Thermally Compensated Lens Layout for Stable Focus Position
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Solution Overview
Problem
Optical systems for image pickup apparatuses face challenges in maintaining high optical performance across varying environmental temperatures, as existing technologies struggle to effectively correct focus position fluctuations caused by temperature changes.
Innovation Solution
The optical system comprises a specific configuration of lenses with carefully managed refractive powers and temperature coefficients, including a first lens with negative refractive power, a second lens with negative refractive power, a third lens with negative refractive power, a fourth lens with positive refractive power, and subsequent lenses, ensuring that at least one of the fourth and fifth lenses has a negative temperature coefficient for the d-line at 20° C. to 40° C., and at least one of the third and sixth lenses has a positive temperature coefficient within the same temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical systems are used, then the structure is simple, but focus position fluctuations occur due to temperature changes
Solution Approach 1:
The patent applies parameter changes by selecting lens materials with specific temperature coefficients of refractive index. The fourth and fifth lenses use materials with negative temperature coefficients, while the third and sixth lenses use materials with positive temperature coefficients. This parameter selection enables the optical system to compensate for focus position fluctuations caused by temperature changes, thereby improving reliability without significantly increasing structural complexity.
Solution Approach 2:
The patent employs composite materials by combining multiple lens materials with different thermal optical properties within a single optical system. Specifically, it integrates lenses made from materials exhibiting opposite temperature coefficient characteristics (positive and negative) to create a composite optical system that inherently compensates for thermal focus shifts, resolving the contradiction between maintaining simple structure and achieving temperature stability.
2Reliability
If lens materials with temperature compensation properties are used, then focus fluctuations are suppressed, but manufacturing complexity increases
Solution Approach 1:
The patent specifies precise parameter ranges for lens materials, requiring that the fourth and fifth lenses have negative temperature coefficients and the third and sixth lenses have positive temperature coefficients. By defining these parameter constraints, the patent enables manufacturers to select from established optical materials that meet these criteria, balancing the need for temperature compensation with manufacturing feasibility.
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
This configuration enables the optical system to maintain high optical performance and effectively suppress focus fluctuations due to temperature changes, ensuring good imaging performance across a range of temperatures.
Implementation Method 1
A sign of a temperature coefficient of a refractive index for d-line of at least one of the fourth lens and the fifth lens at 20° C. to 40° C. is negative. A sign of a temperature coefficient of a refractive index for the d-line of at least one of the third lens and the sixth lens at 20° C. to 40° C. is positive.
Data Source
AI summary
An optical system includes, in order from an object side to an image side, a first lens having negative refractive power, a second lens having negative refractive power, a third lens having negative refractive power, a fourth lens having positive refractive power, an aperture stop, a fifth lens having positive refractive power, a sixth lens having negative refractive power, and a seventh lens. A sign of a temperature coefficient of a refractive index for d-line of at least one of the fourth lens and the fifth lens at 20° C. to 40° C. is negative. A sign of a temperature coefficient of a refractive index for the d-line of at least one of the third lens and the sixth lens at 20° C. to 40° C. is positive.