Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Night Vision shopping experience:
1. Compare - without doubt the biggest advantage that the Night Vision offers shoppers today is the ability to compare thousands of Night Vision at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Night Vision? Wrong! If the Night Vision is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Night Vision then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Night Vision? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Night Vision and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Night Vision wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Night Vision then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Night Vision site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Night Vision, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Night Vision, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
soldiers pictured during the 2003 Iraq War seen through an Image Intensifier
Night vision is the ability to see in a dark environment. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range.
Night Vision Approaches
Spectral range
Night-useful spectral range techniques make the viewer sensitive to types of light that would be invisible to a human observer. Human vision is confined to a small portion of the
electromagnetic spectrum called
visible light. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation (such as near-
infrared or
Ultraviolet radiation). Some animals can see well into the infrared and/or ultraviolet, compared to humans; enough to help them see in conditions humans cannot.
Artificial night vision commonly works in two very different ways, depending on the technology used.
Image enhancement - This works by collecting the tiny amounts of light, including the lower portion of the infrared light spectrum, that are present but may be imperceptible to our eyes, and amplifying it to the point that we can easily observe the image.
Thermal imaging - This technology operates by capturing the upper portion of the infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light. Hotter objects, such as warm bodies, emit more of this light than cooler objects like trees or buildings.
Intensity range
Sufficient intensity range is simply the ability to see with very small quantities of light. Although the human visual system can, in theory, detect single photons under ideal conditions, the neurological
noise filters limit sensitivity to a few tens of photons, even in ideal conditions . Some animals have
evolution better night vision through the use of a larger optical
aperture, improved retina composition that can detect weaker light over a larger spectral range, more photoefficient optics in the eye, and improved neurological filtering which is more tolerant of noise. Enhanced intensity range is achieved via technological means through the use of an
image intensifier, gain multiplication CCD, or other very low-noise and high-sensitivity array of photodetectors.
Biological night vision
In biological night vision, molecules of
rhodopsin in the rods of the
eye undergo a change in shape as light is absorbed by them. Rhodopsin is the chemical that allows night-vision, and is extremely sensitive to light. Exposed to white light, the pigment immediately bleaches, and it takes about 30 minutes to regenerate fully, but most of the adaptation occurs within the first five or ten minutes in the dark. Rhodopsin in the human rods is insensitive to the longer red wavelengths of light, so many people use red light to preserve night vision as it will not deplete the eye's rhodopsin stores in the
rod cells and instead is viewed by the
cone cells.
Some animals, such as cats, dogs, and deer have a structure called tapetum lucidum in the back of the
eye that reflects light back towards the retina, increasing the amount of light it captures. In humans, only 10% of the light that enters the eye falls on photosensitive parts of the
retina. An animal's ability to see in low light levels may be similar to what humans see when using first or perhaps second generation image intensifiers.
Night glasses
Night glasses are telescopes or
binoculars with a large diameter objective. Large lenses can gather and concentrate light, thus intensifying light with purely optical means and enabling the user to see better in the dark than with naked eye alone. Often night glasses also have a fairly large exit pupil of 7 mm or more to let all gathered light into the user's eye. However, many people can't take advantage of this because of the limited dilation of the human pupil. To overcome this, soldiers were sometimes issued
atropine eye drops to dilate pupils. Before the introduction of image intensifiers, night glasses were the only method of night vision, and thus were widely utilized, especially at sea. Second World War era night glasses usually had a lens diameter of 56 mm or more with magnification of seven or eight. Major drawbacks of night glasses are their large size and weight.
Infrared Filters
Infrared (IR) filters are made of polysulphone plastic that blocks over 99% of the visible light spectrum from any “white” light source.Infrared filters allow a maximum of infrared output while maintaining extreme covertness. Currently in use around the world, infrared filters are used in Military, Law Enforcement, Industrial and Commercial applications. The unique makeup of the plastic allows for maximum durability and heat resistance. IR filters provide a more cost effective and time efficient solution over the standard bulb replacement alternative. All Generations of night vision devices are greatly enhanced with the use of IR Filters.
