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UV Coating of Sensors

In order to extend the usable spectral region of the sensors, these can be provided with a specialized coating. In the case of applications with UV light this coating emits visible light, which can be detected by the sensor. Such a coating lowers the lower end of the spectral sensitivity from 350nm down to 100nm.

Starting from 480nm the coating is almost transparency, so that sensitivity in the visible and in the near infrared is hardly affected. For such an UV coating above all sensors with large pixels are suitable. Some often requested sensors can be supplied with UV coating from stock (see table below). For other sensors this is possible on request.

Eureca developed a new method for applying such a coating on image sensors in a three-year research project. The development was supported by the Central Innovation Program of the Mittelstand (ZIM). (Supported by the Federal Ministry of Economics and Energy due to a decision of the German Bundestag)

The core of the technique is a dye called Lumigen, that greenly fluoresces under UV light and makes usually invisible radiation capturable by standard CCD and CMOS sensors. For high-end applications such as precise spectroscopes a very homogeneous coating of the light-sensitive sensors is necessary – a quality which is not provided by manual work as there is also a danger of damages of contacts and surfaces.

The method developed by Eureca thus uses a modified physical vapour deposition method (PVD), that works contactless and enables reproducible uniform layer thicknesses. For this, the cover glass of the sensor is removed carefully with a method adjusted to the sensor and the sensor itself is cleaned. Then it is put on a special holder into the vacuum chamber in which the lumigen is deposited homogeneously. After this the sensor is either equipped with a protective foil or a new window is glued on according the the needs of the customer.

By adjusting the process parameters an optimized layer for the specific application is produced. Thicker layers e.g lead to more dispersion of the incoming light and can thus reduce interferences. This also applies to the coating of microlenses whose surface properties are a challenge for a good and homogeneous layer. For this purpose the company also reasearched methods for layer analysis.

In general this process expands the usable spectral range of image sensors at the short-waved side from 400nm down to 200nm, in ideal settings even down to 100nm. Above 500nm the material is nearly tranparent, so the sensitivity in the visual and infrared wavelength area nearly stays the same. The lifetime of the coating depends on the intensity of the radiation, its wavelengths, the temperatures at which the sensors are used and the exposition times. Experiences with established spectrometers have indicated that with the short arcs used there the coating works for serveral years without problems.

While UV intensivation via lumigen is generally suitable for various kinds of sensors, it is mostly used for line sensors, especially for spectrometers. For this application sensors with oblong pixels are preferred. The coating method developed by Eureca works independently of the kind and geometry of the sensor and is thus suitable for nearly all sensors available on the market.

Eureca already has a variety of different sensor types in the delivery range, other types can be coated on request. You can find a list of sensors, which are coated regularly, below.

Type Manufacturer Pixel Number Pixel Size
Data Rate
fps or Pixel Frequency
ICX098BL-UV Sony 659 x 494 5,6 x 5,6 60 fps
ICX414AL-UV Sony 692 x 504 9,9 x 9,9
ICX424AL-UV Sony 692 x 504 7,4 x 7,4
ILX554B-UV Sony 2048 14,0 x 56,0 2 MHz
ELIS-1024-UV Dynamax 1024 7,8 x 125,0 30 MHz
TCD1205DG-UV Toshiba 2048 14,0 x 200,0 2 MHz
TCD1304DG-UV Toshiba 3648 8,0 x 200,0 1 MHz

illustration example for effective quantum efficiency of a front side illuminated CCD

Example for effective quantum efficiency of a UV coated front side illuminated CCD

You can find closer information about this topic in our PDF document UV coating for image sensors.

Page updated at: 08/23/2016