Search Results (29)

Ultrahigh lateral resolution (UHLR) optical coherence tomography (OCT) technology, also called optical coherence microscopy (OCM), has gained popularity, especially in the field of biomedical imaging. In these systems, high numerical aperture (NA) Microscope objectives (MO) are employed in OCM systems to offer better than 3 µm lateral resolution. However, in the implemented broadband OCM configuration, the use of complex multi-element microscope objectives can reduce the detected returned signal compared with a simpler imaging lens configuration. This reduction in detected returned signals can become an important practical limitation in many OCM applications, particularly for biomedical imaging when high imaging speed is crucial. This study investigates whether a single off-the-shelf lens can provide a practical alternative to conventional MOs, achieving higher throughput while maintaining reasonable spatial resolution. We systematically evaluated 14 commercial lenses using Zemax OpticStudio simulations, identifying an aspherized achromatic lens (Edmund Optics #85302) that best met these key criteria. To validate its feasibility for OCM, performance was tested in both Full-Field Time-Domain OCM (FF-TD-OCM) and Line-Field Spectral-Domain OCM (LF-SD-OCM) configurations. Using a broadband composite Superluminescent Diode (SLD) source (750–920 nm), we quantified the resolvable features, axial resolution, and overall light transmission. The validated system demonstrated near-diffraction-limited performance. In the LF-SD-OCM setup, it successfully resolved features as fine as Group 8, Element 6, corresponding to a 2.2 µm line pair pitch (~1.1 µm line width) and achieved a 2.86 µm axial resolution in air. A through-focus comparison further showed practically useful contrast retention around focus. Additional imaging of onion epidermal tissue and ex vivo porcine corneal tissue demonstrated that the proposed lens could provide interpretable structural images on representative biological samples. Under the tested LF-SD-OCM detection configuration, the selected lens delivered approximately 2.0 dB higher returned signal than the Mitutoyo MY10X-823 objective according to 1.59× larger received signal. Full article

Mosquitoes are key vectors of numerous infectious diseases, making the study of their behavior essential for effective control strategies. This study investigates the color preferences of Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus during foraging, using an ink-based staining method to assess feeding behavior under varying light intensities (0, 130 and 1600 lx). At 0 lx, no consistent visual preferences emerged, confirming reliance on olfactory cues only. Under dusk-like illumination (130 lx), diurnal Aedes exhibited a tendency to approach red stimuli (probably perceived as grey) over darker targets, with Ae. albopictus females and males showing significant preference for red over green responses, indicating early salience of red contrasts. At high illumination (1600 lx), Aedes shifted preference toward black, especially in males, reflecting dominance of achromatic contrast and camouflage considerations. In contrast, crepuscular Cx. quinquefasciatus showed strong attraction to black at dusk-like light in both sexes; at high illumination, females’ preferences shifted from black to red, whereas males maintained or reverted to black preference across assays. These divergent patterns align with differences in photoreceptor sensitivity, contrast processing, and ecological niches governing host- and swarm-seeking. Identifying how dusk-like versus bright light modulates color-driven behavior provides insights for designing trap colors and illumination regimes optimized for specific mosquito species and sexes, thereby enhancing targeted vector-control strategies. Full article

We report a novel phenomenon in which dynamic changes in luminance are perceived as changes in transparency rather than as changes in surface lightness. Participants viewed an achromatic disc on a uniform gray background and indicated whether the observed change was best described in terms of lightness or transparency. In Experiment 1, transparency-change responses were more frequent at low contrast and were strongly biased toward sequences in which contrast decreased over time, revealing a pronounced asymmetry between decreasing and increasing contrast trajectories. Experiment 2 introduced a size manipulation, such that the disc either expanded or contracted during the luminance modulation. Transparency-change responses were highest when contrast decreased and the disc expanded, indicating that spatial expansion further amplifies transparency-related interpretations of the disc’s surface appearance. Overall, the results reveal a systematic asymmetry in how contrast-change direction shapes visual appearance, consistent with a forward bias in the processing of continuously changing visual signals. When contrast dynamically approached the background level, perceptual representations appeared to be weighted toward the upcoming low-contrast state, enhancing impressions of increasing transparency. These findings demonstrate that even minimal displays lacking traditional geometric cues to transparency can evoke strong transparency impressions, driven by predictive weighting of spatiotemporal contrast trajectories rather than by static image properties alone. Full article

