Course 5. Detection and Measurement

Module 1. Microscopes

    1.1 Introductory concepts
        1.1.1 Basic types of microscopes
            1.1.1.1 Simple
            1.1.1.2 Compound
            1.1.1.3 Binocular
        1.1.2 Microscope Structure
            1.1.2.1 Typical structure of an optical microscope
            1.1.2.2 Ocular
            1.1.2.3 Objective
            1.1.2.4 Turret
            1.1.2.5 Stage
            1.1.2.6 Lamp
        1.1.3 Functions
            1.1.3.1 Image formation
            1.1.3.2 Magnification
    1.2 The objective lens
        1.2.1 Structure
            1.2.1.2 Typical design
            1.2.1.3 Achromatic objectives
            1.2.1.4 Flat field objectives
            1.2.1.5 Immersion objectives
        1.2.2 Properties
            1.2.2.1 Power
            1.2.2.2 Numerical aperture
    1.3 The ocular
        1.3.1 Types
            1.3.1.1 Huygens
            1.3.1.2 Compensating plano
            1.3.1.3 Wide field
        1.3.2 Properties
            1.3.2.1 Power
            1.3.2.2 Field of view
    1.4 Other types of microscopes
        1.4.1 Polarizing
            1.4.1.1 Optical design
            1.4.1.2 Used for birefringent specimens
        1.4.2 Dark field
            1.4.2.1 Light scattered from sample
            1.4.2.2 Optical design
        1.4.3 Phase contrast
            1.4.3.1 Two beams, one passes unaffected thru uniform
                        areas, other diffracted by irregular areas
            1.4.3.2 Optical design
            1.4.3.3 Small differences in index made visible
            1.4.3.4 Use for details of structure of living cells
        1.4.4 Interference microscope
            1.4.4.1 Uses 2 beams, which recombine and interfere
            1.4.4.2 Optical design
            1.4.4.3 Use for structure of living cells
    1.5 Operation and maintenance of microscopes
        1.5.1 Operating procedures
        1.5.2 Use of microscope cameras
        1.5.3 Care of microscopes
            


