How small can a UV-B plus UV-A sensor be made?

Rather recently Vishay announced a miniature sensor under the name VEML6075 with two channels centred at . It is not just a sensor but it has all the electronics for temperature compensation and for converting the analogue signal from the sensor into digital data with a rough calibration applied. The package of this sensor is 1 mm thick and 2 mm times 1.25 mm in area. The sensor itself is much smaller and it follows reasonably well the cosine law without any diffuser. Price? Less than 2€… and between 4 and 7 € for a breakout board.

I haven’t tested it yet as a sensor. However, today I was testing a macro lens and I took a pair of photographs at rather high magnification, and as it fits a UV sensor, I photographed it both in visible and in UV-A radiation.

The whole image is 3 mm tall by 4 mm wide. It is slightly cropped from the full frame. Light source Convoy 2+ 365nm UV-A flashlight filtered with a visible blocking filter. Filter on objective zwb1 2mm thick, objective Zuiko 38mm f:3.5 macro (Olympus OM-System ca. 1973-1975+, single coated early version).

Zuiko Macro 38 mm f:3.5, RMS mount, Olympus OM-System ca. 1972-1976.

Camera objectives for UV photography

I have been testing some objectives for their UV transmission using LEDs as sources of radiation. I developed a protocol for such tests. Although used in this example to measure the spectral sensitivity of a camera sensor, the protocol can be easily adapted for the measurements of biological action spectra.

Continue reading Camera objectives for UV photography

PWM-dimming of RGB LEDs


Here I have tested a single individual lamp, of a single brand and type. From the ubiquity of identical or very similar lamps sold under different brand names by numerous sellers in eBay and Aliexpress, this seems to be a “typical” or popular type. The intention is for it to serve as an example of one specific technology for adjustment of the light output of LED lamps. This is not a comparative review. Continue reading PWM-dimming of RGB LEDs