surface quality 60-40

You can focus it to a point, but there's nothing you can do that will fully collimate the beam, i.e. it will always diverge.

The coated component, or witness piece, shall be subjected to an adhesion test using 1/2" (12.7 mm) wide cellophane tape conforming to type I of L-T-90. Press the adhesive surface of the cellophane tape firmly against the coated surface so as to cover the stained area, then quickly remove it at an angle which is normal to the coated surface. Immediately following the removal of the adhesive tape, the coated surface of the component, or witness piece, shall be examined by reflection using the inspection technique specified in 4.6.4. The coating shall conform to the requirements of 3.4.2.1.1. Subsequent to this test the coated component, or witness piece, shall be subjected to the test in 4.6.8.2.

iso 10110-7

6.3.1 Scratch and dig identification. - This is specified by two letters separated by a hyphen (i.e. F-F). The first letter of the pair is the maximum scratch letter. The second letter is the maximum dig letter.

The optical coating industry has adopted the US Military Specifications (often referred to as “MIL specs”) as a standard for testing the mechanical properties of coatings. All NOC coatings are adhesion tested and inspected for surface quality to the grade required by the customer. At NOC we can also test against humidity, abrasion and other MIL specs as necessary.

C7641866

3.4.1.2 Scratches. - Surface scratches (coating and substrate) shall not be in excess of the values specified on the component drawing or procurement document (See 6.2f). Scratches are permissible provided the width does not exceed that specified by the scratch letter. The accumulated length of all maximum scratches shall not exceed 1/4 of the average diameter of the element, The scratch letter and corresponding width are shown in Table I.

A slight vacuum is pulled behind an aluminized mylar plastic film to create a very large convex mirror to collimate the visual system in many aircraft simulators.

The cheesecloth pad shall completely cover the eraser portion of the tester and be secured to the shaft with an elastic band. The cheesecloth pad shall be rubbed across the coated surface from one point to another over the same path for 25 complete cycles (50 strokes) with a minimum force of 1.0 pound (0.45kg) continuously applied. The length of the stroke shall be approximately equal to two widths of the cheesecloth pad when the diameter of the area of the component permits.

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mil-prf-13830b pdf

There are two nouns morion kind of helmet, does not concern us here (it is probably from Spanish smoky quartz, has an interesting etymology: it is from a Latin word here about collimate, from an erroneous reading of Latin collineare; I wonder if there is a list somewhere of words with similar histories?

In fact, if the particles in the jet are fast enough, they can collimate themselves quite nicely due to relativistic effects.

mil-c-675

The abrasion tester shall be held approximately normal to the surface under test during the rubbing operation. Subsequent to the rubbing operation the component, or witness piece, shall be cleaned (see 4.6.1), dried and then subjected to an examination by reflection using the inspection technique specified in 4.6.4 for evidence of physical damage to the coating. The coating on the component, or witness piece, shall meet the requirements of 3.4.2.1.3.

The coated substrate shall be examined for scratches and digs by reflection or transmission, as applicable, using the inspection technique specified in 4.6.4. Magnification shall be used as needed in these examinations. The length and width of scratches, and the dig (hole) diameters shall be determined by use of interferometer, microscopic measuring devices, calibrated precision comparators, or similar applicable precision measuring devices. The width, length and density of all scratches in the coating or substrate shall conform to the requirements of 3.4.1.2 and 3.4.1.2.1. The diameter and density of all digs (holes) in the coating or substrate shall conform to the requirements of 3.4.1.3 and 3.4.1.3.1.

Within one hour after the humidity test of 4.6.8.2 the coated component, or witness piece, shall be subjected to a moderate abrasion be rubbing the coated surface with a 1/4 inch (6.4mm) thick by 3/4 inch (9.5mm) wide pad of clean dry, laundered cheesecloth conforming to CCC-C-440 affixed to an abrasion tester that conforms to drawing D7680606.

Using a light pipe [such as fiber optic] won't help to collimate your beam, total internal reflection means that as the angle of incidence = = the angle of reflection, the light entering the pipe at random angles will exit just as randomly.

mil-c-48497

3.4.1.3 Digs. - Surface digs (coating and substrate) shall not be in excess of the values specified on the component drawing or procurement document (See 6.2g). Digs are permissible on a surface provided the average diameter does not exceed that specified by the dig letter and no more than (1) maximum size dig occurs in any 20mm (0.8”) diameter circle on the substrate. The dig letter and corresponding average diameter are shown in Table II.

In 2005 they used high-power ‘Luxeon’ LEDs, i.e. non-coherent sources, combined with a large Fresnel lens to collimate the non-directional light emitted, and managed two-way audio communications over a distance of 160 km (100 miles!) between mountaintops in Tasmania.

The coated component, or witness piece, shall be placed into an environmental controlled test chamber and exposed to a temperature of +120° +/-4°F (49° +/-2°C) and 95% to 100% relative humidity for a minimum of 24 hours. Subsequent to this exposure the coated component, or witness piece, shall be removed from the test chamber, cleaned (see 4.6.1), dried, and then subjected to the examinations specified in 4.6.7.1 and 4.6.7.3. The coating shall conform to the requirements of 3.4.2.1.2. The coated component, or witness piece, shall then be subjected to the test specified in 4.6.8.3.