Polygon Mirror Research Articles

PSD Sensor Decomposing Multiple Light Spots

Position-sensitive detectors (PSDs) detect light spots point and total lights focused on it. The PSD provides high-speed response and precision due to its simple working principle. Inexpensive one-dimensional (1D) PSDs are commercially available, but when multiple lights focus on the PSD, it can only the center of multiple light positions making it unable to detect individual light positions separately. We propose a sensor that breaks down multiple light spots individua1ys by combing the rotation of a polygon mirror and two 1D PSDs. We consider how many light spots is broken down. We designed and developed a PSD sensor consisting of two 1D PSDs, a polygon mirror, and an actuator for rotating the polygon mirror. We broke down multiple light spots into individuals in scanning at 50.8Hz.

A202 機械的人工心臓僧帽二葉弁装着時の心室内流れ場の解析

Several bi-leaflet prostheses (the St. Jude Medical(SJM) valve etc.) were tested in the mitral position under pulsatile-flow condition. Dynamic PIV system was employed to analyze the flow field affected by the leaflet shapes and valve designs. Scanning PIV was developed to measure the three-dimensional flow inside the ventricular. The pulsed Nd:YLF laser was scanned by a polygon mirror in other to provide several light sheets inside ventricular. Detailed chronological comparison of the flow fields associated with the opening, accelerating, peak and closing phase of the flow revealed the significance of the leaflet and overall valve designs on the flow field. The Scanning PIV system was applied successfully to the study of the three-dimensional flow field.

A Large MEMS Scanning Mirror for Laser Printing Application

A state-of-the-art electrostatic scanning mirror for laser beam printing application has been developed. The large optical scanning angle of the mirror is critical for reducing the linear scanning speed variation. The geometry of the mirror increases the printing resolution and decreases the mirror dynamic deformation. Its maximum optical scanning angle range is above 96 degrees. The diameter of the mirror is as large as 4.2mm and the scanning speed is 3,000 Hz which is equivalent to a hexagonal polygon mirror rotating at 60,000 RPM. The device, coupled with a low speed scanner, is able to print on both flat and curved surfaces. It enables fast printing speed, lowers power consumption and reduces printer size for traditional print media such as paper, labels and cans as well as other applications such as raster scan display for dynamic bill board advertising with an array of such mirrors.

Axial Excitation Response of Polygonal Mirror Scanner Motor Supported by Thrust Magnetic Bearing and Radial Air Bearing

This article describes an axial transient vibration and axial excitation response of a polygonal mirror scanner rotor driven by a flat-type brushless dc motor and supported by a passive thrust magnetic bearing and a radial air bearing. From results of experimental investigations, the following characteristics of the vibration have been deduced: (1) Repulsive magnetic force was induced between the rotor magnet and stator coils of the dc motor under current passage. The force caused axial static displacement and axial transient vibration. (2) Because the stiffness of the thrust magnetic bearing was small, large axial vibration took place due to the axial excitation. (3) Two types of damper were introduced to suppress the axial transient vibration and the axial excitation response; one was an eddy-current damper and the other was an air damper. It was demonstrated that the air damper was effective for reducing the axial vibration.

Banding Reduction in an Electrophotographic Printer

Banding is an image artifact that appears as light and dark bands periodically across a page. Banding can be classified into two categories: fine and rough. A fine banding artifact could be caused by the periodic vibration or motion of optical devices in the optical path with the excitation frequency of the polygon mirror motor. This periodic vibration is mainly related to excitation force due to an imbalance of the rotor part of the polygon mirror motor or structural weakness of laser scanning unit. It is mainly caused by pyramidal errors of the polygon mirror motor. A rough banding artifact in printed images could be caused by the inaccurate motion or vibration of the organic photoconductor (OPC) part or the fusing part of the engine driven by the main driving unit. Printed image patterns have several frequencies, which can be obtained from the position of dots in a specific pattern in a printed image and Fast Fourier Transform (FFT) analysis of the position data. The identified frequencies can be confirmed by referring to the tooth frequencies of the parts on the gearing table. This article proposes a secure way to identify the causes of banding from FFT of the measured position data of dots in a specific pattern of printed images. The experiments were conducted to verify the identified causes of bandings.

Effects of laser beam alignment tolerance on lidar accuracy

One of the major lidar error sources not yet analyzed in the literature is the tolerance of the laser beam alignment with respect to the scanning mirror. In this paper, the problem of quantifying these errors is solved for rotating polygon mirror type lidar systems. An arbitrary deviation of the beam from its design direction–the vector of beam misalignment–can be described by two independent parameters. We choose these as horizontal and vertical components of the misalignment vector in the body frame. Either component affects both, horizontal and vertical lidar accuracy. Horizontal lidar errors appear as scan line distortions—along and across track shifts, rotations and scaling. It is shown that the horizontal component of misalignment results in a scan line first being shifted across the track and then rotated around the vertical at the new center of the scan line. Resulting vertical lidar error, being a linear function of the scan angle, is similar to that produced by a roll bias. The vertical component of the beam misalignment causes scan line scaling and an along track shift. The corresponding vertical error is quadratic with respect to the scan angle. The magnitude of these effects is significant even at tight alignment tolerances and cannot be realistically accounted for in the conventional calibration model, which includes only range, attitude and GPS biases. Therefore, in order to attain better accuracy, this model must be expanded to include the beam misalignment parameters as well. Addition of new parameters into the model raises a question of whether they can be reliably solved for. To give a positive answer to this question, a calibration method must utilize not only ground control information, which is typically very limited, but also the relative accuracy information from the overlapping flight lines.