This study presents an integrated, low-cost system for measuring extremely small displacements in Ionic Polymer–Metal Composite (IPMC) actuators operating in aqueous environments. A custom optical setup was developed, combining a glass tank, a tubular microscope with a 10× achromatic objective, a digital USB camera and uniform LED backlighting, enabling side-view imaging of the actuator with high contrast. The microscopy system achieves a spatial sampling of 0.536 μm/pixel on the horizontal axis and 0.518 μm/pixel on the vertical axis, while lens distortion is limited to a maximum edge deviation of +0.015 μm/pixel (≈+2.8%), ensuring consistent geometric magnification across the field of view. On the image-processing side, a predictive grid-based tracking algorithm is introduced to localize the free tip of the IPMC. The method combines edge detection, Harris corners and a constant-length geometric constraint with an adaptive search over selected grid cells. On 1920 × 1080-pixel frames, the proposed algorithm achieves a mean processing time of about 10 ms per frame and a frame-level detection accuracy of approximately 99% (98.3–99.4% depending on the allowed search radius) for actuation frequencies below 2 Hz, enabling real-time monitoring at 30 fps. In parallel, dedicated electronic circuitry for supply and load monitoring provides overvoltage, undervoltage, open-circuit and short-circuit detection in 100 injected fault events, all faults were detected and no spurious triggers over 3 h of nominal operation. The proposed microscopy and tracking framework offer a compact, reproducible and high-resolution alternative to laser-based or Digital Image Correlation techniques for IPMC displacement characterization and can be extended to other micro-displacement sensing applications in submerged or challenging environments. Full article

Pollination syndromes reflect the convergence of floral traits among plants sharing the same pollinator guild. However, bee-pollinated orchids exhibit striking variation in color and size. This diversity reflects the multiple reward strategies that evolved within the family, each interacting differently with bee sensory biases. Here, we tested whether the complex floral visual displays of orchids differ in signal identity and intensity among reward systems. We also considered intrafloral modularity, measured as the color differentiation among flower parts, and color–size integration. For this, we measured and modeled floral morphometric and reflectance data from sepals, petals, lip tips, and lip bases under bee vision from 95 tropical Epidendroid species to compare chromatic and achromatic contrasts, spectral purity, and mean reflectance across wavebands, plus flower and display size, among reward systems. Reward types included 19 food-deceptive, 8 nectar-offering, 10 oil-offering, 11 fragrance-offering, and 47 orchid species of unknown reward strategy. Principal component analyses on 34 color and 9 size variables summarized major gradients of visual trait variation: first component (19.1%) represented overall green-red reflectance and achromatic contrasts, whereas the second (16.5%) captured chromatic contrast–size covariation. Reward systems differed mostly in signal identity rather than signal intensity. Flower chromatic contrasts presented strong integration with flower size, while achromatic contrasts were negatively associated with display size. While deceptive and nectar-offering orchids tend toward larger solitary flowers with bluer and spectrally purer displays, oil- and fragrance-offering orchids tend toward smaller, brownish, or yellow to green flowers, with larger inflorescences. Rewardless orchids presented more achromatically conspicuous signals than rewarding orchids, but smaller displays. Orchid species clustered by reward both in PCA spaces and in bee hexagon color space. Deceptive orchids were typically associated with UV + White colors, oil orchids with UV + Yellow lip tips, and fragrance orchids with UV-Black lip bases and UV-Green lip tips. Together, these results indicate that orchid reward systems promote qualitative rather than quantitative differentiation in visual signals, integrating display color and size. These long-evolved distinct signals potentially enable foraging bees to discriminate among resource types within the community floral market. Our results demonstrate that color and flower display size are important predictors of reward strategy, likely used by foraging bees for phenotype-reward associations, thus mediating the evolution of floral signals. Full article

