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| public:optical_instruments 2010/07/19 12:14 | public:optical_instruments 2017/05/03 21:53 current | ||
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| ===== Lamps ===== | ===== Lamps ===== | ||
| - | Lams Pare non coherent sources that usually emit light propagate to all directions. In photo physics research, lamps are used both for illumination and calibration. | + | Lamps are non coherent sources that usually emit light propagate to all directions. In photo physics research, lamps are used both for illumination and calibration. |
| ===== Incandescent Lamps ===== | ===== Incandescent Lamps ===== | ||
| Incandescent lamps are the most common type of light source. Typical incandescent lamps emit light by heating the filament and the emitted light continues broadband spectrum, which can be described by black body radiation. \\ | Incandescent lamps are the most common type of light source. Typical incandescent lamps emit light by heating the filament and the emitted light continues broadband spectrum, which can be described by black body radiation. \\ | ||
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| A prism bends light beam with different wavelengths at different angles based on their refraction index. \\ | A prism bends light beam with different wavelengths at different angles based on their refraction index. \\ | ||
| - | {{ :research:optical_instruments:light_dispersion_by_prism.jpg?250 }}\\ | + | {{ :research:optical_instruments:light_dispersion_by_prism.jpg?300 }}\\ |
| - | **Light Dispersion by a Prism \\ | + | **Light Dispersion by a Prism** \\ |
| ===== Spectrometers and Spectrograph ===== | ===== Spectrometers and Spectrograph ===== | ||
| Spectrometers are the mostly used optical instruments in spectroscopy studies that use diffraction gratings to convert the spectral difference of the photons into spatial differences. A common form of spectrometer is the Czerny-Turner design as shown in the following figure. \\ | Spectrometers are the mostly used optical instruments in spectroscopy studies that use diffraction gratings to convert the spectral difference of the photons into spatial differences. A common form of spectrometer is the Czerny-Turner design as shown in the following figure. \\ | ||
| - | {{ :research:optical_instruments:czerny-turner_monochromator.png?350 }} \\ | + | {{ :research:optical_instruments:czerny-turner_monochromator.png?400 }} \\ |
| **Czerny-Turner Monochromator** \\ | **Czerny-Turner Monochromator** \\ | ||
| The input light is focused into the entrance slit, which is at the focus plane of the collimating mirror. The collimated light is then diffracted based on its wavelength on the surface of the rotating grating. The light is finally focused on the exit plane by the focusing mirror. At the exit plane, the input light is spreading out linearly to a spectrum. \\ | The input light is focused into the entrance slit, which is at the focus plane of the collimating mirror. The collimated light is then diffracted based on its wavelength on the surface of the rotating grating. The light is finally focused on the exit plane by the focusing mirror. At the exit plane, the input light is spreading out linearly to a spectrum. \\ | ||
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| - | {{ :research:optical_instruments:dual_monochromator_excitation-emission_fluor_spec.png?350 }} \\ | + | {{ :research:optical_instruments:dual_monochromator_excitation-emission_fluor_spec.png?400 }} \\ |
| **Dual monochromator excitation-emission fluorescence spectrometer** \\ | **Dual monochromator excitation-emission fluorescence spectrometer** \\ | ||
| Typical steady fluorescence emission spectra of Rhodamin B, rose Bengal, 9-cyanoanthracene is shown here. \\ | Typical steady fluorescence emission spectra of Rhodamin B, rose Bengal, 9-cyanoanthracene is shown here. \\ | ||
| - | {{ :research:optical_instruments:fluor_emission_spectra_of_3.png?350 }} \\ | + | {{ :research:optical_instruments:fluor_emission_spectra_of_3.png?400 }} \\ |
| **Fluorescence emission spectra of Rhodamin B, rose Bengal, 9-cyanoanthracene** \\ | **Fluorescence emission spectra of Rhodamin B, rose Bengal, 9-cyanoanthracene** \\ | ||
| ===== Time-Resolved Fluorescence Spectroscopy ===== | ===== Time-Resolved Fluorescence Spectroscopy ===== | ||
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| - | {{ :research:optical_instruments:optical_schematics_of_a_pulse_sampling_system.png?350 }} | + | {{ :research:optical_instruments:optical_schematics_of_a_pulse_sampling_system.png?450 }} |
| **Optical schematics of a pulse sampling time-resolved fluorescence spectroscopy system** \\ | **Optical schematics of a pulse sampling time-resolved fluorescence spectroscopy system** \\ | ||
| Time-resolved fluorescence apparatus usually require far more complex synchronization design. Here is the electronics system design of the above system: \\ | Time-resolved fluorescence apparatus usually require far more complex synchronization design. Here is the electronics system design of the above system: \\ | ||
| - | {{ :research:optical_instruments:electronics_schematics_of_pulse_sampling_system.png?350 }} \\ | + | {{ :research:optical_instruments:electronics_schematics_of_pulse_sampling_system.png?500 }} \\ |
