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technology guidE

sony UV SENSORS

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Applying UV Wavelength-Compatible CMOS Image Sensor to industrial equipment

Growing demand for UV imaging

In the industrial equipment fields, there is high demand for camera-based inspections for a diversity of purposes, and requirements for image sensor performance become increasingly stringent year after year. Against this backdrop, the scope of application for ultraviolet (UV) imaging cameras is expanding. By combining UV lighting and UV-compatible lenses, cameras equipped with UV image sensors can provide special visual information which ordinary cameras for visible light imaging cannot.

Ultraviolet is a spectrum of shorter wavelengths than those of visible light. For this property, it is utilized for detecting minute scratches and other defects that are undetectable in visible light. UV cameras can also identify objects of transparent materials such as plastic and PET, which may not be easily discernible in visible light, as these materials absorb UV rays at different rates. UV imaging thus has a potential for applications such as sorting materials.

The diagram below is a simple illustration of the light spectrum. UV (ultraviolet) is shorter in wavelength, between 10 and 400 nm, than visible light (400–780 nm). IMX487 covers the range between 200–400 nm, which is a segment of UV spectrum that is suitable for industrial use, such as inspections.

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Sony’s UV image sensor technology

High-speed UV imaging enabled by incorporating global shutter function

IMX487, Sony’s latest image sensor with a UV spectrum capability, deploys Pregius S technology, a global shutter pixel technology for active pixel CMOS image sensors designed in our signature back-illuminated pixel structure, enabling it to deliver undistorted images even of fast-moving objects.
The back-illuminated pixel structure offers high flexibility of metal wiring design inside the image sensor, facilitating a high-spec frame rate at 193 fps (when operating in the 10-bit mode). It opens up new applications in areas that demand high speed operations, such as UV-based plastic material sorting at recycling plants.

Design specialized for UV imaging

Quartz glass, which has high UV transmittance, is used for the cover glass of the image sensor while the chip-on lens is also made using a highly-UV-transmissive material, together enabling to deliver the performance dedicated to UV imaging. (Top image in Fig. 2)

The unique light receiving structure specially designed for UV sensing realizes high sensitivity while minimizing noises. (Bottom image in Fig. 2)

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Applications for Sony’s UV image sensors

Defect inspection in semiconductor manufacturing processes

Leveraging the short wavelength property of ultraviolet light, UV cameras can detect defects in minute targets such as semiconductor patterns that cannot be captured in the visible light spectrum. The high-definition image sensor IMX487 realizes both high sensitivity and low noise, enhancing the precision in inspections.

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Sorting of clear plastics, glasses, etc.

While plastics, glasses, and other transparent materials cannot be discerned easily with visible light cameras, UV cameras can be utilized, for example, at recycling plants for the purpose of material sorting, leveraging the varying degrees of UV transmittance of different materials. IMX487 can handle high-speed imaging of, for example, sorting machines by means of the global shutter feature, capable of capturing undistorted images of fast-moving objects.

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Inspection of high voltage power cables for electric discharges

When electric power infrastructure suffers ageing degradation, its power cables may discharge electricity from the damaged part, which would then release ultraviolet radiation. Using UV cameras helps to easily identify deteriorated parts in the power system, making it a possibility to automate, and/or streamline labor costs of, facility maintenance. IMX487 has approximately 8.13 effective megapixels, and this multi-pixel UV image sensor can be deployed outdoor in remote places or for wide-area inspections.

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