Asymmetric Optical Device for Intercanopy Lighting
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Solution Overview
Problem
Current intercanopy lighting systems in greenhouses suffer from uneven vertical and horizontal light distribution, leading to inefficient use of light by plants and obstructing working areas, as they rely on high-intensity discharge lamps with Lambertian light distribution and fixed geometric arrangements.
Innovation Solution
An optical device with asymmetric light distribution, utilizing a cone-shaped truncated lens and reflective surfaces for total internal reflection, along with a substrate with a reflective metal layer, to create a compact and efficient lighting system that directs more light downwards, ensuring homogeneous illumination within a predefined target zone, even when illuminated at an angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If HID lamps are arranged between rows of plants with fixed geometric conditions, then intercanopy lighting is provided, but strongly varying horizontal and vertical irradiance on plant surface results
Solution Approach 1:
The patent applies asymmetry by using optical elements with asymmetric beam patterns that distribute light unevenly in horizontal and vertical directions. This asymmetric light distribution is specifically designed to match the plant canopy structure, providing uniform illumination to leaves at different heights while maintaining a simple fixed geometric arrangement of lamps between plant rows.
2Illumination intensity
If HID lamps are arranged between rows of plants, then intercanopy lighting is achieved, but working area is blocked and inaccessible to workers
Solution Approach 1:
The patent employs retractable lighting devices that can dynamically change position between extended and retracted states. When extended, the lamps provide intercanopy lighting by positioning optical elements close to plant canopies. When retracted, the entire lighting device pulls back to clear the working area, allowing workers free access while maintaining lighting functionality.
3Loss of energy
If Lambertian light distribution is used with fixed geometric arrangement, then lighting is provided, but light reaches only limited plant zones and loss occurs towards floor or ceiling
Solution Approach 1:
The patent applies local quality by using optical elements with directionally selective beam patterns tailored to specific lighting needs. Each optical element is designed to direct light preferentially toward leaf zones at different heights within the canopy, concentrating illumination where plants need it most while minimizing light loss to the floor and ceiling through precise angular control.
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 system achieves high optical efficiency by providing 90% of light to the target zone, ensuring 70% homogeneity in illuminance, and allows for a wider working area by directing light efficiently to the lower parts of plants, thereby increasing crop yield and reducing light loss.
Implementation Method 1
The first and second surfaces are reflecting surfaces arranged such that light received at the light input area and traveling towards the light output surface is redirected towards the centre axis by means of total internal reflection at the first surface and light received at the light input area and traveling towards the light output surface is redirected away from the centre axis by means of total internal reflection at the second surface
Implementation Method 2
The optical element is arranged such that light entering the optical element and traveling along a direction towards the light output surface is collimated, while light traveling in a direction towards the sides of the optical element is directed towards the first and second surfaces
Data Source
Figure 1~2b
Figure 3a~3b
Figure 4a
AI summary
This invention relates to an optical device (100) for intercanopy lighting comprising a light input area (109) for receiving light, a first surface (120) having a first bezier curve, and a second surface (110) having a second bezier curve. The first and second bezier curves are independently selected with respect to each other, and arranged such that the optical device is rotational asymmetric with respect to its centre axis. Received light which is reflected in the first surface is reflected in a direction towards the centre axis, and received light which is reflected in the second surface is reflected in a direction away from the centre axis, thereby providing vertical and horizontal homogeneous illumination distribution in a predefined area, which area is illuminated under an angle. Thus, a vertical intensity distribution can be selected to be narrow, while simultaneously the horizontal intensity can be selected to be wide, which is advantageous for providing intercanopy lighting at a desired target zone for plants. Simultaneously, the vertical intensity distribution is asymmetric, which is advantageous for meeting homogeneity criteria for lighting of plants.