Module 2. Oscilloscopes

    2.1 Basics of oscilloscopes
        2.1.1 Oscilloscope is essentially a graph drawing device
            2.1.1.1 x-axis represents time
            2.1.1.2 y-axis represents voltage
            2.1.1.3 Intensity sometimes called z-axis
        2.1.2 Functions
            2.1.2.1 Determine time and voltage of a signal
            2.1.2.2 Determine frequency components of a signal
            2.1.2.3 Determine how signal changes with time
            2.1.2.4 Determine noise in a signal
        2.1.3 Important specifications
            2.1.3.1 Bandwidth
            2.1.3.2 Vertical resolution
            2.1.3.3 Vertical sensitivity
            2.1.3.4 Maximum input voltage
            2.1.3.5 Linear dynamic range
            2.1.3.6 Time base range
    2.2 Structure of an oscilloscope
        2.2.1 Similar to a small cathode ray tube
            2.2.1.1 Electron gun
            2.2.1.2 Electron beam focusing
            2.2.1.3 Horizontal beam deflection proportional to time
            2.2.1.4 Vertical beam deflection proportional to voltage
            2.2.1.5 Screen
                - Phosphor
                - Ruled grid
            2.2.1.6 Plug-in units
                - Time-base units
                - Amplifiers
            2.2.1.7 Triggering
                - Internal
                - External
                - Free running
            2.2.1.8 Coupling
                - AC coupling
                - DC coupling
    2.3 Oscilloscope types
        2.3.1 Analog oscilloscopes
            2.3.1.1 Directly applies voltage to electron beam moving
                       across screen
            2.3.1.2 Horizontal sweep and vertical deflection create
                       graph of signal on screen
            2.3.1.3 Trigger system starts sweep
        2.3.2 Digitizing oscilloscopes
            2.3.2.1 Signal is sampled at discrete intervals
            2.3.2.2 Analog to digital converters convert voltage to digital information
            2.3.2.3 Sample points stored in memory to make waveform record
            2.3.2.4 Digital information used to reconstruct waveform on screen
            2.3.2.5 Real time sampling with interpolation
            2.3.2.6 Equivalent time sampling
            2.3.2.7 Acquisition scopes
                - Conventional digital scopes spend very small fraction of time
                   capturing waveforms
                - Conventional digital scopes pause after each acquisition to create
                   display image
                - Acquisition scopes use fast chips to move data from acquisition system
                - Allows scope to spend greater fraction of time capturing data
    2.4 Oscilloscope accessories
        2.4.1 Probes
            2.4.1.1 Passive probes
            2.4.1.2 Active probes
            2.4.1.3 Current probes
            2.4.1.4 Impedance matching
            2.4.1.5 Effect of probe on risetime
        2.4.2 Cameras
            2.4.2.1 Optical design
            2.4.2.2 Operation
    2.5 Selecting an oscilloscope
        2.5.1 Bandwidth
            2.5.1.1 Determine highest frequency present in signal
            2.5.1.2 Multiply by 5 to get required bandwidth
            2.5.1.3 Signal risetime times bandwidth approximately equal to 0.4
        2.5.2 Sample rate
            2.5.2.1 Applies to digitizing scopes
            2.5.2.2 Nyquist sampling theorem
            2.5.2.3 High speed signals should be sampled at rate five times greater
                        than highest frequency for faithful reproduction
        2.5.3 Triggering
            2.5.3.1 Trigger on pulses defined by amplitude
            2.5.3.2 Trigger on pulses qualified by time
        2.5.4 Record length
            2.5.4.1 Number of points to make waveform record
            2.5.4.2 Need adequate record length to see the amount of detail required
    2.6 Operating procedures
        2.6.1 Adjust amplification control to adjust amplitude of signal
        2.6.2 Adjust time base to set the time per division represented
                 horizontally across the screen
        2.6.3 Set the trigger level to stabilize a repeating signal or to trigger
                on a single event
        2.6.4 Adjust focus and intensity controls to give sharp visible display


