c. Inspection level All references to inspection levels in this document and its appendixes are to utilize the above Table Ⅱ attributes sample inspection.
4.2 Methods of inspection
4.2.1 Inspection optical components Optical components shall be inspected by approved optical methods and equipment in accordance with applicable item specifications. In absence of approved test methods and equipment, the following procedures of the general specification shall apply. Appropriate sampling procedures may be used with prior approval of the responsible technical activity.
4.2.1.1 Mechanical dimensions Each optical component shall b checked for compliance with the mechanical dimensions of drawing and shall be inspected in accordance with the requirements and tests in this specification.
4.2.1.2 Radioactive material Finished glass shall be tested by X-ray spectrometer techniques, or an approved alternate, for compliance with 3.2.1.1. Equipment and method used in performing X-ray fluorescent must have a minimum detectable level for thorium and other radioactive material of less than 100 parts per million(ppm) with an accuracy of ±25PPM. Should analysis show any sample to exceed the requirement of 3.2.1.1 all glass in the lot from which the sample was obtained shall be rejected.
4.2.2 Surface quality Each element shall be inspected by the following methods for compliance with 3.5.2, 3.5.5, 3.6.1, 3.7.9.1, and 3.7.10.1.
4.2.2.1 Inspection method No.1 The element to be inspected shall be viewed against a ground glass or opal surface illuminated from behind by a 40 watt incandescent or 15 watt cool white fluorescent lamp approximately 3 inches from the glass. Two or more opaque horizontal bars occupying approximately 1/2 the area of the glass shall be placed in front of and in contact with the glass.
4.2.2.2 Inspection method No.2 The light through ground glass from a 40 watt incandescent or 15 watt cool white fluorescent lamp shall be passed through the element. Defects are observed by light scattered from the surface while viewing it at approximately 90 degrees to the path of the beam against a dark background.
4.2.3 Temperature test
4.2.3.1 Test No.1 Three our of the first 10 of each type of cemented or bonded component completed under each contract shall be tested at the high and low temperatures specified in 3.7.1. If there is reason to doubt quality, the right is reserved to test additional samples as the inspector deems necessary. Components subjected to these tests shall have passed all other required tests.
4.2.3.2 Test No.2 The cemented or bonded components shall be subjected to an ambient temperature of minus 80±2 degrees F for 5 hours. When inspected visually at this temperature, and again after remaining five hours at room temperature, the optical assembly shall no evidence of “feathering” or reticulation and there shall be no separation of he components. In performing this test the optical assemblies shall not be subjected to any undue the thermal shocks while being cooled to minus 80 degree F, or while being warmed to room temperature.
4.2.3.3 Test No.3 The cemented or optical assembly shall then be subjected to the following test at the high temperature. One of the components shall be held rigidly in such a manner that the cemented interface shall be approximately in a vertical plane. A weight of such magnitude as to induce in the optical assembly a unit shear stress of 5 ounces per square inch of area of the cemented or bonded surface shall be suspended from the other component. In no case shall the weight be less than one ounce. The entire apparatus shall be allowed to soak at an ambient temperature of plus 160±2 degree F, for 2 hours. The lens shall pass the requirements specified by 4.2.6 when tested at room temperature and the movement or slippage of one component with respect to the other shall not exceed 0.002 inch. In performing this test the optical assemblies shall not be subjected to any undue thermal shocks while being raised to 160 degrees F or while being cooled to room temperature.
4.2.3.4 Failure investigation Failure of one optical assembly shall be cause for stopping shipments pending an investigation of the cause. The contractor shall institute an immediate investigation in the presence of a representative of the contracting officer if the representative desires to be present to determine the cause of failure. If the investigation disclose a fault in cementing or bonding, acceptance of optical assemblies incorporating this fault in shall be stopped pending correction. The contractor shall correct his cementing technique and shall correct all faulty optical assemblies previously produced. Acceptance and shipments will be resumed when ten consecutive optical assemblies of the type rejected have successfully passed the temperature tests.
