RESUMEN
We describe a method of measuring the four paraxial lens parameters-the two radii, the center thickness, and the index-of a realistic-size positive lens using an autostigmatic microscope (ASM). The method is similar to measuring the radius of curvature of a concave mirror with an ASM but slightly more complex in that four characteristic distances must be measured to solve for the four unknown parameters. Once the four distances are measured, it is shown how to use an Excel spreadsheet and the add-in iterative "Solver" to find the four unknown parameters. Finding the paraxial lens parameters is useful for troubleshooting a lens assembly that does not perform as expected due to mislabeling, the incorrect glass type used, insertion into the assembly backward, or for finding a replacement glass type.
RESUMEN
The autostigmatic microscope (ASM) is ubiquitous in the applied optics community and so familiar to those who regularly use it that it is barely mentioned in the literature. In some well-known applied optics books, the ASM's use is implied without ever being explicitly acknowledged because the authors assume no explanation is needed. However, each new generation of optical engineers need to be made aware of the workings and usefulness of the ASM, a tool every bit as useful as an autocollimator or alignment telescope. This note is an attempt to do just that.
RESUMEN
Current metrology tools have limitations when measuring rough aspherical surfaces with 1-2 µm root mean square roughness; thus, the surface cannot be shaped accurately by grinding. To improve the accuracy of grinding, the scanning long-wave optical test system (SLOTS) has been developed to measure rough aspherical surfaces quickly and accurately with high spatial resolution and low cost. It is a long-wave infrared deflectometry device consisting of a heated metal ribbon and an uncooled thermal imaging camera. A slope repeatability of 13.6 µrad and a root-mean-square surface accuracy of 31 nm have been achieved in the measurements of two 4 inch spherical surfaces. The shape of a rough surface ground with 44 µm grits was also measured, and the result matches that from a laser tracker measurement. With further calibration, SLOTS promises to provide robust guidance through the grinding of aspherics.
RESUMEN
Mixed-mode grinding occurs when a bound abrasive works in both brittle and ductile regimes simultaneously. Substrates ground in a mixed-mode behavior show reduced curvature induced by compressive surface forces than loose abrasives as demonstrated by observing the Twyman effect. This reduction in bending corresponds to reduced subsurface damage. This is verified by controlled acid etching, which shows the exponential decay of the compressive force per unit length. Loose abrasive particles, added to maintain pad wear due to low pressures, have no effect on the measured stresses. If loose abrasive wear ceases, the pads glaze. Glazing creates near-specular surfaces while reducing measurable stress. These effects for borosilicate glass and Trizact grinding pads are explored and quantified.
RESUMEN
A software configurable optical test system (SCOTS) based on the geometry of the fringe reflection or phase measuring deflectometry method was developed for rapidly, robustly, and accurately measuring large, highly aspherical shapes such as solar collectors and primary mirrors for astronomical telescopes. In addition to using phase shifting methods for data collection and reduction, we explore the test from the point view of performing traditional optical testing methods, such as Hartmann or Hartmann-Shack tests, in a reverse way. Using this concept, the slope data calculation and unwrapping in the test can also be done with centroiding and line-scanning methods. These concepts expand the test to work in more general situations where fringe illumination is not practical. Experimental results show that the test can be implemented without complex calibration for many applications by taking the geometric advantage of working near the center curvature of the test part. The results also show that the test has a large dynamic range, can achieve measurement accuracy comparable with interferometric methods, and can provide a good complement to interferometric tests in certain circumstances. A variation of this method is also useful for measuring refractive optics and optical systems. As such, SCOTS provides optical manufacturers with a new tool for performing quantitative full field system evaluation.
RESUMEN
Interferometers accurately measure the difference between two wavefronts, one from a reference surface and the other from an unknown surface. If the reference surface is near perfect or is accurately known from some other test, then the shape of the unknown surface can be determined. We investigate the case where neither the reference surface nor the surface under test is well known. By making multiple shear measurements where both surfaces are translated and/or rotated, we obtain sufficient information to reconstruct the figure of both surfaces with a maximum likelihood reconstruction method. The method is demonstrated for the measurement of a 1.6 m flat mirror to 2 nm rms, using a smaller reference mirror that had significant figure error.
RESUMEN
ATP caused platelet aggregation in rat platelet-rich plasma (PRP) but in contrast strongly inhibited ADP-induced human platelet aggregation. ADP-induced aggregation of rat platelets suspended in human plasma was strongly inhibited by ATP, whereas human platelets in rat plasma were aggregated by ADP. The ATP analog ß,γ-methylene ATP which is not dephosphorylated did not induce aggregation in rat PRP. Adenosine, AMP, 2- chloroadenosine, α,ß-methylene ADP and ß,γ-methylene ATP each inhibited ATP-induced aggregation of platelets in rat PRP to a similar extent as ADP-induced aggregation. A solution containing creatine kinase and creatine phosphate (which converts ADP to ATP) rapidly reversed both ADP- and ATP-induced aggregation in rat PRP; preincubation with this solution completely inhibited rat platelet aggregation induced by both ADP and ATP. Adenosine-8-14C-triphosphate ([14C]-ATP) conversion to [14C]-ADP was about five-fold faster in rat plasma than in human plasma. Addition of creatine phosphate to rat PRP strongly inhibited ATP-induced aggregation, while creatine or creatine kinase slightly potentiated aggregation by ATP. Creatine phosphate, creatine, or creatine kinase individually had minimal and varying effects on ADP-induced rat platelet aggregation. These results suggest that the observed phenomenon of ATP-induced aggregation in rat PRP is caused by a higher activity of creatine kinase in rat plasma than in human plasma, which converts the added ATP to ADP, a potent aggregator.