Sensors and Digital Imaging- Lecture 6 Flashcards
List the reasons to change from traditional to digital imaging: (7)
- significantly less radiation
- better image
- lower cost (more net income)
- environmentally friendly (less toxic chemicals are disposed into the sewage systems)
- electronic communication improves efficiency
- rapid acquisition
- image portability (storage, transmission, duplication)
others- eliminates the need for film, processing, dark room setup, chemicals and therefore increases workflow and efficiency
Image created when photons break up the silver halide crystals and the bromine and fluorine crystals float around and create an image based on how their energy was changed:
Film image
Chemical changes in processing occurs with what type of image?
film image
Image created when the shadow created by the object being captured is transferred to electrical charges that are assigned a numerical value by the computer which is then converted to a certain color of grey and an image is created:
digital image
The general steps in digital image formation include: (4)
- x-ray shadow
- shadow image detected by digital sensor
- numerical pixel values sent to the computer
- digital image displayed on computer screen
In the first step of digital image formation (x-ray shadow), the shadow is created by:
an object
In the second step of digital image formation (shadow image detected by digital sensor), the pixels are ___. Each pixel has a ____ charge.
electrified; pre-exposure electrical charge
In the second step of digital image formation (shadow image detected by digital sensor), x-ray photons that make it to the sensor change there ____ in those pixels
electric charge
In the second step of digital image formation (shadow image detected by digital sensor), the thicker/dense the body part:
the less x-photons can affect the electrical charge
In the second step of digital image formation (shadow image detected by digital sensor), what is the net effect?
there is a shadow of electric charges on the sensor relative to the thickness/density of the body part
In the third step of digital image formation (numerical pixel values sent to the computer), electric charge value of each pixel is converted to a:
numerical value (digitized)
In the third step of digital image formation (numerical pixel values sent to the computer), ____ is sent to the computer for further processing.
pixel value
In the fourth step of digital image formation (digital image displayed on the computer screen), the computer assigns a ____ to each number
grey value
In the fourth step of digital image formation (digital image displayed on the computer screen), the gray values are displayed:
in a visual
Pixel is derived from the words:
PEL (picture element)
The smallest portion of a sensor, image, or display that is capable of being recorded and then print or displayed:
Pixel (px)
Each pixel is assigned a ___ and translated to a ___.
numerical value; specific shade of gray
Image quality:
spatial resolution
The smaller the pixel, the ____ the image will be
sharper (/better resolution)
The smaller the pixel, the ___ the processing time
longer
digital has a ___ pixel size compared to film
larger
The ability of the display/computer to distinguish between differences in color intensity:
contrast resolution
The number of gray shades that a pixel is able to display:
Bit depth
What effect does bit depth have on contrast resolution?
An increase in bit depth –> decreases contrast resolution
2 ^(BIT) =
shades of gray visible
If the bit is 2, then how many shades of gray are visible?
2^3= 8 shades
List the different ways of digital image acquisition: (3)
- indirect/hybrid
- digital indirect (semi direct)/computed radiography
- digital direct/ digital radiography
Digital indirect image acquisition may be considered:
semi direct or computed radiography
Digital direct image acquisition may be considered:
digital radiography