Module 3. Amplifiers

    3.1 Basic circuits
        3.1.1 Common emitter circuits
            3.1.1.1 Circuit diagram
            3.1.1.2 This is an inverting configuration
            3.1.1.3 Low input impedance, high output impedance
            3.1.1.4 High gain
        3.1.2 Common base circuits
            3.1.2.1 Circuit diagram
            3.1.2.2 This is a non-inverting configuration
            3.1.2.3 Very low input impedance, very high output impedance
            3.1.2.4 Medium gain
        3.1.3 Common collector circuits
            3.1.3.1 Circuit diagram
            3.1.3.2 This is a non-inverting configuration    
            3.1.3.3 Medium input impedance, low output impedance
            3.1.3.4 Useful for impedance matching, not a good amplifier
    3.2 Amplifier characteristics
        3.2.1 Feedback
            3.2.1.1 Circuit for feedback
            3.2.1.2 Gain of amplifier with feedback
            3.2.1.3 Negative feedback makes gain less sensitive to varying conditions
            3.2.1.4 Positive feedback makes gain more sensitive to varying conditions
        3.2.2 Distortion
            3.2.2.1 Distortion is alteration of the wave shape
            3.2.2.2 Causes of distortion
            3.2.2.3 Harmonic distortion
            3.2.2.4 Reduction of harmonic distortion with negative feedback
        3.2.3 Signal-to-noise ratio
            3.2.3.1 Causes of noise
            3.2.3.2 Measurement of noise
            3.2.3.3 Reduction of noise
        3.2.4 Types of transistors used
            3.2.4.1 Bipolar transistors are current amplifiers
            3.2.4.2 Field Effect Transistors (FETs) are voltage amplifiers
            3.2.4.3 Comparison of bipolar circuits to FET circuits
    3.3 Amplifier classes
        3.3.1 Class A
            3.3.1.1 Circuit diagram
            3.3.1.2 Conducts during whole cycle
            3.3.1.3 Good linearity, but poor efficiency
        3.3.2 Class B
            3.3.2.1 Circuit diagram
            3.3.2.2 Conducts during half cycle
            3.3.2.3 Poorer linearity, but good efficiency
            3.3.2.4 Push-pull configuration
            3.3.2.5 Crossover distortion
        3.3.3 Class AB
            3.3.3.1 Compromise between linearity of class A and efficiency of class B
            3.3.3.2 Circuit diagram
            3.3.3.3 Reduces crossover distortion
        3.3.4 Class C
            3.3.4.1 Circuit diagram
            3.3.4.2 Conducts during less than half cycle
            3.3.4.3 Poor linearity, but very good efficiency
            3.3.4.4 Not useful for audio but may be used for radio frequency circuits
        3.3.5 Higher classes
            3.3.5.1 Class D
            3.3.5.2 Classes E, F and G
            3.3.5.3 Class H
    3.4 Operational amplifiers (op amps)
        3.4.1 Op amp basics
            3.4.1.1 Nature of an op amp
            3.4.1.2 Very high gain controlled by external feedback
            3.4.1.3 Two inputs, inverting and non-inverting
        3.4.2 Ideal op amps
            3.4.2.1 Infinite open loop gain
            3.4.2.2 Infinite input impedance, zero output impedance
            3.4.2.3 Infinite flat frequency response
        3.4.3 Typical op amp circuits
            3.4.3.1 Inverting amplifiers
            3.4.3.2 Non-inverting amplifiers
            3.4.3.3 Differential amplifiers
    3.5 Amplifiers for photodetectors
        3.5.1 Photodiode operation
            3.5.1.1 Current-voltage curve in the dark
            3.5.1.2 Current-voltage curve in the light
            3.5.1.3 Typical circuit for a photodiode
            3.5.1.4 Voltage appears across load resistor
        3.5.2 Amplifier circuits for detectors
            3.5.2.1 Amplifier circuit for amplifying output voltage from photodiode
            3.5.2.2 Amplifier circuit for fiber optic receiver


Module 4. Semiconductor Devices

This module builds on and expands Module 1-4
    4.1 Basics of semiconductors
        4.1.1 Nature of semiconductors
            4.1.1.1 Energy levels vs atomic separation
            4.1.1.2 Covalent bonding
        4.1.2 Electrical characteristics
            4.1.2.1 Insulators
            4.1.2.2 Metals
            4.1.2.3 Semiconductors
    4.2 Semiconductor physics
        4.2.1 Energy levels
            4.2.1.1 Band structure
            4.2.1.2 Band gap
            4.2.1.3 Free electrons and holes
        4.2.2 Intrinsic semiconductors
            4.2.2.1 Excitation of carriers across gap
            4.2.2.2 Current-voltage characteristics
            4.2.2.3 Single crystal silicon
        4.2.3 Extrinsic semiconductors
            4.2.3.1 Impurities
            4.2.3.2 Donors and acceptors
            4.2.3.3 p and n types
            4.2.3.4 p-n junctions
            4.2.3.5 Rectifying characteristics
            4.2.3.6 I-V Curve
            4.2.3.7 Fabrication of a junction
            4.2.3.8 Carrier mobility
            4.2.3.9 Electrical conductivity
    4.3 Types of semiconductors
        4.3.1 Column IV
            4.3.1.1 Silicon
            4.3.1.2 Germanium
`        4.3.1 III-V compounds
            4.3.1.1 Binary, like GaAs
            4.3.1.2 Ternary, like InGaAs
            4.3.1.3 Quaternary, like InGaAsP
        4.3.2 II-VI Compounds
            4.3.2.1 Binary, like CdTe
            4.3.2.2 Ternary, like HgCdTe
    4.4 Semiconductor detectors
        4.4.1 Physical effects used for light detection
            4.1.1.1 Photovoltaic effect
            4.1.1.2 Photoconductive effect
            4.1.1.3 Photoelectromagnetic effect
        4.4.2 Photodiodes
            4.4.2.1 PIN photodiodes
            4.4.2.2 Schottky photodiodes
            4.4.2.3 Planar diffused photodiodes
            4.4.2.4 Circuits for photodiodes
        4.4.3 Photodiode characteristics
            4.4.3.1 IV characteristics
            4.4.3.2 Responsivity
            4.4.3.3 Spectral response
        4.4.4 Avalanche photodiodes
            4.4.4.1 Structure
            4.4.4.2 Circuits
            4.4.4.3 Spectral response
            4.4.4.4 Responsivity
        4.4.5 Photoconductive detectors
            4.4.5.1 Structure
            4.4.5.2 Circuits
            4.4.5.3 Spectral response
            4.4.5.4 Responsivity
        4.4.6 Photovoltaic detectors
            4.4.6.1 Structure
            4.4.6.2 Circuits
            4.4.6.3 Spectral response
            4.4.6.4 Responsivity
        4.4.7 Detector arrays
            4.4.7.1 One-dimensional arrays
            4.4.7.2 Two-dimensional arrays
            4.4.7.3 Number of detectors available


