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A wide-band and high-sensitivity SWIR image sensor technology implemented by the combination of compound semiconductor InGaAs photodiodes and Si readout circuits through Cu-Cu bonding.

Creating SWIR sensors with smaller pixels than in current industrial CMOS sensors has been challenging with conventional bump bonding, because a certain bump pitch must be maintained to bond the indium-gallium-arsenide (InGaAs) photodiode layer to the silicon readout circuit layer. With SenSWIR technology, copper-to-copper connection*1 enables a finer pixel pitch and smaller pixels. As a result, smaller high-resolution cameras can be developed, which can support higher inspection precision.

The top indium-phosphorus (InP*2) layer inevitably absorbs some visible light, but applying Sony SWIR sensor technology makes this layer thinner, so that more light reaches the underlying InGaAs layer. The sensors have high quantum efficiency even in visible wavelengths. This enables broad imaging of wavelengths from 0.4 μm to 1.7 μm. A single camera equipped with the sensor can now cover both visible light and the SWIR spectrum, which previously required separate cameras. This results in lower system costs. Image processing is also less intensive, which accelerates inspection. These advances promise to expand the scope of inspection significantly.

• *2：Substrate that forms the base of the InGaAs layer.

SWIR, Short Wavelength Infra-Red, refers to a type of infrared light. SWIR wavelengths generally lie in the range of 0.9–2.5 μm. Though in the infrared spectrum, they are near wavelengths of visible light. IMX990 and IMX991 sensors cover SWIR wavelengths up to 1.7 μm. Imaging by the sensors also extends to wavelengths of visible light, which has proven difficult for conventional SWIR sensors to capture.

Light in the SWIR band includes wavelengths that reveal water absorption. Imaging in these wavelengths enables detection of moisture content, which is difficult to determine under visible light. This is used in applications such as sorting fruits and vegetables.
(Photos: Detecting bruises on apples)

Properties of light absorption and reflection in SWIR imaging are applied to distinguish substances that would be difficult to differentiate under visible light alone.
This is used in applications such as inspecting products for foreign material.

Light in the SWIR band passes through material made of silicon. This aspect of SWIR imaging is applied in semiconductor production and inspection.
(Photo: A silicon wafer in front of a chart)

Around hot objects, light in the SWIR band shines quite brightly. Temperature can be estimated from differences in brightness among several wavelengths. This is used to estimate the temperature of welds or other hot areas.
(Photo: Detecting the hot portion of a solder tip)

Light in the SWIR band has longer wavelengths than visible light. This makes the light less susceptible to scattering, which is an aspect of SWIR imaging that is applied in remote observation.

SWIR sensors that extend to the visible spectrum
Sony offers two types of SWIR sensors for imaging at both SWIR wavelengths and the visible spectrum.