Overview
Area-scan cameras are a category of industrial cameras widely used in machine vision applications. They use a continuous, two-dimensional scan to acquire a complete image of a target in a single exposure, enabling timely image capture for inspection and analysis.
1. Imaging
Area-scan imaging captures 2D scenes by exposing a matrix of pixels simultaneously, producing a full-frame image that represents the spatial distribution of incoming light across the sensor.
2. Classification
Area-scan cameras can be classified in two main ways:
- By sensor type: CCD cameras and CMOS cameras.
- By image-sensor architecture or charge-transfer arrangement: interline transfer, frame transfer, line transfer, and full-frame transfer.
3. Key Parameters
- Exposure time: The time interval from shutter opening to closing during which pixels collect photons.
- Pixel size: The physical dimension of an individual pixel on the sensor.
- Array size: The number of pixels contained in the sensor, typically expressed as width × height.
- Frame rate: The number of images output by the camera per second.
- Quantum efficiency: The ratio, at a specific wavelength, of the average number of photoelectrons generated per unit time to the number of incident photons; an indicator of photoelectric conversion capability.
- Readout rate: Describes how fast pixel data can be read from the sensor. Commonly specified as full-frame readout rate and the maximum readout rate achievable using partial or parallel readout.
4. Industry Applications
- Electronics manufacturing
- Food and pharmaceutical production
- Logistics and parcel sorting
- Printing and textiles
- Automotive manufacturing
- Renewable energy
5. Use Cases
5.1 Positioning and Measurement
Area-scan cameras provide precise and efficient localization of geometric elements within an image.
- Robust template-matching tools that tolerate translation, rotation, scaling, and lighting variations.
- Fast and accurate detection of circles, lines, spots, edges, vertices, and other geometric features.
- Precise measurement of shape, dimensions, area, distance, angle, intersections, and other geometric properties.
- Provide positional and presence information for robot guidance and other vision tools.
5.2 Defect Detection
Area-scan cameras are used to detect surface, shape, and contour defects on workpieces.
- Deep learning-based methods can detect fine surface scratches and spots, and can be robust to surface texture, color, and noise interference.
- Accurate detection of morphological and contour defects, overcoming burrs, color variations, and noise.
- Reliable comparison tools for standard parts to locate small deviations.
6. Advantages and Limitations
Advantages
- Wide range of applications, including measurement of area, shape, size, position, and in some cases temperature.
- Provides intuitive measurement images and rich two-dimensional visual information.
Limitations
- High total pixel counts and relatively limited pixels per row compared with line-scan sensors can restrict achievable frame rates.
- Due to manufacturing and sensor-size constraints, a single area sensor may not meet the field-of-view requirements of some industrial measurements without additional optics or multiple sensors.