Background/Objectives: Type 2 diabetes (T2DM) is a leading cause of vision loss. Functional measurements (color vision and contrast sensitivity) are sensitive to early changes in eyes even before retinopathy is present. This study evaluates a novel color perimetry device as an indicator of diabetic eye disease. Methods: 40 (age-matched) subjects were divided into three groups by HbA1c or previous diagnosis (control ≤ 5.6%, prediabetes 5.7–6.4%, and diabetes ≥ 6.5%). Additional health metrics gathered included BMI, body fat %, total cholesterol, HDL/LDL levels, blood glucose, and blood pressure. Novel color perimetry which measures chromatic thresholds at four locations, three degrees from the fovea, for five colors (achromatic, red, green, blue, and yellow) was completed. Mars contrast and L’Anthony D15 color testing were also completed. Lens photos excluded those with cataracts. Results: There were differences between the groups for HbA1c (p < 0.001), BMI (p = 0.046), body fat % (p = 0.020), and color perimetry for the yellow condition only (p = 0.013). The achromatic condition was highly associated with Mars contrast sensitivity (p < 0.001). HbA1c was associated with both parvocellular (average of red and green) (p = 0.014) and koniocellular (average of blue and yellow) color perimetry performance (p = 0.022). Conclusions: HbA1c is associated with color perimetry across both retinal pathways. The yellow condition in particular holds promise as a biomarker for the presence of functional changes in diabetes prior to the onset of retinopathy. Other health metrics did not influence chromatic thresholds. More research needs to be conducted to evaluate color perimetry in these patient groups to understand these relationships. Full article

Our purpose is to evaluate the binocular contrast sensitivity function (CSF) in a presbyopic population and compare the results obtained with four different simultaneous-vision center-near multifocal contact lens (MCL) designs for distance vision under two illumination conditions. Additionally, chromatic CSF (red-green and blue-yellow) was evaluated. A randomized crossover pilot study was conducted. Four daily disposable lens designs, based on simultaneous-vision and center-near correction, were compared. The achromatic contrast sensitivity function (CSF) was measured binocularly using the CSV1000e test under two lighting conditions: room light on and off. Chromatic CSF was measured using the OptoPad-CSF test. Comparison of achromatic results with room lighting showed a statistically significant difference only for 3 cpd (p = 0.03) between the baseline visit (with spectacles) and all MCLs. Comparison of achromatic results without room lighting showed no statistically significant differences between the baseline and all MCLs for any spatial frequency (p > 0.05 in all cases). Comparison of CSF-T results showed a statistically significant difference only for 4 cpd (p = 0.002). Comparison of CSF-D results showed no statistically significant difference for all frequencies (p > 0.05 in all cases). The MCL designs analyzed provided satisfactory achromatic contrast sensitivity results for distance vision, similar to those obtained with spectacles, with no remarkable differences between designs. Chromatic contrast sensitivity for the red-green and blue-yellow mechanisms revealed some differences from the baseline that should be further investigated in future studies. Full article

Color vision deficiency (CVD) affects around 300 million people globally due to issues with cone cells, highlighting the need for effective daltonization methods. These methods modify color palettes to enhance detail visibility for individuals with CVD. However, they can also distort the natural appearance of images. This study presents a novel daltonization method that focuses on preserving image naturalness for both normal trichromats and individuals with CVD. Our approach modifies only the achromatic component while enhancing detail visibility for individuals with CVD. To compare our approach with the previously known anisotropic daltonization method, we utilize objective and subjective evaluations that separately assess visibility enhancement and naturalness preservation. Our findings indicate that the proposed method outperforms the anisotropic method in naturalness by over 10 times according to objective criteria. Subjective evaluations revealed that more than 90% of CVD individuals and 95% of trichromats preferred our method for its natural appearance. Although objective contrast metrics suggest inferior visibility enhancement, subjective evaluation indicates comparable performance: contrast improvement was observed in 65% of protan cases for our method versus 70% for the anisotropic method, with contrast deterioration in 18% versus 7%, respectively. Overall, our method offers superior naturalness while maintaining comparable detail discrimination. Full article