Module 5. Photomultiplier Tubes and Power Supplies

    5.1 The photoemissive effect
        5.1.1 Emission of electrons when a photon strives a surface
            5.1.1.1 Minimum photon energy needed
            5.1.1.2 Work function of the surface
        5.1.2 Structure of a photoemissive detector
            5.1.2.1 Vacuum tube
            5.1.2.2 Cathode which emits electrons when illuminated
            5.1.2.3 Anode to which emitted electrons are drawn
    5.2 The photomultiplier
        5.2.1 Photomultiplier is a type of photoemissive detector
            5.2.1.1 Contains secondary emitting surfaces (dynodes)
            5.2.1.2 Electrons from cathode go to 1st dynode and
                        cause more electrons to be emitted
            5.2.1.3 At each dynode, the electron pulse is amplified
            5.2.1.4 Total gain is high (>104)
        5.2.2 Structure of the photomultiplier
            5.2.2.1 Structure of the photocathode
            5.2.2.2 Focusing electrode
            5.2.2.3 Structure of the dynodes
            5.2.2.4 Structure of the anode
            5.2.2.5 The window
    5.3 Properties of the photomultiplier
        5.3.1 Spectral response
            5.3.1.1 Response is that of a photon detector
            5.3.1.2 Response covers ultraviolet, visible and near infrared
            5.3.1.3 Spectral response curves for some representative photocathodes
        5.3.2 Output
            5.3.2.1 Very high gain
            5.3.2.2 Capable of detecting single photon
            5.3.2.3 Quantum efficiency
            5.3.2.4 Responsivity
        5.3.3 Other characteristics
            5.3.3.1 Rise time
            5.3.3.2 Transit time
            5.3.3.3 Anode current
            5.3.3.4 Dark current
    5.4 Photomultiplier power supply
        5.4.1 Photomultiplier gain versus supply voltage
            5.4.1.1 100–300 volts required between dynodes
            5.4.1.2 Use of voltage divider to supply dynode voltage
        5.4.2 Examples of photomultiplier power supplies
            5.4.2.1 Half wave rectifier power supply
            5.4.2.2 Regulated DC power supply
    5.5 Photomultiplier applications
        5.5.1 Colorimetry
        5.5.2 Scintillation counting
        5.5.3 Star tracking
        5.5.4 Photometry and radiometry
        5.5.5 Computerized tomographic X-ray scanning


