The influence of magnification on resolving power of telescopic systems for Foucault test objects of different inherent contrast.
A study has been made of the variation in resolving power with magnification for telescopic systems used to view Foucault test objects of different inherent contrast. The study included the use of a form of the K.D.C. Apparatus. The results of the study indicate the existence of an optimum magnification that can be used to resolve Foucault test objects and that the optimum value of the magnification depends upon the inherent contrast of the test object. As the test object contrast decreases, the optimum amount of magnification decreases. For test objects having an inherent contrast of approximately 100 percent, an optimum amount of magnification was found to be approximately 70× for each 25.4 mm of aperture of the telescopic system under consideration. For objects of 10 percent inherent contrast, the optimum magnification was found to be approximately 30× for each 25.4 mm of aperture.
A method for making precise resolution measurements.
A method for making precise resolving power measurements has been developed. This method makes it possible to take into account the ill effects of stray light as well as the common optical aberrations. The method utilizes a device referred to as “The Kinetic Definition Chart Apparatus” (hereafter abbreviated to K.D.C. apparatus). The K.D.C. apparatus provides a means of continuously varying the angular subtense of the markings of a test object without changing the apparent distance between the test object and the optical device under test. Provision is made to vary the contrast and the brightness level of the test object. In order to simulate natural conditions, the test object is surrounded by a region, referred to as “the artificial sky,” which may be illuminated to any desired brightness level. The Artificial Sky fixes the brightness level at which the observer’s eye is adapted, and provides a means of determining the ill effects on resolution caused by stray light that would normally be present in the optical device under consideration. Fixtures have been made which make it possible to measure the resolution at various field angles for an optical device under test. By means of auxiliary magnification, it is possible to test an optical device at full aperture and practically to eliminate differences among observers by reducing the diameter of the pupil of the observer’s eye to less than 1 mm. For comparison purposes, a high grade telescope, referred to as “the standard telescope” is used. The standard telescope is practically free from aberrations and stray light and has practically no loss in light transmission. This telescope provides a means of acquainting an observer with an image of high quality and resolves 4.51 seconds for each inch of aperture. A quantity, referred to as “the K.D.C. efficiency,” is introduced to describe the performance and the quality of optical devices. The K.D.C. efficiency may assume two different forms depending upon the end use of the data. In predicting the performance of an optical device, such as the telescope, K.D.C. efficiency is a measure of how much farther a given object is visible using the instrument than with the unaided eye. In the case of quality control of optical devices being mass produced, it is convenient to compare the limiting distance of resolution of the device under test with that of the standard telescope having the same entrance pupil as the instrument under test. The two definitions of K.D.C. efficiency are equivalent if the diameter of the pupil of the eye being used in the observations is less than 1 mm. The method described above has been used to determine the performance and quality of telescopic systems, photographic systems, eyepieces, and microscope objectives, and to measure the resolving power of the human eye under a variety of conditions.
Electrochemical detection of copper(II) at a gold electrode modified with a self-assembled monolayer of penicillamine
A penicillamine (PCA) self-assembled monolayer (SAM) was prepared on a gold electrode. It has been found that the modified electrode exhibited a selective response to copper ions. As demonstrated by cyclic voltammetric experiments, the SAM-based electrode showed an attractive ability to preconcentrate efficiently traces of copper(II) from solutions. Under optimum conditions, the anodic peak current was proportional to the concentration of Cu(II) in the range from 8.0 × 10−7 to 1.0 × 10−4 M with a detection limit of 4.0 × 10−7 M. Moreover, this modified gold electrode is also characterized by excellent repeatability, showing a relative standard deviation of 3.2% for nine successive measurements of 1.0 × 10−5 M Cu(II). The PCA/Au SAM gold electrode was used for the determination of Cu(II) in a tap water sample and the results showed a good agreement with the data obtained by atomic emission spectrometry.