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Mindmap-Galerie Photoelectric sensor mind map
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Photoelectric sensor mind map
This is a mind map about photoelectric sensors, including photoelectric devices, fiber optic sensors, etc. Hope this helps you! Welcome to follow and collect~~
Bearbeitet um 2023-11-03 16:50:43
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Photoelectric Sensors
Overview
principle
Composition Radiation source, optical path, optical device
subtopic
light source
natural light source
sunshine
sky light
artificial light source
thermal radiation light source
The higher the temperature of the object, the shorter the wavelength
Incandescent near infrared light source
Tungsten halogen lamp UV radiation source
gas discharge light source
Gases emit light when electric current passes through them
low pressure mercury lamp
sodium lamp
electroluminescent light source
Solid luminescent materials emit light when excited by an electric field
led
Electric luminous screen
Laser light source
Features
High directionality
High monochromaticity
high brightness
Classification
gas laser
liquid laser
solid laser
A semiconductor laser
He-Ne laser
Features
Wide spectrum, not affected by electromagnetic interference, non-contact measurement, high precision, high resolution, high reliability, fast response
Optoelectronic devices
Thermal detection type
Photon detection type
photoelectric effect
The external photoelectric effect when electrons overflow from the surface of a substance, and the electrons which do not overflow from the surface participate in the internal conduction of the substance: the internal photoelectric effect
external photoelectric effect
principle
type
internal photoelectric effect
Photoconductivity effect
photovoltaic effect
CCD
Photoelectric conversion, information storage, delay and sequential transmission of electrical signals
CCD integrates MOS photosensitive unit array and readout shift register to form an image sensor with self-scanning function
subtopic
Fundamental
charge generation
Convert incident light signal into charge output
Internal photoelectric effect Photovoltaic effect
charge storage
When a positive voltage is applied to a metal electrode, under the action of the electric field, the holes in the P-type silicon area under the electrode are driven out, forming a region with very low potential energy, called a potential well.
Under the action of photons, photogenerated electrons are captured
charge transfer
Control pulses are used to transfer charge from one pixel to another to achieve directional movement of charge
Charge detection
Convert output charge to current/voltage
application
camera, image sensor
visual system
Linear array CCD for workpiece size measurement
PSD
photovoltaic effect
lateral photoelectric effect
When a semiconductor optoelectronic device is unevenly spaced by light, electron holes are generated in the illuminated part, and the carrier concentration is greater than in the unilluminated part. A carrier concentration gradient appears, causing carrier diffusion. If electrons diffuse faster than holes, the illuminated part will be positively charged and the unilluminated part will be negatively charged, thus generating an electromotive force.
Two assumptions: ① The resistance of the PSD surface layer is uniform ② The load resistor resistance is ignored Conclusion: ① The current is inversely proportional to the distance from the light spot to the corresponding electrode; ② The sum of I1 and 12 is equal to the total photogenerated current
Px is called the one-dimensional PSD position output signal. It has a linear relationship with the position coordinate x of the light point on the photosensitive surface and has nothing to do with the incident light intensity. This is the position detection characteristic of PSD. It has nothing to do with the spot intensity distribution, symmetry and size on the surface, only the position!
subtopic
application
3D motion measurement
Micro angle measurement
Displacement measurement
Parallelism measurement
Fiber Optic Sensor
Overview
When the optical fiber is affected by external environmental factors, such as temperature, pressure, electric field, magnetic field and other conditions, the transmission characteristics of the optical fiber will change accordingly, and there is a certain corresponding relationship between the two.
Optical fiber and its light transmission principle
Optical fiber structure
subtopic
Light transmission principle
subtopic
subtopic
The main parameters
numerical aperture
Transmission loss
dispersion
Optical fiber transmission mode
single mode
Laser light source, functional type
multimode
LED light source, non-functional
Basic components of fiber optic sensors
light source
coherent light
Various lasers
incoherent light source
White weaving lamp
led
optical fiber
light detector
Photodiode
phototransistor
Classification of fiber optic sensors
Functional type (sensing type)
Non-functional type (light transmission type)
Light modulation method
The process of superimposing an information-carrying signal onto a carrier light wave
emphasize modulation
A method that uses the measured object to directly or indirectly change the intensity of the transmitted light in the optical fiber and then detects the measured object by measuring the change in light intensity.
Microbending impairs light intensity modulation
When the optical fiber is slightly bent under force, part of the core mode energy will be converted into cladding mode energy. By measuring the changes in cladding mode energy or core mode energy, the measured value can be measured.
Light intensity modulation using changes in refractive index
Light intensity modulation using the absorption properties of optical fibers
Radiation such as X-rays and g-rays will increase the absorption loss of optical fiber materials and reduce the output power of optical fibers.
wavelength modulation
Phase modulation and interferometry
The method of using external factors to change the phase of the light wave in the optical fiber and measuring the measured phase by detecting the phase change is called phase modulation.
Known for its high sensitivity.
frequency modulation
polarization modulation
application
Features: extremely high sensitivity and accuracy, inherent safety, high dielectric strength, high temperature resistance, corrosion resistance, good anti-electromagnetic interference ability, light weight, flexibility, wide frequency band.
Applications: machinery, electronic instrumentation, aerospace, communications, biomedicine, environmental protection, food, chemical industry.
blood sample monitoring
stroke analysis
Atherosclerosis analysis
Gas detection
medical endoscope
Fiber optic liquid level sensor
Measurement objects: current magnetic field, voltage electric field, temperature, speed, vibration, pressure, ray, image.
grating sensor
laser sensor