JPH01500234A - Laser output thin film limiter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Laser output thin film limiter Conventional technology 1. Related applications A related application to this patent application is entitled "Laser Hazard Protection Device" and is filed by Geo. rge-F-J-Garlick, Joseph-A Minahan, O and David-R-Lillington et al., July 9, 1986. , filed by Hughes Aircraft Company.

The specification of this related application, which is commonly owned by the Company, is incorporated herein by reference. It is incorporated.

2. Field of application of the invention This invention relates to a visible light and infrared detector and sensor system. Ru. The core of the invention is to protect sensitive sensors from damage caused by heat dissipation from high-power laser sources. It is to protect.

3. Conventional technology Optical technology can be broadly divided into two areas of practice. On the other hand, light (i.e. ultraviolet light) , infrared, electromagnetic radiation) is generated and used for many purposes, including medicine and metrology. It has been treated and validated. And on the other hand, the generated and activated light It is used to make use of its properties to be detected by various sensors. optics In the early days of the discipline, the main light-detecting devices were either the human eye or photographic photosensitizers. Ta. However, in recent years, as this field has developed, more sensitive and more accurate light has been developed. Detection devices have become desirable.

Semiconductor manufacturing technology has provided extremely accurate sensors. Align the focal plane In order to record the incident light on the surface of the semiconductor junction by The photoconductive effect is utilized. A light focusing device, just like you do in a camera When integrated into an optical system, the array of focal planes produces an image of the detected waveform. It will output an electrical signal that copies the wavefront of light with great precision. The output signal is It can be passed through electrical signal processing equipment and used for certain requirements. The above detection net networks form the basic form of television signal generation.

Optical detection systems are part of the world's vast network of artificial satellite cameras and mapping tools. It is something that comes from the heart. If the array of focal planes is tailored to a specific wavelength of light, a map can be created. The creation of satellites uses visible light from the weather on Earth, and infrared light from continents and plants. It is possible to detect the distribution of ultraviolet rays and the interference caused by the sun.

Many laboratories for detection equipment were also built. And, through the use of optical equipment, precision This increases the reliability and accuracy of scientific, technological and industrial sensing equipment. Ta.

The advantage of the new generation of detection devices is that they can record light images even in very dark conditions. However, it was also tested to be a major weakness. Focus a strong light source on the focal plane The resulting momentary pulse of high brightness temporarily damages the thin and fragile surface of the semiconductor. Either destroy it or destroy it completely. Laser light in laboratory laboratory The uneven distribution of these substances has become a major cause of failure of expensive and highly accurate detection equipment. other Military-grade detection equipment (for example, red External IR sensors) are particularly susceptible to interference and damage from laser sources and are easily damaged.

All detection devices used in low light conditions are susceptible to inadvertent or intentional destruction. They must be protected in some way.

Particularly recently, much effort has been devoted to the development of methods of protection for highly sensitive detection devices. is in progress. Examples of various methods of protection against high-power laser radiation include: The issue has been discussed and investigated in detail. The simplest and most obvious protective device is The first step is to provide a mechanical 5hutter. The illuminance If you want to protect the focal plane array when increasing the Just cover the opening. The difficulty with this method is that the protective lid must be moved and placed in place. It essentially takes a long time to set it. from laser radiation Within a few nanoseconds the protective lid closes to protect the laser radiation from reaching the sensor. damage the substrate and destroy the sensor.

In order to improve the rise time of protective measures, various optical phenomena can be It was researched in an attempt to protect detection equipment from light sources. For example, constant gas under high pressure The substance has the property of strongly absorbing radiation of certain wavelengths. However, this method is fatal It has certain drawbacks. Firstly, high pressure gas is dangerous, and secondly, this method The law cannot provide broad protection against various risks. Gas is dangerous Even if the laser light is absorbed, the absorption is not complete, and if the laser light is strong, In the end, the methods of protection are left to us.

Similarly, an optical absorption coating consisting of an insulating film and a metallic film is used. The absorption of light at specific wavelengths was tested. Guess all practical lasers Damage caused by The router is designed and constructed to remove only those wavelengths. but After all, even if such frequency band filter technology is used, it cannot completely eliminate high-brightness lasers. There is no way to protect the laser light from reaching the surface of the detection device. Moreover, Guard belts can also be used to prevent desired radiation at certain wavelengths from entering the detection device. Therefore, the S/N ratio of the sensor is extremely reduced.

Several nonlinear optical effects have been explored for use in sensor protection. Ta. Due to the nonlinear defocus of the liquid crystal, the high-intensity laser light is emitted at this time. This phenomenon can be used for broadband protection against laser damage.

