.0845, -0.0984, -0.1150, -0.1317, -0.1482, and -0.1690, respectively. Comparing the positions from Zoom 1 to Zoom 6, the maximum optical distortion is -14.89% for the Zoom 1 and 1.45% for the Zoom 6. The maximum vertical video distortion is 8.19% for Zoom 1 and 1.00% for Zoom 6. At a 1.0 field of view, the minimum relative illuminance is 71.8% at a magnification of M = -0.1317. Finally, we perform the tolerance analysis and lens resolution analysis at different zooming positions. Our design can obtain high-quality images for capsule endoscope.

Effect of anatomical differences and intraocular lens design on negative dysphotopsia.

To assess the effect of ocular anatomy and intraocular lens (IOL) design on negative dysphotopsia (ND). Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands. Ray-tracing study based on clinical data. Ray-tracing simulations were performed to assess the effect of anatomical differences and differences in IOL design on the peripheral retinal illumination. To that end, eye models that incorporate clinically measured anatomical differences between eyes of patients with ND and eyes of pseudophakic controls were created. The anatomical differences included pupil size, pupil centration, and iris tilt. The simulations were performed with different IOL designs, including a simple biconvex IOL design and a more complex clinical IOL design with a convex-concave anterior surface. Both IOL designs were analyzed using a clear edge and a frosted edge. As ND is generally considered to be caused by a discontinuity in peripheral retinal illumination, this illumination profile was determined for each eye model and the severity of the discontinuity was compared between eye models. The peripheral retinal illumination consistently showed a more severe discontinuity in illumination with ND-specific anatomy. This difference was the least pronounced, 8%, with the frosted edge clinical IOL and the most pronounced, 18%, with the clear edge biconvex IOL. These results show that small differences in the ocular anatomy or IOL design affect the peripheral retinal illumination. Therewith, they can increase the severity of ND by up to 18%.

Ray-transfer functions for camera simulation of 3D scenes with hidden lens design.

Combining image sensor simulation tools with physically based ray tracing enables the design and evaluation (soft prototyping) of novel imaging systems. These methods can also synthesize physically accurate, labeled images for machine learning applications. One practical limitation of soft prototyping has been simulating the optics precisely: lens manufacturers generally prefer to keep lens design confidential. We present a pragmatic solution to this problem using a black box lens model in Zemax; such models provide necessary optical information while preserving the lens designer's intellectual property. First, we describe and provide software to construct a polynomial ray transfer function that characterizes how rays entering the lens at any position and angle subsequently exit the lens. We implement the ray-transfer calculation as a camera model in PBRT and confirm that the PBRT ray-transfer calculations match the Zemax lens calculations for edge spread functions and relative illumination.

Freeform wide-angle camera lens enabling mitigable distortion.

Allowing natural scenes as well as maximizing field of view (FoV) can benefit from the minimization of distortion for the wide-angle camera. The wide-angle camera utilizing freeform surfaces for mitigating distortions, either barrel distortion or pincushion distortion, is therefore of interest. In this paper, the designs of using all-aspherical surfaces and aspherical surfaces combined with freeform surfaces are investigated. To minimize the deviation before and after converting from aspherical surfaces to freeform surfaces, a mathematical conversion scheme is derived. By applying it to the design example, the methodology is shown to be effective in the case of an optical system with a large number of aspherical/freeform surfaces. Additionally, custom freeform analysis tools are developed for quantitative analysis and visualization of the critical characteristics of optical performance, namely, a 2D lateral color field map, 2D relative illumination field map, 2D spot radius field map, and 2D average modulation transfer function (MTF) field map. Compared to classical all-aspherical design, simulation results show that freeform design has the capability to reduce distortion, and other performances such as relative illumination, spot size, and MTF can also be improved, even though there are some compromises on the peripheral FoV. The design approach will have potential important research and application values for lens systems utilized in miniature camera lenses, especially the wide FoV capability.

Non-uniformity correction of wide field of view imaging system.

Requirements for wide field of view (FOV) imaging system reflect the need for both uniform illumination as well as excellent image quality across the entire FOV. As the monocentric lens combined with a parallel array of relay imagers achieves a wide-FOV while maintaining a high resolution, we studied the monocentric cascade imaging system (MCIS). However, the imaging experiment of the prototype shows two issues, including vignetting and non-uniform image quality over the full FOV. They affect the image stitching which is necessary for wide-FOV image acquisition. This paper studies how the position of the aperture stop affects the vignetting and the local aberrations in MCIS. Moving laws of the aperture stop and its relationship with the local aberrations are presented. Moreover, aspheric surfaces on proper surfaces are introduced and studied to balance the local aberrations. Accordingly, an MCIS with uniform illumination and good image quality is presented. The MCIS achieves a wide-FOV of 116.4° and an instantaneous FOV of 0.0021°. It keeps a relative illumination exceeding 97% during the full FOV. The modulation transfer function (MTF) is over 0.285 at the Nyquist frequency of 270 lp/mm. This paper provides a profound theorical reference for further applications and developments of MCIS.

