Image Signal Processing : Insights into Image Enhancement Techniques

image signal processing

Low-light enhancement, high dynamic range (HDR) operation, accurate color reproduction, high frame rates, and capability over a broad spectrum of temperatures with few slowdowns are key desirable qualities of digital cameras. The camera’s integrated architecture, which consists of a lens, an image sensor array, an image signal processor (ISP), and interface electronics, can implement these characteristics. 

The act of taking light out from camera sensor and turning it into high-quality images represents one of the crucial yet challenging processes. For the detection and identification of objects employing color features, including such traffic signs or traffic lights, consistent color reproduction is essential. Through the use of a Bayer (red, green, blue) colour filter array (CFA) on the pixel array, automotive image sensors are capable of generating images in full colour. Demosaicing and automated white balance (AWB) are examples of colour processing that can be done on an ISP when any image sensor array has a Bayer filter. This ISP may be offered as a companion chip or integrated into the image sensor chip. The ISP needs to be calibrated and tuned for appropriate colour reproduction. 

Image Enhancements Techniques

The ability of camera sensors to capture high-quality images under various situations is frequently constrained by cost. Traditional methods to enhance image quality could generate noise and motion blurs, making them less helpful even with current cameras. As a result, image processing algorithms improve images in real-time and under various circumstances. There are numerous image-processing methods for different uses. 

  • Low light enhancement 
  • High dynamic range 
  • Software image pipeline. 

Low Light Enhancement

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A low-noise image sensor array with a low-aperture lens can be used to achieve better low-light performance. It is necessary for functioning in evening or night-time situations. Large pixels generally provide high sensitivity. Therefore, more pixels will lead to a lower resolution for a particular size of the image sensor. A low aperture lens will offer a lower throughput than a large aperture lens from an optical standpoint. However, for high-resolution image processing at low aperture, lenses with several components or aspherical faces may be used. 

High Dynamic Range

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Imaging both bright and dark areas in a single frame without overexposing or underexposing is possible with high dynamic range operation. HDR is essential when the sun is shining in the sky throughout the day or in situations like entering and exiting tunnels. An attribute of the image sensor array is HDR. Therefore, it is important to design the multi-element lens, surface optical coatings, and lens barrel carefully to reduce stray light which might come from strong light sources and reduce the dynamic range of the final image. 

HDR is achieved by either integrating an imaging sensor that inherently has a higher Dynamic Range in terms of 120dB or higher. We can also achieve a wide dynamic range camera by combining the sensor with a Image Signal Processor that is capable of Fusion HDR or Multi-Exposure HDR.

Image Signal Processor (ISP) 

A RAW image from the sensor must undergo extensive processing in order to be transformed into a high-quality image, therefore, ISP is used in this situation. The front-end image sensor’s signal must undergo post-processing, including noise reduction and HDR correction, by the ISP. The ISP is also capable of implementing features like automatic scene identification and face recognition. 

Image Signal Processor Tuning 

In order to generate a high-quality image for a specific camera sensor and use-case, the ISP completes many of the following actions: 

Auto White Balance

To balance the colours and guarantee proper colour constancy in the camera-captured image, ISP utilizes colour correction matrices. 

Auto Exposure 

ISP promises the ability to automatically adjust image brightness in accordance with the amount of light that passes through the camera sensor. 

Auto Focus 

The image’s sharpness is automatically adjusted via auto focus, which enhances the detail of the image. Various actuator forms, lens position adjustments, AF stats engine adjustments, etc. 

Lens Shading Adjustment 

To enhance brightness and color non-uniformity through the edge of the image, lens shading adjustment is used. 

Noise Reduction 

During the image collection process, digital images are vulnerable to a variety of disturbances that cause a rapid change in pixel values which do not accurately depict the true values of the actual scene. Image data is subjected to denoising algorithms, which remove noise produced based on the behavior and kind of data as well as provide clear images. 

Gamma Correction 

Gamma correction adjusts for output displays’ highly nonlinear of intensity level as the value of the frame buffer varies. 

Local Tone Mapping 

In order to boost the local contrast in various sections of an HDR scene, local tone mapping blends many exposures. 

Demosaicing 

The raw image, which is commonly taken using a Bayer colour filter array (CFA), is converted into a colour RGB image upon acquiring Bayer inputs from the image sensor. Some other name for this procedure is demosaicing.

Summing Up

By precise selection of materials, high-density fine pattern technology, thermal/stress measurement, and noise/electromagnetic field study, we have attained automotive-grade value of electronic circuit for the camera module. Due to our unique mechanical design, optical design, and technical elements, we are able to provide premium camera modules with much more precise and steady lens quality. Our unique image control technology helps us achieve better color reproducibility. We will continue to work on developing cameras with improved image sensors. 

Each camera sensor differs significantly and has unique characteristics. Depending on need and applications, camera designs and output image characteristics also vary. To provide the ideal output image for a specific setting, the image signal processor must be customized to these variations. With the help of our service, you can choose the appropriate product for your necessities. Vadzo offers camera solutions for a broad range of sectors, including electrical, industrial, medical, retail, fleet management, asset management, smart homes, and kiosks. Among the services we offer are scanners, CCTV, CCD/CMOS, medical imaging, surveillance systems, machine vision, and night vision equipment. Moreover, we provide ISP optimization for many different sensors, Processor cores, and use cases. 

Do not hesitate to ask your inquiry! Reach out to us.

 

Cheers

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