Optical Sensor Mounting With Spring Preload for Stable Glass Contact

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Solution Overview

Problem

Existing detection devices face challenges in maintaining stable contact between the optical sensor and the protective glass, leading to unreliable detection performance and vulnerability to impacts.

Innovation Solution

A detection device design featuring a back cover with a light transmissive transparent portion, a holder opposing the transparent portion, a circuit board with an optical sensor, and resilient energizing members that press the circuit board and optical sensor towards the transparent portion, using cushioning or spring members to ensure stable contact and buffer impacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If rigid mounting is used to ensure stable contact between optical sensor and protective glass, then detection precision is improved, but vulnerability to impacts increases

Engineering Contradiction:
Improvedetection precisionVSAvoidimpact vulnerability
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the mechanical parameter of the mounting system from rigid to resilient by introducing spring members. These springs maintain stable contact between the optical sensor and protective glass through continuous elastic force, ensuring detection precision while simultaneously providing impact buffering capability that rigid mounting lacks.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The spring members are pre-compressed or pre-positioned to provide continuous resilient force before any impact occurs. This beforehand cushioning ensures that when impacts do occur, the resilient mounting system can absorb and dissipate the shock energy, protecting both the optical sensor and protective glass from damage.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

2Object-affected harmful factors

If resilient mounting is used to buffer impacts, then impact resistance is improved, but contact stability between optical sensor and protective glass deteriorates

Engineering Contradiction:
Improveimpact resistanceVSAvoidcontact stability
Core Design Contradiction:
Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The patent carefully selects spring parameters (coil density, wire diameter, free length) to optimize the balance between resilience and stability. The spring constant is tuned to provide sufficient force for stable optical contact while maintaining enough compliance for impact buffering. This parameter optimization resolves the contradiction between impact resistance and contact stability.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The resilient mounting is applied locally at specific mounting points around the optical sensor assembly, allowing different regions to have different mechanical properties. The spring members provide localized resilient support that maintains contact stability in the optical path while absorbing impact energy, creating a targeted solution that addresses both requirements simultaneously.

Inventive Principle:
Principle #3Local quality

3Measurement precision

If the optical sensor is pressed firmly against the protective glass, then detection performance is improved, but the risk of damage from shocks increases

Engineering Contradiction:
Improvedetection performanceVSAvoidshock resistance
Core Design Contradiction:
Measurement precisionVSStrength

Solution Approach 1:

The spring members are pre-compressed to provide a baseline contact force that ensures optimal optical detection performance under normal conditions. When shocks or impacts occur, the springs can compress further to absorb the shock energy, preventing damage to the optical sensor and protective glass while maintaining detection capability.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The mounting system transitions from a static rigid connection to a dynamic resilient connection. The spring members allow the optical sensor assembly to move slightly in response to impacts, converting rigid stress into elastic deformation. This dynamic response maintains firm contact for detection while providing shock resistance, resolving the contradiction between detection performance and shock resistance.

Inventive Principle:
Principle #15Dynamics

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

Enhances detection performance by ensuring stable contact between the optical sensor and protective glass, reducing noise interference, and buffering impacts to protect the circuit board.

Implementation Method 1

an optical sensor which is provided on one surface of the circuit board opposing the transparent portion to detect light

Methodology Applied
Scientific EffectLight detection: Photoelectric Effect

Implementation Method 2

resilient energizing members which are arranged in compressed states in areas between the undersurface of the holder and the upper surface of the holder circuit board, thereby forcing the circuit board and the optical sensor toward the transparent portion

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP4009120B1Detection device and body-worn device
Publication Date: 2026.02.25 CASIO COMPUTER CO LTD
  • EP4009120B1 patent drawingFigure 1
  • EP4009120B1 patent drawingFigure 2
  • EP4009120B1 patent drawingFigure 3

AI summary

A detection device (10) of a body-worn device including a back cover (5) provided with a protective glass (11) that is a light transmissive transparent section, a holder (12) attached to the back cover (5) and positioned opposing the protective glass (11), a circuit board (13) arranged between the back cover (5) and the holder (12), an optical sensor (14) provided on the undersurface of the circuit board (13) opposing the protective glass (11) so as to detect light, and energizing members (15) arranged between the holder (12) and the circuit board (13) so as to force the circuit board (13) and the optical sensor (14) toward the protective glass (11). By being forced toward the protective glass (11) by the energizing members (15), the circuit board (13) reliably and favorably presses the optical sensor (14) against the protective glass (11), whereby the optical sensor (14) reliably and favorably comes in close contact with the protective glass (11) in a stable state.