Comprehensive Design Approach for Pan-Tilt-Zoom (PTZ) Cameras

Abstract

The Pan-Tilt-Zoom (PTZ) camera is a sophisticated device that has numerous applications, including security and surveillance. This paper provides a comprehensive design method for PTZ cameras, addressing the key aspects such as mechanical design, optical systems, control mechanisms, and software integration. The primary objective is to achieve high-quality imaging, extensive coverage, reliability, user control, and seamless system integration. To learn more about our end-to-end camera design and product engineering services, visit eInfochips’ Camera Design Solutions.

Abbreviations

• PTZ: Pan-Tilt-Zoom
• FoV: Field of View
• GUI: Graphical User Interface
• IP: Ingress Protection
• ONVIF: Open Network Video Interface Forum
• RTSP: Real-Time Streaming Protocol
• CMOS: Complementary Metal-Oxide-Semiconductor

Introduction

Pan-tilt zoom (PTZ) cameras are advanced monitoring equipment that provide versatility in recording high-resolution videos over a wide area. PTZ cameras can pan, tilt, and zoom and are suitable for most applications such as security, traffic monitoring, and wildlife-watching. This paper introduces an overall design strategy for PTZ cameras, including the important aspects, such as mechanical design, optical systems, control mechanisms, and software integration.

Design Objectives

Essential Features of the Cellular IoT Camera

1. 4G LTE Connectivity: Critical for remote supervision where access is limited and the Wi-Fi power is insufficient.

- Motion Detection: Alerts with real-time photo alerts and allows for live or recorded videos viewing via a camera management program on smartphones, tablets, or laptops.
- Outdoor Durability: Waterproof construction is compliant IP-66 and survives a 2-meter fall without any functional damage.

- Temperature Recovery Ability: Operational even at temperatures ranging from -4° to 140° Fahrenheit (-20°C at 60°C).
- Flexible Mounting Options: Equipped with a tripod, a mounting strap, or a Python lock.
- External Port: Equipped with an external port for attaching devices such as an external flash or RF transceiver.
- Internal Storage: Includes internal disk storage and an optional SD card slot, with protection against the use of incompatible SD cards.

- Rechargeable Battery: A Lithium-ion rechargeable battery with 2 to 3 months of regular use duration is provided. It can be charged on-the-go via solar panels or an external battery pack.
- Flash LED IR: Flash LED infrared is used with a minimum light range of sixty feet and the flash models can change.
- Motion Sensors: A single sensor with a 20-meter range and three smaller sensors on the three sides with a 10-meter range are used.
- Customizable Camera Case: Cases are surveillance and outdoor hunting-specific, with customizable color patterns and options such as a universal camera mounting slot, python lock holes, and strap thread holes.
- LED Indicator: The front cover has an LED indicator or screen for showing camera status, with an optional display screen for setup.

Omni-directional Antenna: A built-in option is preferred to prevent damage, with an external antenna connector for better signal reception.

Mechanical Design

Pan-Tilt Mechanism
Pan Mechanism: To set it up, a motor, pulley, and belt are used to let the camera pan. A stepper motor makes sure the movement stays smooth. This motor links to a worm and worm-wheel gearbox, which keeps the mechanism from moving the wrong way and boosts the motor's holding power making its detent torque stronger. The pan mechanism uses a pulley and belt system to mount this motor. The pulley is metal, while the belt is made of Kevlar. This prevents the change in belt tension due to the inextensibility of Kevlar. This is necessary to ensure a tilt time of 4 seconds consistently. The pan mechanism consists of a rotative hub that is mounted into the stationary hub with a built-in shaft and bearing. It is kept steady with the help of an inheritance device that is also combined with assembly for the control pulley.

Tilt Mechanism: With the pulley and belt engine setup, the camera achieves its tilted movement like a pan mechanism. The difference in this case is that employed is the use of a spur gearbox motor as compared to the use of a worm and worm-wheel gearbox motor within the pan mechanism. This is achieved with the aim of conserving space.

Another reason is that the retaining torque needed to keep the mechanism in position is not as much as is needed in keeping a worm and worm-wheel arrangement in position. To consistently achieve the 4-second tilting time, this is especially important. The pan mechanism consists of the rotating hub mounted into the fixed hub with a built-in shaft and bearing. This is guaranteed by the help of a reservoir also acting as a council for the controlled pulley.

Zoom Mechanism

• Optical Zoom: Uses a lens system with different focal lengths. The lens must be optimized to reduce optical distortion and preserve image quality across the zoom range.
• Digital Zoom: Involves digital cropping and image enlargement. This technique is less preferred than optical zoom because of the loss of image quality.

Enclosure Design

The enclosure was designed with the simple goal of keeping all the parts inside the camera and making sure it functions properly. The enclosure is composed of five parts, all of which have been discussed in detail later in the research paper. Let us now discuss the purpose of the enclosure design.

The team carried out a straightforward proof of concept to check out how well the enclosure could tilt and pan, how efficient its mechanisms were, how stable it was when mounted, and how long each function took. This POC, once tested, was subsequently employed to make an ID (Industrial Design) that was designed with considerations like functionality, aspects, and target market in mind.

