In forming an historical perspective of the development of optical scanning, we ask a probing question: What was the first major optical scanning innovation? We offer one having unexpected attributes, and seek audience ideas. We then demonstrate the pioneering work in Optical Scanning for information transfer, some created long before we arrived on the scene. Our job has been and is: Make it <b>Faster</b> and <b>Better</b>. The body of the presentation addresses how our technology advanced to this useful state.

Methods of nonmechanically steering broad spectral band light will enable many low cost electro-optical systems that employ broadband sensors (such as flir or TV). Nonmechanical optical phased array approaches have been demonstrated for narrow band electro-optical systems. However these approaches tend to be highly dispersive because of the diffractive effects associated with the modulo 2p phase resets within the apertures. In this paper we describe approaches to compensate or minimize these dispersive effects. A means to compensate for the dispersion using wavelength independent phase modulators and achromatic Fourier transform lenses is discussed. A means to minimize dispersive effects through the use of larger-than-2p phase resets is also presented, including a possible means of implementing such an approach using cascaded microlens arrays that are electronically controllable. The addition of nonmechanical approaches for steering broadband radiation will significantly accelerate the revolution in electro- optical systems from conventional steering to non-mechanical steering.

Most high resolution scanning applications use a rotationally symmetric scan lens and precision motor polygon mirror assemblies or active facet error correction. The realm of passive motion compensation and low-cost motor polygon assemblies tend to be limited to lower-performance systems. The reason for this lies in the symmetry that is broken by tangential beam input to the rotating polygon mirror. An alternative design method is presented, along with examples of application for UV maskless lithography.

This paper describes a computer model for the design integration of a laser marking system. The virtual marker consists of two sets of optical scan systems for the horizontal axis and the vertical axis, respectively. Each scanner includes a mirror as the beam deflecting device, a galvanometer as the actuator, and associated control electronics. A focusing lens is included in the beam path to reduce the spot size and increase the energy density of the laser beam at the marking surface. The virtual laser marker converts a specified pattern to be marked into images of simulated markings. Simulation results as well as experimental results are presented.

A high capacity aerodynamic air bearing (HCAB) has been developed for the laser scanning market. The need for increasing accuracies in the prepress and print plate-making market is causing a shift from ball bearing to air bearing scanners. Aerostatic air bearings are a good option to meet this demand for better performance however, these bearings tend to be expensive and require an additional air supply, filtering and drying system. Commercially available aerodynamic bearings have been typically limited to small mirrors, on the order of 3.5" diameter and less than 0.5" thick. A large optical facet, hence a larger mirror, is required to generate the high number of pixels needed for this type of application. The larger optic necessitated the development of a high capacity 'self-generating' or aerodynamic air bearing that would meet the needs of the optical scanning market. Its capacity is rated up to 6.0" diameter and 1.0" thick optics. The performance of an aerodynamic air bearing is better than a ball bearing and similar to an aerostatic air bearing. It retains the low costs while eliminating the need for ancillary equipment required by an aerostatic bearing.

The prediction of the behavior of the induction actuated scanners is a problem that involves the modeling of different physical domains as structural and electromagnetic. The Finite Element Approach is a highly viable alternative to obtain reliable predictions for its behavior over other available methods as the analytic, or circuit equivalent methods. In this owrk a finite element model for the structural an electromagnetic domains of the induction actuated scanning mirror was presented. To validate these models two experiments were performed, a laser doppler vibrometry of the double-rotor scanner to identify its modes shapes and natural frequencies and a magnetic field mapping of the actuator to obtain the spatial characteristic of the AC and DC magnetic fields generated by the actuator in the device armature region. There is a good agreement between the FEA models and the experimental results.

This contribution presents an optical module for projection of still images and video sequences. It consists of a laser source, miniature collimator optics, and a special MEMS device, a two-dimensional resonant micro scanning mirror. The laser beam is focused onto the micro mirror by the collimator optics. The micro mirror reflects the beam onto the desired projection area with a flare angle of up to 15 degrees for both axes. Given the resonant oscillation of the mirror, the beam follows a Lissajous figure. By choosing appropriate oscillation frequencies, it can be ensured that the laser beam hits every pixel of a pre-defined geometrical image resolution at a given frame rate. Limitations result from mechanical stability of the mirror plate that has a typical diameter of 1 mm and the CMOS-compatible fabrication process of the MEMS device. Projection of images and video sequences is achieved by modulating the laser diode. An external electronics receives data and transforms it into necessary modulation signals. Since frequency and amplitude of oscillation of the micro mirror are highly precise, no electrical feedback from the mirror to the modulation electronics has to be implemented. The system can be operated in open-loop modus. Currently, a monochrome demonstrator with VGA (640 x 480 pixels) resolution and 50 frames per second has been realized. Because of the compact size of the mirror, integration into mobile devices is fairly easy.