4.2.4 Temperature – relative humidity
4.2.4.1 Sample size Three out of the first 10 of each the of cemented or bonded components at the beginning of each contract, or upon change in method of cementing or change in type cement, shall be tested at the temperature-humidity conditions specified herein. If there is reason to doubt quality, the right is reserved to test additional samples as the inspector deems necessary.
4.2.4.2 Test procedure The cemented or bonded component shall be gradually heated in a dry atmosphere to plus 140±2 degrees F, and then immediately placed in an ambient atmosphere to plus 130±2 degrees F at 95 percent relative humidity for 2 hours. The optical assemblies shall be removed from the humid atmosphere, immediately wiped dry, and allowed to cool to room temperature. After 8 hours at room temperature the components shall be subjected to the tests specified in 4.2.3.2 and 4.2.3.3. The test as specified in this paragraph shall be repeated in the same identical procedure whenever passable optical assemblies having edge separation or cement blisters at the start of the test increase, or additional cement defects develop not in excess of that specified in 3.6. Components failing the initial test, or a change in any cement defects, or the development of additional cement defects after the retest shall be cause for rejection including all optical assemblies having passable cement defects from the corresponding lots offered for inspection. All components subjected to the humidity tests shall be recemented and recoated if required prior to acceptance.
4.2.4.3 Rejection criteria Failure of one component to pass the tests specified in 4.2.4 shall be cause for the components to be treated in the same manner as specified in 4.2.3.4.
4.2.5 Resolution test Resolution test shall be standard and shall be performed using one of the resolving power charts, see Figure 1. Resolving power is a measure of the optical performance. The resolving power is the angular subtense (in seconds of arc) of a series of parallel bars that can just be resolved. Resolving power is measured by viewing charts containing parallel bars of appreciate equal spacings. An auxiliary telescope is used to obtain sufficient magnification. A resolving power chart shall consist of four sets of lines, all sets either entirely three or entirely four lines at 45 degree steps (horizontal, vertical, and 45 degrees). The three lines sets shall contain lines that are five times as long as they are wide. The four line sets shall contain lines that are seven times as long as they are wide. The width of lines and spaces shall be equal. The lines may be either black on a white background, or white on a black background. There all be an identifying numeral in the center of the four sets of lines. The contrast shall be 100:1 minimum. The chart of appropriate dimensions may be located in a collimator, or it may be viewed directly. In the later case, the chart shall be at least 2 M2 feet from the telescope objective, where M is the power of the telescope being tested. The angular subtense of a chart is measured in seconds and equals arc tangent 2W/X, where W is the width a chart line and X is either collimator focal length or distance from chart to telescope under test. The auxiliary telescope is added and oriented to again center the chart. With the diopter scale of the auxiliary telescope at zero, the telescope under test shall be focused on the numeral in the resolving power target. In reading resolution, the auxiliary telescope may be focused plus or minus 1/8 diopter for each of the four meridians. All four meridians shall have the correct line count. The limit of resolution is reached when individual lines within the pattern are no longer clearly separated.
4.2.5.1 Objective and erector When an objective or erector is being inspected by means of the above chart, it shall be placed at the proper distance and the image formed by the objective or erector shall be viewed with a microscope at a given power as required by the item specification or the contracting officer. It shall be possible to discern a line structure in the blocks equivalent to the resolution specified. The chart shall be so illuminated as to give a brightness of the image of 10 to 20 millilamberts.
4.2.5.2 Lens When the effect of lens on the definition of the complete instrument is being checked., the other optical components of the instrument having approved quality shall be arrange exactly as in the actual instrument. The lens to be tested shall then be inserted in position, and the chart shall be viewed through the complete setup by means of an auxiliary telescope giving a combined power of 40 to 60 magnifications per inch of aperture. It shall be possible to discern a line structure in the block representing a line structure required for the specification resolution. The chart shall be so illuminated as to give a brightness of the image of 10 to 20 millilamberts. Any optical elements needs for this test that are not manufactured by the contractor will be furnished by the contracting officer.