Thermal vision
For
infrared, or thermal, sensing is generally not considered night vision because it is constructed with mechanisms substantially different from the methods used to sense visible light. It is possible to construct an imaging device with microwave energy,
sound, or any other signal that is reflected or radiated by objects and can be focused and sensed, but these are also not generally considered night vision.
Some animals have the ability to sense far infrared energy which we perceive as heat. This is prevalent in some
snakes such as Crotalinaes and
Boa (genus). However, this is not actual "vision", but more of a system of thermosensitive pits in the face that can detect the amount of heat and the distance to the heat source. There is still some debate as to what degree this information is perceived as "feeling" heat, and to what degree it is processed as an image by the snake's brain. Since these sense structures lack imaging optics, the spatial sensory perception resolution is considered very poor.
See Thermographic camera.
Image intensifier
The image intensifier is a vacuum-tube based device that converts visible light from an image so that a dimly lit scene can be viewed by a camera or the naked eye. While many believe the light is "amplified," it is not. When IR light strikes a charged photocathode plate electrons are emitted through a vacuum tube that strike the microchannel plate that cause the image screen to illuminate with a picture in the same pattern as the IR light that strikes the photocathode, and is on a frequency that the human eye can see. This is much like a CRT
television, but instead of color guns the photocathode does the emitting. The image is said to become "intensified" because the output visible light is brighter than the incoming IR light, and this effect directly relates to the difference in passive and active night vision goggles. Currently, the most popular image intensifier is the drop-in ANVIS module.
Night vision devices
A
night vision device (NVD) is a device comprising an IR image intensifier tube in a rigid casing, commonly used by military forces. A specific type of NVD, the night vision goggle (or NVG) is a night vision device with dual eyepieces; the device can utilize either one intensifier tube with the same image sent to both eyes, or a separate image intensifier tube for each eye. Other types include monocular night vision devices with only one eyepiece which may be mounted to firearms as night sights.
See also
Patents
- - http://xenonics.sc48.biz/press/articles/article.php?article_id=67
World Manufacturers of Night Vision Devices
External links
- Night Vision & Electronic Sensors Directorate - Fort Belvoir, Virginia
soldiers pictured during the 2003 Iraq War seen through an Image Intensifier
Night vision is the ability to see in a dark environment. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range.
Night Vision Approaches
Spectral range
Night-useful spectral range techniques make the viewer sensitive to types of light that would be invisible to a human observer. Human vision is confined to a small portion of the electromagnetic spectrum called
visible light. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation (such as near-infrared or Ultraviolet radiation). Some animals can see well into the infrared and/or ultraviolet, compared to humans; enough to help them see in conditions humans cannot.
Artificial night vision commonly works in two very different ways, depending on the technology used.
Image enhancement - This works by collecting the tiny amounts of light, including the lower portion of the infrared light spectrum, that are present but may be imperceptible to our eyes, and amplifying it to the point that we can easily observe the image.
Thermal imaging - This technology operates by capturing the upper portion of the infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light. Hotter objects, such as warm bodies, emit more of this light than cooler objects like trees or buildings.
Intensity range
Sufficient intensity range is simply the ability to see with very small quantities of light. Although the human visual system can, in theory, detect single
photons under ideal conditions, the neurological noise filters limit sensitivity to a few tens of photons, even in ideal conditions . Some animals have evolution better night vision through the use of a larger optical aperture, improved
retina composition that can detect weaker light over a larger spectral range, more photoefficient optics in the eye, and improved neurological filtering which is more tolerant of noise. Enhanced intensity range is achieved via technological means through the use of an image intensifier, gain multiplication CCD, or other very low-noise and high-sensitivity array of photodetectors.
Biological night vision
In biological night vision, molecules of
rhodopsin in the rods of the eye undergo a change in shape as light is absorbed by them. Rhodopsin is the chemical that allows night-vision, and is extremely sensitive to light. Exposed to white light, the pigment immediately bleaches, and it takes about 30 minutes to regenerate fully, but most of the adaptation occurs within the first five or ten minutes in the dark. Rhodopsin in the human rods is insensitive to the longer red
wavelengths of light, so many people use red light to preserve night vision as it will not deplete the eye's rhodopsin stores in the
rod cells and instead is viewed by the
cone cells.