Micro Opto Electro Mechanical Systems (MOEMS) reach more and more importance in technical applications. They are smaller than conventional devices, less expensive when fabricated in higher numbers and offer new options concerning reliability and measuring methods. Resonant movable micro-mirrors produced as single crystalline chips with CMOS-compatible technologies provide a broad field of applications. In this paper, we will present different micro-mirrors, which are developed by the Fraunhofer IPMS in Dresden, Germany. They have different layouts and are thus suitable for several applications. Fabricated 1D-mirrors with mechanical angles of ± 16° can be used for laser deflection in bar-code-scanners, 2D-mirrors with different sizes and frequencies are suitable for imaging, displaying etc. Furthermore processes to apply diffractive structures on the micro-mirror surface were developed, showing an increased efficiency in the first diffraction order. Thus a micro-spectrometer has been built up, working in a wavelength range of 900-2500 nm. Due to the Czerny-Turner set-up, only one fast single InGaAs-photodiode is required.

This contribution presents a new scanning principle and device for 3-dimensional digital capturing and measurement of objects based on the triangulation method. The key elements are MOEMS, in particular electrostatically excited, harmonically oscillating micromechanical mirrors, which are useful means for light projection as well as for light detection. A configuration for capturing the trace of a static illumination is described, which applies a micro scanning mirror that oscillates in two axes. A synchronization method is proposed in order to apply micro scanning mirrors for both patterned illumination and light detection. For proving both techniques a test setup has been designed and assembled, and first results based on a static illumination are outlined.

Compared to conventional electromagnetic actuators e.g. voice coil devices, piezoactuators succeed in a wide spectrum of today's applications that require positioning with nm-accuracy, nm-reproducibility, sub-nm-step resolution and long-term stability even within the micron range. Additionally, piezoactuators show a high degree of electromechanical coupling, work abrasion-free, and show no measurable outgassing -they are UV and UHV compatible down to sub-μPa. They function down to almost zero Kelvin and are neither affected by magnetic field strengths, nor do they produce them. Due to their excellent behavior, piezoactuators are well suited for optical applications like fine cell tracking, beam deflection within ion-accelerators, beam shuttering in cryonic UHV spectrometers, sample positioning in UV environments et cetera. Additionally, piezoactuators respond at almost sonic velocities and generate pressure forces up to 100MPa. They are also well suited for optical scanning applications. However, when using piezoelectric positioning systems in the field of fast scanning applications, e.g. scanning microscopy, you have to regard application specific criteria. Generally the optimization of the piezoelectric geared stage has to result in the highest dynamic behavior together with excellent trajectory accuracy while maintaining the highest step resolution. Depending on scanning mode requirements, e.g. harmonic or step shape of motion, working frequency and applied load, the piezoelectric device's stiffness, inertia and robustness should be matched. Additionally state-of-the-art digital amplifiers allow in-situ configuration of controlling parameters, e.g. slew rate adjustment, PID-parameter modification and notch filtering.

Long-standing industry demand for "extended status messages" from galvanometer-based scan heads and ever-increasing dynamical requirements in industrial laser materials processing, e.g. due to advancing laser sources, have lead to the development of digital servo controls for galvanometers. The advanced control algorithms of a digitally controlled scan system lead to highly improved dynamics compared to an analog type where only a very limited number of parameters are used to tune the system to a certain dynamical requirement. Additionally, the abundant data acquired during control with a digital scan system are available for further processing. This paper discusses advantages of having such real-time feedback in laser-based materials processing applications and how e.g. process parameters like scan-speed and velocity can be used for quality control, applications development, or advanced laser control.

An essential part of a LADAR system is the scanner component. The physical scanner and its electrical controller must often be as compact as possible to meet the stringent physical requirements of the system. It is also advantageous to have a reconfigurable electrical scanner controller. This can allow real-time automated dynamic modifications to the scanning characteristics. Via reconfiguration, this can also allow a single scanner controller to be used on multiple physical scanners with different resonant frequencies and reflection angles. The most efficient method to construct a compact scanner with static or dcynamic re-configurability is by using an FPGA-based system. FPGAs are extremely compact, reconfigurable, and can be programmed with very complex algorithms. We show here the design and testing of such an FPGA-based system has been designed and tested. We show here this FPGA-based system is able to drive scanners at arbitrary frequencies with different waveforms and produce appropriate horizontal and vertical syncs of arbitrary pulse width. Several programmable constants are provided to allow re-configurability. Additionally we show how very few essential components are required so the system could potentially be compacted to approximately the size of a cell phone.

For LADAR systems with an arbitrary or undetermined scanner system, the raw video data produced is not usually in a form that can be used by standard video display devices such as a television monitor or frame grabber. This raw data must first be processed and organized into a standard video format or into a custom digital format for further processing. If this system is designed as an FPGA-based system, it can be combined with an FPGA-based scanner controller for an even more compact unit. This FPGA-based system can be extremely complex or simple depending on the desired input/output format. Even better, the system can be made reconfigurable to allow many input and output data formats. Such a system has already been designed and is being tested. Many programmable constants are provided to allow modification of the raw data from the photo-detector at a 4.195KHz horizontal line scan rate and produce a composite RS-170 compliant video signal with a 15.75KHz horizontal line scan rate. The program can adapt to any set of input and output frequencies, sync pulse width, white and black level.

