Optical design for a tent camera obscura

In summary, the conversation revolved around designing an optical system to project images onto a sheet near the ground in a camera-obscura fashion. The design requires a 45 degree mirror, a converging lens, and a pinhole to focus the light onto the screen. Important parameters include imaging far away objects, a distance of 1.5m from lens to screen, and a magnification to produce a 50cm squared final image. The use of an achromatic doublet lens was also discussed for refractive index correction. One member shared their inspiration for the project and suggested using a pinhole instead of a lens. Another member shared their experience setting up a camera obscura and recommended using different-sized pinholes to find an optimal
  • #1
bam707
1
0
Hello all,

I've been trying to come up with an optical design to basically form images onto a sheet positioned near the ground, in an old camera-obscura fashion. Hopefully this image helps to visualize.

http://www.pinholeblender.com/COimages/mirror.gif

I know that I will require a 45 degree mirror as well as a converging lens to focus the light onto the screen. I got stuck in some of the calculations.

Important points / parameters:
  1. Imaging things very far away (>100m)
  2. Distance from lens to screen should be roughly 1.5m
  3. Magnification needs to produce a final image of roughly 50cm squared (larger is okay)
  4. Lens diameter should be equal to or less than 60mm, any focal length is okay
  5. Planning on using an achromatic doublet for wavelength refractive index correction

Here is my inspiration: http://www.abelardomorell.net/posts/tent-camera/

The image in this case is projected onto the ground. I plan on doing the same.

Alternate questions:
>> Is a pinhole required to essentially make the incoming light from a point-source? I want to maximize the number of photons actually on the ground.
>> Because the things I am imaging are a far distance, the light would be entering the lens in a parallel fashion, correct?
>> I was thinking of maybe using two lenses, almost as a projector. Off basis?


I appreciate you all, and thank you for your input.
 
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  • #2
A colleague of mine in the Art department and I set up a camera obscura last year as a Intro Physics demo, it was really amazing:

http://imagizer.imageshack.us/v2/800x600q90/11/fq9y.jpg

Do not use a lens, that's the whole point of a camera obscura. The size of the pinhole is a critical consideration; too small and the image is too dim, too large and the image is too blurry. What we did was to have 'flaps' with differently-sized holes that allowed us to experiment and find an optimal size (about 1/4", as I recall).

There's not much to it, just make sure the room is as dark as possible and have patience until your eyes adjust.
 
Last edited by a moderator:

1. What is the purpose of optical design for a tent camera obscura?

The purpose of optical design for a tent camera obscura is to create a small, portable dark room that uses the principles of optics to project an inverted image of the outside world onto a screen or wall. This allows for a unique viewing experience and can be used for artistic or educational purposes.

2. How does the optical design of a tent camera obscura work?

The optical design of a tent camera obscura involves using a small opening or aperture on one side of the tent, which allows light to enter and project an image onto a screen or wall on the opposite side. The light rays from the outside world pass through the aperture and create an inverted image due to the principles of light refraction and reflection.

3. What materials are needed for the optical design of a tent camera obscura?

To create a tent camera obscura, you will need a small tent, a dark cloth or tarp to cover the tent, a small opening or aperture (such as a pinhole or lens), and a screen or wall to project the image onto. You may also need additional materials such as tape or scissors to create the opening and secure the dark cloth.

4. Can the optical design of a tent camera obscura be adjusted for different lighting conditions?

Yes, the optical design of a tent camera obscura can be adjusted by changing the size of the aperture to accommodate different lighting conditions. A smaller aperture will result in a sharper image, while a larger aperture will allow more light in and create a brighter image. You can also adjust the position and angle of the tent to control the amount and direction of light entering the tent.

5. Are there any safety precautions to consider when using a tent camera obscura?

Yes, it is important to exercise caution when using a tent camera obscura, especially when using a lens as the aperture. Directly looking into the lens can be harmful to your eyes, so it is recommended to use a screen or wall to view the projected image. It is also important to be mindful of the positioning of the tent and any potential hazards in the surrounding area.

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