Abstract: An apparatus and method for locking a focus position of a lens assembly without causing the lens cell to tilt, comprising: a spacer interposed between the lens cell and the focus mount. The spacer is received into a sleeve that is integral with the focus mount. The sleeve projects radially outward from the focus mount such that the spacer can be raised and lowered radially with respect to the focus mount. The spacer has a cylindrical body with a radial flange at one end. Moreover, the spacer has two ridges that extend downward from a lower surface of the flange, each of which is received into a corresponding groove on the sleeve, thus, preventing the spacer from rotating within the sleeve. The spacer also has an upwardly raised rim extending from an upper surface of the flange. The rim is slidably secured into a slot of the focus mount, which prevents lateral movement of the spacer.

Abstract: A process and apparatus for purifying water-insoluble particles is disclosed. The process comprises the steps of continuously recirculating a fluid aqueous suspension of the water-insoluble particles between a filtration system and a suspension reservoir; continuously conducting ultrafiltration of the recirculating suspension at the filtration system to separate an aqueous permeate containing the water-soluble impurities from the recirculating fluid aqueous suspension; continuously discharging the permeate generated by ultrafiltration; adding water to the recirculating fluid aqueous suspension undergoing ultrafiltration at approximately the same volumetric rate per hour as permeate is being discharged; monitoring the purity of the recirculating fluid aqueous suspension; and recovering the purified fluid aqueous suspension after the recirculating fluid aqueous suspension has reached a predetermined purity condition. An apparatus is also disclosed for carrying out the above process.