|
|
|
@ -75,7 +75,7 @@ from an object point generally do not converge towards an image point. |
|
|
|
Fig. 5a. : If we limit the opening of the spherical refracting surface so that only the rays |
|
|
|
meeting the surface near the vertex are refracted through the surface. |
|
|
|
|
|
|
|
<br> |
|
|
|
<br> |
|
|
|
Fig. 5b. : and if the object points remain close to the optical axis, so that the angles of |
|
|
|
incidence and refraction remain small, then for each object point an image point can be almost |
|
|
|
defined, and therefore the spherical refracting surface becomes quasi-stigmatic. |
|
|
|
|