LET225: Quality Assurance of Precision Optics

Transcription

1 LET225: Quality Assurance of Precision Optics Laser Technology Instructor Dr. Brian Monacelli Optical Engineer IVC ATEP Lasers Lab Image courtesy Schott Glass

2 Optical Radiation Although humans can only see the rainbow, the field of optics covers extreme ultraviolet radiation (EUV) of ~10 nm up to very long-wave infrared radiation >100 μm UV- and IR-transmissive materials may also transmit visible radiation optics regime

3 Fundamental Glass Parameters Refractive index is a measure of a glass s ability to refract light, to slow its speed, per: n( λ) = v( λ) c = meters per second in a vacuum refractive indexes range from 1.5 to 2.0 in the visible Abbe number is a measure of a glass s ability to disperse light c

4 Dispersion Dispersion defines how refractive index varies with wavelength, n(λ) Given by a complicated, empirical Sellmeier equation, such as

5 Proper Dispersion

6 Abbe Number Abbe number, V, characterizes a glass's dispersion. The standard definition of Abbe number uses the refractive indexes at three wavelengths in the visible spectrum: the refractive index at a wavelength of nm (a yellow color emitted by excited helium, known as its d-line), written as n d, the refractive index at nm (hydrogen's blue F-line), written as n F, the refractive index at nm (hydrogen's red C-line), written as n C. The standard Abbe number, V d is calculated per industrial standard ISO 7944 as: V Abbe number range from 20 to 90 in the visible d = n n F d 1 n C

7 Types of Optical Glass

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9 Glass Code Based on U.S. military standard MIL-G-174, a six-digit glass code concatenates the first three decimals of the refractive index with the first three significant figures of the Abbe number, both measured at the helium d-line of nm For instance, if the refractive index of a material is 1.ABC and its Abbe number is XY.Z, then its glass code is ABCXYZ For example, if a glass has glass code , it corresponds to a lanthanum flint with n d = and V d = 45.8

10 Types of Flaws within Glass and other TransmissiveOptical Materials Grain boundaries: regions of crystalline at different orientations (shown in red) Internal stress: induced when different parts of the optical material cools at different rates Bubbles: gas trapped within the bulk of the glass Inclusions and Impurities: undesirable external materials that enter a glass melt (not to be confused with desirable dopants) flies in the ointment Striae: regions of refractive index inhomogeneity within the bulk material

11 Grain Boundaries grain boundaries in semiconductor material grain boundaries in metal alloys x350.jpg

12 Grain Boundaries grain boundaries in metals grain boundaries in engineered materials x674.jpg

13 Internal Stress Internal stress in plastic cup

14 Bubbles Image courtesy Schott Glass Bubbles in optical glass (BK7) Bubbles in art glass Bubble%20Paperweight.jpg

15 Inclusions and Impurities natural inclusions in crystals inclusions in art glass

16 Striae Images courtesy Schott Glass

17 Lab 2: Shadowgraphs for Assessment of Internal Flaws Hardware in this class will be industrial-grade, but the components tested may not be optical-grade Labs will be performed in teams of ~3 students Roles and lab groups will be swapped from experiment to experiment Lab notebooks are mandatory and will be graded Lab safety is mandatory

18 Lab and Laser Safety Labs contain many hazards, electrical, optical, and mechanical. There is a general sequence of events that take place in an optics lab to address these risks: 1. Learn which direction the light exits the source and travels through the optical system 2. Direct the light along a clear path well below eye level 3. Mount the source and other optical hardware securely to the lab bench 4. Power on source and ensure no significant amount of light exists the system in an unexpected direction 5. Do not redefine eye level by locating your head near the beam line All lasers used in this lab are class 3R or lower this means that your eyes should be protected by the natural human reflex time of approximately 250 ms, so laser goggles are not required Do not defeat this reaction time and stare at any optical source, especially the sun or a laser, or your eyes may be damaged.

19 Lab Reports All labs will be based on a workplace scenario a task you might be asked to perform while working as a laser technician Labs will be documented and reported in your laboratory notebook or documented in your laboratory notebook reported in a separate document Labs will consist of four sections: 1. Workplace Scenario and Theory: a statement of the industrial situation that requires data to be measured, and a discussion of the theory behind the science that will be studied, including equations and parameter definitions 2. Hardware Setup: simple instructions on how to orient the lab equipment (usually based on a demonstration by the instructor), including a sketch or photograph of the lab setup, and identification of the parameters to be measured 3. Experimental Procedure and Data Acquisition: a description of what data needs to be recorded and how to make measurements, including data-recording methods, measurement resolution, and measurement accuracy (calibration) 4. Data Reduction and Analysis: a comparison of the measurements with theory and discussion of your measured results, including data plots, error analysis, and recommendations for improvement

20 Administrative Topics How is the lab organization? Educational Outreach: Saturday, 16 September: Mars Rover & Juno IEEE Expo at Northrup Grumman C-café in Redondo Beach Professional Societies: OSSC meeting on Wednesday, 11 October at 6pm at NASA JPL von Karman Auditorium in Pasadena Scientists will discuss the Mars2020 SHERLOC Instrument IVC Student Chapter of the OSA to join, ???

21 Field Trips to Precision Optical Field trips to Precision Optical 13 October: cutting and shaping 3 November: grinding and polishing 1 December: inspection and metrology meet by 18:00; park in their lot and on the street Sign the field trip waiver form!

22 From ATEP to Precision Optical 320 Kalmus, Costa Mesa

23 OP-TEC s Quality Assurance of Precision Optics Text Written by IVC faculty Edited by the NSF in partnership with IVC industrial advisors: Precision Optical Schott Glass Diverse Optics Nu-Tek Precision Optics Based on OP-TEC s Precision Optics Technician (POT) Skill Standards