JP2008165094A - Optical component having reflecting surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical component having a reflecting surface characterized by a small temperature-dependent variation of optical characteristics, lightness in weight, and excellent mass productivity. <P>SOLUTION: A substrate is produced using a nanocomposite material formed by impregnating a synthetic resin into microfibrillated cellulose obtained by finely fibrillating plant fibers to the level of nm, a reflective film such as a metal thin film is formed on a smooth surface formed on the substrate, and an attachment functional part and an adjustment functional part made of such a nanocomposite are integrally formed as functional parts incidental to the reflective function, wherein the objective optical component having a reflecting surface is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

Detailed Description of the Invention

Technical field to which the invention belongs

  The present invention relates to a reflecting mirror having a small temperature influence on optical characteristics, lightweight, and characterized by mass productivity and related structures.

  Conventionally, glass materials are generally used for high-precision optical instruments. In other words, it is effective to make the reflecting mirror, which is the main optical element, made of glass to achieve and maintain accuracy, and the refractive index is an important condition for lenses and prisms, so-called optical glass is the basic material. It was.

  An example of an optical instrument that requires highly accurate reflection characteristics is a reflective telescope. In the case of a refracting telescope, the refractive index of the lens material determines the characteristics.On the other hand, in the case of a telescope that uses a concave reflecting mirror instead of the objective convex lens, light does not pass through the material, so the conditions for selecting the material are relaxed In the past, however, there were conditions under which glass was the optimal material for achieving accuracy. (Figure 1)

  The prism has three types of action as shown in FIG. That is, the first is to use the refraction principle of a transparent material to split light into a spectrum, the second is to transmit incident light perpendicular to the surface as it is, and the third is to use light in a specific incident angle range as a refraction principle. Based on this, there is an action of total reflection. Among these three kinds of actions, the former two cannot be substituted with a reflecting mirror, but the total reflection action can be obtained by replacing it with a reflecting mirror.

Problems with conventional technology

  If the effect equivalent to the light refraction effect is realized with a reflector, the influence of the refractive index is avoided, so the conditions for material selection are relaxed, and plastic is considered from the viewpoint of mass productivity, weight, price, etc. However, plastics are greatly deformed due to thermal expansion, and their characteristics change with temperature (focal length change of a curved mirror and distortion of a plane mirror). Therefore, they cannot be used for optical instruments that require high accuracy.

  Based on this situation, it is customary that the high-precision reflector is made of glass, and in particular, the concave reflector is basically manufactured by the conventional polishing technology.

  In other words, conventional concave mirror production uses a glass disk of the required size as the raw material, roughens the target concave curved surface and the corresponding convex curved surface in advance, and implements anti-wear measures on the convex surface side before fine polishing. The particles are sprayed and the concave curved glass is made to face each other to continue sliding friction with each other (FIG. 3).

  Sliding friction is not limited to a specific location for both of the concave and convex materials, and it slides while rotating to each individual, and a fine abrasive is always present without mutual contact between the friction surfaces. Thus, it is necessary to continuously supply the abrasive dispersion under certain conditions.

  The sliding operation between the concave and convex surfaces is repeated many times over the entire circumference, the fineness of the abrasive grains is successively increased to finish smoothness, and a reflective film such as a metal thin film is formed to obtain a mirror surface.

  This mirror material polishing process requires careful attention to the management of the abrasive grains and the control of the sliding operation. Therefore, a long processing time and a high cost are expected.

  In addition, since it is a process whose basic principle is to slide along the uneven surface, the concave surface to be formed must be an inverted spherical surface (hereinafter referred to as a spherical surface), and a parabolic curved surface (hereinafter referred to as a reflecting telescope). In order to obtain a paraboloid), a correction process is required later, and there is a problem of high cost.

  In addition, since it is not possible to make significant changes even by correction processing, a reflector with a small caliber ratio (focal length / reflector diameter) can be manufactured using glass as the material. Therefore, there has been a problem that the optical imaging performance is limited in brightness.

  In the case of glass, it is usual to use a thick material, but glass is difficult to cut and is not suitable for bonding, so when assembling to an optical instrument, another structural part is required. There was a problem to do.

  Furthermore, in the Cassegrain-type reflective telescope (FIG. 1B) that is frequently used, it is necessary to make a hole in the center of the reflector, which is also a problem in processing.

  As a method of arranging an prism in the optical path of image formation and converting an inverted image formed by a telescope into an erect image, there are methods called a poro prism type and a Dach prism type (FIG. 4). Is a clever functional principle that uses both light transmission and total reflection due to the difference in the incident angle of light. Alternatively, it is characterized by being dedicated to transmission (not used in combination).

