X-ray image intensifiers have excellent sensitivity, but they have image distortion that should be corrected in image measurement. For CCDs, it is very difficult to manufacture devices with a large effective area. This is a disadvantage for X-ray imaging of large areas because, unlike visible light, optical lenses cannot be used to focus X-rays. On the other hand, a-Si devices can be manufactured in large sizes but have extremely long decay time, which may cause the problem of image lag during high-speed operation. Flat panel sensors were developed to solve all of these problems. Incorporating CMOS technology allows fabricating devices about mid-way in size between a-Si and CCD devices and that do not have image lag. The comparison table below shows the specifications of these devices.
|X-ray imaging device||Sensitivity||Resolution||Image size||Dynamic range||Cost performance||Distortion||Remarks|
|X-ray image intensifier||High||Low||Large||Very narrow||Good||High||Large camera size|
|CCD||Good||High||Small||Narrow||Low||Low||Difficult to produce devices with large area|
|a-Si||Low||Low||Very large||-||Low||Low||Long decay time & high price|
|Flat panel sensor||Good||Good||Large||Wide||High||Low||-|
Our standard process achieves a high aperture ratio of 79% in 50 × 50 µm pixel sizes and 87% in 100 × 100 µm pixel sizes.
This occurs because the flat panel sensor is accumulating an electrical charge before the software supplies an external trigger. So, exclude the first frame during measurement.
Although depending on the types of flat panel sensors, prepare a frame grabber board or network interface card, a signal cable, a power supply, and a PC, etc. For more details, see the datasheets.
We recommend using a monotonically increasing type series power supply equipped with a power transformer. If a switching power supply that generates high ripple noise is used, horizontal line noise may appear on the acquired images. Switching power supplies may also degrade the image quality when used in combination with a DC/DC converter and a LDO. Use a series power supply with low ripple noise which is within the allowable range required by the system used.
If using an RS422/LVDS type flat panel sensor, then the National Instruments Measurement & Automation Explorer (MAX) and NI IMAQ PCI-1424 grabber card can be used to evaluate the basic functions.
No software is supplied with flat panel sensors. Customers must create software according to the application.
Specifications differ depending on the types, so see the datasheets for details.
Setting the X-ray dosage to a low level within the detectable range or turning off X-rays so that the flat panel sensor is not exposed to radiation except during image capture will extend the flat panel sensor service life. Another effective method is using a pulsed X-ray source. Also recommended is periodically acquiring dark images and shading images for image correction according to fluctuations in the ambient temperature and sensor temperature.
The following criteria are used to determine the life end in our lifetime test.
*Average value of dark increase is 500 GL or less in internal mode. (12-bit output products)
*Sensitivity is 50% or less of the initial value.
*Number of defect lines is double or more the spec value.
We have a demonstration room available for customer use. We will also acquire X-ray images of samples sent to us from customers. Demo devices are also available for loan to customers. Please contact our sales office.
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