The optical design of zoom lenses for projection applications is a task which has to take many different aspects into consideration. The optical designer has to achieve a demanding specification with respect to monochromatic and polychromatic aberrations across a significant magnification range. Besides the requirements on image quality there are usually numerous constraints deriving from fixed mechanical interfaces that already have an impact in the very early design stages of the paraxial and monochromatic design. It has been proven essential to also include cost targets in the figure of merit during the design work. This paper will outline a systematic process for projection zoom lenses design. A solid specification of the design task in terms of magnification range, image quality therein, mechanical and cost requirements is necessary as starting point. Paraxial considerations are helpful to gain insight into the design problem and choose the appropriate zoom design type for further design work. Intermediate designs, which are only monochromatically corrected, proofed invaluable while considering mechanical design requirements. As soon the basic design requirements are fulfilled it makes sense to correct chromatic aberrations. Outstanding color correction requires extensive use of expensive glasses for secondary color correction. In order to find an ideal compromise between potential cost of an optical design and image quality achieved therewith, we employ tools to identify cost drivers as well as tools to simulate the perceived imaging performance. Together these tools also enable us to efficiently discuss specifications that drive cost without aiding perceived image quality.

A stereomicroscope can stereoscopically observe an object with protrusions and recesses as if the object were viewed by both eyes. Such stereomicroscopes use an optical system to create two slightly different viewing angles of an object. The different images are both enlarged and viewed through two eyepieces. Each of the observation optical systems includes a variable magnification mechanism which is called a zoom lens system. In recent years, a demand for stereomicroscopes that can observe a wide variable magnification range has been increasing along with the diversification of applications. However, there are no stereomicroscope zoom lenses with both a high resolution and a large zoom ratio. We developed the “Perfect Zoom System” which can reduce the light flux diameter going through the objective lens in the low-power state. In the “Perfect Zoom System”, the zoom lens groups move along not only the optical axes but also perpendicular to the axes. Therefore, the objective lens could be made smaller by decentering the G2 and G3 group lenses in zoom lens group. We achieved a high resolution and a zoom ratio of 25:1.

In this tutorial the position of the aperture stop, rather than the number of moving groups, is used as a means of examining the design characteristics, and explaining how new designs have evolved. In addition to lens diameters, as determined by paraxial locations and the effects of aberration of the pupils, the position of the pupils, and their shapes as a function of zooming will be examined. The primary objective of the tutorial is to provide insight and a better understanding of zoom lens fundamentals, towards the selection of a design starting point; whether from an existing design, or from basic principles.

Optimizing the power distribution of fixed and moved lens groups as well as the motions of the latter, is typically a challenging part of the whole zoom lens optical design task. Once, the merit function is formulated to optimize an initial approach, the paraxial moving equations are solved implicitly in local optima. Hence, finding local optima becomes an ill posed problem when these equations cannot be solved uniquely for certain zoom configurations. Furthermore, an inappropriate initial power distribution can lead to large overall lengths, sensitive lens groups, small zoom ranges, induced aberrations and much more disadvantageous effects. From these reasons it appears as a logical consequence to first consider a paraxial pre-design of the zoom lens. This paper shows how first order aberrations, centering sensitivities as well as all common paraxial requirements can be formulated as a merit function for finding power distributions and (zooming) air spaces. In particular, the benefit of formulating zoom invariants as constraints in order to apply the Sequential Quadratic Programming (SQP) is shown. Based on a variation approach, an optimizable characteristic is introduced for control of the uniqueness of the moving equations. Global optimization methods like e.g. Differential Evolution can be used to obtain an initial paraxial approach. This approach can be improved using the SQP or the Damped Least Squares (DLS) method. Finally, the generation of an initial real lens system is described.

