Idea for UVB photography

[Stefano]

The Raspberry Pi HQ camera has shown good results for UV photography. Below a couple of topics in which this camera has been discussed:

 

https://www.ultravioletphotography.com/content/index.php?/topic/3883-raspberry-pi-hq-camera-12mp

 

https://www.ultravioletphotography.com/content/index.php?/topic/4178-uv-safety-warning-reaspberry-pi-hq-affordable-fast-uv-sensitive-sensor

 

Universe Kogaku makes two 6 mm UV lenses, one with a fixed aperture of f/2.8 and the other one with a variable aperture from f/3.5 to f/16. Both lenses cover a Raspberry Pi HQ camera sensor (diagonal of 7.9 mm). The f/2.8 lens covers a 4.8*6.4 mm sensor (diagonal of 8 mm) and the variabile aperture lens covers a 5.2*6.9 mm sensor (diagonal of 8.64 mm). This is the datasheet of the variabile aperture lens: https://www.universeoptics.com/wp-content/uploads/UV0635BCM-1.pdf

Also, this lens has a C-mount.

 

These lenses, as the other UV lenses from Universe Kogaku, are not corrected for chromatic aberration.

 

One could rear-mount two 310 nm bandpass filters, to reduce angle-of-incidence effects, if this doesn't degrade image quality too much.

 

One such filter could be this: https://www.edmundoptics.eu/p/10nm-cwl-125mm-dia-hard-coated-od-4-10nm-bandpass-filter/33098/

 

Of course I'm thinking about a monochrome-converted sensor.

[dabateman]

Well you can currently get a grade B sensor for half price.

https://maxmax.com/shopper/product/16158-rasppihq12mpmononoicf-b-raspberry-pi-hq-12mp-camera-module-monochrome-no-ir-cut-filter-grade-b/category_pathway-9539

The cost for the M12 lenses isn't too different than ordering from UKA.

 

[Stefano]

If the price of the lenses is similar, it means they cost around $1000. If one wants a grade A camera, the total cost for the setup (sensor + lens + filters + Raspberry Pi board) would probably be ~$2000. I wonder why those lenses are so expensive, maybe it's because it's a niche market, like for SWIR cameras.

[dabateman]

I think its a volume thing.

The cheapest UKA lens is the C-mount 25mm f2.8 one. But that lens is mass produced and I have even seen it with Pentax badge. The others I think are low volume and are all priced over $1000. 

You can also just make your own fused silica element lens to use with the Pi. The crop factor cuts into the sharpest center area. Just wide angle elements are harder to get cheap. 

[Stefano]

I have designed a wide angle (I think around 70° field of view) fused silica lens with 4 elements all available from Thorlabs that has good performance at f/2.8 and is almost perfect at f/4, but seems like it has barrel distorsion. I will post about it later.

[lukaszgryglicki]

WOW, can't wait for this.

 

[PDL1]

On 5/23/2023 at 11:18 AM, Stefano said:

I have designed a wide angle (I think around 70° field of view) fused silica lens with 4 elements all available from Thorlabs that has good performance at f/2.8 and is almost perfect at f/4, but seems like it has barrel distorsion. I will post about it later.

Hey Stefano, 

 

Just curious, how did this turn out?

[Stefano]

Here it is: 

 

 

But I have also designed two lenses with longer focal length but significantly sharper: