Welcome to Argus technical questions and answers section. The questions below are from customers like you, we hope you will find the answers helpful and informative.
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Questions and Answers
1. Camera engine, core, detector, sensor - what is this?
2. What does Argus use? Detectors or Engines?
3. Why has Argus developed its own engine?
4. What is a detector?
5. What is a Lens Assembly? Why do you need it?
6. What is Refresh Rate?
7. What are NETD and MDTD? What is best?
8. High, Low, Extended Low Gain Modes, what does this mean?
9. What is Recalibration, Image Freezing?
10. What are Dynamic / Temperature Range?
11. What is the best Field of View?
12. Why do some cameras have stretched images?
13. What is the best LCD Resolution? How should I calculate it?
14. What is Digital Processing?
15. Why a dynamic range 1000 degrees Celsius?
1. Camera engine, core, detector, sensor – what is this?
The words camera “engine”, “core”, “detector” and “sensor” have almost the same meaning but are, can and do have differences. These differences need describing to understand.
Camera engines or cores refer to a complete camera package including a detector, electronics and lens assembly. Some of these engines or cores can be supplied as complete cameras in housings. These are supplied by an original equipment manufacturer (OEM) as a complete ready-to-use camera without any protective plastics for fire fighting environments. A camera engine or core from an OEM can be used for security, surveillance or commercial application and may not have been specifically built, designed and set up for the fire applications. Examples of engines are shown below.
Camera detectors or sensors refer to the main infrared detection device inside all types of thermal cameras. To get an image from these detectors a lens assembly, electronics and specialised software have to be designed to run the detectors and to make a camera engine or core. By designing the electronics to match the detector it allows the camera to be developed specifically for a particular application, for example fire or police use. Examples of detectors are shown below.
2. What does Argus use? Detectors or Engines?
Argus4™ cameras use detectors and we have designed, developed and built our own engines. We have taken the detectors and designed the electronics to drive the detector, developed the specialised software to control and run the detectors and have designed a specific lens assembly to maximise the performance for fire applications.
The advantage of producing engines from the three components rather than allowing an OEM to provide the “engine” is that Argus:
- Has complete control over the performance of the camera
- Uses the correct lens assembly for the application
- Has designed the camera and electronics together
- Can specify high performance components and materials
- Does not rely on OEM performance limits and specifications
The Argus4™ cameras have been set-up, designed and developed for fire fighting applications. A core or engine from an OEM has not and may let you down when you need it most.
3. Why has Argus developed its own engine?
Argus has had nearly 30 years of experience in developing thermal image cameras and engines for fire fighting applications. This knowledge and experience allows us to pass onto the fire fighter the best possible performance of any thermal image camera.
By developing our own engine it allows us to:
- Offer the highest dynamic/temperature range
- Have the best image quality
- Have the best performance across three gain levels
- Add features easily and quickly
- React to customer specific needs and requirements.
An example is the dynamic/temperature range of the Argus cameras versus our competitors. The performance of our cameras can be 70 - 80% better than a camera using an engine/core supplier, for example our Argus4™ camera has a temperature range of 1000°C, and our closest engine user has a temperature range of 600°C.
4. What is a detector?
Detectors are small Focal Plane Array (FPA) devices that convert the infrared energy into signals that are then processed to produce a viewable thermal image. A FPA is similar to an Integrated Circuit (IC) package with legs that are soldered onto a Printed Circuit Board (PCB). They are the central part of any thermal imaging camera.
5. What is a Lens Assembly? Why do you need it?
The Lens Assembly gives the user a focused thermal image. Without a lens assembly you would see a blank screen. The lens assembly has other uses:
- It focuses the infrared energy onto the detector to ensure the maximum performance is achieved.
- Houses the shutter assembly to allow recalibration of the detector to maintain the cameras performance.
The Argus4 lens assembly has been designed to have stable performance across a wide ambient temperature range. This ensures that the image quality does not deteriorate when the camera is moved from cool/cold storage and enters a hot flash-over condition.
The lens assembly is made from a special material called germanium.
6. What is Refresh Rate?
The detector in the Argus4™ is refreshed at 120 Hz. To deliver the best image to the LCD display, the image refresh rate is reduced to 60Hz which eliminates noise when presented onto the LCD. Most users would not know by looking at an LCD that a camera is being refreshed at 30, 50 or 60 Hertz.
A reduced refresh rate camera is also available from Argus, this has the refresh rate capped at 9Hz for export control reasons.
7. What are NETD and MDTD? What is best?
Noise equivalent temperature difference (NETD) is a measure of the sensitivity of a detector's thermal radiation and is a measure of the internal noise of the detector.
Minimum Detectable Temperature Difference (MDTD) is not the same measure of performance as NETD. MDTD is a measure of the performance of infrared cameras and is tested as a measure of visibility.
Argus uses the MDTD value as it is a system value. Our competitors use a detector value. Losses are introduced into the system when a lens and germanium windows are put in front of the detector. These losses can be as much 10% per element in front of the detector. Argus value includes these losses. Actual figures could be 60 - 65mK for a competitor’s camera with a specification value of 50mK.