We developed software design tools in MATLAB that are compatible with Code V for supporting the process of designing zoom lenses. These tools simplify the process of finding paraxial solutions and evaluating intermediary design steps. Paraxial solutions are found through a partially random search for four group zoom systems with moving second and third groups. It requires several user-specified system parameters and then randomly assigns powers to each group. This process of randomly assigning powers is done a set number of times and only the valid solutions where no lenses crash are considered for further use. The valid designs are plotted over different design criteria and can then be selected to retrieve the first order design parameters. For the intermediate design process, the software displays lens specifications and diagnostic results across zoom for the entire lens as well as the individual groups. Systematic evaluation of the intermediate design steps is useful in determining how to proceed and improve the design. The design process is described for two different zoom lenses to show the efficiency and utility of these tools. The two zoom lenses are a 16x surveillance camera zoom lens working in the visible and a 3X zoom lens working in the visible and short wave infrared. The design procedure for these lenses covers finding the paraxial solutions to evaluating the lens for further improvement.

Monolithic beam expansion elements, which can be used as a cascade and achieve construction lengths much smaller than those of conventional systems are presented. Furthermore, this system is diffraction-limited, and offers a high level of flexibility and continuous extensibility using new elements. The compensation for wavefront errors and divergence introduce by changing the wavelength away from the design wavelength is achieved by employing an add-on element, the SPA Waveλdapt, which enables the use of monolithic beam expanders from 500nm to 1600nm. We will present experimental results on the diffraction limited performance for some typical combinations out of the 230 possible setups. Furthermore, another module – a zoom lens - is introduced. Adding this element overcomes the discreet incrementation of the monolithic elements and allows for continuous enlargement from 1x to 32x.

When a zoom lens views a tilted finite conjugate object, its image plane is both tilted and distorted depending on magnification. Our camera image plane moves with six degrees of freedom; only one moving doublet lens is required to change magnification. Two lens design models were analyzed. The first required the optical and mechanical axes to be collinear, resulting in a tilted stop. The second allowed the optical axis to be tilted from the lens mechanical axis with an untilted stop moving along the mechanical axis. Both designs produced useful zoom lenses with excellent resolution for a distorted image. For both lens designs, the stop is anchored to the moving doublet and its diameter is unchanged throughout magnification changes. This unusual outcome allows the light level at each camera pixel to remain constant, independent of magnification. As-built tolerance analysis is used to compare both optical models. The design application is for proton radiography. At the end of an accelerator, protons exit an aluminum vacuum window producing a shadowgraph image onto an LYSO (lutetium yttrium orthosilicate) scintillator. The 5″ square scintillator emission reflects off a pellicle and is collected by the zoom lenses located 24″ away. Four zoom lenses will view the same pellicle at different alpha and beta angles. Blue emission from the scintillator is viewed at an alpha angle of –14° or –23° and beta angles of ±9° or ±25°. The pellicle directs the light backwards to a zone where adequate shielding of the cameras can be achieved against radiation scattered from the aluminum window.

The selection of compensators for a cam-driven zoom lens is more complex than for a prime lens, because tolerances cause the back focal distance to shift by different amounts in different zoom positions, i.e, the system loses parfocality. Adjustment of the back focal distance can bring one, but not all, of the zoom positions back into focus. Furthermore, compensator selection is more complex because it is usually desirable to avoid adjustments within the moving groups. In this paper, we examine the effects of tolerances and compensators on a photographicformat zoom lens. We begin by assigning reasonable tolerances to all surfaces, materials, and groups, and then examine in detail how these tolerances affect the image quality. We determine the relative amount of degradation caused by transverse tolerances (decenters and tilts) compared to rotationally symmetric tolerances (power, index, thicknesses and spacings). For the rotationally symmetric tolerances, we examine the efficacy of shifting the detector, shifting the fixed groups, and respacing elements within the fixed groups. Similarly, for the transverse tolerances, we examine the efficacy of implementing decenter compensators within the fixed groups.

