How many Spectral Bands does it measure?

As HERA does not employ spectral filters or dispersive elements to direct the different colors of the incoming light to the different pixels of a sensor, it is not possible to determine the exact number of spectral bands. In fact, as the spectrum at each pixel of the image is the Fourier Transformation of the interference signal, the spectrum is a continuous function (or curve). Of course, when plotting the data, one needs to sample the spectrum with a proper number of points…but please note that does not affect the spectral resolution of the measurement and it is not an indication of the number of spectral bands!

The “real” answer to this question is that one needs to refer to the spectral resolution provided by the camera, rather than to the number of spectral bands.

Which is the illumination requirement?

Due to its extremely high sensitivity, HERA can work under low-light illumination conditions. This advantage is a consequence of the Fourier transform approach, as the employed interferometer (and the absence of the entrance slit) guarantees a much higher throughput compared to the dispersive- or grating-based technologies.

The camera is therefore very well suited in those applications in which intense and powerful illumination sources are not allowed, as they would damage the sample, such as in biology or cultural heritage. For example, HERA hyperspectral camera is so sensitive that it can measure hyperspectral images of the fluorescence signal emitted by a sample.

How does the Software work?

HERA comes with two software packages: one to acquire the hyperspectral images, see a preview of the measured data and save the measurement to your PC, and the other for a deeper data analysis. You can also export the hyperspectral data-cube in ENVI format.

As the hyperspectral data are heavy files, we strongly suggest to employ a computer with at least 16 Gb RAM and SSD drive.

How to calculate the Spatial Resolution?

HERA employs a 1.3 MP internal sensor and a 25 mm objective, providing 16° FOV. The working range varies from 25 cm to infinity. As an example, the lateral field of view of a scene at 1 m distance corresponds to: 2*tan(8°)*1 m = 28 cm.

Which is the typical Measurement Time?

HERA requires a few tens of seconds to capture the image of the scene and prepare the hyperspectral data-cube. Under low illumination conditions, acquisition time could be longer. During this time, the sample and the camera should remain static with respect to each other.

Also, the spectral resolution (which can be easily set via software) affects the measurement time: the better the spectral resolution, the longer the measurement time.

Is HERA a push-broom or a snapshot hyperspectral camera?

HERA is not a push-broom nor a snapshot hyperspectral camera. Instead, HERA is based on a patented Fourier-Transform approach, guaranteeing an extremely high throughput and sensitivity.
HERA works with a “staring” modality: it can be mounted on a tripod or clamped on an optical table, and there is no need to move the sample in order to acquire the hyperspectral image.
The acquisition software (provided together with the camera) automatically controls the movement of the interferometer during the acquisition, directly providing the user with the calibrated hyperspectral image.