Simultaneous color contrast is a perceptual phenomenon in which a target stimulus appears to change its hue due to color induction from the surrounding background. In this study, we investigated whether this phenomenon is influenced by the structural complexity and identity of the stimuli used. In Experiment 1, we created two sets of stimuli varying in structural complexity and asked participants to perform a color-matching task on the achromatic target. Low-complexity targets consisted of simple squares, while high-complexity targets were stylized cars. The results showed that high-complexity stimuli triggered stronger color induction from the background and exhibited greater interindividual variation in perceived color saturation. Conversely, low-complexity stimuli were predominantly perceived as achromatic across all participants. In Experiment 2, we further explored whether these effects were influenced by differences in the stimuli’s topology and identity. Topological factors were controlled by ensuring similar organizations of stimulus elements across conditions, while the role of stimulus identity was examined by including a condition in which the high-complexity stimuli from Experiment 1 were presented in a scrambled arrangement, preventing recognition. The results demonstrated that color contrast increased with the complexity of the stimuli but also highlighted the role of identity, as the condition where the car was recognizable elicited the strongest color induction. We conclude that simultaneous color contrast is strengthened by factors that pertain to both the complexity of the stimuli used and their identity. Full article

Background: Recent evidence in systems neuroscience suggests that lighting conditions affect the whole chain of brain processing, from retina to high-level cortical networks, for perceptual and cognitive function. Here, visual adaptation levels to three different environmental lighting conditions, (1) darkness, (2) daylight, and (3) prolonged exposure to very bright light akin to sunlight, were simulated in lab to investigate the effects of light adaptation levels on classic cases of subjective contrast, assimilation, and contrast-induced relative depth in achromatic, i.e., ON–OFF pathway mediated visual configurations. Methods: After adaptation/exposure to a given lighting condition, configurations were shown in grouped and ungrouped conditions in random order to healthy young humans in computer-controlled two-alternative forced-choice procedures that consisted of deciding, as quickly as possible, which of two background patterns in a given configuration of achromatic contrast appeared lighter, or which of two foreground patterns appeared to stand out in front, as if it were nearer to the observer. Results: We found a statistically significant effect of the adaptation levels on the consciously perceived subjective contrast (F(2,23) = 20.73; p < 0.001) and the relative depth (F(2,23) = 12.67; p < 0.001), a statistically significant interaction between the adaptation levels and the grouping factor (F(2,23) = 4.73; p < 0.05) on subjective contrast, and a statistically significant effect of the grouping factor on the relative depth (F(2,23) = 13.71; p < 0.01). Conclusions: Visual adaption to different lighting conditions significantly alters the conscious perception of contrast and assimilation, classically linked to non-linear functional synergies between ON and OFF processing channels in the visual brain, and modulates the repeatedly demonstrated effectiveness of luminance contrast as a depth cue; the physically brighter pattern regions in the configurations are no longer consistently perceived as nearer to a conscious observer under daylight and extreme bright light adapted (rod-saturated) conditions. Full article

In 2000, David Batchelor utilized chromophobia to describe how achromaticity has been favoured among Western intelligentsia since Aristotle. In contrast to white, hues have been linked to the feminine, the dangerous and the chaotic, and they have often been perceived to be something to abandon or control. The ominous associations remain the same when hues are desired (chromophilia), but in these instances, one desires to lose oneself to the somewhat ominous realm of colour. By approaching the Hebrew Bible with Batchelor’s framework, and with a view to human agency, various texts of transitions between chromaticity and achromaticity are examined (Ps 51:9; Isa 1:18; Jon 3:6; Lam 4:7–8; Num 12:10; Exod 25–31). It is argued that colours, in some cases, are abandoned and controlled and that they receive a specific evaluation depending on whether an agent voluntarily desired or involuntarily suffered a transition between chromaticity and achromaticity. Full article

In recent years, there has been intense development of digital diagnostic tests for vision. All of these tests must be validated for clinical use. The current study enrolled 51 healthy individuals (age 19–72 years) in which achromatic contrast sensitivity function (CSF) in near vision was measured with the printed Vistech VCTS test (Stereo Optical Co., Inc., Chicago, IL, USA) and the Optopad-CSF (developed by our research group to be used on an iPad). Likewise, chromatic CSF was evaluated with a digital test. Statistically significant differences between tests were only found for the two higher spatial frequencies evaluated (p = 0.012 and <0.001, respectively). The mean achromatic index of contrast sensitivity (ICS) was 0.02 ± 1.07 and −0.76 ± 1.63 for the Vistech VCTS and Optopad tests, respectively (p < 0.001). The ranges of agreement between tests were 0.55, 0.76, 0.78, and 0.69 log units for the spatial frequencies of 1.5, 3, 6, and 12 cpd, respectively. The mean chromatic ICS values were −20.56 ± 0.96 and −0.16 ± 0.99 for the CSF-T and CSF-D plates, respectively (p < 0.001). Furthermore, better achromatic, red–green, and blue–yellow CSF values were found in the youngest groups. The digital test allows the fast measurement of near-achromatic and chromatic CSF using a colorimetrically calibrated iPad, but the achromatic measures cannot be used interchangeably with those obtained with a conventional printed test. Full article

