Last Updated on October 22, 2023 by Kevin Chen
Image source: Support Articles
We are in the digital era where image matters. Billions of images are posted everyday on various web platforms. In fact, image has evolved to be a critical format of passing messages.
But, have you ever thought of the process of getting that image to the form that it is? How is an average camera able to capture a clear and image?
Well, it is all about image processing.
And hat does the job? An image signal processor.
There is a massive technology behind the image signal processing phenomenon.
In this guide, we are going to look at everything you should know about ISP.
If you are in the business of building products that will involve image processing, you will find this guide useful.
At the end of it, you will be in a perfect position to buy the right image signal processor for your application.
What is image signal processing?
Image processing is a special type of signal processing that entails processing an image by manipulating its individual pixels.
It includes deploying various techniques that are aimed at extracting and improving various characteristics of an image.
The processing can encompass activities such as image recognition, noise reduction, edge extraction, image enhancement among many others.
What is an image signal processor?
Now that you know what processing is, let’s discuss the processor.
An image signal processor (ISP) is a type processor designed to process data and signals for digital images.
It is not only limited to the static images but also videos.
The processor is mainly designed for the digital cameras as they are heavily involved with capturing images and videos.
Smartphones, tablets, and computers are other devices that heavily rely on the ISPs.
Once the camera is ready for action, the processor will collect all the relevant data about the image and processes them to be more useful.
Image enhancement, stabilization and noise reduction are just some of the core activities of the image processors.
Also, the processor can perform data management activities of the raw data that it collects from the image.
For example, it can convert the raw data into a form that can be easily processed by the camera.
It can also store and transfer the data into their party devices where they can be more useful. For example, when you are doing a livestream, the image will have to be processed before being transmitted to the target livestream platform that you are using.
Thus explains why the whole smartphone camera system is backed by a powerful image signal processor.
Image signal processor working principle
How does an image signal processor work and ho is it able to execute its functions?
Well, there is a lot that goes on in the background of the image processing.
Image source: Path Partner
First, let’s look at the basic terminologies behind image processors.
-Raw image: A raw image is basically an uncompressed image file. It is the image that has been taken by the camera and nothing has been done on it. It has not yet been processed hence has all the images that still needs some work to be done.
Bayer pattern: The bayer pattern refers to the array of arranging RGB color filters on a grid photo sensors. The arrangement on the square grid mainly focuses on the red, green and blue colors and they filter above the millions of light-sensitive sensor chip.
YUV image: YUV refers to a color-encoding system that is usually encased to be part of the image pipeline. The system is designed to encode the color image hence allowing a reduced bandwidth for the chrominance components.
–CMOS sensor: This is a sensor powered by the complimentary metal oxide source. It comprises of pixel arrays whereby each pixel has an active amplifier and a photo detector. It is used on most digital cameras, especially the ones found in smartphones, web cams and CCTVs.
-Image sensor: In the spectrum of image signal processing, an image sensor is a device that captures a ray of light that strikes on the lens and converts it into electronic signals. It then transmits the signals to an imaging device processor whereby the signals are further transformed into a digital image.
Auto-exposure (AE) and Auto-white balance(AWB): This is a feature or technology that automatically detect the changing light quality and ambiance of a scene that you are photographing or imaging.
-Image signal processing pipeline: This refers to a method of converting an image into digital form. The goal of this pipeline is to ensure that you get a high-quality image.
How the sensor works
Now that you know the basic terms, let’s look at how a typical image sensor processor works.
Image processing by the sensor starts at the point of capturing, where the camera captures the image. The sensor will capture the raw data.
This data will then be processed by an algorithm that is embedded on the the sensor. This algorithm is installed at the point of manufacturing the sensor and determines the actions that the sensor will take on an image during the image processing.
The algorithm will perform various processing techniques such as noise reduction,white balancing, color correction, color-encoding and other enhancements.
Once the image has been processed, it will be converted into a form that can be displayed on the target device or even user.
Keep in mind that the same algorithm is designed to work on the video output. It can perform functions such as encoding, buffering, resolution management and frame rate management.
Other than working on the image an image signal processor performs some power management actions. It ensures that there is right utilization of power during the processing. It also minimizes the incidences of overheating.
How is the image signal processor able to execute these functions?
It is all about the components that make up the image signal processor and how they work together to achieve the intended goal.
The processor is made up of various components such as microcontroller, memory controller among many other hardware electronic components.