Effects of Temporal Light Modulation on Working Performance, Subjective Visual Fatigue and Pupillary Light Response at 50 lx

Recent studies revealed that the visual perception of temporal light modulation (TLM), particularly the visibility threshold, were illuminance dependent and subjects exhibited significantly different response at 50 lx. Some novel studies suggested TLM at 50 lx could be particularly useful in terms of promoting alertness and increasing comfort. Therefore, in this study, working performance, subjective visual fatigue and pupillary light response (PLR) were measured under different frequency of TLM at 50 lx to evaluate such phenomenon and its possible application. Results showed that all three parameters measured at 50 lx followed a U-shaped curve with the increasing frequency, instead of the monotonically increasing trend reported in earlier research at relative higher illuminance levels (300–400) lx. Comparing to 100 Hz or 1000 Hz, 300 Hz was the best in terms of visual fatigue (P<0.01) and worst in terms of working performance (P<0.01) while PLR also showed smaller percent change under 316 Hz and 562 Hz (P<0.01). These results supported the hypotheses that at 50 lx illuminance level, the relationship between the effect of TLM and frequency was non-monotonic and was different than the monotonically increasing trend discovered under higher illuminance. Furthermore, such difference not only affects working performance and visual fatigue, but also pupillary light response, which then might affect more physiological outcome. These results could potentially be useful for reducing visual fatigue at scenarios such as operating displays in vehicles or aircrafts at night.

Processing RGB Color Sensors for Measuring the Circadian Stimulus of Artificial and Daylight Light Sources

The three main tasks of modern lighting design are to support the visual performance, satisfy color emotion (color quality), and promote positive non-visual outcomes. In view of large-scale applications, the use of simple and inexpensive RGB color sensors to monitor related visual and non-visual illumination parameters seems to be of great promise for the future development of human-centered lighting control systems. In this context, the present work proposes a new methodology to assess the circadian effectiveness of the prevalent lighting conditions for daylight and artificial light sources in terms of the physiologically relevant circadian stimulus (CS) metric using such color sensors. In the case of daylight, the raw sensor readouts were processed in such a way that the CIE daylight model can be applied as an intermediate step to estimate its spectral composition, from which CS can eventually be calculated straightforwardly. Maximal CS prediction errors of less than 0.0025 were observed when tested on real data. For artificial light sources, on the other hand, the CS approximation method of Truong et al. was applied to estimate its circadian effectiveness from the sensor readouts. In this case, a maximal CS prediction error of 0.028 must be reported, which is considerably larger compared to daylight, but still in an acceptable range for typical indoor lighting applications. The use of RGB color sensors is thus shown to be suitable for estimating the circadian effectiveness of both types of illumination with sufficient accuracy for practical applications.

Survival Analysis to Predict How Color Influences the Shelf Life of Strawberry Leather.

Color change of fruit-based products during storage is an important quality parameter to determine their shelf life. In this study, a combination of relative humidity (RH) and illumination was evaluated on the stability of strawberry leathers. Samples were conditioned at 25 °C, in chambers with RH of 22.5% and 52.3% and under two levels of illumination (no illumination and with a light-emitting diode (LED) illumination at 1010 lx). Samples were analyzed during storage by instrumental color measurements, total anthocyanin content, and consumers’ acceptance/rejection of the product color. Current-status survival analysis was performed to estimate the sensory-based shelf-life of the strawberry leather. The chromatic parameters (a* and ΔE* values) and anthocyanin content changed with increasing storage time and RH, fitting a first-order fractional conversion model. Samples conditioned at the higher RH showed a higher reduction of a* values and anthocyanins losses when stored under LED illumination than those without illumination. The increase of RH resulted in a faster increase of the consumer rejection probability and a shorter shelf life of the strawberry leather. For 50% of consumers’ rejection, the sensory shelf life of the strawberry leather equilibrated at 22.5% RH was estimated as at least 54 days, while it was reduced to approximately 2 days at 52.3% RH. The red chromatic parameter (a* value) strongly correlated to the percentage of consumer rejection in all storage conditions, suggesting that this analytical parameter can be useful as a predictor of strawberry leather’s shelf life. Therefore, the results of this study show the applicability of an approach that integrates instrumental and sensory data to acquire faster information on color changes during the storage of strawberry leather and product shelf-life prediction.