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| | | O Wide Spectral Range Detection Technology (Including Invisible Light) | | |
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| | | We can only see light within an extremely limited range. That range Is about 400 nm(nanometers) to 700 nm and is called the visible light range. The other light ranges that we cannot normally see contain vast quantities of hidden information. At Ha-mamatsu Photonics we are developing systems capable of detecting and imaging a wide spectrum of light up to the X-ray and infrared ray ranges. | | •Infrared reflectography Old pillar painting (Amida Hall of Hohkai Temple, Kyoto, Japan) (Photo courtesy of Mr. Sadatoshi Miura, National Research Institute for Cultural Properties, Tokyo) | | |
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| | | White light | | |
| | | [Light Spectrum] | | |
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| | | ▲Normal photograph •X-ray image | | ▲Infrared reflectogram taken with Ir camera (Enlarged view of head: A picture hidder under soot and dust appears visible.) | | |
| | | Prism | | |
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| | | Light spectrum | | |
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| | | | | | | | | | | ™ X-ray ^UV ray | □ | Infrared ^ Far infrared ray ray Radio wave | | | | Invisible regions | Visible | Invisible regions | | | | Short wavelength — | regions | —Long wavelength | | | | | | | | | | |
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| | | Inspection of canned food ► (foreign matter in circle) | | |
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| | | Approx. 400 to 700 nm | | |
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| | | [Imaging sensitivity comparison] | | |
| | | Light is a stream of particles called photons. Our everyday environment is filled to overflowing with photons. About 200 trillion photons rain down on us at an average indoor brightness (200 lux to 400 lux). That figure drops to 1/1000th of a lux for starlight on a moonless night and declines even further in the region called extremely low light levels where the brightness of light is less than one billionth of a lux and is completely impossible to see with the naked eye. In this region there are only a few photons each second per one square millimeter. The signal received from one photon is so small that it cannot be captured by the typical high sensitivity industrial camera. Photon counting imaging is a technique for visualiz | | |
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| | | ||Generatpurpose vkleo camera |||| III General-purpose video camerali | | |
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| | | || I High sensitivity camera (SIT, etc.)|||| | | |
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| | | Photon counting imaging | | |
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| | | Starlight | | |
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| | | 104 106 108 photons/mm2 - sec (wavelength = 550 nm) | | |
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| | | ing an image in extremely low light levels, by de-
| | •Examples of photon counting imaging | | |
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| | | tecting individual photons and their positions and then by integrating the detected signals. | | |
| | | OYoung's interference experiment | | OHuman facial image | | |
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| | | i ▲ 10-minute Integrator | | |
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| | | Young's experiment was conducted in an extremely low light region. Results prove light has properties of both a wave and a particle. | | |
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| | | ▲ 10-seconC integration | | |
| | | ▲ 10-seconc integration | | | ▲6.5-hour integration | | |
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| | | •Images taken with streak camera | | |
| | | The streak camera is a device for measuring ultra high speed (ultra-short) phenomenon. Unlike the ordinary camera that captures actual images, the streak camera captures the state within the extremely short time that the light intensity changes. The principle of the streak camera is simple. Light input in the form of a slit is converted into electrons on the photoelectric surface called "photocathode". These electrons are then swept at high speed (from top to bottom) and reconverted back into a light image on the phosphor screen. The changes in the input light intensity over time can in this way be observed as variations in image brightness that change from top to bottom. Hamamatsu Pho- | | |
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| | | tonics developed and marketed an advanced streak camera with a time resolution down to 200 femtoseconds. | | [Operating principle of streak camera] Streak tube | | |
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| | | ▲Intensity profile and streak image of pulsed light from a CPM ring laser | | ▲Optical fiber chromatic dispersion (Shows the difference in arriva times according to the light wavelength conveyed in the cable.) | | |
| | | Input light (pulsed light) | | |
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| | | Phosphor screen | | |
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| | | Electron trajectories | | |
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