X-ray detectors include many kinds. I don't know what you mean.
Take the common X-ray detector as an example. The crystals were separated by tungstic acid, cesium iodide and gallium sulfide. They are all converted into visible light by X-rays, and then amplified by photodiodes to form digital signals, which are transmitted to computers.
CCD camera? Is it a normal camera or a nondestructive ray camera? Judging from your supplementary question, most people understand what you mean. It is a CCD camera for nondestructive testing.
CCD: It consists of scintillator or phosphor, optical lens and CCD (Charge Coupled Device). Image formation is completed in two steps. In the first step, X-rays pass through scintillation crystals (cesium iodide or phosphorus) to generate visible light. In the second step, visible light is converted into charge by CCD through photoelectric conversion.
Comparison:
1, technical comparison
1. 1 amorphous silicon flat panel detector
It consists of scintillator or phosphor layer coated with amorphous silicon layer with photodiode tube function and TFT array. The smallest unit (pixel) in the matrix is a photodiode made of thin-film amorphous silicon, which is used to convert light into charge deposition. The photodiode matrix is covered with thallium-doped cesium iodide scintillation photoelectric crystals. The incident X-ray passing through the object excites the photodiode to generate current, and then integrates on the photodiode's own capacitance to form stored charge. The charge stored in each pixel is directly proportional to the energy and number of incident X-ray photons in the corresponding range. The technical difficulty of amorphous silicon flat panel detector lies in the complex manufacturing process of structural CSI, which requires photodiode.
1.2, amorphous selenium flat panel detector
Amorphous selenium is coated on the TFT array, and after passing through the object, electron-hole pairs are generated in the incident X-ray selenium layer. Under the action of external bias electric field, electrons and holes move in opposite directions to form current, which is then integrated in TFT to form stored charge. Thinfilm transistor TFT) technology is used to make high-resolution real-time imaging board to collect images. The technical difficulty of amorphous selenium flat panel detector is that adding thousands of volts of high voltage will pose a threat to TFT switch.
1.3, CCD detector
Imaging composed of scintillator or phosphor, optical lens and CCD (Charge Coupled Device) is completed in two steps. In the first step, X-rays pass through scintillation crystals (cesium iodide or phosphorus) to generate visible light. In the second step, visible light is converted into charge by CCD through photoelectric conversion. Technical difficulties of CCD, optical energy loss, geometric distortion of optical lens.
2 performance comparison
Amorphous selenium flat panel detector is a real direct digital photography. Because there is no visible light in the imaging process, it will not cause the loss of light energy, the increase of exposure dose and the optical geometric distortion caused by the scattering and refraction of visible light, and realize high-resolution real-time imaging.
Amorphous silicon flat panel detector is a large-area flat panel structure similar to amorphous selenium flat panel detector. No amplification is needed, and there is no geometric distortion.
CCD detector, a single CCD chip can be made, 5*5cm, which can increase the pixel to 654.38+0.7 million pixels. The parallel light and photosensitive layer of CCD adopts tin-selenium oxide material to enhance the transmittance of visible light, which can minimize the loss of light energy and geometric distortion, and has the characteristics of fast imaging speed and small exposure dose.
3 stability comparison
Selenium and silicon exist in the form of crystals in nature, so the stability of amorphous selenium and silicon at room temperature is poor. Flat amorphous silicon and selenium require high ambient temperature and take a long time to prepare the equipment. CCD detector technology has a history of about 30 years, so it is relatively mature, with low environmental requirements and short equipment preparation time.