ASNT Level III- Visual & Optical Testing

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PART 2: MEASUREMENT OF THE PROPERTIES OF LIGHT 2.0 General: The most widely used detector of light is the human eye. Other common, mechanical detectors are photovoltaic cells, photoconductive cells, photoelectric tubes, photodiodes, phototransistors and photographic film. Charlie Chong/ Fion Zhang
2.1 Photovoltaic Cells Photovoltaic cells typically include selenium barrier layer cells and silicon or gallium arsenide, photodiodes operated in the photovoltaic or unbiased mode. These devices depend on the generation of a current resulting from the absorption of a photon. The cell is comprised of 1. a p-type material, typically a metal plate coated with a semiconductor, such as selenium on iron; and 2. a semitransparent n-type material such as cadmium oxide. Unless there is an external circuit, electrons liberated from the semiconductor are trapped at the p-n junction after exposure to light. The device thereby converts radiant energy to electric energy, which can be used directly or amplified to drive a micro-ammeter (see Fig. 4). Photovoltaic cells can be filtered to correct their spectral response so that the micro-ammeter can be calibrated in units of illuminance. Factors such as response time, fatigue, temperature effects, linearity stability, noise and magnitude of current influence the choice of cell and circuit for a given application. Charlie Chong/ Fion Zhang
Page 1 and 2: ASNT Level III- Visual & Optical Te
Page 3 and 4: Reading 4 ASNT Nondestructive Handb
Page 5 and 6: SECTION 2 THE PHYSICS OF LIGHT Char
Page 7 and 8: SECTION 2: The Physics of Light PAR
Page 9 and 10: 1.1 Radiant Energy Theories Several
Page 11 and 12: Electromagnetic Theory The electrom
Page 13 and 14: Unified Theory The unified theory o
Page 15 and 16: 1.2 Light and the Energy Spectrum T
Page 17 and 18: Keywords: • The velocity of light
Page 19 and 20: Table 1 gives the speed of light in
Page 21 and 22: FIGURE 1. Small aperture in an encl
Page 23 and 24: Although planets and stars are neit
Page 25 and 26: FIGURE 2. Blackbody radiation curve
Page 31 and 32: 1.3.2 Wien Radiation Law In the tem
Page 33 and 34: 1.3.3 Stefan-Boltzmann Law The Stef
Page 35 and 36: 1.3.6 Selective Radiators The emiss
Page 37 and 38: FIGURE 3. Radiation curves for blac
Page 39 and 40: The apertures between coils of the
Page 41 and 42: After absorption of sufficient ener
Page 43 and 44: This equation can he converted to a
Page 45 and 46: The standard spectral luminous effi
Page 47: 1.6 Luminous Efficiency of Light So
Page 51 and 52: FIGURE 4. Cross section of a barrie
Page 53 and 54: FIGURE 4. Cross section of a barrie
Page 55 and 56: Photoconductor Cells Charlie Chong/
Page 57 and 58: FIGURE 5. By the photoelectric effe
Page 59 and 60: Photoelectric Effects & Secondary r
Page 61 and 62: 2.4 Photodiodes and Phototransistor
Page 63 and 64: Schematic cross section of an integ
Page 65 and 66: Phototransistors Charlie Chong/ Fio
Page 67 and 68: 2.5 Photometry Progress in the scie
Page 69 and 70: 2.5.2 Photopic and Scotopic Vision
Page 71 and 72: Photopic and Scotopic Vision Charli
Page 73 and 74: Photopic and Scotopic Vision Charli
Page 75 and 76: TABLE 2. Measurable characteristics
Page 77 and 78: Inverse Square Law http://pondscien
Page 79 and 80: Lambert Cosine Law Charlie Chong/ F
Page 81 and 82: 2.6.4 Photometric Applications Phot
Page 83 and 84: Various types of neutral filters of
Page 85 and 86: 2.7 Photometers A photometer is a d
Page 87 and 88: Photometry Charlie Chong/ Fion Zhan
Page 89 and 90: Some portable illuminance meters co
Page 91 and 92: FIGURE 7. Average spectral sensitiv
Page 93 and 94: 2.8.3 Effect of Incidence Angle At
Page 95 and 96: 2.8.4 Effect of Temperature. Wide t
Page 97 and 98: 2.8.6 Photometer Zeroing It is impo
Page 99 and 100:
2.9 Meters Using Photomultiplier Tu
Page 101 and 102:
2.9.1 Luminance Photometers The bas
Page 103 and 104:
2.9.1 Brightness Spot Meter The bri
Page 105 and 106:
High Sensitivity Photometer Charlie
Page 107 and 108:
2.10 Equivalent Sphere Illumination
Page 109 and 110:
2.10.3 Visual Equivalent Sphere Ill
Page 111 and 112:
Visual Equivalent Sphere Illuminati
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Visual Equivalent Sphere Illuminati
Page 115 and 116:
2.10.4 Physical Equivalent Sphere I
Page 117 and 118:
2.10.5 Visual Task Photometers The
Page 119 and 120:
Another type of reflectometer (see
Page 121 and 122:
FIGURE 8. A light cell reflectomete
Page 123 and 124:
When a monochromator is used to dis
Page 125 and 126:
In all radiometric work, it is impo
Page 127 and 128:
These devices consist basically of
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Spectrophotometers Charlie Chong/ F
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Page 135 and 136:
2.14.2 Distribution Photometers Lum
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FIGURE 9. Goniometer variations: (a
Page 139 and 140:
FIGURE 10. Schematic side elevation
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FIGURE 11. Schematic side elevation
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2.14.7 Integrating Sphere Photomete
Page 145 and 146:
Integrating Sphere Photometer Charl
Page 147:
Charlie Chong/ Fion Zhang
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ASNT Level III- Visual & Optical Testing

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