Lens array passive athermalization

Patent metadata

Field	Value
Publication number	US-2016291283-A1
Application number	US-201514676295-A
Country	US
Kind code	A1
Filing date	Apr 1, 2015
Priority date	Apr 1, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

A lens housing includes a main housing, a lens array, a lens housing, and an athermalization bushing. The lens array has a thermally variable focal length that determines a focal point along a focal axis. The lens housing contains the lens array and is situated within the main housing, and is capable of translating relative to the main housing along the focal axis. The athermalization bushing is situated axially between the lens housing and the main housing, such that thermal expansion of the athermalization bushing translates the lens housing along the focal axis. This translation causes the focal point to remain substantially fixed relative to the main housing as the focal length of the lens array varies across an operational temperature range.

First claim

1 . A lens system comprising:
a main housing; a lens array of thermally variable focal length determining a focal point along a focal axis; a lens housing containing the lens array and situated within the main housing, and capable of translating relative to the main housing along the focal axis; an athermalization bushing situated axially between the lens housing and the main housing, such that thermal expansion of the athermalization bushing translates the lens housing along the focal axis, causing the focal point to remain substantially fixed relative to the main housing as the focal length of the lens array varies across an operational temperature range.

2 . The lens system of claim 1 , wherein the lens housing further comprises a positioning flange extending radially outward from a lens cylinder, and wherein the athermalization bushing axially abuts the positioning flange.

3 . The lens system of claim 1 , wherein the main housing further comprises a locator nut that axially abuts the athermalization bushing.

4 . The lens system of claim 1 , further comprising a bias element that applies an axial load retaining the lens housing in contact with the athermalization bushing.

5 . The lens system of claim 4 , wherein the bias element is a spring situated axially between the main housing and the lens housing.

6 . The lens system of claim 5 , wherein the spring is a wave spring.

7 . The lens system of claim 1 , wherein the compensation bushing is formed of a material selected from the group consisting of polyethylene, polyvinylidene, and acetal.

8 . The lens system of claim 1 , wherein the focal length is substantially linear as a function of temperature within the operational temperature range.

9 . The lens system of claim 1 , wherein an axial length of the athermalization bushing increases as the focal length decreases, and decreases as the focal length increases.

10 . The lens system of claim 1 , wherein the lens array comprises a plurality of distinct lenses, and the focal length is an aggregate focal length of the plurality of distinct lenses.

11 . A method of compensating for shift in a focal point location of a lens array due to thermal drift of a focal length of the lens array across an operating temperature range, the method comprising:
securing the lens array in a lens housing with a radially extending positioning flange; situating the lens housing within a main housing with an axial stop, such that the lens housing is capable of translating along a focal axis of the lens array, relative to a main housing; selecting a material and an axial length of an athermalization bushing based on the thermal drift; positioning the athermalization bushing axially between the positioning flange and the axial stop, such that thermal expansion of the athermalization bushing translates the lens housing relative to the main housing, thereby fixing the focal point location; and securing the axial stop at a location determined based on the axial length.

12 . The method of claim 11 , wherein selecting a material and an axial length of an athermalization bushing comprises selecting an axial length L b and a material with coefficient of thermal expansion α L such that α L *L b =ΔL f /ΔT, where ΔL f is the thermal drift in the focal length and ΔT is the operating temperature range.

13 . The method of claim 11 , wherein the axial stop is a locator nut secured to the main housing, and wherein securing the axial stop comprises attaching the locator nut to the main housing.

14 . The method of claim 13 , wherein attaching the nut comprises threading the nut radially onto radially inner threads of the main housing.

15 . The method of claim 1 , further comprising biasing the lens housing against the athermalization bushing.

16 . The method of claim 15 , wherein the main housing further comprises a radially extending retention flange, and wherein biasing the lens housing against the athermalization bushing comprises applying an axial load via a spring situated between the between the retention flange and the positioning flange.

Assignees

• Sensors Unlimited Inc

Inventors

• Tagle John
• Foster John T
• Winkler Robert
• Balcazar Gustavo A

Classifications

• G02B7/028 Primary

  with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation · CPC title

• G02B7/04

  with mechanism for focusing or varying magnification · CPC title

• G02B7/10

  by relative axial movement of several lenses, e.g. of varifocal objective lens · CPC title