However, for a protective effect, the rise time in this case is rather too long. many kinds Techniques using nonlinear phase coupling have been investigated to protect the surface of sensing devices. Ta. Among these efforts, ribbon piping using a sensor-based laser light source has been developed. Possible damage from high-intensity laser light when using non-linear media You can make it escape backwards. Unfortunately, however, this phase coupling method is extremely It is important to know in advance that laser light is dangerous. There is. In addition, due to the defocusing effect of nonlinearity, this technique works previously Therefore, high power density is required. Many nonlinear effects can be seen in other fields of optics. is as effective as, but unsuitable for protecting broadband and sensitive sensing systems. That's true.

dangerous! , -- Instead of protecting the focal plane from laser radiation, the focal plane of the detection device is made rigid! , an attempt was made to do so. U.S. Pat. No. 4,117, by Kruer et al. 329. The manufacturing technology of the sensing device according to the Techniques for forming a detector are described. The configuration formed in this way the absorbed heat is effectively carried away from the photoconductive material on the surface of the sensing device. Can be done.

Responsible for comprehensive protection against all conceivable laser radiation damage. No invention or method yet exists that provides such a statement. The normal detection device A way to protect a detector system over a wide range without interfering with its functionality. No equipment exists.

The focal plane arrangement of the detection device can be changed without major changes to the configuration of the conventional detection device. A practical and reliable technique to protect against damage caused by the radiation of high-intensity laser light is This will likely lead to remarkable progress in the field of optical technology. This way Such inventions will continue to meet demand for a long time, as optical technology organizations require at least 20 years of experience. I'll probably go there. Manufacturers of sensors and detection equipment likely to be affected by laser For all types of sensors, this product conveniently protects expensive and highly sensitive sensors. will use innovative ideas such as This invention can be applied to a wide range of sensor systems. It is often used for stems and arrays of sensing devices, and is useful in a wide range of applications. - Enables consistent and reliable application.

Summary of the invention The purpose of this invention is to assist major scientific and technological developments. laser power The thin-film restrictor protects any sensor from potential laser radiation damage. , which provides a simple, flexible and effective method of protection. With this invention opto-mechanical engineers in various sensing device systems This makes it possible to implement safety measures of a higher standard.

Laser thin-film power limiters consist of a thin film plastic substrate and a reflective It consists of a painted surface. The paint film is applied to the ring that maintains the flatness of the thin reflective area. Stretched and stretched. Caps just like in a tape recorder As well as tongues, shafts, bearings and motors support and require thin film rings. Rotate accordingly. The invention is based on a special sensor that is protected by a It functions as just another reflective surface. enters the sensor The light is focused by lenses and mirrors before reaching the reflective surface of the thin film. That's it Well, all the light is formed as tiny dots on the surface of the thin film. Normal operation This focusing operation does not impair the optical function. by thin film The reflected light projects an image on an optical component ahead of it, and is detected by the focal plane array of the detection device. It will be done. However, if a large laser pulse enters the aperture of the detector, the focus will be The focused laser energy absorbs heat from the plastic used in the thin film. Causes high output beyond the limit. Thin films absorb energy, remove it, and evaporate it. let And instead of reflecting the laser energy off the reflective surface of the thin film, It passes through the membrane and is absorbed by the beam emitter.

Once the laser threat is reduced, the energy dissipates inside the beam emitter and At the new position, the thin film reflective surface rotates and normal sensor operation resumes. thin film Laser output limiter protection prevents excessive laser radiation from causing damage to detection equipment. It does not interfere with the normal functioning of the sensor system except during the waking period. difference Furthermore, since the spot size of the light incident on the thin film varies, it is difficult to protect the device. The thresholds used are used for various applications and laser energies.

Therefore, it is necessary to protect the sensor system from various possible laser interferences. It is the purpose of this invention to

Another object of the invention is to prevent an array of detection devices in a simple and inexpensive manner. It is to protect.

In addition, for other purposes, it can also be used for special sensor systems and environmental differences. The structure may be such that a laser output limiter can be easily provided.

Also, for other purposes, to counter damaging continuous laser pulses. It is an object of the present invention to provide a continuously reproducible laser output limiter.

Additionally, the sensor can also be protected against extremely short laser pulses. One of the objectives is to create a protective device that has an extremely fast start-up time.

An understanding of other purposes, purposes of this invention, or a more complete and understandable description is provided below. This can be understood by studying the description of the embodiments or the accompanying drawings.

Brief description of the drawing Figure 1 shows a laser with a focus coupling element, a detector group, and an attached beam absorber. 1 is a schematic diagram of a comprehensive sensor system consisting of a thin film output limiter and a thin film output limiter.

Figure 2 shows a thin film membrane showing many combustion holes and retaining rings penetrating the surface of the membrane. FIG.

