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= photopyroelectric = Photopyroelectric can be understanding as –Photo +Pyroelectric which can be describe as any optical system that uses a pyroelectric detector or imaging system Pyroelectricity could be depicted as the capability of the components to formulate the transient voltage under the circumstance of being heated or cooled. The location of atom will be changed in a slight manner in the structure of crystal once the temperature they are depending on is changed. This changing process can also be referred as the polarisation of materials. As a consequence, the voltage going across the crystal would be initiated by this changing of polarisation. To explain it further, the voltage in the photopyroelectric will progressively disappear because of the leakage current on the circumstance when the temperature in the engine maintains constant for a period. In this sense, the leakage is mainly caused by several ways, for example, the-electrons which is moving through the crystal, ions which is moving through the air, or current which is leaking through a voltmeter attached across the crystal.

Technical Base of Photopyroelectric
The photopyroelectric refers to the technique of the optimal system which is mainly based on the imaginary system and the pyroelectric detector.

Pyroelectric detector
In terms of the pyroelectric detector, it works as a sensor to support the system. Due to the unipolar axis characteristics of the pyroelectric crystal, it is characterized by asymmetry. Polarization due to changes in temperature, the so-called pyroelectric effect, is currently widely used in sensor technology. Pyroelectric crystals need to be very thin to prepare and are plated in a direction perpendicular to the polar axis. An absorbing layer (blackening layer) is also required on the upper electrode. When this absorbing layer is exposed to infrared radiation, the pyroelectric chip is heated and produces a surface electrode. If the amount of radiation is interrupted, a charge is generated that is opposite to the direction of polarization. However, such charges are very small, so the charge is converted to a signal voltage by an ultra low noise and ultra low leakage field effect transistor (JFET) or operational amplifier (OpAmp) before being neutralized by the internal resistance of the crystal. Pyroelectric detectors exhibit a high signal-to-noise ratio even at 4K Hz (Mandelis, 1995). For example, in a Fourier infrared spectrometer, a thermopile can only perform better at a few hertz.

Imaginary system
In terms of the imaginary system, it is a general term for various types of remote sensor systems that acquire remote sensing images of objects without photography. Scanning is usually used for imaging, tape recording or indirect recording on film. According to the structure of the system, the scanning method and the detector parts, it is roughly divided into:

1. optomechanical scanning. Such as multi-spectral scanners. The mirror is used to scan the object surface, and the image data is output after being split, detected and photoelectrically converted.

2. electronic scanning. Such as a return beam guide TV camera, is an image-side scanning method. The process is optical imaging on the target surface of the light guide, and the signal is amplified and output after being scanned by the electron beam.

3. solid self-scanning. For example, the photoelectric scanning sensor of the French SPOT satellite is also an image scanning method. The object is imaged by an objective lens on a detector array composed of a plurality of charge coupled devices (CCDs), which are photoelectrically converted and output.

4. antenna scanning. Such as side-view radar, an active remote sensing imaging system that is a surface scanning method. It transmits the microwave beam through the antenna and receives the echo reflected by the scene, which is demodulated and output (Mandelis, 1995).

Photopyroelectric calorimetry of composite materials
The use of photopyroelectric which tells us that the previous optoelectronics structure was used to inspect the thermal efficiency of certain materials which are composite and inserted into the detection unit as a liner. This technique is depended on the coupled fluid thickness scanning process (TWRC method). Two special composites were chosen for the study :(I) a liquid: nanofluids which is based on water and contains gold nanoparticles (ii)a more solid type: urea—fumaric acid cocrystal whose proportion is 1:1. It has been found that the thermal effusivity has no relation with the volume nor the concentration in the gold particles. With the consideration of the cocrystal featuring the urea—fumaric acid, it is reasonable to conclude that the value of compound of the thermal effusivity has a lot of difference with the pure starting materials. This illustrates the generation of the compound (Dadarlat et al., 2013).

Self – consistence photopyroelectric calorimetry for liquids
This photopyroelectric as well and demonstrate the photopyroelectric (FPPE) configuration in the front is also important. In addition, it also gives a clear explanation of the thermal-wave resonator cavity (TWRC) method which has been used with the aim to inspect the liquids in its thermal effusivity and the diffusivity. It has been illustrated that the same type of technique is capable for the generation of all kinds of static and dynamic thermal parameters. In addition, among these parameters, two of them are inspected and calculated in a direct manner while the other two are remained to be calculated in an indirect manner (Dadarlat & Pop, 2012) This method displays the principle of sustainability in that it investigates on certain liquids, for example, various oils, water, glycerine, ethylene glycol and so forth.

