Zoom beam expander

Abstract: An achromatic zoom beam expander of the Galilean type. The disclosed zoom beam expander has three components (10, 12, 14), each having a doublet that is individually color corrected such that the zoom beam expander may be used with a laser such as an argon ion laser which generates light energy at several different wavelengths.

Description: The present invention relates to a zoom beam expander, and more particularly relates to an achromatic zoom beam expander which is particularly useful in laser chemical deposition tools. AU-B-548528 discloses a zoom beam expander comprising the features of the precharacterizing part of claim 1. US-A-4 353 617 to Tokumitsu et al. for "Optical System Capable of Continuously Varying the Diameter of a Beam Spot" issued Oct. 12, 1982 discloses an afocal zoom lens which continuously varies the diameter of a beam spot. The afocal zoom lens disclosed appears to be useful for only one wavelength. US-A-4 461 546 to Muffoletto et al. for "Diffraction-Limited Achromatic Beam Expanding Telescope" issued July 24, 1984 discloses a laser beam expander having four air-spaced all-spherical-surface lenses arranged in two pairs of Galilean telescope type series. The disclosed telescope is not a zoom lens, does not appear to be color corrected and requires adjustment for each change of wavelength. US-A-3 609 006 to Pospisil issued July 8, 1971, US-A-3 994 571 to Hirose issued Nov. 30. 1976, US-A-4 372 654 to Fujioka et al. issued Feb. 8, 1983, US-A-4 460 251 to Okudaira issued July 17, 1984, US-A-4 466 708 to Betensky issued Aug. 21, 1984, US-A-4 623 226 to Fujii issued Nov. 18, 1986, and US-A-4 836 662 to Ogata et al. issued June 6, 1989 are all directed to zoom lenses. None of these patents discloses a Galilean zoom beam expander. US-A-4 621 890 to Suzuki et al. for "Optical Apparatus Including Two Afocal Systems" issued Nov. 11, 1986 discloses an optical apparatus for imaging light from a laser device into a spot shape. The disclosed apparatus does not include a zoom beam expander and is directed to providing an apparatus in which the amount of light at the spot will not be changed upon variations of the emitting angle in the laser. The present invention, as defined in Claim 1, relates to an achromatic zoom beam expander which expands the beam size from a laser. The zoom beam expander includes three individually color corrected doublet components wherein one doublet component is fixed and the other doublet components are movable with respect to the fixed doublet component and with respect to each other. The disclosed zoom beam expander is an expander of the Galilean type which expands a collimated laser beam to an expanded collimated laser beam having a larger diameter. It is a primary object of the present invention to provide an achromatic zoom beam expander useful for expanding a collimated beam from a laser. It is another object of the present invention to provide a zoom beam expander having three doublet components, one doublet component being fixed and the other doublet components being movable with respect to the fixed doublet component and to each other. It is another object of the present invention to provide a zoom beam expander wherein the doublet components are individually color corrected. It is another object of the present invention to provide a zoom beam expander wherein the doublet components are air spaced doublets. Ways of carrying out the invention are described in detail below with reference to drawings illustrating only specific embodiments in which. Fig. 1 is a cross-sectional view of a zoom beam expander of the present invention arranged to have a magnification of 4.251X; Fig. 2 is a cross-sectional view of the zoom beam expander of the present invention arranged to have a magnification of 6.79X; Fig. 3 is a chart showing the distance setting of the zoom beam expander for various magnifications varying from the minimum setting of Fig. 1 to the maximum setting of Fig. 2; Fig. 4 is a chart showing the design specifications of the lens elements of the zoom beam expander of Figs. 1 and 2; Fig. 5 is a spectrum diagram of the spectra emitted from an argon ion laser showing the color correction limits of the zoom beam expander of Figs. 1 and 2 having lens elements designed in accordance with the chart of Fig. 4; Fig. 6 is a graph showing the angular ray aberrations of the zoom beam expander of Fig. 1; Fig. 7 is a graph showing the angular ray aberrations of the zoom beam expander of Fig. 2; Fig. 8 is a graph showing the optical path differences of the zoom beam expander of Fig. 1; and Fig. 9 is a graph showing the optical path differences of the zoom beam expander of Fig. 2. The zoom beam expander of the present invention may be used with a laser deposition tool of the type in which a collimated laser beam is focused by an objective lens onto a substrate in a vacuum chamber containing a gaseous organic metallic compound. The energy of the laser is sufficient to cause a layer of metal to be deposited onto the substrate for forming a conductor on the substrate, as desired. The width of the resulting conductor is determined by the diameter of the collimated laser beam being focused by the objective lens onto the substrate. Lasers are known which produce a collimated light beam having the required energy to perform the described laser deposition. One such laser is the argon ion laser. The present zoom beam expander is a zoom lens of the Galilean type which expands the collimated beam from the laser to give a collimated beam having various enlarged diameters, as desired. The use of the present zoom beam expander thus allows metal conductors of various widths, as desired, to be deposited on a substrate using the laser deposition technique. Figs. 1 and 