FIG. 3 is a cross-sectional view of the thin film reflective surface. Figure 3a is a cross-sectional view of the entire thin film reflective surface. Ru. Figure 3b shows the plastic substrate facing the incident laser and its bottom reflection. It is a thin film consisting of a radiation layer.

Figure 4 shows the intensity of continuous laser light based on time as a function of the brightness of the surface of the detection device. This is the graph shown. One is that if a laser thin-film output limiter is not used, The other is a graph showing the trajectory of the brightness on the surface of the detection device when it is used.

Figure 5 shows the brightness of the surface of the detection device with respect to the instantaneous laser intensity as a time axis. It is a graph of the locus of degrees. On the other hand, when using a thin film output limiter for laser light, The other is a graph of the trajectory of brightness when not used.

Description of examples Figure 1 describes a protective sensor using a thin-film output limiter for laser light. . When using a conventional synchrotron radiation type detection device, the incident light beam 10 is , passes through the objective lens 12 and the video lens 1B, and focuses on the focal plane of the detection bag device. Converged. However, in order to protect against damage from laser radiation, the present invention, A laser light thin film output limiter 4 is inserted in the middle of the optical path. Objective lens 1 2 first focuses a beam of light on a thin film reflective surface 28. This reflective surface is reflected onto the lens 16. (The lens 16 may be replaced with an array of multiple lenses.

) The imaging lens 16 focuses the bundle of rays 10 onto a focal plane 18 .

The objective lens 12 securely converges the light beam IO onto the surface of the thin film 28. , a lot of radiant energy, like that from a powerful laser source, is placed at a focal point. It generates a huge amount of energy. Rapid increase in energy flow on thin films Noboru melts the plastic and reflective paint, burns holes in the film, and directs the emitted light into the film. It is sent to the beam excluder 20 behind it. Beam excluder 20 is used to absorb heat. consists of a cavity filled with a medium, which may be metallic or synthetic. The cavity is surrounded by a fluid cooling jacket made of plastic, or Alternatively, heat is dissipated by causing convection. The amount of heat dissipation required is It is determined by the amount of energy required. The opening of the cavity is such that all the ray bundles are beam-excluded. It is sized so that the heat is absorbed before the ray bundle escapes. Ru.

Several types of power meters can be placed inside the beam excluder. Ru. The output meter is a regular copper constantan thermocouple, and the voltage changes with temperature. It is something. When the output decreases to a harmless level, the sensing device 18 resumes normal operation. Output sensor senses to allow restart. This is common knowledge in this field. Using an easily configured electronic feedback system 21, The power meter is connected to the rotating mechanism of the thin film laser power limiter.

One form of such a feedback system 21 is a voltage gauge attached to a thermocouple. A person who monitors the controller and operates the machine. The voltage has dropped to the level for normal operation. be at a point where the luminance energy is not removed by the beam excluder 20 if it falls; is displayed and the operator can manually move the membrane to a new location. in two If I had to choose one, I would use an electronic feedback system 21 like the one described. Once the radiation threat has ceased, the motors 17a, b or The capstans 15a, b, which are operated by other rotating means The laser output limiter 14 is replaced with a thin film of a new part that is a good part that has not been damaged. rotate to. In this regard, the sensor is once again fully operationally ready.

Thin membrane so that many membrane surfaces are used before the equipment requires membrane replacement. is rotated. These various operations are performed near the capstans 15a, b in FIG. It is shown and illustrated by arrows.

2 and 3 provide an overview of various thin film laser power limiters. figure 2 shows many combustion holes 31 along the arc of the membrane surface 24, while FIG. A cross section of the thin film is shown. The thin film is an optically horizontally coated polymer film structure 2 4 and is stretched taut across the support ring 22. The thin film 24 is The bevel 30 is attached around the outer corner of the ring 22. epoxy adhesive is used as an adhesive medium for attachment to the support ring of the membrane facing. Thin The membrane 24 is formed using conventional techniques known in the art to obtain an optical plane. By repeatedly testing various methods such as casting, rotary coating, and vapor deposition, we were able to obtain an optically flat surface. Rukoto can. Such a method can reach an optical plane that is one-tenth of the wavelength of light. and even better results are obtained in the infrared spectrum. Hence, Ideal thin film reflective coating quality is sufficient for most sensors and sensing devices right.

