Multi sensor Prism based line scan cameras

Multi-sensor prism-based line scan cameras play a key role in high-precision color inspection. Explore how this technology works, when to use it, and the advantages it offers over other line scan technologies, especially in applications demanding accurate color reproduction and stable imaging performance.

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What is a multi-sensor, prism line scan camera?

In a multi sensor prism-based line scan camera, every individual light ray follows a single optical path. In other words, they take one line at a time and split this internally, so that all three color channels are derived from the same line capture. So, even if objects change in orientation, the single optical path in prism cameras ensures that each pixel on each sensor is focused on exactly the same point at the same time.

Separation of light inside a prism block.

When to choose a multi-sensor, prism line scan camera?

Multi-sensor, prism-based line scan cameras are often the preferred choice for applications that require the highest levels of color accuracy and long-term stability. By separating incoming light into RGB channels using a prism and capturing all three channels simultaneously on independent sensors, these cameras eliminate spatial offset between color channels.

This design ensures reliable color reproduction even in challenging conditions, such as angled camera setups, varying conveyor speeds, or applications where the inspected web may exhibit ripples or changes in orientation. In contrast, single-sensor bilinear or trilinear cameras rely on spatially offset lines, which can introduce color artifacts if motion or alignment is not perfectly controlled.

Prism-based systems also provide greater flexibility in color calibration. Because each color channel is captured on a dedicated sensor, white balancing can be achieved through exposure adjustments rather than relying primarily on gain. This approach can help maintain low noise levels and consistent image quality, particularly in demanding inspection environments.

In addition, dichroic prism optics typically offer higher optical efficiency compared to color filter-based designs. This allows more effective use of available light, enabling lower illumination intensity while still achieving reliable signal levels. The optical properties of prism systems are also inherently stable over time, supporting consistent performance in long-term industrial operation.

What are the advantages of prism cameras for color line scan applications?

Precise RGB alignment without spatial offset: Dichroic prism-based cameras split incoming light into red, green, and blue channels and direct them onto separate sensors, all aligned on a common optical axis. This ensures that each channel captures the exact same point at the same time, eliminating line-gap compensation required in bilinear or trilinear designs.
Accurate multi-channel registration: Precise sensor alignment ensures exact R, G, B (and NIR/SWIR, if applicable) channel registration, eliminating color artifacts such as halo (HOLO) effects.
Reduced readout noise: Advanced sensor features such as floating diffusion binning increase signal strength while requiring only a single readout, improving image quality and signal-to-noise ratio.
Independent exposure control per channel: Dedicated sensors for each color channel allow individual exposure adjustment, enabling optimized signal-to-noise ratio and improved image quality compared to gain-based balancing methods.
Integrated color processing: Built-in color space conversion delivers image data directly in the required output format, simplifying system integration and reducing downstream processing.
Precise waveband separation: The sharp spectral characteristics of the prism minimize channel overlap, enabling accurate color separation and supporting parallel multi-light-source inspections.

Want to know more about the advantages of prism-based cameras for color line scan applications?

Watch our on-demand webinar to learn more about the advantages of prism-based cameras for color line scan applications.

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For which applications are multi sensor prism based line scan cameras most suitable?

Multi-sensor, prism-based line scan cameras are often the preferred choice for applications that require the highest levels of color accuracy and long-term stability.

Steel metal and coin inspection.

Label inspection

"Unwrapping" of cylindrical items such as bottles, cans, pens etc., for 360-degree label inspection

Color sorting and quality inspection

Color sorting and quality inspection of jelly bears.

Print inspection of bank notes

Sorting of lumber

Sorting of lumber by color and grain pattern, color matching on laminates and other flooring products.

Sorting of vegetables

Sorting and quality of carrots, potatoes and other vegetables.

Food sorting

Inspection and separation

Inspection and separation of valuable mineral ores from waste rock.

Sorting and inspection

Sorting and inspection in recycling and waste streams.

How can you improve Free-Fall Food Sorting with Prism-Based Line Scan Cameras?

When objects roll and move randomly leading to slight changes in orientation and position, that can be challenging for image capture.

In the case of trilinear cameras, the sensor consists of three lines – one per color channel – which are spatially distributed in the direction of scan. This arrangement means color information from a specific line on the target is captured at three separate points in time and then added together by an algorithm inside the camera. This spatial compensation algorithm is not able to account for changes in orientation of the object that may occur between the three line captures, resulting in image distortion or color fringes known as the halo effect.

On the other hand, in a prism-based line scan camera, every individual light ray follows a single optical path. In other words, they take one line at a time and split this internally, so that all three color channels are derived from the same line capture. So, even if objects change in orientation, the single optical path in prism cameras ensures that each pixel on each sensor is focused on exactly the same point at the same time.

Complete Inspection Data from One Camera

Find the best camera for your needs

Prism-based line scan technology is particularly well suited for high-speed, continuous inspection tasks. The Sweep+ Series includes advanced prism-based line scan cameras available in 3-sensor RGB and 4-sensor RGB + NIR or RGB + SWIR configurations, designed for high-performance industrial inspection. By using a dichroic prism to split incoming light onto multiple precisely aligned sensors, these cameras capture true color and multispectral image data simultaneously through a single optical path. These camera models are the preferred choice when maximum color accuracy, multispectral capability, and stable imaging under dynamic conditions are required, particularly in high-speed or complex inspection setups where conventional line scan approaches may fall short.

Sweep+ Series

Multi-sensor prism-based line scan cameras combining color precision, sensitivity and NIR or SWIR multispectral options.

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