Reflective Encoder Light Emitter Structure for Leakage Light Suppression
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Solution Overview
Problem
Light emitting elements used in reflective-type encoders suffer from reduced detection accuracy due to leakage light from the side surfaces of the mesa portion, which is detected as noise by the light receiving element.
Innovation Solution
A light emitting element design featuring a metal layer with a second part extending along the side surface via an insulating and resin layer, overlapping the active layer to block leakage light, and a resin layer with a thickness decreasing toward the substrate to enhance light attenuation, ensuring effective suppression of side surface leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a metal layer is formed on the side surface of the mesa portion to block leakage light, then detection accuracy is improved, but it becomes difficult to satisfactorily form the metal layer on the curved side surface
Solution Approach 1:
An insulating layer is introduced as an intermediary between the mesa portion and the metal layer. This insulating layer provides a planarized surface that facilitates satisfactory formation of the metal layer, even on curved side surfaces of the mesa portion, while the metal layer continues to function as a light shield to block leakage light and improve detection accuracy.
2Object-generated harmful factors
If the metal layer is extended to cover the entire side surface, then light leakage is suppressed more effectively, but the region for external connection at the top surface is reduced
Solution Approach 1:
The metal layer is configured with different functions in different regions: the first part on the top surface provides external connection and contains a light passage opening, while the second part on the side surface provides light shielding. This local differentiation allows the metal layer to simultaneously suppress leakage light and maintain adequate external connection area.
3Ease of operation
If the light passage opening is positioned closer to the edge for easier external connection, then ease of connection is improved, but light leakage from that side surface increases
Solution Approach 1:
The metal layer is segmented into two distinct parts: the first part on the top surface that facilitates external connection and the second part on the side surface that suppresses light leakage. This segmentation allows the light passage opening to be positioned for ease of connection while the separate side surface portion of the metal layer continues to effectively block leakage light.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses leakage light, thereby maintaining detection accuracy in reflective-type encoders by ensuring the metal layer can be satisfactorily formed on the side surface and efficiently attenuating light leakage, even on curved surfaces.
Implementation Method 1
the second part overlaps at least the active layer when viewed in a direction perpendicular to a thickness direction of the substrate. As a result, light leaking out of the side surface of the mesa portion can be blocked by the second part
Implementation Method 2
light that has leaked out to the resin layer from the side surface of the mesa portion is attenuated by being repeatedly reflected between the side surface of the mesa portion and the second part of the metal layer
Data Source
AI summary
A light emitting element includes: a substrate; a mesa portion formed on the substrate and including an active layer, a first semiconductor layer, and a second semiconductor layer; a metal layer including a first metal part disposed on a top surface of the mesa portion and connected to the second semiconductor layer and a second metal part formed integrally with the first metal part and extending along a side surface of the mesa portion; an insulating layer formed on the side surface; and a resin layer formed on the insulating layer. The first metal part includes an opening region formed with a light passage opening and a connection region for external connection. The second metal part is formed on the side surface via the insulating layer and the resin layer and overlaps the active layer when viewed in a direction perpendicular to a thickness direction of the substrate.