How Does A Digital Camera Sensor Work | Everything In Details

How Does A Digital Camera Sensor Work

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Digital cameras are all around us, and these are being used in a variety of different fields. You’ll find digital cameras not just in our smartphones but also in surveillance applications, traffic monitoring, modern production lines, and many other industries.

A digital camera captures an image by converting the image information from the lens and what makes the conversion process possible is the image sensor. It is also considered the heart of a digital camera as the camera cannot function without it. So, how does a digital camera sensor work?

Contents

What Is A Camera Sensor?

The camera sensor is the mother component of every camera, and the sensor makes it possible to capture an image. To form an image, it requires light. Lights come from the object, and it hit the camera sensor.

The sensor captures the light and converts the light into a digital form. This digital form is what we called a digital image.

The sensor is a solid-state device, and it is made up of some small components. These are

Color filter array

The camera sensor can only capture the light but not the color. The color filter array gives the sensor the ability to see color. Different camera sensor manufacturer uses different types of an array; the most common array is Bayer GRGB.

It is placed on every pixel to detect color, and each pixel can detect only one color. So, this color filter array produces incomplete color samples. Then, using the demosaicing process, the camera reconstructs an image with full colors.

Low-pass filter

If high-frequency light passes through the sensor, it can produce some parts of the image blurry. A low pass filter is used to suppress the frequency of incident light, making the image safe from aliasing.

Aliasing can cause repetitive details in an image such result in a blur. But limiting the light frequency decreases the details in images. Manufactures sharpen the photo to make those seem detailed.

Infrared filter

Infrared light can cause color casts in an image, and the image sensor is very sensitive to infrared light. There is a mirror between the lens and low pass filter to prevent the infrared light from reaching the sensor. This mirror is the infrared filter.

Circuitry

Though every sensor does the same work, these differ in their construction. The two most common sensor type is CCD and CMOS camera sensor. CCD-type sensors collect the charge from each cavity or photo site and transfer the charge from the sensor using a vertical array of light-shielded pixels.

CMOS- type sensors have a signal amplifier at every pixel. It collects the charge from the cavity, then converts the charge into voltage and amplifies it on the pixels. This sensor produces voltage rather than charge like a CCD sensor.

But as it amplifies the charge at every pixel so there could be noise in the image, most of the COMS sensor contains an extra noise reduction circuit.

Pixels

Pixel measures the amount of incident light that falls on it by using a sensitive photodetector. These light or photons causes electron releasing from the silicone, forming charge at the photo site.

Microlenses

Micro lenses are a very important part of the sensor. It increases the sensitivity of the sensor by funneling the light into the pixels. The circuits of the sensor take a portion of every pixel, so micro lenses funnel the light in, and the light does not get affected by the circuits.

All these components work together to convert the light information into a digital image.

How Does A Digital Camera Sensor Work?

A digital camera doesn’t even take a whole millisecond to capture an image, but within this short time, it completes many tasks. The camera sensor itself performs the primary operations.

What it does is capture the incident light and convert the light into digital form. That’s it, but the process of doing it is not very simple.

When you press the camera’s shutter button, the cavities of the sensor get exposed to light. There are millions of pixels in a sensor, and the pixel numbers of a sensor are the same as the cavities, and these cavities are called photo sites.

The photo sites are light-sensitive, and this part of the sensor captures the light. When the camera’s shutter button is pressed, these photo sites are exposed to light and closes upon ending the exposure.

Between this short exposure time, light hits the photo sites, and the photo sites produce a little electrical charge or signal.

The longer the exposure time will be, the greater amount of light will hit the photo sites. The same goes for the brighter light, which means bright lighting conditions allow more photons to hit the photo sites.

The more photons hit the photo sites, the more electrical signal will produce and the sharper the image will be.

So, each pixel photo sites will produce a different amount of electrical signal. The camera will measure these signals, and the measured result will be further converted into a digital value using an analog to digital converter. The resultant value is what we call an image.

As the photo sites cannot see color so the electrical signal can be converted, noting but in a grey scale. So, the image sensor uses an array of color filters to detect the color. The most common type of array color filter is the Bayer filter array.

On top of each photo site, there is this Bayer filter. One-fourth of a pixel measures red color, another one-fourth measures the blue color, and half of a pixel measures the green color. Each pixel can capture only one color.

The blue filter captures blue, red captured red, and green captures green color. The light that does not match the filter color gets bounced. That means we lose two-third of the indecent light for capturing each color so, the brightness of an image is three times more than the color resolution.

Each photo site captures one light color, and then the camera guesses the other two colors preset in that light. Overall, the camera now interpolates the color signal from all neighboring pixels and calculates the complete color value for each pixel.

The color information from all pixels is stitched together, and that makes a digital image.

Read next: How to read a camera lens

Frequently Asked Question (FAQ)

How can the camera sensor see the light?

The digital camera sensor has millions of photo sites that are light-sensitive. When the camera’s shutter button is pressed, these photo sites are exposed to light, capturing the light(photon) that hit these.

How does the sensor capture an image?

When light hits the sensor cavities, it creates an electrical signal. The camera sensor measures the information and converts those data into a digital form. Then, it stitched all these digital data together, and that results in an image.

Final Words

Capturing an image is not a big deal. But the process that goes on inside the camera sensor is not simple at all. Hopefully, this guide will give you a good idea of how does a digital camera sensor work.

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