2 are cross-sectional views of a zoom beam expander of the present invention. In Figs. 1 and 2, a collimated beam of light travels from left to right through the expander. The expander includes three air spaced lens doublets 10, 12 and 14, with the doublet 10 being fixed and the doublets 12 and 14 being movable with respect to doublet 10 and with respect to each other. As shown in Fig. 2, the doublet 10 has lens elements 20 and 21, the doublet 12 has lens elements 22 and 23, and the doublet 14 has lens elements 24 and 25. The distance between the doublets 12 and 14 is referred to herein as T4, and the distance between the doublets 10 and 12 is referred to herein as T8. The spacings for T4 and T8 as shown in Fig. 1 is for the smallest magnification of the expander (4.251X), and the spacings shown in Fig. 2 is for the maximum magnification (6.79X). Fig. 3 is a chart which shows the T4 and T8 distances for various magnifications varying from 4.251X to a maximum of 6.79X. The positions of the lens doublets 10, 12 and 14 shown in Fig. 1 are shown in the first line of the chart of Fig. 3, and the positions shown in Fig. 2 are shown in the last line. Fig. 4 is a chart showing the design of the lens elements 20-25 of Figs. 1 and 2. The surface column of the chart of Fig. 4 identifies the surface of the lens element, the radius column gives the radius in mm of the surface, the thick column gives the center thickness in mm from the surface to the following surface, and the clear aperture column gives the diameter of the clear aperture in the center of the surface. The glass column identifies glass available from Schott Glass Technologies, Inc. of Duryea, Pennsylvania. The next three columns give the index of refraction of the glass for three wavelengths of light passing through the glass. The three wavelengths are 0.514 µm, 0.5435 µm and 0.488 µm. The last column of the chart of Fig. 4 is the Abbe number of d light (V d ) for the glass. The index of refraction for d light (n d ) is 1.58913 for glass having a V d of 61.27, and 1.80518 for glass having a V d of 25.43. The radii for surfaces a and h have negative numbers, indicating that the center point for the arc of that surface is to the left of the surface. Referring to Fig. 1 and 2, lens element 20 has surfaces a and b, lens element 21 has surfaces c and d, lens element 22 has surfaces e and f, lens element 23 has surfaces g and h, lens element 24 has surfaces i and j, and lens element 25 has surfaces k and l. There are 0.025 mm air spaces between the surfaces b and c, f and g, and j and k to form the doublet components 10, 12 and 14, respectively. Surfaces a, b, d, f and j are concave surfaces, and surfaces c, e, g, h, i, k and l are convex surfaces. It will be understood that one skilled in the art may design the lens elements 20-25 from the information shown in Fig. 4. The zoom beam expander made in accordance with Fig. 4 is an achromatic zoom beam expander wherein each doublet is individually color corrected, with the first and second doublet components 10 and 12 forming a divergent lens group and the third doublet component 14 forming a collimator. Since each of the doublets 10, 12 and 14 are individually color corrected, a variety of light having different wavelengths may be simultaneously focused by an objective lens after having been expanded. Fig. 5 is a spectrum diagram of the spectra emitted from an argon ion laser. The zoom beam expander of Figs. 1 and 2 is color corrected between the limits of about 486.1 nm and about 632.8 nm. These limits are shown as dotted lines on Fig. 5, and illustrate that an argon ion laser may be expanded by the present zoom beam expander without a significant loss of energy in the dominant energies of the spectra. Also, as can be seen in Fig. 5, the range of the zoom beam expander includes 543.5 nm which is the emission of green light from a green helium neon laser, and 632.8 nm which is the wavelength of red light emitted from a red helium neon laser. This has the advantage that calibration and alignment of a device using the present zoom beam expander may be made using relatively inexpensive helium neon lasers before the installation of an expensive high energy output argon ion lasers in the device. Fig. 6 is a graph showing the angular ray aberrations of the configuration of Fig. 1 wherein the zoom beam expander has a magnification of 4.25X. The aberations for red light having a wavelength of 632.8 nm is shown by line 30 of Fig. 6, the aberrations for green light having a wavelength of 514.5 nm is shown by line 32, and the aberrations for blue light having a wavelength of 488.0 nm is shown by line 34. It can be seen that the maximum aberration for the chart of Fig. 6 is about 0.087 seconds of angle for red light, and is very nearly zero for the blue and green light. Fig. 7 is a similar graph showing the angular ray aberrations for the configuration of Fig. 2 wherein the zoom beam expander has a magnification of 6.8X. The aberration of red light is shown by line 36, the aberration for green light is shown by line 38, and the aberration for blue light is shown by line 40. Fig. 8 is a chart showing the optical path differences of the configuration of Fig. 1 wherein the zoom beam expander has a magnification of 4.25X. The optical path difference for red light is shown by line 42, and the optical path difference for blue and green light is so small that it cannot be seen on the chart of Fig. 8. Fig. 9 is a chart showing the optical path differences of the configuration of Fig. 2 wherein the zoom beam expander has a magnification of 6.8X. The optical path difference for red light is shown by line 44, the optical path difference for green light is shown by line 48, and the optical path difference of blue light is shown by line 46.