The enclosure design is divided into the following parts:

• Camera Module: The camera module consists of a camera sensor, a camera PCB, and camera mounting. The enclosure is made of aluminum and has an IP rating. Shafts on both sides of the enclosure are designed to be installed in the camera hub module using bearings.
• Camera Hub Module: The camera hub module consists of two main components, the camera hub that contains an internal fixed arm and a removable arm. The arms are meant to act as a casing for the bearings and the bearing retainers in a way that the camera hub shafts are installed into the same. One arm can be removed to make the camera hub fitment more useful. Additionally, the camera hub serves as a driver-board PCB and a tilt-motor mounting device. These combination components make up the camera module assembly. It also includes a gasket for an IP rating of the enclosure. This assembly rotates inside the pan hub assembly.
• Pan Hub Assembly: The pan hub assembly consists of two key components: a fixed hub and a rotating hub. The rotating hub is where one finds both the pan assembly mechanism and the pan motor neatly housed together. The fixed and rotating hub assembly are both mounted with a hub, a bearing, and a bearing-retainer through the fixed hub's integrated shaft. This whole pan assembly is mounted on the PIR Module using the mounting bosses on the top surface.
• PIR Module Assembly: The PIR module is made up of two principal components, the PIR module and the top cover and PIR sensor assemblies. This assembly has four PIR sensors positioned around its edge to detect motion. These sensors are covered by a black translucent Fresnel lens which is mounted to a lens holder using adhesive.
• Mounting Bracket Assembly: The mounting bracket assembly is made up of battery casing, bracket casing, and camera hinge. The battery casing is the name given to the cover of the detachable battery. The camera hinge and battery casing are joined by the bracket casing. Additionally, it must route the necessary wires and make sure there is some room between the main camera body and the camera mount. The hinge of the camera is mounted on the casing of the bracket and is used as a mounting and quick release system for the main camera body.

Optical System

Lens Selection

• Field of View (FoV): It is important to take into account the coverage of the lens when selecting a lens. Although they offer greater coverage, wide-angle lenses may cause edge distortion.
• Aperture Size: Usage of larger apertures is preferred for improved low-light performance, but it could make the lens larger and more expensive.

Sensor Selection

• Resolution: Higher resolution sensors, such as 4K or 8K, provide clearer images.
• Low-Light Performance: Sensors with higher sensitivity, like back-illuminated CMOS sensors, perform better in low-light environments.

Control Mechanisms

*Mechanical Control *

• Servo Motors: High-precision servo motors control pan, tilt, and zoom functions, ensuring smooth and accurate operation.
• Feedback Systems: Implement feedback systems, such as encoders, for precise control and positioning.

*Electronic Control *

• Control Interface: Provide various control methods, including manual, remote, and automated options. Interfaces may include joysticks, web-based applications, or third-party software integration.
• **Communication Protocols: **Compatibility with standard protocols, such as ONVIF, RTSP, or proprietary APIs, for seamless system integration is vital.

Software Integration

*8.1 Firmware Development *

• The firmware should be optimized for performance and stability, handling control commands, image processing, and system communication.
• Updates to the firmware are needed regularly to enhance functionality and address security vulnerabilities.

8.2 User Interface

• An intuitive Graphical User Interface (GUI) should be provided to enable easy configuration of camera settings, PTZ controls, and access to live or recorded footage.
• Compatibility with mobile devices should be ensured to facilitate remote access and control.

Testing and Validation

Performance Testing

Image quality must be tested for resolution, color accuracy, and distortion over the range of zoom.

It is necessary to test the precision and fluidity of the pan, tilt, and zoom functions.

Durability testing must be performed to test performance in different environmental conditions, including elevated temperatures, humidity, and exposure to the elements.

User Feedback

To improve the control scheme and interface, usability testing should be done.

Prototypes should be released into the real world for field testing to assess overall performance and obtain information for enhancement.

Conclusion

Designing a PTZ camera involves inputs from many different fields, including programming, electronics, mechanical engineering, and optics. High-quality imaging, robust performance, and usability are key considerations. Ongoing testing and optimization are required to guarantee efficient real-world function.

Author(s) Bio:
Harsh Chaudhary
Harsh Chaudhary is a Mechanical Design Engineer at eInfochips, with two years of experience in CAD modeling, product development, and designing IP-rated Internet of Things devices, including PTZ cameras and machine vision. His innovative effort has been patented and recognized with awards such as the AP-Expo and IIT Kharagpur's Indian Student Space Challenge award. Harsh is now pursuing a master’s degree in design engineering. He graduated with a B. Tech in Mechanical Engineering from ABES Engineering College. He is known for his technical competence, critical thinking, and enthusiasm for engineering innovation.

Abhiraj Kasana:
Abhiraj Kasana is a Mechanical Engineer with experience spanning more than a decade in product development, mechanical design, and manufacturing systems. He has been instrumental in the introduction of more than ten successful products in a variety of sectors, including consumer electronics, industrial automation, and medical devices. Skilled in applications including SolidWorks and Autodesk Inventor, Abhiraj has expertise in rapid prototyping and Design for Manufacturing (DFM). Some of his accomplishments are obtaining patents and achieving awards such as the Most Innovative Project Award in AP-Expo and achievement at IIT Kharagpur's Indian Student Space Challenge. Abhiraj has also worked with MIT on new projects like the COVID Detection System and the Automated Disease Sample Collector. Having a bachelor’s degree in mechanical engineering from ABES Engineering College, he is committed to pushing engineering solutions with an emphasis on efficiency, reliability, and sustainability.

Lovkesh Singh:
Lovkesh Singh is a Mechanical Design Engineer with 14 years of experience in new product introduction, product sustenance engineering, and product development. He has experience in medical devices, home appliances, IoT solutions, and farm equipment. He has experience in CAD tools like Creo, SolidWorks, and NX. Lovkesh also possesses strong knowledge of international standards such as ISO 13485 and ISO 14971.
In his career, he has spearheaded cross-functional teams, cost-reduction activities, and has overseen intricate electromechanical product designs from concept through production. He is known for his technical prowess and leadership and has a Bachelor of Science in Mechanical Engineering. Lovkesh believes in furthering user-centered, dependable design engineering solutions.