Gigahertz Optik GmbH (Headquarter)
Phone: +49 (0)8193-93700-0

Gigahertz-Optik, Inc. (US office)
Phone: +1-978-462-1818


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Image sensor

The testing and characterization of devices such as image sensors, industrial cameras, hyperspectral imaging sensors and optoelectronic detectors requires the use of light sources with highly uniform light distribution. Gigahertz-Optik GmbH produces a wide range of homogenous (uniform) light sources with integrating spheres and LED panels with which the uniformity and performance of image sensors and industrial cameras can be determined. Some application examples are presented on this page.

+49 (8193) 93 700-0

Integrating sphere light sources with continuous emission spectrum

To measure the sensitivity, linearity and non-uniformity of imaging sensors, a test setup with a reference light source is required which homogeneously irradiates the test specimen. Integrating sphere light sources with quasi monochromatic emission spectra can be used for qualifying grayscale and color sensors and camera systems. However, for the characterization of imaging sensors and systems required for more demanding photometric and spectroradiometric measurement tasks, light sources with a continuous emission spectrum are necessary. The standard illuminant for such applications is the quartz halogen lamp. The only suitable light source with a broadband continuous emission spectrum from ultraviolet to infrared is the quartz-halogen lamp. Their spectral emission curve closely matches that of a black body over the wavelength range from 250 nm to 2500 nm. Therefore, a quartz-halogen lamp’s color temperature is approximately the operating temperature of the lamp’s filament.

Reference light source for EMVA 1288 testing of imaging sensors and cameras

The selection of a suitable sensor is an important step in the design of image processing systems. For the user, however, the choice is not always easy, as the information provided by different sensor manufacturers does not support a direct comparison of the available products. This problem has motivated the European Machine Vision Association to generate the EMVA 1288 standard [1]. The parameters listed therein and the description of the measuring methods offer the user the necessary comparability in the selection of imaging sensors and cameras

To measure sensitivity, linearity and non-uniformity, the EMVA 1288 standard recommends that integrating sphere based light sources should be used as the reference [2]. As a special feature, the standard states that spheres must be configured with LED sources.

Compact integrating sphere calibration lamp for the spectral radiance

The need for a compact spectral radiance calibration standard arises when the available space in or around the instrument to be calibrated is limited or from the need of a transfer standard or for service purposes. Depending on the application, additional requirements may arise in addition to the need for a compact version of integrating sphere.

An example of limited space availability is the calibration of fluorescence spectrophotometers with respect to the absolute spectral radiance sensitivity of the luminescence measurements. The development and characterization of the necessary spectral radiance transfer standard was carried out by Gigahertz-Optik GmbH and Physikalisch-Technische Bundesanstalt (PTB).

App. 032

Reference light source for sensitivity adjustment of combined rain and ambient light sensors

Integrating sphere light sources are widely used in the characterization and calibration of imaging sensors and cameras. In this application, the integrating sphere light source serves as a reference light source that can uniformly illuminate all of the many individual light-sensitive detectors (pixels). This enables the relative sensitivity of the pixels to be adjusted as required.

App. 033

Quantifying the veiling glare of imaging systems

Veiling glare is most apparent when bright light spots or bright scenes are within the field of view of an imaging system. It is produced by unwanted scattered and reflected light from the image forming beam within the camera system that eventually impinges the image plane. It doesn’t form an image, but may be quite uniformly distributed resulting in image fogging and a reduction in image contrast. There are numerous causes of veiling glare including internal multiple reflections between the surfaces of lenses; scatter from lens imperfections; scatter and reflections from components and internal surfaces of the camera body; fluorescence; bulk scatter within lenses.