In medical situations, head-mounted displays have gained significant attention for providing physicians with immediate access to patient information. Traditional vital signs monitoring needs physical contact to patient and separates display to physicians. However, it is difficult to integrate the advanced computer-human interaction with contactless vital signs monitoring device. This paper discusses the design and implementation of HoloCV, a scalable mixed reality-based system that supports contactless vital signs monitoring and presents real-time pre-diagnostic results of patient to the visual field of physicians. HoloCV is supported by a distributed architecture divided into three interrelated applications responsible for advanced computer-human interaction, radar and thermal infrared device integration, computation and communication infrastructure, respectively. To monitor vital signs contactlessly and continuously, the HoloCV utilizes Impulse-Radio Ultra-WideBand(IR-UWB) radar and thermal infrared camera to achieve monitoring respiration rate, heart rate, blood pressure, and temperature. By running the YOLOv7-Tiny model directly on Microsoft Hololens2 head-mounted displays, HoloCV can achieve real-time object detection and present real-time visualizations of vital signs data on the detected targets. The overall weight of the system is less than or equal to 5 kilograms. It has a detection range of 0.5m to 3m, and can continuously operate for more than 1 hour with a standby time of 5 hours. The working environment temperature ranges from 0°C to 46°C. The heart rate measurement range is from 50 to 150 BPM, the respiratory rate measurement range is from 10 to 50 BPM. The temperature measurement range is from 32 degrees Celsius to 42 degrees Celsius, and the blood pressure measurement range is from 50 to 180 mmHg. With its capability for real-time and non-contact monitoring of vital signs, this HoloCV system differentiates itself from traditional contact-based device...