JPH03200109A - Lens with metal frame - Google Patents

Abstract

PURPOSE:To obtain the lens with a metal frame which has high assembly accuracy, does not require additional working and allows easy disassembly and reassembly by integrating two pieces of rings, two sets of balls and two pieces of hollow disks which are fixed to both end faces of the metal frame so as to pinch the lenses, two pieces of the rings and two sets of the balls. CONSTITUTION:The metal frame having both end faces perpendicular to the generator of a cylinder is provided. Two pieces of the rings 502, 503 which are fitted to inscribe the metal frame and are disposed to pinch the lens spherical faces 1a, 1b and have the end faces parallel with the rectangular section, two sets of the balls 511, 512 of an equal diameter, one set of which consists of at least >=3 pieces of the balls disposed to come into contact with the three: the end faces of the rings 502, 503, the lens spherical faces 1a, 1b and the cylinder in the metal frame, and two pieces of the hollow disks 504, 505 fixed to both end faces of the metal frame so at to pinch the lens 1, two pieces of the rings 502, 503 and two sets of the balls 511, 512, are integrated.The lens with the metal frame having the high alignment accuracy of the center of the metal frame and the optical axis of the lens is obtd. in this way.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a lens with a metal frame used in a relatively large assembled lens, and more specifically to a projection lens that can be used in a semiconductor device exposure apparatus. This invention relates to a lens with a metal frame.

(Prior art) Projection lenses used in exposure equipment for semiconductor devices are required to have extremely small aberrations, so they are often composed of about 20 spherical lenses, and the accuracy of the lens spherical surface is about λ/20. In addition, high assembly accuracy is required to suppress errors in tilt and shift, which are the deviations of each lens from the optical axis, and in the distance between the lenses to within several μm.

Conventionally, as a method for assembling a plurality of lenses so that their optical axes coincide with each other, there is, for example, a method shown in a partial cross-sectional view shown in FIG. The lens barrel 3 is provided with a step 30 for receiving the spherical outer circumferential portion of the lens, and the lens 1 is tightened thereon with a ring-shaped set screw 4. In this method, a gap is provided between the lens outer circumferential cylindrical surface 1c and the lens barrel inner surface 34 so that the lens 1 can be fitted, and the guiding effect by the spherical surfaces 1a and lb on both sides of the lens 1 itself, that is, the step edge 30a. The set screw edges 4a are fixed so that the distance between them is minimized. In this case, the accuracy of machining the step on the inner diameter part of the m cylinder cannot be very high, so if you tighten it strongly with the set screw, the lens spherical surface 1a will be formed.

There is a problem that the lens is distorted due to non-uniform contact between the cover b and the stepped edge 30a. If the tightening is too weak, the spherical surface of the lens 1.
Due to the J9 friction between a and lb, the step edge 30a, and the push screw edge 4a, it cannot be positioned at the correct position. A second conventional method, which replaces the above-mentioned conventional method, is to closely fit a lens A with a metal frame as shown in FIG. There is a way to do it. In this case, the lens 1 is fixed in the metal frame 5 with a coupling agent 51, and in this situation, the outer cylindrical surface 22 of the metal frame 5 is perfectly circular with respect to the optical axis ]00 of the lens 1, and the end surfaces 23 and 24 are perpendicular. In this method, additional machining is performed so that the outer diameter of the lens barrel 3 is slightly smaller than the inner diameter of the lens barrel 3, and the lens barrel 3 is fitted into the inner diameter of the lens barrel 3 to be assembled.

The distance between adjacent lenses is determined by spacing rings 71 and 72. In this case, problems include displacement of the lens position due to thermal deformation of the adhesive 51 and difficulty in assembling the metal lens into the lens barrel.

(Problems to be Solved by the Invention) An object of the present invention is to provide a lens with a metal frame that has high assembly accuracy, does not require additional machining, and can be disassembled and reassembled.

(Means for Solving the Problems) The present invention provides a lens with a metal frame in which a lens and a holding metal frame are integrally assembled, in which a disc-shaped lens and inner and outer cylinders that fit into the lens with a gap have extremely high roundness. A metal frame finished concentrically and having both end faces perpendicular to the cylindrical generatrix, and two metal frames having end faces parallel to a rectangular cross section that are internally fitted into the metal frame and arranged to sandwich the lens spherical surface. a ring, two sets of equal diameter balls each consisting of at least three balls arranged so as to be in contact with the end face of the ring, the spherical surface of the lens, and the king of the cylinder within the metal frame; the lens and the two balls; This is a lens with a metal frame, characterized in that it is formed by integrating two hollow discs fixed to both end surfaces of the metal frame so as to sandwich the two sets of balls.

(Function) In the lens with a metal frame of the present invention, if the lens spherical surface is placed so as to touch a plurality of spheres of equal diameter arranged circularly on the same plane, the perpendicular line at the center of the above will be the same as that of the lens spherical surface at that point. Since it coincides with the perpendicular line, it is constructed so that both sides of the lens's spherical surface can be formed at the same time, and by combining spherical and right cylindrical parts that can be easily machined with high precision, the optical axis of the lens can be set without any additional machining after assembly! : It is possible to match the axis of the all-metal frame.

(Actual 1i! 1 Example) FIG. 1 is a diagram showing an embodiment of the present invention. End face fN50
4 is fastened to the outer cylinder 501 with a screw 506, and a ring 502 with a rectangular cross section is inserted therein. ring 50
2, three or more spheres 511 are placed on top of the lens 1, and a sphere 512 and a ring 503 are placed on top of the lens 1. The end plate 505 is placed and fixed so that the end plate 505 is parallel to the end plate 504.

