In this post, we are going to discuss and explain the concept of Image Sensor. In the world of technology, images play an important role. We are identifying and classifying the objects with the help of Machine learning concepts. This all possible with the help of Image Sensors.

But, before discussing image sensor deeper, let discuss what are sensors?

What are sensors?

There are various definitions regarding what a sensor is nevertheless I might want to characterize a Sensor as an information gadget which gives an output concerning a particular input.

Another unique definition of a Sensor is as follows: It is a device that converts signals from one energy domain to electrical domain. Let consider the example to better understand the working of sensor.

The simple example is Light sensor that detects the intensity of light. The basic light sensor is LDR (Light Dependent Resistor). It resistance varies according to the light intensity and hence, changes the voltage across LDR.  So, it is converting the Light (Energy) to Electricity (Energy).

Now, let discuss the working principle of Image Sensor.

Working Principle of Image Sensor

Image sensor is equivalent of biological eye. Image sensors provide us the ability to capture high quality images and videos more directly into a digital format for easy usage.

In the human eye, rod and cone receptors work in combination with ganglion cells to convert photons into an electrochemical signal which the occipital lobe in your brain can then process.

But, In the case of an image sensor, photons are captured as charged electrons and silicon and converted to a voltage value through the use of capacitors and amplifiers, then later transferred into digital code which can be processed by a computer.

This is a basic principle of image sensor. Most image sensor operate in a similar way. But a major difference is the way they process stimuli.

There are two more readily available forms of sensors. These are

• CCD (Charge Coupled Device)
• CMOS (Complementary Metal Oxide Semiconductor)

CCD (Charge Coupled Device):

A charge-coupled device (CCD) is an integrated circuit containing an array of linked or coupled capacitors. Also, each capacitor can transfer its electric charge to a neighboring capacitor under the control of an external circuit. Moreover, the pixels represent the Metal Oxide Semiconductor (MOS) capacitors. After electron charges are captured in this pixel array, they are then processed from the bottom to the top of the grid into a serial shift register and pushed out a single charge at a time to be converted into an analogue voltage that is then transformed into coding by way of an analogue to digital converter.

CMOS (Complementary Metal Oxide Semiconductor):

A Complementary Metal Oxide Semiconductor (CMOS) is also an integrating an array of linked, or coupled, capacitors. Also, the working principle is same as CCD but instead of shuffling electron charges along an array to then be modified. CMOS sensors adds extra circuitry to each pixel, allowing it to pretty much do all of the processing individually with the signal, then sending it directly down the line to the CPU.

Comparison between types of image sensor

CCD:

• More expensive
• Consumes more power
• Less digital noise
• Works Better in low light

CMOS:

• Less expensive
• Consumes less power
• More digital noise
• Have Rolling shutter issues

We hope it cleared a few things up for you and helped you understand how your camera works just a little bit more.

For more articles on sensors, click here.