| - | **Electronics schematic of a pulse sampling time-resolved fluorescence spectrometer \\ | + | **Electronics schematic of a pulse sampling time-resolved fluorescence spectrometer** \\ |
| Time-resolved fluorescence spectrum of Rhodamin B and 9-cyanoanthracene mixture solution is shown here. Rhodamin B has emission peak at 580nm and lifetime of 3.03ns while 9-cyanoanthracene has emission peak at 445nm and lifetime of 12ns. \\ | Time-resolved fluorescence spectrum of Rhodamin B and 9-cyanoanthracene mixture solution is shown here. Rhodamin B has emission peak at 580nm and lifetime of 3.03ns while 9-cyanoanthracene has emission peak at 445nm and lifetime of 12ns. \\ | ||
| - | {{:research:optical_instruments:rhodamin_b_and_9-cyanoathracene.png}} \\ | + | {{ :research:optical_instruments:rhodamin_b_and_9-cyanoathracene.png?850 }} \\ |
| **Time-resolved fluorescence spectral of the mixture solution of Rhodamin B and 9-cyanoanthracene** \\ | **Time-resolved fluorescence spectral of the mixture solution of Rhodamin B and 9-cyanoanthracene** \\ | ||
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| ====== Why Are Lasers Dangerous? ====== | ====== Why Are Lasers Dangerous? ====== | ||
| - | The light sources and detectors used in optical instruments are potential sources of hazards to human if not properly operated. These hazards primarily come from the optical radiation, high voltage electrical devices, and chemicals. \\ | + | The light sources and detectors used in optical instruments are potential sources of hazards to human if not properly operated. These hazards primarily come from the optical radiation, high voltage electrical devices, and chemicals. |
| + | \\ | ||
| ===== Laser and Light Radiation Safety ===== | ===== Laser and Light Radiation Safety ===== | ||
| - | Optical radiation hazards from the Sun light and high intensity lamps to human have long been discovered since their use in scientific research. They had not been systematically studied, however, before the invention of laser in the 1960s. Comparing with other light sources, the collimated beam of laser is capable of concentrating light energy in a tiny volume and short period of time. In another word, low energy lasers light can have very high irradiance, which is defined as the amount of energy per unit volume and time. \\ | + | Optical radiation hazards from the Sun light and high intensity lamps to human have long been discovered since their use in scientific research. They had not been systematically studied, however, before the invention of laser in the 1960s. Comparing with other light sources, the collimated beam of laser is capable of concentrating light energy in a tiny volume and short period of time. In another word, low energy lasers light can have very high irradiance, which is defined as the amount of energy per unit volume and time. \\ \\ |
| - | Lasers are classified into four categories according to their potential optical radiation hazards: \\ | + | Lasers are classified into four categories according to their potential optical radiation hazards |
| - | Class I: not considered as hazards such as laser scanners used at super market \\ | + | * Class I: not considered as hazards, such as laser scanners used at super market |
| - | Class II: low power and low risk. Will cause damage only if the person overcomes his/her nature aversion response to continuously stares at the source. The risk is considered very low and is the same as vision damage caused by staring at a high intensity lamp or the Sun. \\ | + | * Class II: low power and low risk. Will cause damage only if the person overcomes his/her nature aversion response to continuously stares at the source. The risk is considered very low and is the same as vision damage caused by staring at a high intensity lamp or the Sun. |
| - | Class III: medium power and moderate risk. Most of laser systems used in photobiology \\ | + | * Class III: medium power and moderate risk. Most of laser systems used in photobiology |
| - | Class IIIa: may only lead to visual damage by direct exposure of the laser beam; \\ | + | * Class IIIa: may only lead to visual damage by direct exposure of the laser beam |
| - | Class IIIb: potential damage by both direct exposure and diffused light; \\ | + | * Class IIIb: potential damage by both direct exposure and diffused light |
| - | Class IV: high power and high risk. Lasers used for machining and surgery. \\ \\ | + | * Class IV: high power and high risk. Lasers used for machining and surgery |
| - | + | \\ \\ | |
| - | Most of the laser systems used in photobiology research belong to Class III that are not capable of causing serious skin injury or vision injury by diffuse reflections under normal use. General precautions while operating these lasers include: \\ | + | Most of the laser systems used in photobiology research belong to Class III that are not capable of causing serious skin injury or vision injury by diffuse reflections under normal use. General precautions while operating these lasers include |
| - | 1. Never direct looking at the laser beam at all wavelengths. \\ | + | * Never direct looking at the laser beam at all wavelengths. |