FIG. 2 explains the principle by which high-precision assembly is possible. In FIG. 2, the inner diameter of the outer cylinder 501 has a very good roundness, and the ball 511 (at least When the spherical surface 1a of the lens 1 contacts the spherical surface 1a of the lens 1, the center line 101 of the outer cylinder 501 and the spherical surface 1a intersect perpendicularly at this portion. However, the outer periphery of the lens is generally not necessarily processed around the optical axis, but has a thickness deviation along the circumferential direction called a wedge, so the optical axis is shifted to 102 in the figure. This means that the parallel plane ring 503 is placed on at least three or more spheres 512 evenly arranged on the outer circumference of the lens spherical surface 1b so as to be in contact with the inner diameter of the outer cylinder 501.
By measuring the height from the reference point, All+
It can be known as the difference (inclination) in height from a predetermined height.

Therefore, in order to avoid this difference in height, the lens straddle is adjusted by moving the lens laterally inside the outer cylinder 501 (in the case of Fig. 2, the lens is moved to the left).
01 and the optical axis of the lens (the line connecting the centers of the spherical surfaces 1a and 1b of the lens 1)]02 can be made to match. Since the support 101 is finished with good concentric precision of the inner and outer diameters, it serves as the axis of the inner diameter of the outer cylinder 501 as well as the axis of the outer diameter. Therefore, the lens is assembled in the correct position relative to the outer diameter and end surface of the outer cylinder 5, which is the base surface for assembly. Figure 1 shows this completed diagram. Note that the pressing allowance in the axial direction of the lens can be determined by determining the height difference between the outer cylinder 501 and the ring 503 in FIG. 2, and the dimension can be reduced by additionally machining one of these two. It can be adjusted by If the pushing distance is too large, the lens will be damaged or distorted, and if it is less than 0, play will occur and the lens will shift, so it must be set appropriately. This can be easily accomplished through a cycle of disassembly, additional machining of one part, and reassembly.

The machining accuracy of these parts will be described below.

The outer cylinder 501 has inner and outer diameters finished with high concentricity and roundness, and both end faces are machined to be parallel planes perpendicular to the cylinder axis. Since it is a simple right cylinder with a relatively large diameter and short axial length, the outer diameter of the cylinder can be finished by milling, and the inner diameter can be finished with high roundness by internal grinding. The parallel planes on both end faces can be finished by grinding or lapping. Although the rings 502 and 503 are thin, they have the same shape as the outer cylinder 501 and are easy to process. In these rings 502 and 503, the concentricity of the inner and outer diameters.

Regarding the roundness, a particularly high precision is not required, but high flatness and parallelism of both end faces are required. This parallel plane, which requires particularly high precision, can be achieved by the same grinding and lapping as the outer cylinder 501. end plate 504,
505 also requires special precision because it has parallel planes on both sides, which can be achieved by grinding or lapping. The spheres 5]1.5]2 are, for example, steel balls for use in rolling bearings, and have submicron diameter variations and sphericity. In addition, lens spherical surface 1. a.1. Not only b but also λ/
It is a high-precision surface polished to an accuracy of .20. However, the outer circumferential surface of the lens does not necessarily have to be processed correctly around the optical axis.

(Effects of the Invention) As described above, according to the present invention, even if the outer periphery of the lens is not necessarily rounded around the optical axis, the spherical outer periphery of both surfaces can be used as the base. It is possible to obtain a lens with a metal frame in which the center of the metal frame and the lens optical axis are aligned with high accuracy. No additional work is required after assembly to the metal frame. The strength of the lens holder can be adjusted as appropriate by additional machining of the disassembled individual parts (outer cylinder or ring), so there is no risk of lens damage and there is no need for cleaning. If this lens with a metal frame is assembled with a lens frame via a sphere as shown in FIG. 6, a highly accurate assembled lens can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the lens with a metal frame of the present invention. FIG. 2 is a diagram illustrating the principle of assembly accuracy of the lens with a metal frame of the present invention. FIGS. 3 and 4 are sectional views showing parts of a conventional assembled lens. FIG. 5 is a sectional view showing a conventional lens with a metal frame. FIG. 6 is a sectional view showing a portion of an assembled lens assembled using the lens with a metal frame of the present invention. 1... Lens la, 'lb... Lens spherical surface IC... Lens outer periphery cylindrical surface 3... Lens barrel 4... Ring-shaped push screw 4a... Push screw edge 5... Metal frame 5a, 5b...metal frame flat part 21...metal frame step edge 22...metal frame outer cylindrical surface 23.24...metal frame end face 30...lens barrel inner surface level difference 30a... Step edge 34... Lens barrel inner surface 51... Adhesive 61-63... Spheres 71-73... Spacing rings 100-102... Optical axis 101... Outer cylinder axis 501...・Outer cylinder 502.503...Ring 504.505...End plate 506.507...Screw 51], 512...Sphere

Claims (1)

[Claims] (1) In a lens with a metal frame in which the lens and the holding metal frame are integrally assembled, the disc-shaped lens and the inner and outer cylinders that fit into the lens with a gap are finished with extremely high roundness and concentricity,
A metal frame having both end surfaces perpendicular to the cylinder generatrix, two rings having end surfaces parallel to a rectangular cross section that are internally fitted into the metal frame and arranged to sandwich the lens spherical surface; two sets of equal-diameter balls each consisting of at least three balls arranged so as to be in contact with the end face, the spherical surface of the lens, and the cylinder within the metal frame; the lens, the two rings, and the two sets; A lens with a metal frame, characterized in that it is formed by integrating two hollow disks fixed to both end surfaces of the metal frame so as to sandwich the sphere between the metal frame and the metal frame.