文档介绍：Chapter 7 Digital Camera Example
太原房产网
1
Outline
Introduction to a simple digital camera
Designer’s perspective
Requirements specification
Design
Four implementations
2
Putting it all together
General-purpose processor
Single-purpose processor
Custom
Standard
Memory
Interfacing
Knowledge applied to designing a simple digital camera
General-purpose vs. single-purpose processors
Partitioning of functionality among different processor types
Introduction
3
Introduction to a simple digital camera
Captures images
Stores images in digital format
No film
Multiple images stored in camera
Number depends on amount of memory and bits used per image
Downloads images to PC
Only recently possible
Systems-on-a-chip
Multiple processors and memories on one IC
High-capacity flash memory
Very simple description used for example
Many more features with real digital camera
Variable size images, image deletion, digital stretching, zooming in and out, etc.
4
Designer’s perspective
Two key tasks
Processing images and storing in memory
When shutter pressed:
Image captured
Converted to digital form by charge-coupled device (CCD)
Compressed and archived in internal memory
Uploading images to PC
Digital camera attached to PC
Special mands camera to transmit archived images serially
5
Charge-coupled device (CCD)
Special sensor that captures an image
Light-sensitive silicon solid-state posed of many cells
When exposed to light, each cell es electrically charged. This charge can then be converted to a 8-bit value where 0 represents no exposure while 255 represents very intense exposure of that cell to light.
Some of the columns are covered with a black strip of paint. The light-intensity of these pixels is used for zero-bias adjustments of all the cells.
The electromechanical shutter is activated to expose the cells to light for a brief moment.
The electronic circuitry, manded, discharges the cells, activates the electromechanical shutter, and then reads the 8-bit charge value