All of these measurements are taken at ambient temperature and using a chart set to 25°C. These NETD/MTDT figures decrease when the cameras are in the low gain mode. These figures can drop to as low 500mK.
8. High, Low, Extended Low Gain Modes, what does this mean?
All microbolometer detectors have at least two gain modes to expand their dynamic/temperature range. These can be called Normal/High gain and Low gain modes. What Argus has done is introduce a third gain mode called Extended Low gain mode which increases the dynamic/temperature range further. This then gives you the extra performance in the mid range compared to our competitors.
Most cameras will show the user what gain mode the camera is using via a graphical symbol or wording on the LCD display. In most cameras this is only when the cameras are in the low gain setting and is normally represented by an “EI” symbol. For the Argus cameras this is represented by a colour M symbol at the top of the LCD display as follows:
- Green M – High gain mode, temperature range up to 150°C (300°F)
- Amber M – Low gain mode, temperature range up to 450°C (840°F)
- Red M – Extended low gain mode, temperature range up to 1000°C (1850°F) in the Argus HR320, up to 800°C for the Argus 320.
Each time the camera changes gain mode a recalibration is performed to maximise the performance and image quality.
9. What is Recalibration, Image Freezing?
All microbolometer detectors need to recalibrate during their use to maintain the image quality and performance of the cameras. When the cameras recalibrate, for a short moment the image will freeze and during this time the camera reads the internal temperature of the camera and adjusts its settings based upon that internal temperature.
This recalibration/freezing of the image should be no longer than 200ms (0.2 seconds). Anything longer than that would dramatically reduce the usability of the camera.
Also the better the detector/engine manufacture ability to control the internal temperatures of the camera/detector/engine the less there will be a need to perform a recalibration. Some cameras perform recalibration every 20 – 30 seconds, the Argus cameras calibrates every 2 minutes.
10. What is Dynamic Range?
The dynamic range of a camera relates to how many temperatures can be displayed in any given scene. Each camera has a maximum range of temperatures between black (cold) and white (hot). The larger this range, the greater the range of temperatures that can be viewed. In a very dynamic scene (lots of different temperatures), this generally results in a higher quality image.
Competitor comparisons should be performed using scenes with high dynamic/temperature ranges and not performed in office environments. Cameras that have been set up to perform well in an office will perform poorly in normal operating conditions. The Argus cameras have been specifically developed to give maximum performance over a wide range of temperatures. This is why we have the three gain modes.
11. What is the best Field of View?
The 50° field of view in the Fire TIC series has been chosen to allow rapid coverage of a given area; you see more of a scene at any given time. With a narrower field of view the user would have to scan back and forwards, up and down and risk missing a vital object. Narrower fields of view are better for seeing detail in a smaller object at a greater distance and are typically preferred for security and surveillance applications.
12. Why do some cameras have stretched images?
The Argus camera matches the resolution of the detector to the LCD. There is no stretching of the image to make it fit. Argus cameras have "bi-linear interpolation" for resizing of image as this is performed digitally. The analogue signal provided in our competitors' cameras are stretched to fit. All detectors are 4:3 format, Argus LCD is 4:3 format. Bullard LCD, for example, is 16:9 format and 5:3.
13. What is the best LCD Resolution? How should I calculate it?
An LCD is made up of a number of pixels and each of these pixels has Red, Green and Blue elements. When calculating the resolution of an LCD these elements should not be taken into consideration. For example:
Argus4™ LCD format 320 x 240, resolution equals 76,800 pixels, not 320 x 720 (240 x 3) equaling 230,400.
Bullard Eclipse, 234 x 160 equals 37,440, not 112,320 (234 x 480).
14. What is Digital Signal Processing?
The Argus camera has all digital signal processing. This maintains the image quality from the detector to the LCD. Any digital to analog conversion will introduce some image degradation. The best way to determine if a camera is using digital processing is to view the on-screen graphics. If the graphics are crisp and clear, it is usually digitally driven, if they are poor and fuzzy it's analogue driven.
The Argus4™ uses the digital inputs available on the LCD display to maintain the image quality. This process is similar to the HDMI inputs versus analogue inputs on a standard LCD TV.
Camera manufacturers using OEM engines are likely to be using analogue video on the LCD.
15. Why a dynamic range of 1832°F (1000°C)?
Once the camera reaches its maximum dynamic range all temperatures above that value will be white. If the viewed scene has very high temperatures then the image will become non-discernible.
Extending the dynamic range gives the user confidence he can view high temperatures without the loss of image quality. This is achieved in the Argus4™ by having three gains modes that stretches the gain / performance over a greater temperature range.
Also, the Argus4™ uses advance software techniques that maximise the contrast and sharpness of the viewed scene. Therefore, temperatures as low as 80°F can be viewed alongside temperatures of over 1500°F. If you have a victim laying on the floor in front of a very high heat source you will see the distinct outline of the person, not just a white spot!