| - | 2. Track the laser beam propagation. Confine the light within the setup by blocking multiple reflections and exit beam using a beam dumper. Pay extra attention to those working in the invisible spectral range such as ultra violet and inferred. A piece of fluorescence paper is usually used to track UV laser beam propagations and special IR sensitive cards are used to track laser beam in the inferred region. \\ | + | * Track the laser beam propagation. Confine the light within the setup by blocking multiple reflections and exit beam using a beam dumper. Pay extra attention to those working in the invisible spectral range such as ultra violet and inferred. A piece of fluorescence paper is usually used to track UV laser beam propagations and special IR sensitive cards are used to track laser beam in the inferred region. |
| - | 3. Wear proper laser protection gaggles while working with them. There are no universal gaggles that will protect you from all lasers. They only working at a specified spectral range. \\ | + | * Wear proper laser protection goggles while working with them. There are no universal gaggles that will protect you from all lasers. They only working at a specified spectral range. |
| - | 4. Avoid direct exposure of UV light to skin. Studies have shown that excess UV light may cause skin cancers. \\ | + | * Avoid direct exposure of UV light to skin. Studies have shown that excess UV light may cause skin cancers. |
| + | \\ | ||
| ===== Electrical Safety ===== | ===== Electrical Safety ===== | ||
| - | Except for LED and semiconductor diode lasers, most of the laser systems have high voltage power supplies. Some gas discharge lamps and detector systems such as PMT and intensifiers for CCD or streak cameras also have electrical system with line voltage exceeding tens of thousands of volts. In addition, high energy pulsed laser systems have capacitors charged to several kilovolts with associated energy of hundreds of joules. These high voltages and energies constitute potentially lethal shock hazards. Although most of the complete commercial systems come in enclosed cases that provide some form of protection, most of bench top systems used in research laboratories require periodically maintenance that access to open circuit is needed. Working with the large capacitor banks and very high voltage devices in light sources and detectors requires special attention. Carelessly working around these high voltage electrical devices has the potential of causing severe electrical shock or even possibly result in electrocution. Strict adherence to electrical guidelines and instrument manuals is the key to prevent accidents. Some simple guidelines are listed here: \\ | + | Except for LED and semiconductor diode lasers, most of the laser systems have high voltage power supplies. Some gas discharge lamps and detector systems such as PMT and intensifiers for CCD or streak cameras also have electrical system with line voltage exceeding tens of thousands of volts. In addition, high energy pulsed laser systems have capacitors charged to several kilovolts with associated energy of hundreds of joules. These high voltages and energies constitute potentially lethal shock hazards. Although most of the complete commercial systems come in enclosed cases that provide some form of protection, most of bench top systems used in research laboratories require periodically maintenance that access to open circuit is needed. Working with the large capacitor banks and very high voltage devices in light sources and detectors requires special attention. Carelessly working around these high voltage electrical devices has the potential of causing severe electrical shock or even possibly result in electrocution. Strict adherence to electrical guidelines and instrument manuals is the key to prevent accidents. \\ |
| - | 1. Carefully read the operating and maintenance manual supplied by the manufacture. Be familiar with which components have the potential to cause electrical hazards. \\ | + | |
| - | 2. Use only one hand for any manipulation of circuits whenever possible. \\ | + | Some simple guidelines are |
| - | 3. Work in a dry environment. \\ | + | * Carefully read the operating and maintenance manual supplied by the manufacture. Be familiar with which components have the potential to cause electrical hazards. \\ |
| - | 4. Before any work, ground the whole circuit and use a portable multi-meter check the voltage. \\ | + | * Use only one hand for any manipulation of circuits whenever possible. \\ |
| + | * Work in a dry environment. \\ | ||
| + | * Before any work, ground the whole circuit and use a portable multi-meter check the voltage. | ||
| + | \\ | ||
| ===== Chemical Safety ===== | ===== Chemical Safety ===== | ||
| Many gas lasers and dye laser systems also contain highly toxic chemicals, which are also fire hazards in many cases. Proper face masks and skin protection should be worn during maintenance procedures. In some particular types of laser systems, respiratory devices should also have been used. \\ \\ | Many gas lasers and dye laser systems also contain highly toxic chemicals, which are also fire hazards in many cases. Proper face masks and skin protection should be worn during maintenance procedures. In some particular types of laser systems, respiratory devices should also have been used. \\ \\ | ||
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