Common lexicon in imaging systems includes the frequently used term digital zoom. Of course this term is somewhat of a misnomer as there is no actual zooming in such systems. Instead, digital zoom describes the zoom effect that comes with an image rewriting or reprinting that perhaps can be more accurately described as cropping and enlarging an image (a pixel remapping) for viewing. If done properly, users of the overall hybrid digital-optical system do not know the methodology employed. Hence the essential question, pondered and manipulated since the advent of mature digital image science, really becomes “do we have enough pixels to avoid optical zoom.” This paper discusses known imaging factors for hybrid digital-optical systems, most notably resolution considerations. The paper is fundamentally about communication, and thereby includes information useful to the greater consumer, technical, and business community who all have an interest in understanding the key technical details that have driven the amazing technology and development of zoom systems.

Pixel binning actively changes the pixel size of a detector element in an optical system. When combined with a fixed focal length lens it has the same effect on field of view as changing the focal length of a lens with a fixed pixel size. The change in pixel size scales the instantaneous field of view, and if the size of the FPA scales equally, so does the field of view. This capability can be combined with traditional optical zoom lenses to significantly increase the overall zoom range of an optical system. In a multi-spectral, dual band zoom lens, the combination of optical and pixel zoom reduces the complexity of the optics while significantly increasing the overall zoom range. The benefits of combining both optical and pixel zoom in a dual band infrared system is explored in this paper.

Optical systems can provide simultaneous imaging in several spectral bands and thus be much more useful. A new and current generation of focal plane arrays is allowing detection in more than one spectral region. The design of a refractive imaging lens for such detectors requires correcting chromatic aberrations over the wider range of wavelengths. However, the fewer available refracting materials, the material properties that change between the spectral bands, and the system transmission requirements make the design of such lenses particularly challenging. We present a dual-field zoom lens designed for a cooled detector sensing across short-wave infrared (SWIR) and midwave infrared (MWIR) spectral bands (continuous imaging for 1-5 μm). This zoom lens has a 75 mm focal length in the wide mode and a 250mm focal length in the narrow mode, and operates at f/4.7 in both discrete zoom positions. The lens is actively compensated to work in thermal environments from -20°C to +60°C. We discuss the optical design methodology, review the selection of materials and coatings for the optical elements, and analyze the transmission of the lens and optical performance. A prototype system has been manufactured and assembled. We validate our design with experimental data.

A design study is compiled for a VIS-SWIR dual band 3X zoom lens. The initial first order design study investigated zoom motion, power in each lens group, and aperture stop location. All designs were constrained to have both the first and last lens groups fixed, with two middle moving groups. The first order solutions were filtered based on zoom motion, performance, and size constraints, and were then modified to thick lens solutions for the SWIR spectrum. Successful solutions in the SWIR were next extended to the VIS-SWIR. The resulting nine solutions are all nearly diffraction limited using either PNNP or PNPZ (“Z” indicating the fourth group has a near-zero power) design forms with two moving groups. Solutions were found with the aperture stop in each of the four lens groups. Fixed f-number solutions exist when the aperture stop is located at the first and last lens groups, while varying f-number solutions occur when it is placed at either of the middle moving groups. Design exploration included trade-offs between parameters such as diameter, overall length, back focal length, number of elements, materials, and performance.

With the advancement in sensors, hyperspectral imaging in short wave infrared (SWIR 0.9 μm to 1.7 μm) now has wide applications, including night vision, haze-penetrating imaging, etc. Most conventional optical glasses can be material candidates for designing in the SWIR as they transmit up to 2.2 μm. However, since SWIR is in the middle of the glasses’ major absorption wavebands in UV and IR, the flint glasses in SWIR are less dispersive than in the visible spectrum. As a result, the glass map in the SWIR is highly compressed, with crowns and flints all clustering together. Thus correcting for chromatic aberration is more challenging in the SWIR, since the Abbé number ratio of the same glass combination is reduced. Conventionally, fluorides, such as CaF₂ and BaF₂, are widely used in designing SWIR system due to their unique dispersion properties, even though they are notorious for poor manufacturability or even high toxicity. For lens elements in a zoom system, the ray bundle samples different sections of the each lens aperture as the lens zooms. This creates extra uncertainty in correcting chromatic aberrations. This paper focuses on using only commercially available optical glasses to color-correct a 3X dual-band zoom lens system in the VIS-SWIR. The design tools and techniques are detailed in terms of material selections to minimize the chromatic aberrations in such a large spectrum band and all zoom positions. Examples are discussed for designs with different aperture stop locations, which considerably affect the material choices.