The microcontroller is the most important component of an image signal processor. Its work is to control various components and executes the algorithms required for image processing.
On the other hand, the memory controller is responsible for the memory management. It manages issues such as buffering and how the raw data is stored during the processing. This controller is always in communication with the device’s memory.
There are other hardware electronic components such as actuators, transistors among others.
Main functions of image signal processors
From the working principle, it is easy to tell the functions of the image signal processors. These functions include the following.
This is among the very basic functions of the ISP. It helps to eliminate noise from the image. Noise in this context refers to the unwanted elements that are within the image. They include the unwanted speckles that tend to form on the scene and can cause some level of interference.
The signal processor filters these elements so that at the end of the day you have a sharp and clear image.
The ISP uses an array of techniques to achieve this goal. These methods include application of the spatial filters, frequency filters and even temporal filters. Each of this filters is designed to work on a specific type of noise. A spatial filter will work on the spatial noise while the temporal filter will work on the temporal noise.
Image enhancement refers to the process of improving the outlook of an image. It makes the image look better than its raw form.
Image enhancement increases the contrast of an image by sharpening its edges. This image processing technique can be achieved by adjusting the brightness and coloration of the image.
Advanced image signal processors are capable of detecting and removing the unwanted artifacts from images.
This is quite a common feature in most modern smartphones. It is a technology that can be used to enhance security of a device or even an application. All this is possible because of an image signal processor.
The processor is embedded with advanced algorithms such as machine learning and AI so that it can have the capability of identify the unique aspects of an image and distinguishing it from others.
Some cameras are good at capturing large photos, yet you need smaller digital images maybe for streaming and display.
This is where an image signal processor comes in handy. It is capable of reducing the size of an image without affecting the quality.
Using their algorithms, the processors will eliminate the unwanted data from the image, and that’s why you will still end up with a small-sized image yet it still has the same quality.
Interpolation refers to the process of enhancing the the detail and accuracy of an image. The processor, using its relevant algorithm ensures that every detail of an image comes out without distortion. It uses the surrounding pixels to fill data that may be missing on an image.
Defect pixel correction
The pixels on a raw image may not always be correctly highlighted. It is the function of an image processor to identify these defects and correct them. Using a median filtering algorithm, the processor will analyze each pixel of an image. It will the use its mechanism to ensure that the pixel is corrected.
Other critical functions of image signal processors include lens shading correction, gamma correction, local tone mapping, auto focus and auto exposure.
So, when buying an ISP, inquire about its capabilities or the functions that it can perform. From there, you can tell whether it will suit your application needs.
Image signal processor tuning
Tuning is all all about getting the best results from a device. Image signal processor is also tuned to ensure that it delivers optimal performance when it comes to signal processing of images.
ISP tuning incorporates an array of activities that change the parameters of the processor until you get the best. These actions include the following.
This ranks as the first step of ISP tuning. The process entails adjusting the offset, black level and offset of the processor so that the image can be well exposed.
The gain of the processor determines the amount of light that gets into the sensor while the offset is responsible for controlling the black level of the sensor.
During the calibration, the black level is usually the point at which a processor considers an image to be completely black. So, calibration ensures that the image is not too dark or extremely bright.
Color and image parameters
These two parameters are also considered during the process of ISP tuning. The color temperature, color sharpness and white balance of an image are adjusted. The color temperature adjustment is designed to control the warmth and coolness of an image. Sharpness controls the details of the image while the white balance controls the general color of an image.
Another important aspect of ISP tuning entails adjusting the exposure settings of the processor.
These settings will adjust the shutter, aperture and speed of exposure.
When you adjust the shutter speed, it will determine how long the sensor will be exposed to light. On the other hand, the shutter adjustment will determine how much light gets into the sensor.
In general, exposure settings have a major impact on the quality of the final image.
Even after tuning, you have to test the ISP against several parameters to ensure that it is capable of producing the the desired images. Testing usually involves checking the image quality and sharpness. Does the image meet all these requirements? If not, you will have to redo the tuning.
Now you know all that entails image signal processor. It is an important electronic component used in devices that are used for imaging, photography and videography.
If you are working on the image signal processing projects, you have an idea of what the component will do.
And if you want to buy , ensure you get from reliable image signal processor suppliers in China. This way, you will be sure of getting the right product.
Otherwise, we at ICRFQ will help you find quality ISPs for sale.
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