How Can a Near Object Be Focused While Looking at Distant Objects?

[jstwinkles]

Hi, I have what might seem like an odd question. Suppose that someone is looking at an object in the distance, and there is an object placed about an inch in front of one of the person's eye. Obviously, this object would appear out of focus. My question is this: how would one bring this object into focus so that when the person is looking at distant objects it appears in focus? Could a small positive fresnel lens be used? If not, any ideas on how to go about doing this or any alternatives? Sorry if this sounds like a vague question, I have relatively little experience in optics.

Thanks ahead of time.

 

[drummin]

A small convex (magnifing) lens does the trick. For example an prismatic compass uses such a lens to allow the user to view the moving compass card (a couple inches from the eye) and a landmark in the distance (miles away) at the same time for accurate readings.

 

[Andy Resnick]

Hi, I have what might seem like an odd question. Suppose that someone is looking at an object in the distance, and there is an object placed about an inch in front of one of the person's eye. Obviously, this object would appear out of focus. My question is this: how would one bring this object into focus so that when the person is looking at distant objects it appears in focus? Could a small positive fresnel lens be used? If not, any ideas on how to go about doing this or any alternatives? Sorry if this sounds like a vague question, I have relatively little experience in optics.

Thanks ahead of time.

bifocals?

 

[jstwinkles]

A small convex (magnifing) lens does the trick. For example an prismatic compass uses such a lens to allow the user to view the moving compass card (a couple inches from the eye) and a landmark in the distance (miles away) at the same time for accurate readings.

Thanks, drummin, that's exactly what I needed to know! I appreciate it.

 

[pallidin]

A small convex (magnifing) lens does the trick. For example an prismatic compass uses such a lens to allow the user to view the moving compass card (a couple inches from the eye) and a landmark in the distance (miles away) at the same time for accurate readings.

Very interesting. I did not know that could be done. Thanks.