Upon acquisition of a non-corrected LADAR image, a noticeable sinusoidal spatial distortion is present in the image. Resonant horizontal scanners must oscillate at high frequencies (in the kilohertz), and therefore they must scan in a sinusoidal pattern. As a result, the laser beam scans slower at the left and right edges of the object and scans the fastest at the center of the object. When the pixels are sampled at a constant rate with respect to time, as it is most commonly done, the resulting image will be noticeably compressed at the center and expanded at the left and right side. The design and testing of an FPGA-based embedded method for correction of this non-linear distortion upon acquisition is the focus of this paper. A working prototype has been currently obtained. This method incorporates dynamic adjustment of the sampling rate upon acquisition. Instead of sampling at a constant rate with respect to time, it is the goal of this system to sample at a constant rate with respect to position (of the deflected laser beam). The sampling rate with respect to time must therefore vary in a non-linear fashion. This is easiest if it is done within an FPGA that controls the acquisition of the data through the ADC (Analog to Digital Conversion), as we show in this work.

In this paper, a method is discussed for reducing the vertical spatial distortion due to physical scanner characteristics. Unlike methods of spatial correction during acquisition, the distortion in this case can be noticeably reduced before it is ever even produced. Instead of spatial correction, this method can be thought of as distortion reduction. This method is advantageous because it can be applied before a given Ladar image acquisition phase. During the acquisition phase, error is introduced due to approximations, and noise among other things. If the distortion can be reduced before the acquisition phase occurs, a higher accuracy can be achieved. The method presented here is based on the way the vertical scanner is driven. We show that if the vertical scanner is driven with a square wave of the correct frequency, a much more uniform vertical scanning pattern can be realized. We also show that this can easily be incorporated into an FPGA-based laser scanner controller.

We describe the scanning photon microscopy (SPM), a new method of microscopic image formation that is analogous to the scanning electron microscopy but carried out entirely by optical means and therefore is without the cumbersome sample preparation procedures. A laser beam is focused and raster-scanned over the surface of an object by means of an a motorized micrometer. The light reflected from the object surface is collected by a detector that is placed at a finite angle with respect to the incident beam. The geometry of the system is such that it yields images reminiscent of the scanning electron microscopy with striking three-dimensional impression and the effects of shadowing and diffuse reflection. In the preliminary experiments several artificial and biological objects are imaged using this technique obtaining images with about 5 micron resolution and reasonable image quality. Because this is a scanned optical system, the optical quality requirement is significantly relaxed in comparison to conventional wide-field imaging system. We also consider the possibility of surpassing the wide-field system in terms of the resolution and depth of focus by use of Bessel optics. The simple concept can be extended in many directions such as fluorescence and nonlinear optical imaging.

In this research, the method how to estimate the image quality for different scanning rate is suggested and experimentally shown with the laboratory-built confocal laser scanning microscope. The confocal microscope is designed for in vivo reflectance imaging of a biological tissue, which uses the refractive index mismatch at the boundaries of a tissue to generate an image without any additional staining process. The two-dimensional scanning mechanism is built up with a polygonal mirror and a galvanometric mirror that can be controlled to operate at a specific speed. To examine the effect of scanning rate on the image contrast, confocal scanning images of a biological specimen are acquired with various scanning rate while the other conditions are kept same. The contrast of confocal microscopic image is transformed into the numeric expression to describe the relation between image contrast and scanning rate quantitatively. Results suggest some useful methodology of how to determine the allowable maximum scanning rate for the specific application of confocal microscopy.

A new model for the optical transfer function (OTF) of an imaging system during angular motion is presented. In the traditional analysis, the optic's point spread function (PSF) is assumed to be fixed and therefore, cascading the motion OTF with the optics' OTF is allowed. However, this method is found to be not accurate in the situation of varying viewing angle, which occurs during an angular motion of the imager. In angular motion conditions, the image is affected by space-variant wavefront aberrations, space-variant motion blur and space-variant defocus. The proposed model considers these effects and formulates a combined space-variant OTF obtained from the angle-dependent optics' PSF and the motion PSF which acts as a weighing function. Results of comparison between the new angular motion-dependent OTF and the traditional OTF show significant differences when the imaged object points are apart from the optical axis. To simplify the proposed OTF model, an efficient approximation is suggested and evaluated.

Modern optical systems rely on scanning platform not only to broaden the field of view but also to enhance the viewing resolution. This paper presents a computer aided engineering (CAE) approach to a novel high speed optical scanning platform [1]. By the aid of complete system identification, system dynamics simulation and analysis, the resulted scanning platform is able to comply with high performance motion requirements. The optical scanning platform [1] uses piezoelectric transducers (PZT) with flexure joints. The scanning range of the novel optical scanning platform [1] can reach as wide as ±3.84 mrads after feedback. Different scanning reference demands are scheduled with different controllers in an attempt to achieve enhanced resolutions. For step and scan reference commands, we adopt a modified PID controller to obtain an improved performance over the simple PID controllers. The repeated continuous scanning, on the other hand, uses an iterative learning controller (ILC). The scanning resolutions are 10 μrad and 6.67 μrad in each scanning direction when operated under the modified PID controller and the ILC controller, respectively. Experimental results are provided to show the efficacy of the proposed approach.