Figure 3b shows the outline of a good coated film. Incident ray bundle 10 is converged on the reflective layer 28 and reflected. For example, carbon dioxide with a wavelength of 1000 μm Rear reflective coating to protect against certain energy threats like carbon lasers structure is used. The light beam lO passes through the thin film substrate 26 on the rear reflective membrane 28. Converge. Specified materials that require protection and absorb large amounts at specific wavelengths. A polymer is selected. Large numbers of wavelengths that are strongly absorbed by thin plastic films When radiation enters the system, the reflected ray bundle is focused and first By melting the film 26 and then removing the film, the beam of light passes through the film. The beam passes through and reaches the beam excluder 20.

Certain selected plastics that strongly absorb specific wavelengths in the infrared range are , a rear reflective membrane is beneficial since it absorbs almost all the dangerous radiation. .

An ideal thin-film laser power limiter system would have many changing parameters. It's like getting a data rate.

The spot size at the focal point depends on the focal length, the quality of the objective lens 12, and the thin film lens. It is determined by the distance to the laser output limiter 14. When faced with a high-power threat, The focal spot size determines the amount of power the system delivers on the thin film surface. Ru. Therefore, the sensitivity of the system to damage is reduced by changing the focal spot size. It can be adjusted with. In addition, certain plastics and reflectively painted surfaces can reduce the absorbency of the system. selected to trim the pike and ensure that the system is under threat of radiation as described above. prevent the

Figures 4 and 5 show continuous wave (CW) and pulsed wave laser threats over time. It shows the intensity contour of the surface of the sensing device. In Figure 4, line 32 is a continuous wave signal. shows the laser intensity of the laser source. The rise time of the intensity depends on the surface of the sensor. is determined by the twist rate of the laser beam across the Even the shooting changes. Rise time of protection system for thin film laser power limiter and the threshold are indicated by line 34. The threshold is that the laser energy This is the point where the beam excluder is reached. The diagonal line drawn under curve 34 is Complete absorption of energy by the sensing device.

Energy absorption is a small portion of the energy received by unprotected systems. Part of it.

Line 36 in FIG. 5 shows a typical intensity profile for a pulsed laser. this place In this case, rise time is a fundamental characteristic of lasers. (TEA carbon dioxide For lasers, this rise time would be 25 nanoseconds. ) line 38 is the protection system again, the diagonal line indicates a large decrease in the energy of the sensing device. ing.

This invention has been described in detail with reference to specific embodiments; Any person having ordinary knowledge in the field of technology will be able to understand the spirit and scope of this invention. It can be modified and implemented in various ways without coming off.

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Claims (7)

[Claims] 1. Electromagnetic radiation is directed onto a reflective surface supported by a medium that is removed by the application of heat. the step of making the electromagnetic radiation incident, and the step of making the electromagnetic radiation reflecting the electromagnetic radiation from the reflective surface toward a light sensing device; When the power density of electromagnetic radiation is greater than the threshold, a hole is formed in the medium and the reflective surface. and passing the electromagnetic radiation through holes formed in the reflective surface. A method for emitting electromagnetic radiation from a light sensing device, characterized by comprising the step of: Law. 2. a reflective first part and a second part that is removed by application of heat; a divergence means arranged in front of the first part and facing the electromagnetic radiation, and in front of said divergence means; means for converging the electromagnetic waves on the first reflecting section; and a light sensing device for detecting the reflected electromagnetic waves. emitting electromagnetic radiation from a light-sensing device characterized by comprising means for directing the electromagnetic radiation toward the means to do so. 3. a reflective layer placed in front of said reflective layer and transparent to light facing the incident electromagnetic radiation; a thin film reflector made of a transparent support layer; and a thin film reflector made of a transparent support layer; means for focusing the electromagnetic radiation onto the reflective layer; and a means positioned after the thin film reflector. means for receiving and dissipating the electromagnetic radiation; and means for receiving and dissipating the electromagnetic radiation that has passed through the thin film reflector. power measuring means for detecting whether radiant energy exists or not, and the convergence the thin film reflector such that the electromagnetic radiation that has been applied is incident on new areas of the reflective layer. means for moving the thin film reflector; and a signal from the power measuring means for moving the thin film reflector. and feedback means for feeding the electromagnetic radiation to the means for emitting electromagnetic radiation. means of dissipation. 4. The thin film reflector includes mounting means for maintaining optical flatness of the reflective layer; and a coupling means for coupling the thin film layer to the mounting means. The device according to claim 3. 5. Claim 1, wherein the reflective layer is a thin metal coating. The device according to item 4. 6. The transparent substrate is made of a thin organic polymer that strongly absorbs electromagnetic radiation at a given wavelength. 5. The device according to claim 4, wherein the device is a membrane. 7. The electromagnetic radiation dissipation means dissipates heat generated by dissipation of electromagnetic energy. the presence of electromagnetic energy incident on the heat dissipation means emitted and the electromagnetic radiation dissipation means; 4. The device according to claim 3, further comprising means for detecting.