Smart Intensity Control in Surgical Lights for Efficient Shadow Reduction Using Ultrasonic Sensor

Abstract

Surgical lights with single or multiple light heads assemblies are required to provide illumination at surgical sites, but it has been observed that manual intervention is required to move the light head each time the surgeon changes their position to reduce the effect of shadows, this causes obstruction in surgical procedure as well contamination of instruments such as surgical light head, resulting into more frequent sterilisation cycles. This research approach aims at designing a system capable of detecting the surgeon's head and based on the distance between the surgeon and the light head, sufficient rise in intensity is provided to compensate for the loss of intensity due to obstruction. Gesture control is provided as an alternative to enable touchless control. It was found that the intensity compensation provided was in most cases identical to the original intensity values obtained without obstruction, and slightly lower in few extreme cases. Taking into account the hardware limits of light head assembly as well as the maximum achievable intensity limit approved, it was observed that the system with automatic intensity compensation performed better than the original system. Gesture control implementation was found adaptable and a useful feature in majority based on the mock tests conducted with the users.

Appendix A

Working Instructions for Gesture Control System

• 1. Turn ON the Mains power supply.

• 2. Switch over to the gesture control mode.

• 3. Place the hand below any of the three light-head sub-assemblies (i.e. near the sensor) at a distance of at least 30 cm below the light head.

• 4. If the hand is placed below either Left or Right sensor, after 2 s slowly move the hand downwards ensuring that hand is vertically aligned with the sensor.

• 5. If the hand is aligned with Left sensor the intensity of the light-head should start decreasing and for the right sensor the intensity should start increasing.

• 6. If the hand is placed under the front sensor, after 2 s the light-head should go under standby mode.

• 7. For switching from one sensor to another, Remove hand from under the sensor, wait for 4–5 s and then repeat the above-mentioned procedure again for that respective sensor.

• 8. After the testing, turn OFF the light-head assembly.

LED Power Calculations

Light-head consists of 3 LED strings, each string having 9 LEDs.

Forward voltage of each single LED is 3.1V at max and a forward current of 700 mA is supplied at max.

There the power consumption is calculated as

$$\begin{aligned} P & = {\text{number of LEDs }} \times {\text{ Forward voltage }} \times {\text{ Current through LED}} \\ P & = \, \left( {{9} \times {3}} \right) \, \times {3}.{1 } \times 0.{7} \\ P & = {58}.{59}\;{\text{W}}{.} \\ \end{aligned}$$

Let us consider the driver efficiency of 80%, so the actual power consumption will be

$$\begin{gathered} P = 58.59/0.8 \hfill \\ P = 73.23{\text{ W}} \hfill \\ \end{gathered}$$

Hence, the AC–DC power supply that is used is of 100 watt and has foldback protection.

The current driver used is a boost converter with an output range of 12–64 VDC, 700 mA.