4.2.5.3 Image
lane components used external to a optical system. The definition shall be tested by observing through the appreciate free aperture of the component, the image of a target of the form show in Figure 1. The image shall be observed with a telescope of at 5-power greater than the power of the optical system between the component and the eye.
4.2.5.4 Optical components or partial systems Optical components or partial systems procured as such and not as complete systems shall be tested in accordance with the detail specification or contractual document.
4.2.6 Concentricity of lenses Cemented and single lenses shall be checked for conformance with the concentricity requirements of 3.7.9.3. The instrument specified in 4.2.8 with modifications, may be used for this test except that the reticle in the collimator shall be capable of being focused to permit and the lens undergoing test for concentricity, and the stage shall be constructed to permit the lens to rotate about the geometric axis.
4.2.7 Deviation of prisms The angle of deviation of prisms shall be tested be tested by checking the deviation of light rays passing through the prisms, by standard or approved spectrometer practices.
4.2.8
arallelism Windows, wedges, reticles or similar flat surfaces elements shall be tested for parallelism of flat surfaces by checking the deviation of the light rays passing through the element.
4.2.9 Inspection of optical systems procured unassembled
4.2.9.1 Optical elements The optical elements of these systems shall be subjected to the inspection specified in 4.2.1 thru 4.2.8.
4.2.9.2 Systems, grouped The elements shall be grouped into systems for inspection and shipments. They shall be spaced, in accordance with the optical diagram pertaining to the systems, and assembled in a master instrument or tester and tested for definition and quality of image. Elements causing unsatisfactory performance shall be replaced before acceptance of the system (see Figure 1 for testing targets, and 4.2.10.2 and 4.2.10.3 for outline of inspection).
4.2.10 Inspection of assembled optical systems
4.2.10.1 Optical elements The optical elements of these systems shall be subjected to the inspection specified in 4.2.
4.2.10.2 Target Targets used in testing optical systems may be either actual size targets or miniature targets contained in collimators. The actual size can be made by printing black lines on a white background. The target in a collimator may be an etched or photographic reticle duplicating in miniature form, a full size target. The targets will vary, as required, by the detailed specification, from plain crosslines to targets containing a plumb line, level line, tolerance limit lines, and graduated scales (see Figure 1 for resolution testing target).
4.2.10.2.1 Collimator reticle The reticle cell of the collimator is adjustable so that the reticle may be moved toward or way from the objective to represent different outside distances at which an outside target would be placed. For example, suppose that the specification for a telescope required that the instruments be free from parallax when viewing a target at a distance of 200 yards and a collimator target is to be used for testing. It is necessary to adjust the collimator reticle to represent this distance. This may be accomplished by removing parallax in a sample instrument when observing an outside target at 200 yards and then using this sample telescope to adjust the collimator reticle until there is no parallax observed when sighting through the sample telescope at the collimator reticle.
4.2.10.2.2 Image quality When a collimator target is used to test the image quality or a telescope, due allowance shall be made for any aberrations of the collimator objective which will appear to be defects of telescope being tested. Caution shall be exercised to eliminate the effect of these aberrations.
4.2.10.3 Instrument inspection Where necessary, the field may be observed by the use of a dioptomenter of an equivalent auxiliary telescope to compensate for the individual inspector’s eye accommodation.
4.2.10.4
arallax
arallax shall be removed at the center of the field unless otherwise specified in the detail specification.
4.2.10.5 Reticle scale spacings Accuracy of angular subtense of reticle scale spacings of each reticle shall be tested by checking them against a target, which is an enlarged facsimile of the reticle; or a collimator reticle target. The enlarged target shall have black lines or marks against a white background and be placed at the proper distance with the faces of the target perpendicular to the line of sight of the telescopes being tested.