Module 6. Power and Energy Meters

    6.1 Calorimeters
        6.1.1 Basic structure
            6.1.1.1 Target that absorbs incident light and heats
            6.1.1.2 Thermal sensor
            6.1.1.3 Readout
        6.1.2 Targets
            6.1.2.1 Materials
            6.1.2.2 Surface absorbing
            6.1.2.3 Volume absorbing
            6.1.2.4 Use of absorbing cones
        6.1.3 Sensors
            6.1.3.1 Thermocouples
            6.1.3.2 Thermopiles
            6.1.3.3 Thermistors
            6.1.3.4 Bolometers
        6.1.4 Thermal losses
            6.1.4.1 For energy meters, loss must be small compared
                        to energy being measured
            6.1.4.2 For power meters, energy transfer to environment
                        must be at known rate
        6.1.5 Spectral response
            6.1.5.1 Thermal detectors used
            6.1.5.2 Response over broad wavelength range
            6.1.5.3 Response is relatively flat
    6.2 Photoelectric devices
        6.2.1 Silicon photodiode devices
            6.2.1.1 Common in visible and near infrared
            6.2.1.2 Responsivity
            6.2.1.3 Spectral response
            6.2.1.4 Use of compensating filters for spectral variation
        6.2.2 Infrared photodiode devices
            6.2.2.1 Materials
            6.2.2.2 Responsivity
            6.2.2.3 Spectral response
    6.3 Pyroelectric devices
        6.3.1 The pyroelectric effect
            6.3.1.1 Crystal shows spontaneous polarization when surface is heated
            6.3.1.2 Materials used
        6.3.2 Pyroelectric energy meters
            6.3.2.1 Polarization measured as voltage at electrodes attached to crystal
            6.3.2.2 Spectral response
    6.4 Electrical calibration
        6.4.1 Principles
            6.4.1.1 Electric heater added to absorbing element
            6.4.1.2 Rely on assumption that deposition of a given amount of energy
                        causes same response whether energy is optical or electrical
        6.4.2 Operation
            6.4.2.1 Electrical resistance heater heats absorber
            6.4.2.2 Electrical power determined from electrical measurements
            6.4.2.3 Measured response to electrical input gives the calibration
    6.5 Commercial power and energy meters
        6.5.1 Wide variety available
            6.5.1.1 Plug-in heads can accommodate many laser types
            6.5.1.2 Calibration with NIST traceable standards
            6.5.1.3 Direct input to computer available
        6.5.2 Spectral range
            6.5.2.1 Devices cover range from ultraviolet to near infrared
            6.5.2.2 Automatic compensation for wavelength variation of
                       response is available
        6.5.3 Analog and digital outputs
            6.5.3.1 Analog useful for fast laser tuning
            6.5.3.2 Digital useful for precision
        6.5.4 Power/energy capabilities
            6.5.4.1 Power meters available to cover range from nanowatts to kilowatts
            6.5.4.2 Energy meters available to cover range from microjoules to hundreds of joules