Some animals, such as
cats, dogs, and
deer have a structure called
tapetum lucidum in the back of the
eye that reflects light back towards the retina, increasing the amount of light it captures. In humans, only 10% of the light that enters the eye falls on photosensitive parts of the retina. An animal's ability to see in low light levels may be similar to what humans see when using first or perhaps second generation image intensifiers.
Night glasses
Night glasses are
telescopes or binoculars with a large diameter objective. Large lenses can gather and concentrate light, thus intensifying light with purely optical means and enabling the user to see better in the dark than with naked eye alone. Often night glasses also have a fairly large exit pupil of 7 mm or more to let all gathered light into the user's eye. However, many people can't take advantage of this because of the limited dilation of the human pupil. To overcome this, soldiers were sometimes issued
atropine eye drops to dilate pupils. Before the introduction of image intensifiers, night glasses were the only method of night vision, and thus were widely utilized, especially at sea. Second World War era night glasses usually had a lens diameter of 56 mm or more with magnification of seven or eight. Major drawbacks of night glasses are their large size and weight.
Infrared Filters
Infrared (IR) filters are made of polysulphone plastic that blocks over 99% of the visible light spectrum from any “white” light source.Infrared filters allow a maximum of infrared output while maintaining extreme covertness. Currently in use around the world, infrared filters are used in Military, Law Enforcement, Industrial and Commercial applications. The unique makeup of the plastic allows for maximum durability and heat resistance. IR filters provide a more cost effective and time efficient solution over the standard bulb replacement alternative. All Generations of night vision devices are greatly enhanced with the use of IR Filters.
Thermal vision
For
infrared, or thermal, sensing is generally not considered night vision because it is constructed with mechanisms substantially different from the methods used to sense visible light. It is possible to construct an imaging device with microwave energy,
sound, or any other signal that is reflected or radiated by objects and can be focused and sensed, but these are also not generally considered night vision.
Some animals have the ability to sense far infrared energy which we perceive as heat. This is prevalent in some snakes such as Crotalinaes and
Boa (genus). However, this is not actual "vision", but more of a system of thermosensitive pits in the face that can detect the amount of heat and the distance to the heat source. There is still some debate as to what degree this information is perceived as "feeling" heat, and to what degree it is processed as an image by the snake's brain. Since these sense structures lack imaging optics, the spatial sensory perception resolution is considered very poor.
See
Thermographic camera.
Image intensifier
The image intensifier is a vacuum-tube based device that converts visible light from an image so that a dimly lit scene can be viewed by a camera or the naked eye. While many believe the light is "amplified," it is not. When IR light strikes a charged
photocathode plate electrons are emitted through a vacuum tube that strike the microchannel plate that cause the image screen to illuminate with a picture in the same pattern as the IR light that strikes the photocathode, and is on a frequency that the human eye can see. This is much like a CRT television, but instead of color guns the photocathode does the emitting. The image is said to become "intensified" because the output visible light is brighter than the incoming IR light, and this effect directly relates to the difference in passive and active
night vision goggles. Currently, the most popular image intensifier is the drop-in ANVIS module.
Night vision devices
A
night vision device (NVD) is a device comprising an IR image intensifier tube in a rigid casing, commonly used by military forces. A specific type of NVD, the night vision goggle (or NVG) is a night vision device with dual eyepieces; the device can utilize either one intensifier tube with the same image sent to both eyes, or a separate image intensifier tube for each eye. Other types include monocular night vision devices with only one eyepiece which may be mounted to firearms as night sights.
See also
Patents
- - http://xenonics.sc48.biz/press/articles/article.php?article_id=67
World Manufacturers of Night Vision Devices
External links
- Night Vision & Electronic Sensors Directorate - Fort Belvoir, Virginia
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Night vision - Wikipedia, the free encyclopedia
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Night Vision Optical Equipment :: Cobra Optics:ASP:Yukon Optics ...
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