Our purpose is to develop and validate a new iPad-based contrast sensitivity (CS) test for measuring the contrast sensitivity function at near vision (Optopad-CSF). A total of 200 eyes of 100 healthy subjects (ages 17–63) were evaluated in a comparative study between the Optopad-CSF test (near vision) and the CSV-1000E test (distance vision). The agreement between tests was assessed with the index of contrast sensitivity (ICS) and the area under the curve (AUC). CS for all the spatial frequencies in both eyes showed a negative significant correlation with age, and corrected distance, and near visual acuities (r ≤ −0.512, p ≤ 0.013). A significantly lower CS was found with the Optopad-CSF test in the over-40-year-old subgroup for all the spatial frequencies evaluated compared to the below-40 subgroup (p ≤ 0.008). The mean AUC of the Optopad-CSF test (5.84) was twice that of the CSV-1000E test (2.76). The mean ICS of the Optopad-CSF (−0.019) and CSV-1000E (−0.075) tests showed similar values, both close to 0 (p = 0.3). There was a weak but significant correlation between the Optopad-CSF and CSV-1000E ICS tests (r = 0.246, p < 0.02). A range of normality for the values obtained with the Optopad-CSF test was calculated. The mean CS values in 16 bilateral cataract patients were out of the normal range for all the spatial frequencies evaluated (p < 0.001). Optopad-CSF is a valid portable system for measuring CS at near vision for five spatial frequencies, allowing the detection of age-related changes in CSF with age and CSF loss in cataracts, with no ceiling effect. Full article

The interaction between bees and flowering plants is mediated by floral cues that enable bees to find foraging plants. We tested floral cue preferences among three common wild bee species: Lasioglossum villosulum, Osmia bicornis, and Bombus terrestris. Preferences are well studied in eusocial bees but almost unknown in solitary or non-eusocial generalist bee species. Using standardized artificial flowers altered in single cues, we tested preferences for color hue, achromatic contrast, scent complexity, corolla size, and flower depth. We found common attractive cues among all tested bees. Intensively colored flowers and large floral displays were highly attractive. No preferences were observed in scent complexity experiments, and the number of volatiles did not influence the behavior of bees. Differing preferences were found for color hue. The specific behaviors were probably influenced by foraging experience and depended on the flower choice preferences of the tested bee species. In experiments testing different flower depths of reward presentation, the bees chose flat flowers that afforded low energy costs. The results reveal that generalist wild bee species other than well-studied honeybees and bumblebees show strong preferences for distinct floral cues to find potential host plants. The diverse preferences of wild bees ensure the pollination of various flowering plants. Full article

Dispersion control is a critical aspect in nano-optical systems. Moreover, chromatic aberration significantly impacts image quality. Despite metasurfaces being a novel approach to tackle chromatic aberration in diffractive lenses, numerous challenges hinder their practical implementation due to the complexity of 3D fabrication techniques and high manufacturing costs. In contrast, ultra-thin graphene oxide lenses are simpler and less expensive to manufacture. The optical performance of graphene oxide lenses, such as high focusing efficiency, large depth of field, wide bandwidth, and zooming capability, depends on the design of the positional arrangement of reduced graphene oxide regions. In this study, we utilized the self-constructed datasets to train machine learning models based on the structure of the graphene oxide lens and combined it with intelligent optimization algorithms. This approach facilitated the design of the graphene oxide achromatic lens in multi-wavelengths with high-performance. Experimental results substantiate that the designed ultra-thin graphene oxide lens, with a thickness of ~200 nm, effectively controls dispersion across multiple incident wavelengths (450, 550, and 650 nm) and achieves super resolution with consistent intensity at the focal point. Our graphene oxide lens holds the potential for integration into micro-optical systems that demand dispersion control, providing broad applications in optical imaging, optical communication, the biomedical field, and beyond. Full article