Module 7. Monochromators

    7.1 Introduction to monochromator
        7.1.1 Monochromator functions
            7.1.1.1 Use as a wavelength analyzer
            7.1.1.2 Use as a wavelength source
            7.1.1.3 Definition of resolution
        7.1.2 Difference between monochromators and spectrometers
            7.1.2.1 Both use same basic principles
            7.1.2.2 Monochromator: different wavelengths appear
                        successively at one exit slit
            7.1.2.3 Spectrometer: Wavelengths emerge at different angles
    7.2 Types of monochromators
        7.2.1 Grating
            7.2.1.1 Grating may be reflection or transmission
            7.2.1.2 Diagram of grating spectrometer
            7.2.1.3 Equation relating grating spacing, wavelength and angles of
                        incident and emerging light
            7.2.1.4 Order of diffraction
            7.2.1.5 Resolution of typical devices
            7.2.1.6 Spectral range
        7.2.2 Prism
            7.2.2.1 Prism may be in a variety of configurations- give typical examples
            7.2.2.2 Diagram of prism spectrometer
            7.2.2.3 Resolution of typical devices
            7.2.2.4 Spectral range
    7.3 Structure of a monochromator
        7.3.1 Typical configurations
            7.3.1.1 Czerny-Turner
            7.3.1.2 Loci
            7.3.1.3 Seya-Namioka
            7.3.1.4 Grazing incidence
        7.3.2 Entrance and exit slits
            7.3.2.1 Slit width effect on resolution
            7.3.2.2 Adjustment of slit width
            7.3.2.3 Dual exit slits
        7.3.3 Detectors for monochromators
            7.3.3.1 Thermopiles
            7.3.3.2 Radiometers
            7.3.3.3 Photomultipliers
            7.3.5.4 Photodiodes
    7.4 Uses and operation of monochromators
        7.4.1 Monochromator used as wavelength analyzer
            7.4.1.1 Diagram of typical arrangement
            7.4.1.2 Typical application (e.g. fluorescence measurement)
        7.4.2 Monochromator used as monochromatic light source
            7.4.2.1 Diagram of typical arrangement
            7.4.2.2 Typical application (e.g. spectroscopy)
        7.4.3 Operation and maintenance
            7.4.3.1 Alignment
            7.4.3.2 Operating procedures
            7.4.3.3 Cleaning
            


Module 8. Spectrometers

    8.1 Introduction to spectrometers
        8.1.1 Spectrometer functions
            8.1.1.1 Use as wavelength analyzer
            8.1.1.2 Use to measure spectral transmission and reflectivity of materials
        8.1.2 Difference between monochromators and spectrometers
            8.1.2.1 Both use same basic principles
            8.1.2.2 Monochromator: different wavelengths appear successively
                        at one exit slit
            8.1.2.3 Spectrometer: Wavelengths emerge at different angles
        8.1.3 Types of spectrometers
            8.1.3.1 Prism
            8.1.3.2 Grating
            8.1.3.3 Fourier transform infrared (FTIR)
    8.2 Prism spectrometers
        8.2.1 Typical optical configuration
            8.2.1.1 Entrance and exit slits
            8.2.1.2 Mirrors
            8.2.1.3 Collimators
            8.2.1.3 Mounts
            8.2.1.4 Filters
            8.2.1.5 Detectors
        8.2.2 Simple theory
            8.2.2.1 Dispersion
            8.2.2.2 Angle of deviation vs wavelength
        8.2.3 Spectrometer characteristics
            8.2.3.1 Dispersive power
            8.2.3.2 Resolving power
            8.2.3.3 Spectral range
    8.3 Grating spectrometers
        8.3.1 Types of gratings
            8.3.1.1 Reflection
            8.3.1.2 Transmission
            8.3.1.3 Plane
            8.3.1.4 Curved
            8.3.1.5 Blazing of gratings
        8.3.2. Typical optical configuration
            8.3.2.1 Entrance and exit slits
            8.3.2.2 Mirrors
            8.3.2.3 Collimators
            8.3.2.3 Mounts
            8.3.2.4 Filters
            8.3.2.5 Detectors
            8.3.2.6 Interchangeable gratings
            8.3.2.7 The Czerny-Tyrner spectrograph
        8.3.3 Simple theory
            8.3.3.1 The grating equation
            8.3.3.2 Possible overlap of different orders
        8.3.4 Spectrometer characteristics
            8.3.4.1 Linear dispersion
            8.3.4.2 Resolution
            8.3.4.3 Spectral range
    8.4 Fourier Transform Infrared (FTIR) spectrometers
        8.4.1 Configuration
            8.4.1.1 Michelson interferometer
            8.4.1.2 Scanner
            8.4.1.3 Detector
            8.4.1.4 Computer
        8.4.2 Principles
            8.4.2.1 Pathlength varied in one arm of interferometer
            8.4.2.2 Interferogram recorded
            8.4.2.3 Computer takes Fourier transform of interferogram
            8.4.2.4 Converts signal vs pathlength to signal vs frequency (or wavelength)
    8.5 Miniature spectrometers
        8.5.1 Integrated unit
            8.5.1.1 May be mounted on card
            8.5.1.2 Contains grating spectrometer and detector array
        8.5.2 Input/output
            8.5.2.1 Input may be thru fiber
            8.5.2.2 Output directly to computer
        8.5.3 Properties
            8.5.3.1 Size
            8.5.3.2 Number of pixels
            8.5.3.3 Resolution
            8.5.3.4 Spectral range
    8.6 Uses and operation of spectrometers
        8.6.1 Spectrometer used as wavelength analyzer
            8.6.1.1 Diagram of typical arrangement
            8.6.1.2 Typical application (like determining spectrum of a star)
        8.6.2 Measurement of transmission and reflectivity of materials
            8.6.2.1 Accessories for transmission and reflectivity
            8.6.2.2 Diagram of typical arrangement
            8.6.2.3 Typical application (like measurement of absorption
                        spectra of organic materials)
        8.6.3 Operation and maintenance
            8.6.3.1 Alignment
            8.6.3.2 Operating procedures
            8.6.3.3 Cleaning
            8.6.3.4 Replacement of gratings


