We propose a miniaturised light stage for measuring the bidirectional reflectance distribution function (BRDF) and the bidirectional texture function (BTF) of surfaces on site in real world application scenarios. The main principle of our lightweight BTF acquisition gantry is a compact hemispherical skeleton with cameras along the meridian and with light emitting diode (LED) modules shining light onto a sample surface. The proposed device is portable and achieves a high speed of measurement while maintaining high degree of accuracy. While the positions of the LEDs are fixed on the hemisphere, the cameras allow us to cover the range of the zenith angle from 0 ${}^{\circ }$ to 75 ${}^{\circ }$ and by rotating the cameras along the axis of the hemisphere we can cover all possible camera directions. This allows us to take measurements with almost the same quality as existing stationary BTF gantries. Two degrees of freedom can be set arbitrarily for measurements and the other two degrees of freedom are fixed, which provides a tradeoff between accuracy of measurements and practical applicability. Assuming that a measured sample is locally flat and spatially accessible, we can set the correct perpendicular direction against the measured sample by means of an auto-collimator prior to measuring. Further, we have designed and used a marker sticker method to allow for the easy rectification and alignment of acquired images during data processing. We show the results of our approach by images rendered for 36 measured material samples.

Optical systems are traditionally used for accurate recording and measurement of the real world’s appearance. Present techniques allow us to form a computer-based virtual world, which is used in a variety of technical fields. The crucial issue for future applications of virtual reality is the fidelity of rendered images to real-world objects. This is strongly affected by the appearance of the rendered object’s surfaces. Currently, the most applied method of describing a surface’s visual appearance of spatially nonuniform surfaces is bidirectional texture function (BTF). We have designed, optimized, built, and tested a unique portable instrument based on a rotary kaleidoscope principle for BTF acquisition in situ. To the best of our knowledge, such an instrument has never been used before to measure BTF of a surface. We enhanced a common static kaleidoscope by adding rotation, which allows us to get a larger number of images of the sample for more combinations of illumination directions and viewing directions. This results in a higher directional and spatial resolution of measured BTF data. In this paper, we focus on the optomechanical design of the rotary BTF measurement instrument and issues related to its alignment to keep the desired mechanical precision.

The task of imaging optics design starts with choosing a subset of imaging parameters such as the object distance, the image magnification, the image resolution, and the depth of field. It is clear that the imaging parameters are inter-related and their appropriate trade-off is the key problem of final optical design. We provide a novel analy-sis of the optical design considering diffractive imaging phenomena and thin lens approximation, and we derive formulas for the solution of individual parameters. We show that combinations of three independent optical design input variables determine all other optical and geometrical parameters under diffraction-limited optical imaging. We also formulate an invariant relation in the object space if the depth of field is one of the design's target parameters. (c) 2022 Optica Publishing Group

Endoscopic techniques are broadly used in medicine. Small diameter endoscopes are either made as fiber bundles or, beneficially, as graded index lenses. Fiber bundles can withstand a mechanical load during their use but the GRIN lens's performance can be affected by its deflection. Here, we analyze the effect of deflection on the image quality and unwanted associated effects with relation to the eye endoscope we designed and built. We also present the result of our effort to make a reliable model of a bent GRIN lens in the OpticStudio software.(c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Background: The accurate measurement of the distances within the airways during bronchoscopy is necessary for diagnostic purposes; however, a reliable and simple device does not exist. Methods: The LJ system, consisting of a probe, a box with a display, an encoder, and a microcontroller, has been developed, and its prototype has been tested in vitro and validated in clinical practice in suitable procedures of interventional bronchoscopy. Results: In vitro, the device measurements showed a good correlation with the control performed with a digital caliper. Subsequently, ten patients were included in a pilot study evaluating this novel prototype of a measurement device. The device was used on four patients with tracheal stenosis indicated for Y-stent placement, four patients indicated for open surgery, and two cases of tracheoesophageal fistula. The measurements have been validated using computed tomography imaging or by direct inspection and measurement during open surgical procedures. Conclusions: The first experience and pilot study evaluating this novel instrument for distance measurements during interventional bronchology procedures showed that the LJ device can provide precise readings of the distance from the vocal cords, the lengths of tracheal stenoses, or the size of tumorous and other lesions. Its use might be widened to other endoscopic indications.

This article demonstrates that 3D-printed parts can replace metal parts in optomechanics in the correct circumstances. Three examples are shown: a clamping fork for pedestal holders where stability is important, an adjustable mirror holder where the rigidity is the main criterion, and a stray light shield where the transmissivity is critical. By combining carbon-fiber-reinforced polymers (CFRPs) with 3D printing, it is possible to produce components that fill the gap between standard 3D-printed plastics and metal parts in terms of strength and stability. These parts are designed to be lighter, more compact, and easier to modify, while keeping good mechanical properties such as resistance to vibration, shape accuracy, and controlled thermal expansion. The article focuses on the application of composite 3D printing on optomechanical components. It compares different methods of composite 3D printing, including fused filament fabrication (FFF) with either chopped fibers or with continuous fiber reinforcement. Three examples from the HiLASE Centre demonstrate how these parts are used in practice, confirming that it is indeed possible to 3D print components that are lighter and cheaper yet still highly functional compared to their off-the-shelf counterparts—for example, lightweight and stiff mounts, shielding against stray laser light, or flexible elements allowing fine mechanical adjustments. Simulations of the deformations are included to compare the printed and metal versions. The article ends with a summary of the benefits and limitations of using 3D-printed composites in optomechanics.