What Is Push-Broom Imaging

Push-broom imaging is a specialised scanning technique used in remote sensing and spectral imaging systems. Unlike conventional frame-based imaging systems that capture entire scenes at once, push-broom sensors collect data one line at a time as the sensor platform moves forward, similar to how a broom pushes debris as it moves across a floor. This linear scanning approach creates high-resolution images by building them line by line. When combined with spectral capabilities, this technique becomes push broom hyperspectral imaging, which can capture hundreds of narrow, contiguous spectral bands for each pixel in the scanned line.

How Push-Broom Imaging Works

In a push-broom scanner, a linear array of detectors is mounted perpendicular to the direction of the platform’s movement. As the platform (satellite, aircraft, or ground vehicle) moves forward, the scanner captures a continuous strip of imagery. Each detector in the array collects data for a single pixel in the cross-track direction, whilst the forward motion provides data collection in the along-track direction.

Modern systems may feature automatic push broom capabilities, where computerised systems control the scanning process without manual intervention. These systems optimise scan rates, adjust for platform speed variations, and automatically process collected data, significantly enhancing operational efficiency.

The key components typically include:

1. A linear detector array (typically CCD or CMOS)
2. Specialised optics to focus light onto the detectors
3. A dispersive element (in spectral systems) to separate light into different wavelengths
4. Data processing systems to compile the line scans into complete images

Applications of Push-Broom Imaging

Push-broom imaging technology has found applications across numerous industries and scientific disciplines:

• Environmental monitoring: Tracking changes in vegetation health, water quality, and land use over time
• Agriculture: Precision farming applications including crop health assessment, stress detection, and yield prediction
• Mineral exploration: Identifying mineral deposits through their unique spectral signatures
• Infrastructure inspection: Examining roads, railways, and pipelines for defects or damage
• Defence and security: Surveillance, target detection, and camouflage penetration
• Food quality control: Detecting contaminants, assessing freshness, and ensuring product uniformity

Companies have pioneered adaptations of this technology to offer potential solutions in quality control, where their systems may detect material anomalies invisible to conventional imaging. Their implementation of automatic push broom capabilities has shown promise for production line integration, potentially enabling real-time analysis. Living Optics’ hyperspectral imaging technology provides additional insights for quality assurance workflows as it enables to monitor changes in samples as it moves.

The ability to capture detailed spatial and spectral information simultaneously makes this technology particularly valuable for applications requiring both high resolution and material identification capabilities.

Comparison with Other Imaging Techniques

When compared to alternative imaging methodologies, push-broom scanning offers several distinct advantages:

Feature	Push-Broom Imaging	Whiskbroom Scanning	Frame-Based Imaging
Data collection	Line by line	Point by point	Full frame
Spatial resolution	High	High	Moderate
Integration time	Longer	Short	Short
Mechanical complexity	Moderate	High	Low
Signal-to-noise ratio	Higher	Lower	Varies
Motion compensation	Required	Required	Less critical

The most significant advantages of push-broom systems include higher light sensitivity (due to longer dwell times per pixel), better geometric integrity (with no moving parts in the optical path), and superior spectral fidelity when used in hyperspectral applications.

However, these systems do present challenges including the need for precise platform movement, complex calibration requirements, and sophisticated data processing to handle the large volumes of information collected.

Frequently Asked Questions

What’s the difference between push-broom and whiskbroom scanners? 

Push-broom scanners use a line of detectors to capture an entire line of an image simultaneously, while whiskbroom scanners use a single detector with a moving mirror to scan across each line point by point.

How does push-broom imaging relate to hyperspectral imaging? 

Push broom hyperspectral imaging combines the line-scanning approach with spectral decomposition, allowing each pixel to contain information from many wavelength bands. This creates a data cube with two spatial dimensions and one spectral dimension.

What resolution can be achieved with push-broom technology? 

Resolution depends on the detector array specifications, platform altitude/distance, and optical design. Modern systems can achieve sub-metre spatial resolution from aerial platforms and several metres from satellite altitudes.

Does push-broom imaging work in low-light conditions? 

Due to its longer integration time per pixel compared to whiskbroom scanners, push-broom systems generally perform better in low-light conditions, though they still require adequate illumination of the target.