A, solid-state image sensor (CCD)

Its working process is: first, to the object being measured by optical system imaging on CCD receives, receives many photosensitive unit formed under many pixels, these pixels will be projected to its light intensity signal and converted to charge storage. Then under the clock pulse signal control, the light will be reflected as the output signal is read and stored charge order, thus completed from light image to electrical signal conversion process. CCD sensor is composed of MOS capacitor, metals and Si substrate is capacitor poles, SiO2 as medium. Forward voltage on metal gate UG, electrons are attracted to the substrate in the Si and SiO2 boundary surface, hole were excluded, and under the electrode to form a negatively charged surface depletion region.

1. The basic structure and principle of the CCD

Basic structure of the CCD, is in the N or P type silicon substrate to generate a layer of silicon dioxide layer thickness of about 120 nm, and then on the sio2 layer deposited metal electrode according to certain order, form the MOS capacitor array, then add the input and output side then constitutes the CCD device. Working principle of CCD is based on the basic function of CCD, the charge of the production, storage and transfer.

(1) the charge of the produce, store, constitute the basic unit of the CCD is MOS capacitor, the structure of the semiconductor P type silicon, for example, metal electrodes and the silicon substrate is capacitor poles, SiO2 as medium. Forward voltage on metal electrode (grid) G, the resulting electric field across the SiO2 thin layer, and absorbing the electronic silicon in Si - SiO2 interface, and rejection of Si - SiO2 interface near the hole, thus forming a negatively charged surface, and there are no electrons and holes in the depletion region. At the same time, Si - SiO2 interface potential corresponding changes (called a surface potential S), if the potential in the silicon substrate is zero, positive direction of the surface potential S down, as shown in figure 1-45 b. When the metal electrodes and the voltage of G more than open voltage MOS transistor, Si - SiO2 interface can store electronic. Because of the electronic potential energy is low, there can be figuratively speaking, formed on the surface of the semiconductor electronic potential well, habit according to the storage charge for the charge packet in the MOS potential well. graphic

When the signal light irradiation to CCD silicon surface, near the gate of the depletion region absorb photons - hole of electrons. Under the action of grid voltage G at this moment, the holes were excluded the depletion region and electronics are collected in the potential well, form the signal charge storage. If G duration is not long, in each MOS capacitor potential well accumulation of charge depends on the intensity of exposure to that point. Therefore, the accumulation of a MOS capacitor potential well in charge, can be used as the light intensity at a measurement.

(2) the transfer of charge packet

If the MOS capacitor arranged closely enough between adjacent MOS capacitor electrode gap (usually less than 3 microns), make the adjacent MOS capacitor potential well communicate with each other, the mutual coupling, then can make the signal charge (electronic) transfer in the potential well, and to the position of the surface potential S largest accumulation. Therefore, in each grid are different positive pulse amplitude G, can change their corresponding MOS surface potential S, which will change the depth of potential well, so that the signal charge free to move from shallow trap to deep well. Three MOS capacitor in three-phase overlap under the action of pulse voltage and the charge packet coupling transfer process as shown.

(3) the output of the electric charge (testing) the output of the CCD signal in charge way there are many ways, the floating diffusion amplifier output structure as shown.

2. The application of the CCD

Second, the optical fiber sensor

Optical fiber sensor based on the quantity of optical transformation, based on optical signal conversion and transmission of the carrier, using the optical fiber transmission light sensor signal. According to the effect of optical fiber, optical fiber sensors can be divided into the functional and light transmission type two kinds. Functional role to play in transmission light signal optical fiber sensor is, as a sensitive element; The optical fiber is only plays a role of transmission light signal.

1. The fiber structure and the principle of light

Optical fiber is commonly cylindrical structure, composed of fiber core and cladding and protective layer. Fiber core consists of quartz glass or plastic form, located in the middle of the fiber diameter is 5 ~ 75 microns; Fiber core is outside the cladding, a layer or multilayer structure, total about 100-200 microns in diameter, cladding materials mixed trace impurities in the pure SiO2 is commonly, the refractive index is slightly lower than the fiber core refractive index 2 1; Package layer is coated with paint (protection layer), its role is to protect the fiber is not compromised, enhance mechanical strength, protective layer refractive index 3 is far greater than 2. This structure can limit light wave transmitting in the fiber core. Total reflection principle Optical fiber transmission principle

2. The application of optical fiber sensor

1) numeration device (2) level control device

3. Optical fiber displacement sensor 4. Reflective fiber optic sensor

Inhibition of 5. 6. Total internal reflection type sensor prism type of total internal reflection type sensor

Third, amorphous alloy sensor

Amorphous alloy is developed in the late 70 s a new type of material, has a very unique microstructure, its atomic arrangement without rules, namely long-range disorder; And the number and arrangement of neighboring atoms has rules, namely the short-range order; It has no common boundary defects in amorphous alloys, but on the whole and has a high defect density, more than 10 /. This kind of structure makes the amorphous alloy has many excellent properties, and become a new generation of functional materials, in areas such as electronics, electrical and mechanical is becoming more and more widely used.

Amorphous alloy as the sensor is sensitive to the material, complete conversion function related to the physical phenomenon, belongs to the physical sensitive materials. Now found that it is the most sensitive function of main mechanical quantity, the quantity of electricity and magnetism of three mutual transformation and influence each other.

1. Magnetic - variant in function and sensors

Magnetostrictive effect is produced with magnetized specimen mechanical strain. Iron base amorphous alloy thin strip with high magnetostrictive properties, combined with optical fiber composition fiber Mach - Zehnder interferometric weak magnetic field sensor. In addition to the magnetic field detection, available amorphous alloy magnetostrictive effect testing physical quantities, such as temperature, distance and material level.

The inverse magnetostrictive effect is affected by mechanical stress specimen after the magnetization state changes. Using this effect to stress, strain, torque, impact test, sound, pressure, vibration, etc.

A typical structure of force sensor as shown. Figure china-africa made inductance coil and amorphous alloy core, when magnetic core stress change, amorphous alloy magnetic susceptibility changes, so that the coil inductance changes, the inductance L and stress has a certain relationship.

Pressure sensor tension sensor

2. The magnetic - electricity transformation function and sensors

Amorphous alloy magnetic - electrical conversion functions, mainly refers to the physical effect of amorphous alloy is used to change the magnetic field parameters into a power function. The main physical effect are electromagnetic induction, hall effect, magnetoresistance effect and so on.

Electromagnetic induction described in Faraday's law of electromagnetic induction. Equipped with a magnetic induction intensity for magnetic core, it has a number of turns around for N coil, the coil will induction electromotive force type

- through the coil magnetic flux;

- the core area;

- core permeability;

- the magnetic field strength.

By type: visible on a constant bias magnetic field, through the inverse magnetostrictive effect the change of the stress into the change of permeability, is converted to electromotive force change through electromagnetic induction, can make a force sensor; If the material permeability does not change with time, can be used to detect the magnetic field changes, and to make magnetic field sensor.

Fourth, smart sensors

So far, there is no unified definition of smart sensors. It is generally believed: sensor with microprocessor and gives the function of artificial intelligence, but also the information detection and information processing function of the sensor is smart sensors.