4.2.10.6 Surface quality reticle Each reticle shall be checked for compliance with 3.7.11.1 by viewing with a magnifier whose magnification is equal to or greater than the pertinent viewing lenses of the telescope of which it is a component. The light an method shall be the same as specified in 4.2.2.
4.2.10.7 Vibration test Each optical instrument shall be mounted singly or in groups on an approved vibration machine and fixture and vibrated at an amplitude of not less than 1/16 inch (1/8 inch total movement at the center of the mounting face of the fixture) at a frequency of 30 Hz for 2 to 2 1/2 minutes.
4.2.10.8 Shock test Shock testing of bonded and cement-supported assemblies. In absence of specific requirements each assembly shall be subjected to shock acceleration in a direction parallel to the plane of the joint in test for poor adherence or incomplete curing in the bonded or cemented joint. The time variation of the acceleration shall be roughly that of a half cycle of sine function in which the time for increase of the acceleration from zero to maximum is 0.7 to 2.0 milliseconds. The amplitude of high frequency components in the time vs. acceleration curve shall not exceed 30 percent of the fundamental amplitude. Unless otherwise specification specified by the item specification, each assembly shall be subjected to six shocks of 150 G peak acceleration.
4.2.10.9 Cleanliness Each optical system shall be examined through the objective and eyepiece ends with the unaided eye. Inspection for moisture shall be made by the technique of shadowing. Inspection for dust particles shall be made by viewing a uniformly illuminated field having a brightness of approximately 300 apparent foot-lamberts.
5.
ACKAGING
5.1 Packaging For acquisition purposes, the packaging requirements shall be as specified in the contract or order. When actual packaging of material is to be performed by DoD personnel, these personal need to contract the responsible packaging activity to ascertain requisite packaging requirements. Packaging requirements are maintained by the Inventory Control Point’s packaging activity within the Military Department of Defense Agency, or within the Military Department’s System Department of Defense Agency, or within the Military Department’s System Command. Packaging data retrieval is available from the managing Military Department’s or Defense Agency’s automated packaging files, CD-ROM products, or by contracting the responsible packaging activity.
6. NOTES
(This section contains in formation of a general or explanatory nature that may be helpful, but is not mandatory)
6.1 Intended use The finished optical components are to be used for fire control instruments such as sights, telescopes, periscopes and range finders either as individual elements, partial or complete systems, and assembled or unassembled, as required by contract.
6.2 Acquisition requirements Acquisition documents should specify the following:
a. Title, number and date of this specification.
b. Selection of an applicable level of preservation, packaging and packing.
c. Certified test reports are to be made available to the procuring activity upon request (see Appendix A and Appendix D).
6.3 Definitions
6.3.1 Scratch Any marking or tearing of the surface. Scratch types are identified as the following:
a. Block reek – chain-like or interrupted scratches that are aligned.
b. Runner – cut or cutter marks – curved scratch caused in grinding.
c. Sleek – hairline scratch.
d. Crush or rub – series of small surface scratches generally caused by mishandling.
6.3.2 Dig A small rough spot on the polished surface similar to pits in appearance, generally residuals of subsurface damage caused by grinding that didn’t polish out or bubbles that open up.
6.3.3 Feathering The physical change in cement causing the cement to lose its adhesion and develop into a feather like pattern.
6.4 Submission of alternative conformance provisions All contractor proposed alternative conformance provisions will be submitted to the Government for evaluation/approval as directed by the contracting activity.
6.5 Drawings Drawings listed in Section 2 of this specification under the heating U.S. Army Armament, Research, Development and Engineering Center (ARDEC) may also include drawings prepared by, and identified as U.S. Army Armament, Research and Development Command (ARRADCOM), Frankford Arsenal, Rock Island Arsenal or Picatinny Arsenal drawings. Technical data originally prepared by these activities is now under cognizance of ARDEC.
6.6 Subject term (keyword) listing.
Digs
Reticles
Scratches
Surface Quality
6.7 Changes from previous issue Marginal notations are not used in this revision to identify changes with respect to the previous issue due to the extent of the changes.
