Optical encoder module

• US 20050068773A1
• Filed: 08/15/2001
• Published: 03/31/2005
• Est. Priority Date: 08/17/2000
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Lee, Chi-Yun, Ng, Kee-Yean, Chong, Chee-Keong, Chin, Yee-Loong, Fo, Kok-Hing
• Granted Patent: US 7,279,674 B2
• Time in Patent Office: Days
• US Class Current: 362/253
• CPC Class Codes: G01D 5/34715 Scale reading or illumination devices

Abstract

An optical encoder module is employed to detect light modulated by a moveable member (e.g., code wheel). The optical encoder includes an emitter having a light-emitting element, and a transparent medium encapsulating the light-emitting element. The transparent medium has a convex aspherical external surface shaped so as to focus light received from the light-emitting element into a substantially collimated beam of light using a single refractive interface for illuminating the movable member. The optical encode module also includes a detector facing the emitter for detecting modulated light of the collimated beam transmitted through the movable member.

Claims

1. An optical encoder, comprising:

a light-emitting element;

a transparent medium encapsulating the light-emitting element, the transparent medium having a convex aspherical external surface shaped so as to focus light received from the light-emitting element into a substantially collimated beam of light using a single refractive interface;

a detector facing the light-emitting element to detect the collimated beam of light from the light-emitting element via the convex aspherical surface of the transparent medium;

a movable module placed between the light-emitting element and the detector to modulate the collimated beam of light to the detector.

2. The optical encoder according to claim 1, wherein the convex aspherical external surface is radially symmetric about an optical axis.

3. The optical encoder according to claim 2, wherein the light-emitting element is positioned substantially on the optical axis of the convex aspherical external surface.

4. The optical encoder according to claim 3, wherein the transparent encapsulating medium is an epoxy compound.

5. The optical encoder according to claim 1, wherein the convex aspherical external surface is produce by molding the transparent encapsulating medium.

6. The optical encoder according to claim 1, wherein the light-emitting element is a light emitting diode.

7. The optical encoder according to claim 1, wherein the light emitting element is electrically coupled to a lead-frame, the lead-frame being partially encapsulated by the transparent medium.

8. The optical encoder according to claim 1, wherein the movable member is a code wheel.

9. The optical encoder according to claim 1, wherein the detector is also encapsulated to have an locking projection that locks the light-emitting device and the detector into a locking position with respect to each other.