image sensor

22
SEMINAR ON IMAGE SENSOR

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This is the image sensing technology base pwerpoint presentation which highlights the basics of image sensing... Image sensing is a technology of recognising a image or comparing a image or taking a image...

TRANSCRIPT

Page 1: Image sensor

SEMINAR ON

IMAGE SENSOR

Page 2: Image sensor

CONTENTS o What is a Sensor?o Types of Sensorso What is an Image Sensor?o Types of Image Sensorso What is CCD?o What is CMOS?o CCD vs CMOSo Applications of Image Sensorso Conclusion

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WHAT IS A SENSOR? A sensor is a device that measures a

physical quantity and converts it into a signal which can be read by an observer or by an instrument.

For example, a thermocouple converts temperature to an output voltage which can be read by a voltmeter.

For accuracy, all sensors need to be calibrated against known standards.

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TYPES OF SENSORS Thermal Energy Sensors

Electromagnetic Sensors

Mechanical Sensors

Chemical Sensors

Optical and Radiation Sensors

Acoustic Sensors

Biological Sensors

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WHAT IS AN IMAGE SENSOR?

Unlike traditional camera, An Image Sensor is a photosensitive device that converts light signals into digital signals (colours/RGB data). It uses film to capture and store an image.

Image sensors contain millions of photosensitive diodes known as photosites.

When you take a picture, the camera's shutter opens briefly and each photo site on the image sensor records the brightness of the light that falls on it by accumulating photons. The more light that hits a photo site, the more photons it records.

The brightness recorded by each photosite is then stored  as a set of numbers (digital numbers) that can then be used to set the color and brightness of a single pixel on the screen or ink on the printed page to reconstruct the image.

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IMAGE SENSOR HISTORY

Before 1960 mainly film photography was done and vacuum tubes were being used.

From 1960-1975 early research and development was done in the fields of CCD and CMOS.

From 1975-1990 commercialization of CCD took place.

After 1990 re-emergence of CMOS took place and amorphous Si also came into the picture.

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TYPES OF IMAGE SENSORS

An image sensor is typically of two types:

1. Charged Coupled Device (CCD)

2. Complementary Metal Oxide Semiconductor (CMOS)

Page 9: Image sensor

WHAT IS CCD? Charge-coupled devices (CCDs) are silicon-

based integrated circuits consisting of a dense matrix of photodiodes that operate by converting light energy in the form of photons into an electronic charge.

Electrons generated by the interaction of photons with silicon atoms are stored in a potential well and can subsequently be transferred across the chip through registers and output to an amplifier.

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CHARGED COUPLED DEVICE (CCD)

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WHAT IS CMOS? “CMOS" refers to both a particular style of

digital circuitry design, and the family of processes used to implement that circuitry on integrated circuits (chips).

CMOS circuitry dissipates less power when static, and is denser than other implementations having the same functionality.

CMOS circuits use a combination of p-type and n-type metal–oxide–semiconductor field-effect transistors (MOSFETs) to implement logic gates and other digital circuits found in computers, telecommunications equipment, and signal processing equipment.

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COMPLEMENTARY METAL OXIDE SEMICONDUCTOR (CMOS)

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CCD VS CMOS CMOS image sensors can incorporate other circuits on the

same chip, eliminating the many separate chips required for a CCD.

This also allows additional on-chip features to be added at little extra cost. These features include image stabilization and image compression.

Not only does this make the camera smaller, lighter, and cheaper; it also requires less power so batteries last longer.

CMOS image sensors can switch modes on the fly between still photography and video.

CMOS sensors excel in the capture of outdoor pictures on sunny days, they suffer in low light conditions.

Their sensitivity to light is decreased because part of each photosite is covered with circuitry that filters out noise and performs other functions.

The percentage of a pixel devoted to collecting light is called the pixel’s fill factor. CCDs have a 100% fill factor but CMOS cameras have much less.

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APPLICATION OF

IMAGE SENSORS

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Digital Cameras

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PERSONAL DIGITAL ASSISTANCE (PDA)

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CAMCORDERS

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TOYS AND ROBOTS

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FINGERPRINT SCANNER

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SOME OTHER APPLICATIONSBiometrics.

Optical Mouse.

Video Conferencing.

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CONCLUSION

Image sensors are an emergent solution for practically every automation-focused machine-vision application.

New electronic fabrication processes, software implementations, and new application fields will dictate the growth of image-sensor technology in the future.

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