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JAI color line scan technology

JAI’s color line scan cameras are easy-to-use multi-sensor cameras providing extremely precise color imaging ideal in many industrial line scan inspection applications such as fruit/vegetable sorting, food inspection, 2D/3D print inspection and web inspection.

The camera technology features a built-in light beam splitter prism and multiple sensors, making is possible to detect the red, green, blue and near Infrared light spectrum bands in up to four separate channels simultaneously.

Prism-based color line scan technology:
JAI’s prism-based line scan technology has a number of advantages compared to other line scan camera technologies available on the market such as tri-linear and dual-line technology.

The prism-block technology in JAI’s cameras enables users to avoid the complex alignment and image synchronization issues associated with tri-linear line scan cameras, especially in applications with off-axis viewing, variations in conveyor speeds, surface undulations, or applications where objects roll or move as they pass through the camera’s field of view.

Because JAI’s prism-based camera solutions have a common optical path there is no need to compensate for angle, rotation, speed, waviness, object motion, or other variables present in industrial inspection tasks.

As the diagram above illustrates, when inspecting undulating objects, non-flat objects or if the camera is positioned off-axis, tri-linear technology (left) gives different magnification for the spectral bands resulting in distorted color registration and unwanted halo effects! JAI's prism-based line scan technology (right) utilizes a common optical path for all sensors and precise co-site alignment to eliminate haloing, regardless of the viewing angle.

The cameras deliver high quality and perfectly aligned line scan images independent of the viewing angle to the inspected object, independent of variations on conveyer belt speed and independent of the object’s topology (i.e the object has a wavy or curved texture which is the case e.g. with inspection of cylindrical objects and fruit).

This makes inspection systems built with JAI’s prism-based cameras faster and easier for end-users to setup, calibrate and maintain, offering precise image alignment and precise color registration.

Dichroic coatings on the prism glass surfaces:
To be able to detect the different colors in the light spectrum on separate CCD sensors (or CMOS sensors depending on camera type) the light must first be split into red, green, blue and near infrared wavelengths using a specially designed built-in prism. This prism is treated with dichroic coatings on the glass surfaces.

The different properties of the coatings, allows the light to pass through or be reflected by the different glass surfaces in the prism. The drawing below shows how the coatings work:

A): Glass surface reflects blue light. Red and green light transmit fully through the prism coating.
B): Glass surface reflects red light. Green color transmits fully through the prism coating.
C) and D): One-way reflective prism coating.
 
Precise wavelength cutoffs for higher color precision:
JAI’s prism cameras use hard dichroic coatings on the prism to split the incoming light by wavelengths

The dichroic coatings ensure more precise wavelength cutoffs (steeper spectral curves) than can be provided with other line scan technologies such as tri-linear technology that uses conventional polymer dye color filters affixed to the sensors.

JAI’s line scan technology therefore provides less ambiguity where colors overlap (“color crosstalk”), for crisper color representations.

Hard dichroic prism coatings produce steep spectral curves with little overlap for high color precision Soft polymer dyes in tri-linear filters produce much greater overlap causing uncertainty in color values


Pixel-to-pixel (co-site sampling) accuracy:

JAI uses an extremely precise manufacturing process to align the three or four prism-mounted sensors. The prisms are aligned with sub-pixel accuracy providing a level of precision (co-site sampling) that’s not possible with two separate cameras. This pixel-to-pixel accuracy ensures both color precision and spatial precision for better edge detection and the ability to discern smaller details.

Individual RGB exposure control
Unlike tri-linear cameras and even other prism cameras, JAI’s color line scan cameras offer individual electronic shutter control for each of the sensor channels. This means that white balancing the camera for proper color representation does not have to be done by boosting the gain of the deficient color channel(s). Instead, providing there is sufficient lighting, white balancing can be performed by adjusting shutter speeds, thereby avoiding gain adjustments and the possibility of introducing extra noise in the image.

Typical applications:
JAI’s line scan cameras can be used in a number of industries where automated inspection with line scan camera technology is most suitable:

  • Fruit and vegetable sorting. Inspecting colors, ripeness, damages, signs for early decay and foreign objects (e.g. stones, leafs etc).
  • Food inspection (e.g. frozen food, rice grains, coffee beans, peas, cereals, tea and tobacco).
  • Web inspection (textiles, paper, glass).
  • Wood inspection (looking for wood structures like knots, grain and color to be able to make correct cuttings and sorting in different qualities).
  • Tiles inspection (inspection of colors variations and imperfections in glaze).
  • 2D print inspection - magazines and currency. (Currency: simultaneous inspection of color correctness, water marks and security features woven into the bank notes).
  • 3D print inspection (inspection of labels on cylindrical items like cans, bottles, pens etc. or rotating objects).
  • Mechanical parts inspection to look for scratches/blemishes.
  • Surface inspection of flat panels/displays looking for scratches and defective screen pixels.
  • Raw cotton sorting (sorting for color variations, foreign objects etc.)
  • Paint coat applications (e.g. checking color correctness, that paint has been applied evenly on the car body, and checking for a flawless surface).
  • PCB inspection (inspecting for imperfections in circuit layout etc.).

JAI line scan cameras:
JAI has a family of prism-based color line scan cameras. More information is available on the following product pages:

LQ-200CL (4-CCD RGB + NIR camera)
LT-200CL (3-CMOS RGB camera)
 
LT-400CL (3-CMOS RGB camera)
CV-L107CL (3-CCD RGB camera)
CV-L108CL (3-CCD RGB camera)

Technology customization:
JAI is in full control of the prism assembly process making JAI capable of offering customized spectral light filter prism coatings for specific inspection applications. This customization service is offered, if the project is economically feasible to all business partners.

More information:
For more information about prism-based color line scan technology and products, please contact JAI.

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