Simple Estimates for the Effects of Mid-spatial-Frequency Surface Errors on Image Quality.

Mid-spatial-frequency surface errors can be introduced by various manufacturing processes. These errors bridge the gap between traditional figure and finish errors. Although the effects of mid-spatial-frequency errors on the imagery of an optical system can be modeled with a ray-based approach, simply tracing rays provides little insight. We present an alternative method that treats surface errors as perturbations to the nominal surface profile. This approach, combined with standard statistical methods, allows one to make simple back-of-the-envelope predictions of the effects of mid-spatial-frequency errors for various measures of optical performance. Two examples illustrating the effectiveness of this approach are presented.

Imaging with three spherical mirrors.

Unobstructed, plane-symmetric systems of three spherical mirrors are investigated. Twelve parameters are necessary to specify the configuration of such a system. Constraints are determined to eliminate four of these parameters as independent degrees of freedom. These constraints ensure appropriate first-order behavior and are used to aid in two example design studies--one for a class of systems with the object at infinity and another for a class of finite conjugate projection systems. For the first study, a portion of the associated merit-function space is systematically evaluated and plotted, and the results are compared with those obtained when a global optimizer is used. For the second study, a global optimizer is employed as the primary search tool. Example systems from both studies are presented.

Imaging with four spherical mirrors.

We investigate unobstructed, plane-symmetric imaging systems of four spherical mirrors. Fifteen parameters are necessary to specify the configuration of such a system. Constraints are determined that ensure that any resultant system possesses a given set of first-order properties. These constraints remove four parameters as available degrees of freedom. To illustrate the efficacy of this design approach, we present two example studies: one for a class of systems with the object at infinity and another for finite-conjugate projection systems. For each study a global optimizer is used as the primary search tool. Example systems from these studies are presented.

Cost-based tolerancing of optical systems.

When designing an optical system it is generally accepted that it is too costly to generate the entire Hessian for every iteration of an optimizer. However, the Hessian also is useful in tolerance analysis for which it needs to be calculated only once. We propose using the Hessian as part of a cost-based tolerancing procedure. Considerations for the general implementation of the proposed ideas are discussed, and the utility of this approach is demonstrated by way of an example. In the example optimal manufacturing tolerances are determined for a doublet. As expected, the optimal tolerances change as quantities such as the requisite image quality for finished systems, manufacturing yields, and relative expenses of meeting given tolerances are varied.

Imaging a point to a line with a single spherical mirror.

Methods for imaging a single point source to a line image are discussed, and a design study of single spherical mirror systems that form aberration-free line images is presented. An expression forthe ray density along the line image is derived for such systems in the cases of (i) uniform beam profiles and (ii) Gaussian beam profiles. The resulting ray density profiles are illustrated for single spherical mirror systems over a wide range of design parameters.

Measles, mumps, rubella vaccine administration in egg-sensitive children: systemic reactions during vaccine desensitization.

In egg-sensitive children, measles-mumps-rubella (MMR) vaccination may cause acute allergic reactions; therefore, current recommendations are to perform skin testing with the commercial vaccine before administration to egg-allergic children. In children with positive skin tests, desensitization with the measles-mumps-rubella vaccine should be done in order to administer a full dose of the vaccine. Twelve egg-allergic children, aged 12 months to 5 years of age, were referred to our pediatric allergy clinic for MMR administration over a 20-month period. Three children had positive skin prick or intradermal tests to the MMR vaccine. Two of these three patients experienced systemic hypersensitivity reactions while undergoing desensitization to the MMR. All reactions occurred with injections of the undiluted vaccine. Based upon this experience, we recommend that egg-allergic children should continue to have cutaneous tests done to the MMR vaccine and careful observation during desensitization in those children with positive skin tests.

Increased incidence of stings in venom-sensitive patients.

We compared the histories of 29 venom-sensitive and 28 control subjects who were selected from our venom referral and general allergy clinics respectively. The variables in the study included insect avoidance knowledge, the number of stings during the previous 2 years, insects involved, and time spent out of doors per week. There was no significant difference between the two groups with respect to age. All venom-sensitive patients were well versed in avoidance techniques while only 3 of 28 controls (11%) claimed such knowledge. Venom-sensitive subjects were stung almost ten times more frequently than control subjects. Wasp stings were the most common, followed by yellow jacket, honey bee, and hornet. The venom-sensitive patients also reported spending a greater amount of time outdoors (x 17.4 hours versus x 11.8, P < .05). An analysis of covariance showed that this difference in outdoor exposure was insufficient to account for the disparity in the number of stings. We conclude that other factors such as intrinsic attractants must be responsible for this phenomenon.

Inflammatory cells and mediator release during ragweed challenge: correlation between histamine content in nasal secretions and appearance of inflammatory cells.

The early and late phase responses in the nasal tissues exhibit release of inflammatory mediators and a mixed cellular influx in separate nasal challenges. To explore this phenomenon further, histamine concentration was determined along with characterization of cell influx during dose-dependent ragweed challenges. Ten subjects with allergic rhinitis underwent two unilateral nasal lavages using incremental 3-fold concentrations of short ragweed. Low doses of ragweed (0.016 to 0.114 units Amb a I) rarely induced cell influx (1/18 challenges), whereas moderate doses (0.432 to 1.3 units Amb a I) caused cell influxes in 7/18 and high doses (3.39 to 11.7 units Amb a I) resulted in cell influxes in 8/17. The eluent contained greater than 50% neutrophils in seven challenges; greater than 50% eosinophils in three; and a mixed pattern in six. There was a significant association between the dose of antigen and the level of histamine. Challenges with an eosinophilic influx tended to be associated with higher concentrations of histamine than neutrophilic influxes. Similar to the immediate skin response, the early allergic response in the nose demonstrated a cell influx with release of histamine. Nasal cellular inflammation therefore can occur within minutes of allergen exposure.

Nasal inflammatory mediator release in ragweed allergic rhinitis: correlation with cellular influx into nasal secretions.

Lipid-derived mediators are found in nasal secretions during the early and late phase of allergic responses. To explore this early response further, concentrations of inflammatory mediators were measured along with characterization of specific cell influx during dose-dependent ragweed challenges. Ten allergic rhinitis subjects underwent two unilateral nasal lavages using 3-fold concentrations of short ragweed antigen. Low doses of ragweed (0.016-0.114 units Amb a I) did not provoke cell influx (1 of 18 challenges), whereas moderate doses (0.432-1.3 units Amb a I) induced cell influxes in 7 of 18 and at high doses in 8 of 17 challenges (3.39-11.7 units Amb a I). The differential of the cellular influx was greater than 50% neutrophils in 7 challenges; greater than 50% eosinophils in 3, and a mixed pattern in 6. There was a significant association between the dose of antigen and the level of prostaglandin D2 (PGD2), leukotrienes (LTs) C4, D4 and E4. Challenges with an eosinophilic influx tended to be associated with higher concentrations of mediators than neutrophilic influxes. Similar to the immediate skin response, the early allergic response in the nose demonstrated a cell influx with release of PGD2, LTsC4, D4 and E4. Nasal cellular inflammation therefore can occur within minutes of allergen exposure.