Diffuser for Light Meter app

I thought about using a Light Meter app for the houseplants I grow indoors, but some Light Meter apps require a diffuser to be attached to the phone for measurement. There are no inexpensive diffusers specifically for smartphones, so I made a diffuser that uses a clip-on lens attachment for smartphones.
Although it is known that white copy paper can be used as a simple diffuser, I found that an attachment of paper to clip-on lens attachment for a smartphone worked well.
Since it is quite troublesome to cut paper into round pieces, I decided to use copy paper cut into 30 mm squares.
The clip-on lens attachment I bought at the $1 store (100yen shop in Japan) had a 17mm thread diameter, so I designed the body with Fusion using ISO 17ISO Metric profile M17x1 threads. For clips with different diameters, adjust the attached STEP file.
Prints use supports and brims. Set the support in the slicer software so that the support material does not stick to the threads.
When mounting a piece of paper, use a thin ruler to ensure that the paper fits into the corners.