  Therefore, the Dach prism type function cannot be realized by a combination of reflecting mirrors, but the Porro prism type function can also be realized by a reflecting mirror structure.

  However, it has been extremely difficult in the past to perform four reflection actions with four reflectors that are assembled with high precision and are strong enough to withstand the vibrations of carrying, even if the parts are expensive and heavy. In general, the prism type is considered to be advantageous, and there has never been a practical use of a functionally simple reflector.

  In addition to the telescope's Polo prism structure, there is a corner cube that uses the function of multiple reflection in a prism (Fig. 5).

  If a plane mirror is assembled so that it is reflected on the inside in a shape equivalent to the three surfaces sharing one vertex of the cube, and light is incident on the opening, the plane mirror receives 3 degrees of reflection at every incident angle. Finally, reflected light that is opposite to the incident light in the same direction can be obtained.

  Conventionally, large corner cubes are usually made of plane reflectors, and small ones are usually prismatic right-angled pyramid prisms. Once the prisms are completed, there is no need for readjustment. Although it is an advantage, a brittle and heavy glass material has a problem in that it is not easy to handle.

Problems to be solved by the invention

  Issue 1 is to create a curved mirror with the same precision as conventional glass products and excellent productivity, and if possible, to improve the limit value of the aperture ratio associated with glass.

  Issue 2 is to avoid the use of prisms for optical functions that can be done with flat reflectors, and to realize rationality in terms of weight and price.

  Problem 3 is to develop technical means that can avoid the difficulty in assembling because the mirror glass and the metal holding and adjusting mechanism are different.

Means for solving the problem

  The above-mentioned enumeration problem is that a synthetic resin (plastic) is assembled into a collection of microfibrillated cellulose (hereinafter referred to as cellulose nanofiber) obtained by finely defibrating plant fibers to the nanometer level as a material of the reflector and the parts constituting the reflector. ) Can be used to solve the problem (hereinafter referred to as nanocomposite).

  As the coefficient of thermal expansion, quartz 0.4 ppm / K, heat-resistant glass 3 ppm / K, window glass 8 ppm / K, pure iron 12 ppm / K, acrylic resin 80 ppm / K, polyethylene 100 to 200 ppm / K, etc. are generally recognized. However, the nanocomposite used in the present invention has a track record of 3 ppm / K, depending on the composition ratio of cellulose nanofibers and plastics and molding conditions, and is expected to achieve a smaller expansion coefficient in the future.

  In other words, plastic materials cannot be used for high-precision optical instruments due to their high coefficient of thermal expansion, but their practicality has been proven because nanocomposites are equivalent to heat-resistant glass.

  Since the nanocomposite is an aggregate of fine fibers, the surface state at the micro level is assumed to be smooth and disturbed, and there was some concern about whether it was so smooth that it could truly be a reflector. In this regard, as a dimension of one cellulose nanofiber, for example, one side of the thickness is observed to be 4 nanometers and the length is 20 nanometers, and the nanocomposite is a collection of materials distributed in the vicinity of the size, It is small enough for 400 to 700 nanometers, known as the wavelength of visible light, and does not interfere with the passage of light, so the nanocomposite plate is transparent, but for the same reason, in nanocomposites, cellulose nanofibers Even in areas where the surface is partially exposed to the surface, the size of the disturbance is compared to the wavelength of visible light. Since minute small, can be defined as a whole is sufficiently smooth, it's not disabled as a reflecting mirror.

  Although carbon fiber reinforced plastic is known as a material with almost the same thermal expansion coefficient as thermal expansion characteristics, it is not a material for reflectors.

  That is, in the carbon fiber reinforced plastic, the carbon fiber constituting the carbon fiber is, for example, as large as 10 micrometers in diameter (10000 nanometers) and a length of millimeter to meter, and the exposed portion of the fiber cannot have a smoothness at a specular level. Therefore, it is fundamentally different from nanocomposites in that it cannot be used as a reflector material.

  In addition, as mentioned above, there is a limit to reducing the aperture ratio (making a bright optical image) with a concave concave mirror made of glass. However, when creating a concave reflective mirror using a nanocomposite, the formation of a curved surface is not possible. In addition to polishing like glass, as will be described later, it is possible to heat and press the material using a mold, and according to the processing method, there is no particular difficulty in making a small aperture ratio .

  As described above, the nanocomposite as an optical reflector material is not a substitute for a glass reflector as a material for a reflector, but is a new material that easily realizes product specifications that are difficult to achieve with a glass material.

