Centering of an optical element using edge contact mounting

Patent metadata

Field	Value
Publication number	US-11320623-B2
Application number	US-202016793957-A
Country	US
Kind code	B2
Filing date	Feb 18, 2020
Priority date	Feb 18, 2019
Publication date	May 3, 2022
Grant date	May 3, 2022

Abstract

Optical assemblies are provided in which an optical element is centered in the cavity of a barrel. The optical element is secured between a seat in the cavity and a retaining ring. The retaining ring has ring threads complementary to the barrel threads. The retaining ring has an abutment surface engaging a peripheral mounting edge of the optical element along a circular edge contact line. In some embodiments, the abutment surface has a frustro-spherical profile having a radius of curvature selected in view of the thread angle to maintain a centering of the optical element even when the retaining ring is decentered in the cavity. In other variants, the abutment surface has a frustro-conical profile having an inclination angle with respect to the center axis of the cavity selected in view of the thread angle to maintain said centering.

First claim

The invention claimed is:

1. An optical assembly, comprising:
a barrel having a cavity and a set of barrel threads;
a seat provided in the cavity of the barrel;
an optical element having a first surface resting on the seat and a second surface opposite to the first surface, said optical element having a peripheral mounting edge; and
a retaining ring affixed to the barrel through a set of ring threads complementary to the barrel threads and having a thread angle, the retaining ring comprising an abutment surface engaging the peripheral mounting edge of the optical element along a circular edge contact line, thereby securing the optical element between the seat and the retaining ring, the abutment surface having a frustro-spherical profile having a radius of curvature R Ring given by the formula:

R
Ring

=

[

d
ring

2
⁢

tan
⁡

(

φ
threads

⁢

/

⁢
2

)

-
h
-

T
⁢

/

⁢
2

]

2

+

Y
2

where:
d ring is a diameter of the retaining ring along the ring threads;
φ thread is a value of a thread angle;
Y is a half-diameter of the peripheral mounting edge;
h is a distance between (i) a first point of contact of the barrel threads with the ring threads proximate to the optical element and (ii) the edge contact line; and
T is a distance between (i) the first point of contact of the barrel threads with the ring threads proximate to the optical element and (ii) a last point of contact of the barrel threads with the ring threads farthest from the optical element diametrically opposite to the first point of contact.

2. The optical assembly according to claim 1 , wherein the peripheral mounting edge is located at a junction of the second surface with a peripheral side wall of the optical element.

3. The optical assembly according to claim 1 , wherein the optical element comprises a bevelled surface joining the second surface to a peripheral side wall of the optical element, and the peripheral mounting edge is located at a junction of said bevelled surface with the second surface.

4. The optical assembly according to claim 1 , wherein the optical element comprises a bevelled surface joining the second surface to a peripheral side wall of the optical element, and the peripheral mounting edge is located at a junction of said bevelled surface with the peripheral side wall.

5. The optical assembly according to claim 1 , wherein the optical element comprises a bevelled surface joining the second surface to a peripheral side wall of the optical element, first and second peripheral mounting edges being defined at respective junctions of said bevelled surface with the peripheral side wall and the second surface, the abutment surface engaging both the first and second peripheral mounting edges.

6. The optical assembly according to claim 1 , wherein the seat comprises one of an annular shoulder protruding from an inner wall of the barrel, a rearward facing surface of an additional optical element and an additional retaining ring inserted inside the cavity forward to the optical element.

7. The optical assembly according to claim 1 , wherein the optical element comprises:
a lens, a mirror, a diffractive optical element or a pinhole, having the first surface resting on the seat; and
a spacer provided in the cavity and located between the retaining ring and said lens, mirror, diffractive optical element or pinhole, the peripheral mounting edge being provided on said spacer.

8. The optical assembly according to claim 1 , wherein:
the second surface of the optical element is concave;
the barrel threads extend on an outer wall of the barrel;
the retaining ring comprises an outer annular segment extending outside of the barrel and provided with the ring threads, said ring threads facing towards the barrel, the retaining ring further comprising an inner annular segment extending inside of the cavity and including the abutment surface.

9. An optical assembly, comprising:
a barrel having a cavity and a set of barrel threads, the cavity having a longitudinal center axis;
a seat provided in the cavity of the barrel;
an optical element having first surface resting on the seat and a second surface opposite the first surface, said optical element having a peripheral mounting edge along the second surface; and
a retaining ring affixed to the barrel through a set of ring threads complementary to the barrel threads and having a thread angle, the retaining ring comprising an abutment surface engaging the peripheral mounting edge of the optical element along a circular edge contact line or band, thereby securing the optical element between the seat and the retaining ring, the abutment surface having a frustro-conical profile having an inclination angle a with respect to a plane perpendicular to the longitudinal center axis of the cavity given by the formula:

α
=

sin

-
1

(

Y

[

d
ring

2
⁢

tan
⁡

(

φ
threads

Assignees

• Institut Nat Doptique

Inventors

• Savard Maxime
• Lamontagne Frédéric

Classifications

• G02B7/026 Primary

  using retaining rings or springs (G02B7/027 takes precedence) · CPC title