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Chapter 6 CCD CMOS Image Capture test with 100% correct answers.docx, Exams of Biology

Chapter 6 CCD CMOS Image Capture test with 100% correct answers.docx

Typology: Exams

2024/2025

Available from 01/03/2025

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Chapter 6 CCD/CMOS Image

Capture test with 100%

correct answers

Define Charge Coupled Device the oldest indirect conversion digital radiography system used to acquire a digital image -signal transmitted by lenses or fiberoptics to CCD, capacitor converts light into electrical charge, where the charge is stored and released line by line to ADC Structure and Function (CCD) Photosensitive receptor in a silicon chip, incident light hits detector and hole-pairs are produced, amount of hole pairs is related to light absorbed Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0: / 0: Full screen Brainpower Read More The Chip is made of (CCD)

Polysilicon layer- contains electron gates Silicon Dioxide layer- insulator Silicon Substrate- charge storage area The Del Element contains (CCD) three electrodes, formed by voltage gates, that open and close the gates to allow the flow of electrons, to collect charge voltage sign is changed, moving electrons by rows down the columns- this whole process is known as bucket brigade scheme Reducing image size involves what components Scintillator Light collection component Noise The way the Scintillator is constructed determines -how many x-ray photons are absorbed -how much light is produced -wavelength or color of the light Within the Scintillator what are the two main types od phosphors? Csl- considered structured, because of the needle-like crystals Gd2O2- considered unstructured, because of powder like grains What do lenses and fiberoptics do? focus light onto the CCD chip -the more light sent to the chip without noise, the more efficient the system -the design of optics is crucial in imaging performance What is Quantum efficiency? amount of electrons produced relative to incident light from scintillator -QE represents efficiency of light collection and signal in chip -QE affects DQE- which is ratio of output signal to signal to noise ratio Spectrum sensitivity must match (QE) the spectral output of the phosphor -the less sensitive the CCD to light spectrum, less efficient the CCD

What are the three types of noise associated with CCD technology? Statistical Dark/Current Amplification What is Statistical noise? created by lack of light photons, also known as quantum mottle -to few light photons produced, then to few electrons are generated, output signal will be noisy What is Dark/Current Noise? CCd chip operates without radiation stimulation -dark noise can be as much as 10,000 electrons per pixel per second -40 degree drop can reduce dark noise by 100 What is amplification noise? common to digital, no CCDs without it -the more bad pixels, the worse the detector efficiency -the cheaper the CCD the more defects What are other areas that CCDs are applied in radiology Digital fluoroscopy Stereotactic breast biopsy Digital mammography General radiography Advantages and disadvantages to CCDs Simple and modular Cheaper than TFT Demagnification issues reduce DQE Define Complementary Metal Oxide Silicon uses a scintillator that, when struck with x-ray photons, converts x- rays into light photons -each pixel is switched on and off converting light photons into electrical charges -voltage converted by ADC Is CMOS a conductor or semiconductor?

semiconductor, conducting electricity under some conditions but not others, good medium for electrical current What is added to the semiconductor to make them highly conductive? impurities or dopants -most popular semiconductor material is silicon Most CMOs semiconductors have N-type (negative charge) and P-type (positive charge) carriers, this is so they can form a gate that can be controlled electrically What are the differences between CCD and CMOS sensors? -cmos more susceptible to noise -light sensitivity is lower in cmos -cmos uses little power -cmos is less expensive -pixel fill factor is greater with CCDs than CMOS