Photopyroelectric Effect and Pyroelectric Measurement
photopyroelectric effect and pyroelectric measurement and substract because of the fluid dealing between the sample and the detector, the photoelectric technique used in the standard profile systematically underestimates the solid sample in regards to its thermal diffusivity. A brand-new method would be proposed in order to tackle with the negative effect in the process of dealing with the fluids in this research. It depends on the application of transparent pyroelectric sensors as well as the transparently coupled fluids, as well as a self-normalization process. In this sense, it is easy to measure the accurate opaque and solid example in its thermal diffusivity as well as the a translucent solid sample in terms of its coefficient light absorption (Salazar et al, 2012).

Photopyroelectric for the Simultaneous Thermal
Photopyroelectric for the simultaneous thermal which shows thermophysical research is very important and critical in many related academic scientific fields. The ability of heating is closely associated with the microstructure of confessed materials and it is of great importance in the monitoring of the energy content of the system. Therefore, calorimetry is playing an important role in the cataloguing of physical systems, especially near stage transitions in which the fluctuation of energy is of a great importance. In this paper, the capability of photoelectricity thermography to research on the change of certain heat and other thermal parameters with temperature which is closely related to the transition has been comprehensively summarized (Zammit et al, 2011).The principle applied during work, theoretical basis, the structure for experiments and added benefits of this technology compared with traditional technology are described in detail. Integrals in calorimetric Settings provide the possibility of conducting calorimetric studies while complementary properties of optical, structural and electrical properties have also been depicted. In this paper, the high temperature resolution results of several phase transition parameters in different systems under various possible structures are reviewed.

Optimized configuration of the pyroelectric sensor in photopyroelectric technique
Optimized configuration of the pyroelectric sensor in photopyroelectric technique. It has been demonstrated that under the context of the constant laser power, the response of the pyroelectric sensor would not rely on the spatial allocation of the intensity of the laser beam. Therefore, according to the model of voltage, the signal amplitude will be in the inverse proportional to the effective scope of the sensor. In addition, once the effective area decreases while the total area of the sensor maintains constant, the pyroelectric signal is likely to be increased. Based on this, a method is prompted to improve PPE signal measured in voltage mode by optimizing the metal electrode structure of the sensor(Ivanov et al, 2013). The experiment shows that this improved method can increase the signal amplitude by 10 times without increasing the electrical noise.

Types of deficiency
The so-called optical component surface defects mainly refer to surface rickets and surface contaminants. Surface rickets refer to various processing defects such as pitting, scratches, open bubbles, broken edges, and broken spots on the surface of polished optical components. The main reason is the processing or subsequent processing.

Scratches refer to scratches on the surface of the optical element. Due to the length of the scratch, it can be divided into long scratches and short scratches, with a limit of 2 mm. If the scratch length is greater than 2 mm, it is a long scratch, and if it is less than 2 mm, it is a short scratch (Lopez, 2011). For short scratches, the evaluation criteria are the cumulative length at which they are detected. Relatively speaking, scratches are easier to detect than defects such as pitting.

Pitting refers to pits, and defects on the surface of the optical element. The surface roughness in the pit is large, the width and depth are approximately the same, and the edges are irregular. In general, defects with an aspect ratio greater than 4:1 are scratches, whereas defects less than 4:1 are pockmarks.

The bubble is formed by a gas that is not removed in time during the production or processing of the optical element. Since the pressure of the gas in each direction is uniformly distributed, the shape of the bubble is generally spherical. Broken edge is a criticism of the edge of optical components. Although it is outside the effective area of ​​the light source, it is also a source of light scattering, which also has a certain impact on optical performance.

Negative impact caused by the deficiency
Surface rickets, as a microscopic local defect caused by man-made process, have a certain influence on the surface properties of optical components, which may cause serious consequences such as optical instrument operation errors. In short, the surface defects of optical components can be detrimental to the performance of optical systems, and the root cause is the scattering characteristics of light (Lopez, 2011).

The damage of optical component surface defects to itself and the entire optical system is manifested in the following aspects:

• The quality of the beam is degraded. The surface scattering defect of the component produces a scattering effect of light, so that the energy of the beam is greatly consumed after passing through the defect, thereby reducing the quality of the beam.

•The thermal effect of defects. Since the area where the surface defects are located absorbs more energy than other areas, the thermal effect phenomenon may cause local deformation of the component, damage the film layer, etc., and thus damage the entire optical system.

•Damage to other optical components in the system. In a laser system, under the illumination of a high-energy laser beam, the scattered light generated by the surface of the component is absorbed by other optical components in the system, resulting in uneven light reception of the component. When the damage threshold of the optical component material is reached, The quality of the transmitted light is affected, and the optical components are damaged, which is more likely to cause serious damage to the optical system.

• Rickets can affect the cleanliness of the field of view. When there are too many rickets on the optical components, it will affect the microscopic aesthetics. In addition, the cockroaches will leave tiny dust, microorganisms, polishing powder and other impurities, which will cause the components to be corroded, moldy, and foggy. Will significantly affect the basic performance of the component.