  Next, the nanocomposite material provides a good solution to the prism reflection mechanism.

  In other words, if the mechanism of the Porro prism is made with a four-sided reflector structure, it has been difficult to assemble and maintain it with high accuracy. However, according to the technology for forming the nanocomposite material, there is no particular difficulty. Compared to prism products, it can achieve superior properties in all aspects such as lightness, vibration durability, and mass productivity.

  In addition, with regard to the corner cube, due to the features such as the smooth surface of the nanocomposite and sufficient precision due to low thermal expansion, the large light receiving aperture shape possible due to robustness, the flexible mounting structure for installation due to processing adaptability, etc. Excellent practicality can be achieved compared to prisms.

  As described above, the reflection of the mirror and the total reflection of the prism have been described. The effect principle when using the nanocomposite can be widely applied to the effects of multiple reflection and multi-surface reflection in optical instruments. It is expected to have an excellent effect by combining the lightness and the precision and robustness of the prism type.

About processability

  Nanocomposites are characterized by a low coefficient of thermal expansion, and are stable and highly accurate reflector materials in a wide range of temperature environments. They also have excellent adaptability to various processing technologies due to their characteristic properties.

  Since nanocomposites are impregnated with synthetic resin, adhesives and welding agents applied to the resin material are effective, so it is possible to join parts and easily realize the structure required for equipment assembly. is there.

  Nanocomposites are made of vegetable cellulose and resin and have relatively low rigidity. Therefore, it is conceivable that the rigidity of the product is insufficient with only a reflector. On the other hand, the tensile strength is about 300 Pascal and the bending strength is about 400 Pascal. The actual measured value is obtained, and this value is difficult to compare because the glass cannot be determined for the tensile strength, but it is impressively several times higher, and the bending strength is 10 to 15 Pascal for the glass. Therefore, it is 20 to 30 times larger, almost like steel, and by these characteristics, if a reasonable reinforcement structure is made, the robustness as a product can be made equal to or higher than that of glass. .

  In addition, the low hardness of nanocomposites due to the elements of vegetable cellulose and resin is also the ease of cutting, which brings a wider range of applications compared to glass reflectors.

  In addition, since the nanocomposite is a resin-impregnated material, it is often thermoplastic, and various effective shapes can be realized depending on its properties.

  In other words, it is possible to mold the nanocomposite material into the required surface shape (concave, convex, flat) by cutting and polishing, but unlike the case of glass, this material is common to the case of resin molding, It is possible to apply techniques of injection molding and heat-pressure molding (including vacuum molding).

  When nanocomposites are molded by this processing method specific to resin materials, there is no difficulty in realizing spherical molding and parabolic molding, and hyperboloids and other special curved surfaces can be freely prepared by preparing a mold. Can be mass-produced.

  When nanocomposites are formed by such a processing method, there is no particular difficulty with the deep concave surface, so it is possible to make one with a smaller optical aperture ratio than conventional glass-polished concave mirrors. There are advantages that can be made.

  By utilizing the various features described above, it is possible to achieve high precision with a single reflector using nanocomposites, and a structure that combines multiple reflecting surfaces is constructed with precise mutual positions and is robust. Many optical instruments can be put to practical use by adding a reinforcing structure and a coupling mechanism.

The invention's effect

  As a material for reflectors, glass is excellent in finishing accuracy and maintaining accuracy with respect to temperature changes, but there is a limit to workability, but resin can be processed freely, but accuracy is lost due to temperature changes after completion. It has drawbacks and cannot be used in optical systems that require high accuracy.

  In contrast, nanocomposites do not have any of the disadvantages and have the best physical properties as a reflector material.

  The nanocomposite also has the characteristics that can apply the processing technology such as pressure molding, injection molding, and cutting / polishing to integrate the reflector and its related parts in various shapes in a robust and inexpensive manner. ing.

  The present invention takes advantage of these physical properties and characteristics of nanocomposites to provide a precision optical instrument in a new form.

Claims (3)

A substrate is made from a nanocomposite made by impregnating a synthetic resin into a collection of microfibrillated cellulose that is finely fibrillated from plant fibers to the nanometer level, and reflected by a thin metal film on the smooth surface formed on the substrate. An optical component having a reflective surface, wherein a surface is formed. 2. The optical component having a plurality of reflecting surfaces according to claim 1, wherein each of the plurality of reflecting surfaces is related and functions integrally. 3. An optical component having the reflecting surface according to claim 1 or the reflecting surface group according to claim 2, wherein an attachment function portion and an adjustment function portion made of nanocomposite are integrally formed as an incidental function portion of the reflection function.

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