Today's customer requires zoom lens designs that are compact, inexpensive, and at six-sigma quality levels. While incorporating these customer requirements, a design team must often work within compressed design cycles and minimal product development budgets. These customer and project constraints, coupled with the inherent complexity of a zoom lens module, force the design team to try new and innovative techniques to deliver their products. This paper presents the methods used to develop lens barrels for several zoom lens module projects at Eastman Kodak Company. The lens barrel, a critical interface between the mechanical and optical systems, presented a technical barrier from both an engineering analysis and manufacturing perspective. The method used to overcome these barriers consisted of identifying several key functional parameters, creating a parameter-driven 3-D solid model in a commercially available CAD system, and then using the model to make iterative, data-driven design decisions while leveraging the model to create engineering drawings and the necessary prototypes and production tooling. As a result, the designs were able to meet their size, cost, and design cycle time requirements while realizing a better than anticipated first pass yield and quality level.
In many complex technological fields the primary source of useful information lies not in books or periodicals but rather in the patent literature. Nowhere is this truer than in the field of zoom lens design, where in-depth discussion in books is very scarce but patents number several thousand. Several different types of zoom lenses that are commercially important today have roots in designs that are decades old, and the detailed path of development is publicly documented in the patent literature. These zoom types include the positive-negative type, which has been used extensively in compact 35mm and APS point-and-shoot cameras; the negative positive type, which was originally developed for 35mm SLR cameras and has been widely adopted for use in digital still cameras; and the positive-negative-positive type, which has been used in many applications ranging from 35mm still photography to cinematography to ultra-wide range TV camera objectives. Many innovations have fueled the development of these designs, including the use of aspheric surfaces, plastic lens elements, the use of abnormal partial dispersion glasses to achieve apochromatic correction, and the use of a variety of focusing techniques. Given that the patent literature is the best source of information on zoom lenses, there are a number of reasons that a designer or perhaps a product engineer would want to study this information. First and foremost is to gain a very broad historical understanding and appreciation for the technology. Next is to discover what has been done before by others in order to avoid re-inventing it, and also to increase the likelihood that a new design will be a genuine improvement over past efforts. This alone can save countless hours of work and potentially millions of dollars in development costs. Just as important as finding out has been done is finding out what hasn't been done. This can alert a designer to potentially over-ambitious specifications on a project. It can also aid in the process of creating new and valuable intellectual property. Another highly useful benefit of patent study is that it provides an almost limitless supply of starting points for new design projects. This is especially important in zoom lens design, where the final performance is more heavily dependent on the starting point than simpler fixed focal length lenses. Starting points can also be constructed from numerous different patent designs. For example the negative variator in a PNP type design can be inserted from dozens of different sources into the same basic starting point in order to find the optimum variator form.
A 10:1 telecentric zoom lens has been designed for metrology purposes. In addition to the specifications for high quality imaging, and less than 0.5 percent distortion throughout the range of magnification, the system has to fit within a predetermined mechanical space, and allow for coaxial illumination inserted directly into the optical axis in the space after the objective lens. This combination of specifications eliminates the possibility of using a conventional zoom lens type, primarily because the entrance pupil requirement would necessarily place the aperture stop where both size and aberrations could not be controlled. The design described includes a reimaging relay lens between the collimating objective and the zoom lens. The use of this reimaging relay lens allows for full correction of all of the aberrations, including distortion, and satisfies the mechanical requirements because the entrance pupil position for the zooming groups can be nearly ideally located. Because the coaxial illumination is a source of unwanted surface reflections from the objective lens, the objective lens must have a minimum number of air-glass surfaces. A cemented triplet including an aspherical surface satisfies this requirement.
Assuming that exit pupil position is fixed, it is presented a zoom lens having a focusing mechanism which does not give rise to any changes in the angular field of view. A frontal part set in front of the zooming part consists of two movable components for focusing. The paraxial condition in which no focus breathing phenomena exist is, in general, derived. Explicit expressions of component-displacement are obtained together with the relation to one-movable component focusing method. According to the analysis, a zoom lens is designed to show the usefulness of the analysis.
The automation of the designer's documentation making process gives rise to necessity in search of new possibilities for the even greater facilitation of the instruments designing process. Now in the field of optical instruments designing is felt a deficiency in the area of the software for automation of the designer's documentation formation. The development of ZOOM-objectives optics requires complex and laborious work of optics-designer and creation of new forms of realization of the projects for improvement of creative work too. The given report is devoted to development of the mathematical foundation and software for a construction of the mount of the optical system automized design.
A procedure is described for the third order optical design of zoom objectives. Formulae derived from the stopshift equations are developed to enable computation of component spherical aberration and central coma targets necessary for seidel aberration stability through zoom and focus.
In this paper a fast wide angle two element Wavefront Coded zoom lens is discussed. A traditional optics-only fast wide angle two element zoom system can not provide good imaging quality over a large field of view. Wavefront Coding techniques allow us to correct misfocus aberrations thus simplifying the optical system design while also providing good imaging quality. Imaging with an optical/digital system requires digital image processing that removes the spatial effect of Wavefront Coding.
This paper describes the theoretical background in design and examples of image stabilizing optical system. 'Image point based' aberration theory in image stabilizing optical system is introduced and applied for the concrete design examples of the Lens-shift type optical system. In the examples, the decentered aberrations are theoretically analyzed and reduced. The prototype of the image stabilizing zoom lens is also fabricated and its image stabilizing characteristic is also evaluated.
This paper describes the optical design of a 10x zoom objective lens for the visible wavelength band that was required to fit within a limited envelope. The paper describes the design approach and results, including some practical issues that must be addressed when a design is to be fabricated and deployed. The scope of the paper includes discussion of generating a starting point, optimization for best overall configuration and for maximum MTF, glass selection considering both chromatic and thermo-optical issues, configuration choices for minimum tolerance sensitivity, boresight error analysis, and lens length budgeting.
A preliminary investigation has been conducted into the feasibility of athermalizing an infrared zoom lens system for target detection in the eight to twelve micrometer region of the wavelength spectrum. The starting point for this study is an all-germanium 3 to 1 zoom lens operating at 20 degrees Centigrade that has been previously described in the literature. In the current study, this system has been athermalized over a large temperature range by means of active compensation of one of the zooming components. Another approach that has also been conducted in this study is to utilize the glass substitution capability in ZEMAX Global Search as an aid in selecting suitable optical materials for athermalization. ZEMAX has recently been modified to allow for simultaneous computer optimization of a zoom lens over an extended thermal range of operation. With the help of Global Search, certain optical materials have been selected with lower dn/dt than germanium. A solution using these materials has been obtained by this method which provides good image quality with passive compensation. These results are presented and compared with the starting solution.
The metrology community traditionally used fixed telecentric lenses to do optical measurement. The need to investigate varying fields of view led to the use of several fixed magnification lenses; this approach eventually yielded to zoom lenses. The majority of zoom lenses are designed to hold one set of conjugates constant, usually the object and the image. Such zoom lenses typically have the entrance pupil internal to the zoom groups; thus varying in position during zooming. By placing a stop external to the zoom groups, a constant entrance pupil position can be achieved. This idea can be extended to a telecentric stop position, and hence a telecentric zoom lens.