The structure of the newly-developed image sensor (source: IEDM)
[Click to enlarge image]

Olympus Corp developed a device by integrating a color visible-light image sensor and a near-infrared image sensor.

Olympus used a lamination technique to stack them. The company made this announcement Dec 9, 2015, at IEDM 2015 (thesis number 30.1).

The device is expected to be used for (1) medical purposes such as examination of veins under skin with a near-infrared sensor and pathological examination of living tissues with a fluorescent material, (2) security applications such as vein authentication and (3) distance measurement based on the time difference between irradiation and reception of infrared light.

The laminated image sensor is made by combining (1) an image sensor equipped with an RGB color filter for visible light (top layer) and (2) a near-infrared image sensor (bottom layer). Each layer functions as an independent sensor and independently outputs video signals.

The visible-light image sensor is a backside-illuminated type, and its light-receiving layer (made of semiconductor) is as thin as 3μm. Each pixel measures 3.8 x 3.8μm, and the number of pixels is 4,224 x 240.

One of the concerns about such a laminated type is that infrared light becomes a noise for visible-light images. In many cases, conventional visible-light image sensors remove the influence of infrared light on visible-light images by using an infrared filter.

This time, Olympus dispelled such concerns by reconstituting visible-light images without infrared components based on signals output from the top and bottom layers, the company said.