Traditional surgical shadowless halogen lamps are generally designed as projection type with many light bulbs, which can produce not only mercury pollution but also heat radiation that are serious problems to patient. The study utilized Runge-Kutta methods and mathematical algorithms to design and optimize the freeform lens. The LED (light-emitting diode) was adopted to replace the traditional halogen lamp. A uniform lens was designed and fabricated based on the energy conservation. At first, the light field of LED is concentrated through the freeform lens to improve the optical efficiency. Second, the three-shell elliptic curves are applied to the reflective surgical shadowless lamps, where only few LED chips are needed. Light rays emitting from different directions to the target plane can achieve the goal of shadowless. In this study, the LED’s luminance flux is 1,895 lm. The shadow dilution on the target plane is 54%.
The light source of traditional surgical shadowless lamps is usually halogen lamp, but it can cause serious environmental pollution. In order to achieve the goal of environmental protection, light emitting diode (LED) is applied to this research as light source; the advantages of LED are cold light, low color temperature, high color rendering, and long life term [
Surgical shadowless lamp which is designed to reduce the shadow generated by hands or surgical tools to meet the regulation plays a critically important role in the surgery room. But the energy consumption of projective shadowless lamps is too high to generate the problem of irradiance heat because there were many halogen lamps used as light source. Compared with projective surgical lamps, reflective shadowless lamps have been developed for a long time, a surgical lamp designed by an elliptic curve reflector was invented by Dorman in 1970 [
Illumination system can be separated into three different parts, projection, reflection, and optical fiber. Freeform lenses are wildly used in projection system; light can be concentrated/diffused while going through two different materials. We can determine any kind of light field with freeform lens by using calculation and simulation process. The light in reflection system can be reflected to target plane by several reflective layers, which is calculated through math method. The illumination system in surgical room is required to have high illumination, high color rendering, glare free, and little irradiance.
The first part is stacked elliptic curve reflector. There are several methods to design and fabricate surgical lamps, such as refracting light to target plane by Fresnel lens which is composed of many different prisms [
The reflector is stacked by three elliptic curves with different focuses. Each elliptic curve is an independent light source that makes light emit to the target plane from different angles, and the goal of the shadowless can be achieved. Equation (
Ellipse diagram.
The depth of reflector and the position of light source which is one of the focuses of the first elliptic curve have to be determined at the beginning. The diameter of light field on the target plane is set as 30 cm. Figure
First elliptic curve and light source.
Predicted curve of stacked ellipse.
The structure of stacked elliptic curve.
LED light source can be considered a Lambertian distribution, and the light emission of half intensity angle is 60° that affects the uniformity of light distribution on the target plane. A secondary optical uniform lens is fabricated to solve the problems and the uniformity can be enhanced by using this design [
At first, the Cartesian plane and a spherical coordinate are established with the same origin of coordinate, where
Sketch of reflection.
Sketch of refraction.
Profile of the free-form lens.
Table
The simulation results of different curves.
Curve | 2 | 3 | 4 | 5 |
---|---|---|---|---|
|
101,110 | 114,900 | 109,520 | 112,170 |
|
57% | 64% | 63% | 63% |
The blocking of masks can lead to the decay of luminance. The central illuminance
Simulation results of the stacked shadowless lamp.
Item | No mask | 1 mask | 2 masks |
---|---|---|---|
|
114,900 | 64,983 | 78,032 |
|
0.640 | 0.570 | 0.680 |
Shadowless dilution | — | 0.553 | 0.645 |
The light field diameter
The CREE CXA1816 LED chip.
(a) Single mask and (b) double masks.
Figures
Simulation result of the light emission and irradiance map without mask.
Simulation result of the light emission and irradiance map with single mask.
Simulation result of the light emission and irradiance map with double mask.
3D (three-dimensional) printing technology is used to fabricate the ABS resin mold of this stacked shadowless lamp. Vacuum evaporation process is adopted to coat the reflective aluminum-based material on the surface of the mold, as shown in Figure
Vacuum evaporation process.
Figure
Actual measurement data of stacked shadowless lamp.
Item | No mask | 1 mask | 2 masks |
---|---|---|---|
|
102,500 | 59,144 | 68,147 |
|
0.680 | 0.540 | 0.559 |
Shadowless dilution | — | 0.577 | 0.665 |
Actual emission pattern on target plane.
In this research, we brought up a modified stacked elliptic curves shadowless lamp combined with uniform free-form lens. LED is used to the light source. The mold is fabricated by 3D printing technology and vacuum evaporation process. The
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors would like to thank the Ministry of Science and Technology of Taiwan for financially supporting this research through Grants nos. 103-2221-E-327-039-, 103-2623-E-110-003-ET, 102-2622-E-110-008-CC2, and 102-2622-E-110-006-CC3.