White LED Illumination Device Tone Uniformity
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Solution Overview
Problem
Conventional white LED illumination devices with wavelength conversion materials emit light with uneven tone distribution, leading to bluish white light in the front direction and yellowish white light in the slanting direction, resulting in optical characteristics with uneven tone, which complicates achieving even white light with high color rendering properties over an illumination surface.
Innovation Solution
A white LED illumination device is designed with an optical lens system where the optical axes of the LED and lens are aligned, featuring a convex light incident surface and a light emitting surface with different curvatures at the center and periphery, allowing bluish and yellowish white light to be introduced and mixed through the lens, thereby achieving a single optical path for even tone distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a wavelength conversion material is used with an LED chip to generate white light, then the structure is simplified compared to using three separate LED chips, but the emitted light exhibits uneven tone distribution (bluish in front direction, yellowish in slanting direction)
Solution Approach 1:
The patent segments the light emission into two distinct paths: a front direction optical path for bluish white light and slanting direction optical paths for yellowish white light. By spatially separating these optical paths and their corresponding wavelength conversion materials, the invention resolves the tone uniformity issue while maintaining structural simplicity.
Solution Approach 2:
The patent applies local quality by positioning different wavelength conversion materials (with different conversion characteristics) in different spatial locations within the light emitting portion. The front region uses materials optimized for bluish light conversion, while slanting regions use materials for yellowish light conversion, ensuring each region contributes its appropriate tone to the overall illumination.
2Illumination intensity
If blue light from an LED chip excites a fluorescent material to emit yellow light, then white light is generated by additive color mixture, but the optical path length varies with emission direction causing tone unevenness
Solution Approach 1:
The patent transitions from a single isotropic light emitting portion to an anisotropic structure with distinct front and slanting direction emission regions. By introducing directional dimensionality and creating separate optical paths for different emission angles, the invention compensates for the optical path length variation and achieves tone consistency across different viewing angles.
3Area of stationary object
If the light emitting surface emits light in multiple directions, then wide illumination coverage is achieved, but the tone becomes uneven with directionality (front vs. slanting directions)
Solution Approach 1:
The patent makes different regions of the light emitting portion have different emission characteristics. The front direction light emitting region is optimized for bluish light emission, while slanting direction regions are optimized for yellowish light emission. This local differentiation ensures that each direction contributes the appropriate tone to achieve overall uniformity across the wide illumination area.
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 device produces white light with high color rendering properties and reduced tone unevenness by aligning the optical axes and using a biconvex lens to mix bluish and yellowish white light, ensuring consistent illumination across the surface.
Implementation Method 1
The wavelength conversion material such as a fluorescent material is excited by the light from the LED chip and performs wavelength conversion to emit, for example, yellow or yellowish green fluorescence which is a complementary color of blue
Implementation Method 2
A white LED illumination device is designed with an optical lens system where the optical axes of the LED and lens are aligned, featuring a convex light incident surface and a light emitting surface with different curvatures at the center and periphery, allowing bluish and yellowish white light to be introduced and mixed through the lens
Implementation Method 3
The device produces white light with high color rendering properties and reduced tone unevenness by aligning the optical axes and using a biconvex lens to mix bluish and yellowish white light
Data Source
AI summary
A white LED illumination device can include a white LED that has unevenness in tone and is used as a light source. The white LED illumination device can emit white light with high color rendering properties without unevenness in tone and can include the above noted white LED located adjacent an optical lens. The white LED and optical lens can be arranged so that the optical axes of both are substantially aligned with each other. The white LED can include an LED chip which emits light having a peak wavelength in the blue wavelength range and a fluorescent material which can be excited by the light emitted from the LED chip to emit yellow or yellowish green fluorescence (i.e., complementary colors to blue) by use of wavelength conversion. The optical lens can have a recessed light incident surface having an opening, a light emitting surface, and a totally reflective surface positioned between the light incident surface and the light emitting surface. The inner bottom of the recessed light incident surface can include a convex shape having a convex surface. The light emitting surface can be composed of a convex portion having a center and a periphery that can be formed in different shapes or curvatures, and can include a flat surface surrounding the convex portion.