Central to the rapid evolution of 4K image capture technology in the past few years, deployment of large-format cameras with Super35mm Single Sensors is increasing in TV production for diverse shows such as dramas, documentaries, wildlife, and sports. While large format image capture has been the standard in the cinema world for quite some time, the recent experiences within the broadcast industry have revealed a variety of requirement differences for large format lenses compared to those of the cinema industry. A typical requirement for a broadcast lens is a considerably higher zoom ratio in order to avoid changing lenses in the middle of a live event, which is mostly not the case for traditional cinema productions. Another example is the need for compact size, light weight, and servo operability for a single camera operator shooting in a shoulder-mount ENG style. On the other hand, there are new requirements that are common to both worlds, such as smooth and seamless change in angle of view throughout the long zoom range, which potentially offers new image expression that never existed in the past. This paper will discuss the requirements from the two industries of cinema and broadcast, while at the same time introducing the new technologies and new optical design concepts applied to our latest “CINE-SERVO” lens series which presently consists of two models, CN7x17KAS-S and CN20x50IAS-H. It will further explain how Canon has realized 4K optical performance and fast servo control while simultaneously achieving compact size, light weight and high zoom ratio, by referring to patent-pending technologies such as the optical power layout, lens construction, and glass material combinations.

Traditional high dynamic range (HDR) photography is performed by capturing multiple images of the same scene with different exposure times, which are then digitally combined to produce an image with great detail in both its light and dark areas. However, this method is not viable for moving subjects since the multiple exposures are not captured simultaneously. Recently an alternative method has been developed in which beamsplitters are utilized to simultaneously record the same image on three identical sensors at different illumination levels. This process enables single-shot HDR photography as well as continuous HDR video. This paper describes the design of a 2.5x zoom lens for use in this application. The design satisfies the challenging working distance and ray angle constraints imposed by the placement of two beamsplitters between the lens and the image plane. The particular importance of first-order layout when designing a retrofocus zoom lens is also discussed.

Over the past decades zoom lenses have become an important type of objective. Due to their ability to dynamically change magnification or field angle they are being used in many fields of application. Most zoom lenses consist of a number of lenses or lens groups. The magnification can be changed by axial shifting some of these lens groups with a more or less complicated moving function.

However, in principle it should be possible to construct zoom lenses that do not rely on the movement of some of its components. Instead, the change in magnification is achieved by changing the optical power of at least two lenses within the system (optical power zoom - OPZ). Moreover, for broadband applications it is highly favorable to use mirrors instead of lenses due to the absence of chromatic aberrations.

Based on a "Schiefspiegler" approach an all-reflective OPZ objective with a zoom power of three consisting of four mirrors has been designed. Two mirrors are assumed to have a variable radius of curvature for changing optical power. During aberration correction special consideration has been given to the reduction of field curvature, since the optical power change strongly influences field curvature for different zoom positions. The simulation shows adequate image quality for photographic applications over the whole zooming range.

For the realization of such an OPZ objective deformable mirrors with a comparatively large stroke are needed. Before starting a complex development of such devices three setups with different fixed focal lengths were built to prove and evaluate the concept for digital imaging.

The main purpose of this paper is to introduce a high speed zoom lens for photography. The lens operates with a full field angle that encompasses more than 86 degrees and the corner illumination is more than 60 percent at the wide end. In addition, the paper provides guidance on how to effectively use an aspheric surface in the first lens group consisting of an NPNPP (negative, positive, negative, positive, and positive). This treatment includes distortion considerations. Useful design solutions using an aspheric surface are introduced along with assessment of the resulting designs. Finally, a strategy to correct field curvature in this zoom lens is shown with an example.