Module 9. Optical Spectrum Analyzers

    9.1 Fabry-Perot interferometer spectrum analyzer
        9.1.1 Basics of Fabry-Perot interferometer
            9.1.1.1 Basic configuration
            9.1.1.2 nl = 2d cos q
            9.1.1.3 Implications of above equation
            9.1.1.4 Formation and motion of rings
        9.1.2 The plane Fabry-Perot interferometer
            9.1.2.1 Structure
            9.1.2.2 Tuning
            9.1.2.3 Free spectral range
            9.1.2.4 Finesse
            9.1.2.5 Minimum resolvable bandwidth
            9.1.2.6 Contrast
            9.1.2.7 Maximum transmission
        9.1.3 Confocal Fabry-Perot interferometer
            9.1.3.1 Structure
            9.1.3.2 Tuning
            9.1.3.3 Free spectral range
            9.1.3.4 Finesse
            9.1.3.5 Minimum resolvable bandwidth
            9.1.3.6 Contrast
            9.1.3.7 Maximum transmission
        9.1.4 Etalons
            9.1.4.1 Solid
            9.1.4.2 Air-spaced
            9.1.4.3 Performance of etalons
        9.1.5 Applications
            9.1.5.1 Laser mode analysis
            9.1.5.2 Wavelength filter
            9.1.5.3 Laser output spectrum
            9.1.5.4 Spectrum of spectral lamps
        9.1.6 Use as spectrum analyzer
            9.1.6.1 Interpretation of ring patterns
            9.1.6.2 Optical spectral analyzer systems based on Fabry-Perot interferometers
            9.1.6.3 Software for automatic data reduction
            9.1.6.4 Wavelength range
            9.1.6.5 Wavelength accuracy
        9.1.7 Operation and Maintenance
            9.1.7.1 Alignment
            9.1.7.2 Cleaning of mirrors
            9.1.7.3 Operation of drives
    9.2 Spectrum analyzers based on monochromators
        9.2.1 Basic configuration
            9.2.1.1 Unknown light source illuminates entrance slit
            9.2.1.2 Detector at output slit
            9.2.1.3 Grating or prism scanned
            9.2.1.4 Signal vs time yields source intensity vs wavelength
        9.2.2 Commercial models
            9.2.2.1 Spectral range
            9.2.2.2 Resolution
    9.3 Spectrum analyzers using miniature spectrometers
        9.3.1 Configuration
            9.3.1.1 Grating apectrometer and photodiode array sealed on a PC plug-in card
            9.3.1.2 Light input via fiber optic bundle
            9.3.1.3 Grating sends light of different wavelengths to different detectors
            9.3.1.4 Output goes directly to computer
        9.3.2 Performance characteristics
            9.3.2.1 Spectral range
            9.3.2.2 Resolution

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