Claims: An achromatic zoom beam expander comprising a first lens component (10), a second lens component (12), and a third lens component (14), said first and second lens components (10, 12) being movable with respect to said third lens component (14) and with respect to each other for providing a continuous variation in beam magnification, said first and second lens components (10, 12) forming a divergent lens group, and said third lens component (14) forming a collimator, characterized in that each of said first, second and third lens components are constituted by an air spaced lens doublet (20, 21; 22, 23; 24, 25), each of said air spaced lens doublets being individually color corrected in the range of about 486.1 nm to about 632.8 nm, said third lens component being fixed in the zoom beam expander. The achromatic zoom beam expander of claim 1 wherein said doublet components (10, 12, 14) are corrected for light including wavelengths of about 632.8 nm and of about 543.5 nm. The achromatic zoom beam expander of claim 1 or 2 wherein said doublet components (10, 12, 14) are corrected for a divergence caused by chromatic aberration of within about plus or minus 0.087 seconds of angle. The achromatic zoom beam expander of one or more of the preceding claims 1 to 3 wherein the distance between said second (12) and third (14) doublet components is adjustable from about 5 mm to about 169 mm. The achromatic zoom beam expander of one or more of the preceding claims 1 to 4 wherein the distance between said first and second doublet components (10, 12) is dependent on the spacing between said second (12) and third (14) doublet components, and said spacing between said first (10) and second (12) doublet components is adjustable from a minimum magnification setting of 72.475 mm when the distance between said second (12) and third (14) doublet components is 5 mm to a maximum magnification setting of 5.84 mm when the distance between said second (12) and third (14) doublet components is 169 mm. The achromatic zoom beam expander defined in claim 5 wherein the magnification of the beam varies from about 4.25X to about 6.8X as the spacings between said doublet components (10, 12, 14) are varied from said minimum magnification setting to said maximum magnification setting. The achromatic zoom beam expander of one or more of the preceding claims 1 to 6 wherein said first doublet component (10) comprises: a first element (20) including a first surface (a) having a concave radius of curvature of 15.23 mm, a second surface (b) having a concave radius of curvature of 26.85 mm and a center thickness of 3.0 mm; a second element (21) including a first surface (c) having a convex radius of curvature of 26.85 mm, a second surface (d) having a concave radius of curvature of 134.8 mm, and a center thickness of 3.0 mm; and an air space intermediate said first and second elements (20, 21) having a center thickness of 0.025 mm. The achromatic zoom beam expander of claim 7 wherein said first element (20) of said first doublet (10) is made of glass having an index n d of refraction for d light of 1.58913 and an Abbe number V d of d light of 61.27, and said second element (21) of said first doublet (10) is made of glass having a n d of 1.80518 and a V d of 25.43. The achromatic zoom beam expander of one or more of the preceding claims 1 to 8 wherein said second doublet (12) component comprises: a first element (22) including a first surface (e) having a convex radius of curvature of 678.83 mm, a second surface (f) having a concave radius of curvature of 192.5 mm and a center thickness of 4.0 mm; a second element (23) including a first surface (g) having a convex radius of curvature of 192.5 mm, a second surface (h) having a convex radius of curvature of 132.16 mm, and a center thickness of 8.0 mm; and an air space intermediate said first and second elements (22, 23) having a center thickness of 0.025 mm. The achromatic zoom beam expander of one or more of the preceding claims 1 to 8 wherein said third doublet (14) component comprises: a first element (24) including a first surface (i) having a convex radius of curvature of 709.6 mm, a second surface (j) having a concave radius of curvature of 203.2 mm, and a center thickness of 4.0 mm; a second element (25) including a first surface (k) having a convex radius of curvature of 203.2 mm, a second surface (1) having a convex radius of curvature of 137.48 mm, and a center thickness of 8.0 mm; and an air space intermediate said first and second elements (24, 25) having a center thickness of 0.025 mm. The achromatic zoom beam expander defined in claim 9 or 10 wherein said first element (22, 24) of said second or third doublet (12, 14) is made of glass having an index n d of refraction for d light of 1.80518 and an Abbe number V d of d light of 25.43, and said second element (23, 25) of said second or third doublet (10, 12) is made of glass having a n d of 1.58913 and a V d of 61.27.

Inventors: COBB JOSHUA M, COBB, JOSHUA M.
Applicants: IBM, INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1991
Main classification: G02B13
IPC codes: G02B15, G02B13