Introduction: Pinhole Reading Assist
A small 'pinhole' in a flat disc acts as a lens focusing the object we are looking at. Based on this well known 'pinhole effect' I have made a simple device which can be carried in my purse along with my credit/debit cards.
I am 68 years old and need glasses with a power of +2.75 for reading text and looking at close objects. However, as my distance vision is normal I use these glasses only when required and carry them in my shirt pocket.
Unfortunately, I often forget them and find it difficult to read text such as price and expiry-date information on products while shopping.
'My Pinhole Card' is a standard sized plastic card which has four sets of pinholes drilled through it. Two sets of single pinholes and another two sets of five pinholes of 1.0 mm and 1.5 mm diameter. When carried along with my credit/debit cards it is always available to me while shopping.
Looking at small text through the pinholes in this card focuses the text so that it is readable without the use of prescription glasses.
The diameter and combination of pinholes is based on a subjective evaluation I carried out for different hole-diameters and hole-groups which made reading small text comfortable.
- Assorted Plastic Cards ( Old Credit Cards are suitable)
- Miniature drill bits 0.5 mm, 0.8 mm, 1.0 mm and 1.5 mm diameter
- PCB drilling machine (hand operated are suitable)
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Step 1: Subjective Evaluation
I checked out the performance improvement in my ability to read small text using pinholes of different drill-size and hole-combinations. I checked out pinhole sizes of 0.5 mm, 0.8 mm, 1.0 mm and 1.5 mm diameter.
The following are my conclusions:
1. Each pinhole provides an independent image
2. Smaller pinhole size give better focus but intensity of the text is reduced
3. Having two pinholes side-by-side provides overlapping images and helps reading running text
4. Having a five-hole combination appears optimum for area coverage without multiple-Image, double-vision effects
5. Finally 1.0 mm/1.5 mm diameter pinholes appear to be most suitable in terms of focus and intensity and having both the one-hole / five-hole patterns is optimum
Step 2: Pinhole Drilling
The pinholes of different sizes and in the form of different clusters can be drilled using the handheld PCB drill.
I initially drilled several holes and combinations as a trial in one of the cards to get a idea of the improvement in close vision possible.
I then drilled the single, double and five-hole pattern using 0.5 mm, 0.8 mm, 1.0 mm and 1.5 mm diameter bits on the evaluation card.
I found the 1.0 mm and 1.5 mm diameter most suitable and drilled the single and five-hole pattern with these drill bits on my final card.
I carry this card in my purse always
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