JPH036881Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a structural system for a lightweight and highly accurate reflecting mirror.

[Conventional technology]

Reflectors with a Sanderch structure have been widely developed as reflectors for antennas of space equipment such as artificial satellites. Its basic structure is shown, for example, on page 187 of the book ``Space Development and Design Technology,'' and Figure 3 is a cross-sectional view showing its structure.
In FIG. 3, 4 is a mirror surface plate, 2 is a rear surface plate, and 3 is a core such as a honeycomb core.

In the reflecting mirror with the Sanderch structure shown in FIG. 3, the two front plates, the mirror surface and the rear surface, are made of the same material and have the same thickness. Since the mirror surface of this reflector is molded using a mold, the neutral plane of the reflector always coincides with the center plane of the plate thickness of the reflector, and even if the temperature of the reflector changes, the Bending deformation of the reflecting mirror due to the difference in stretching force does not occur, and the precision of the mirror surface does not deteriorate.

However, the conventional Sanderch structure reflector is
Since it was developed mainly for use as an antenna in the radio wave region, the mirror surface accuracy is even the best.
The RMS value is about 100μm, and in order to be used as a reflector in the infrared or visible light range,
The mirror accuracy was not sufficient. In general, the mirror surface precision required for reflective mirrors used in the infrared or visible light region is an RMS value of 10 μm or less, and it is difficult to achieve this precision by mirror molding with a mold. It is necessary to obtain the required mirror surface precision by machining such as polishing or cutting similar to that used for telescope reflectors. A drawback of the method that uses machining in combination is that the thickness of the mirror surface plate becomes different from the thickness of the rear surface plate due to the processing, so if the temperature of the reflector changes, the thickness of both surface plates will change. The difference in stretching force causes minute bending deformation in the reflecting mirror, which deteriorates the precision of the mirror surface. Additionally, processing the back surface plate into the same shape as the mirror surface plate in order to prevent this drawback is problematic in terms of processing costs and the like.

This idea was made to solve the above problems, and even after securing the required mirror surface accuracy through machining, it is necessary to balance the expansion and contraction forces due to temperature changes between the mirror surface and the back surface plate. It is an object of the present invention to provide a reflecting mirror structure system with a Sanderch structure that can prevent deterioration of mirror surface accuracy.

[Means for solving problems]

The reflecting mirror structure method based on this idea uses a thinner surface plate on the back surface than the mirror surface plate when molding the reflector using a mold, and then a plate of an appropriate thickness is added after machining the mirror surface. It is partially glued onto the back surface plate to balance the expansion and contraction forces when the temperature changes with the mirror side.

[Example of idea]

Hereinafter, embodiments of this invention will be described with reference to the drawings. In Figure 1, 1 is a mirror surface plate after machining, 2 is a back surface plate, 3 is a core to maintain the distance between both surface plates at a predetermined value, and 4 is a bonded surface plate on the back surface plate. It is a thin plate.

As shown in FIG. 1, in this type of reflecting mirror structure, the thickness of the mirror surface plate 1 after machining varies depending on the location, and also differs from the thickness of the rear surface plate 2. For this reason, when a temperature change occurs in the reflector, there will be a difference between the expansion and contraction force of the mirror surface plate and the expansion and contraction force of the rear surface plate, and the magnitude of the difference differs depending on the position on the mirror surface. Therefore, non-uniform minute bending deformation occurs over the entire surface of the reflecting mirror, causing deterioration of mirror surface accuracy. Thin plate 4 glued onto the back surface plate 2
By partially increasing the stretching force of the back surface plate, the neutral plane of the relevant part of the mirror surface is brought closer to the thickness center plane of the reflecting mirror, thereby reducing the above-mentioned minute bending deformation and the resulting mirror surface accuracy. Prevent deterioration. The thickness of this thin plate may be determined by taking into consideration the magnitude of the difference in expansion and contraction force between the two surface plates when the temperature changes, and there is no problem even if the materials are different from those of the two surface plates.

In addition, in the above embodiment, a method was shown in which a thin plate for balance was glued onto the back surface plate, but as shown in Fig. 2, the thickness of the back surface plate was The back surface plate was made thicker than the front surface plate, and the expansion and contraction force of both surface plates was examined when the temperature changed after machining the mirror surface, and the back surface plate was machined to balance the expansion and contraction forces of both sides. It is also possible to change the plate thickness. The method shown in FIG. 2 has the advantage that the back surface plate only needs to be machined partially, and there are no strict requirements for the roughness of the machined surface.

[Effect of idea]

As described above, according to this invention, after the reflecting mirror is molded using a mold, the mirror surface is machined to obtain the required mirror precision, and the back face plate is machined to provide stability during temperature changes. Since the structure is designed to balance the expansion and contraction forces of the surface plate, it is possible to obtain a reflecting mirror that does not suffer from deterioration in mirror surface precision due to the unbalanced expansion and contraction forces described above, through simple and inexpensive processing.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of a reflecting mirror according to one embodiment of this invention, Fig. 2 is a sectional view showing the structure of a reflecting mirror according to another embodiment of this invention, and Fig. 3 is a sectional view of a conventional reflecting mirror. FIG. In the figure, 1 is a mirror surface plate after machining,
2 is the back surface plate, and 4 is the thin plate for balance. still,
The same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims for Utility Model Registration] (1) A mirror plate whose thickness is uneven during the process of being finished into a mirror surface by machining, and a portion of the mirror plate that corresponds to the thick part is relatively thick and a thin part The corresponding part is a reflective mirror structure that includes a thinly formed back plate and a core that holds the back plate to the mirror. (2) The reflecting mirror structure according to claim 1, wherein the back plate is formed by adhering a thin balance plate to a plate of a constant thickness. (3) The reflecting mirror structure according to claim 1, wherein the back plate is formed by partially thinning a plate having a certain thickness.