Zoom lens has been developed around lens applications of consumer still camera and TV broadcast cameras from about 1960s. Among, zoom lens as an interchangeable lens of a single-lens camera has made the most significant evolution in technically. In this paper, I describe the change of optical design concept about focusing function in zoom lens including introduction of some topic specific lenses.

In this paper, we propose a multi-channel imaging system, which combines the principles of an insect’s compound eye and optical zoom. We use the distance between two aspherical lenses to achieve zoom effect. In order to shrink the thickness of the system, we use the multi-channel structure which consists of curved micolens array. With this architecture, we can achieve the same effect like lens group. Each partial image passes through each channel separately and is stitched together at the image sensor. In our design, the thickness is 6.57 mm (wide), 6.25 mm (mid), 6.4 mm (tele) and the effective focal length is 2.2 mm( wide), 2.97 mm (mid), 4.04 mm (tele). Zoom ratio is close to 2 times. The size of image sensor is 6 mm in diameter. Due to the advance in microlens fabrication of microlens, this design has the potential to bed used inside mobile phone camera in future.

*avella@ur.rochester.edu Design study for a 16x zoom lens system for visible surveillance camera Anthony Vella*, Heng Li, Yang Zhao, Isaac Trumper, Gustavo A. Gandara-Montano, Di Xu, Daniel K. Nikolov, Changchen Chen, Nicolas S. Brown, Andres Guevara-Torres, Hae Won Jung, Jacob Reimers, Julie Bentley The Institute of Optics, University of Rochester, Wilmot Building, 275 Hutchison Rd, Rochester, NY, USA 14627-0186 ABSTRACT High zoom ratio zoom lenses have extensive applications in broadcasting, cinema, and surveillance. Here, we present a design study on a 16x zoom lens with 4 groups (including two internal moving groups), designed for, but not limited to, a visible spectrum surveillance camera. Fifteen different solutions were discovered with nearly diffraction limited performance, using PNPX or PNNP design forms with the stop located in either the third or fourth group. Some interesting patterns and trends in the summarized results include the following: (a) in designs with such a large zoom ratio, the potential of locating the aperture stop in the front half of the system is limited, with ray height variations through zoom necessitating a very large lens diameter; (b) in many cases, the lens zoom motion has significant freedom to vary due to near zero total power in the middle two groups; and (c) we discuss the trade-offs between zoom configuration, stop location, packaging factors, and zoom group aberration sensitivity.

In this report a novel optical system for very thin zoom lenses is shown. The key point of this system is the use of the intermediate image. The system consists of 3 lens groups with the positive optical power. The possibility of the zooming and focusing types is investigated, as well as the possibility of the power distribution of 3 lens groups. Finally the procedure to realize such an unprecedented optical system is shown.

This paper proposes a new zoom lens design with intermediate image. The concept of intermediate optics is applied in this paper in order to minimize size of front diameter. The final layout shows the proposed 9x zoom lens can effectively miniature the front diameter of lens about 44.25%.

By filling a liquid droplet in the hole of a dielectric elastomer (DE) film directly, we prepared two small liquid lenses. The aperture of one lens is macro size and the other is micro size. The liquid droplet in each hole of the DE film exhibits a lens character due to its biconvex shape. In relaxed state, the focal length of each liquid droplet is the longest. When a sufficiently high DC voltage is applied, the diameter of each DE hole is decreased by the generated Maxwell stress, causing the curvature of its droplet to increase. As a result, the focal length of each lens is reduced. Here the DE film functions as an actuator. In contrast to previous approaches, our miniature liquid lenses possess the advantages of simple fabrication, fast response time (~ 540 ms), and high optical performance (~ 114 lp/mm). Moreover, the micro-sized liquid lens presents good mechanical stability.