Diagnostic Technique for Real-Time Measurement of Optical and Scan Properties of Optical Printheads

A diagnostic technique has been developed for rapid characterization of optical and scan properties in optical printers. The technique provides simultaneous real-time measures of beam profiles, including spot size, centroid and energy, at all or multiple positions along the print scan line for dynamically moving beams in laser printers or for static optical beams in LED printers. As such, it facilitates adjustments of f- lenses in laser printheads with air bearing spindles without the need to stop the polygonal scanning mirror. Also, since an entire raster is measured at once, measurements of the scan line bow and linearity characteristics are obtained in real-time. Polygonal scanner jitter characteristics can be measured in seconds. For LED printheads, it provides for optimal adjustment of lens/array assemblies, and for measurement of the many thousands of LEDs in seconds, yielding linearity, MTF, and power compensation values. When compared to conventional slit-scanning diagnostic methods, the 3σ measurement accuracy for spot size is slightly less, but the 3σ centroid accuracy is improved, primarily because there are no moving parts. For instruments using this diagnostic technique, real-time performance yields up to a thousandfold increase in measurement speed, with corresponding reductions in test time, allowing for vast improvement in fabrication tools and in quality control and assurance in printhead manufacturing.

3834 流体騒音を誘起するポリゴンミラーの流れ構造に与えるレイノルズ数の影響(J15-4 流体関連の騒音と振動(4)-機器・設備-,J15 流体関連の騒音と振動,2005年度年次大会)

3834 流体騒音を誘起するポリゴンミラーの流れ構造に与えるレイノルズ数の影響(J15-4 流体関連の騒音と振動(4)-機器・設備-,J15 流体関連の騒音と振動,2005年度年次大会)

Improved common-path fast-scanning heterodyne interferometer system as potential dense-plasma diagnostics

An improved common-path fast-scanning heterodyne interferometer system has been developed. The mechanical vibration is one of the most critical error sources in typical interferometry system. These errors can be mostly eliminated in a common-path interferometry using a full common-mode rejection scheme. Taking advantage of it, the common-path interferometry is suitable for the measurements in noisy environments and can be applied even to the scanning interferometry. A prototype common-path interferometer system with He–Ne laser has been constructed with the capability of fast scanning by adding a rotating polygon mirror. A test of this system has been completed successfully by measuring the thickness profile of the scratched glass. In this study, the interferometer system is proposed and discussed as a potential density profile diagnostics for dense plasmas. By using a CO2 laser instead of a He–Ne laser, it may also be applied to get the time evolution of steep density profiles of plasma transport barriers in tokamak plasmas.

Fast scanning method for one-dimensional surface profile measurement by detecting angular deflection of a laser beam.

A fast scanning method for one-dimensional surface profile measurement is proposed. The profile is measured by integration of a slope distribution of the surface obtained from angular deflection of a scanning laser beam. A scanning optical system that consists principally of a spherical concave mirror and a rotating scanner mirror has reasonably low cost and is insensitive to mechanical vibration because of its high-speed scanning, of the order of milliseconds. A surface profile of a polygonal mirror along a 5-mm width was measured with the scanning method and with an interferometer. The root-mean-square difference between the two measured results is 0.98 nm.

Development of a polygon scanner motor using single-axis controlled repulsive type magnetic bearing system

This paper reports on the configuration and performance characteristics of a repulsive type magnetic bearing system, which contains a vertical shaft type inner rotor with polygon mirror facets. Generally, low cost, high-speed rotation, power saving and rotational accuracy are important factors for the polygon mirror system. The experimental model introduced in this paper has achieved the stable rotation without contact at 50,000 rpm and low power consumption for a motor drive under low vacuum condition.

Flow Structure Around a Rotating Polygon Mirror

A polygon mirror is one of the important optical scanning components for a laser beam printer, a copy machine and so on. It has the serious troubles related to the fluid dynamic flow structures such as high frequency noise, frosted mirror and jittering of the rotating mirror under high rotating speed condition. The flow structures around the rotating polygon mirror were investigated by the flow visualization using a Particle Image Velocimetry and the velocity measurement using a Laser Doppler Velocimetry. As the results, significant flow structures were clarified and associated with these troubles. The first is the periodical fluctuating structure, which induces the high frequency noise, showing as a bow-shaped region and a pair of the vortex tubes. The second is an alternative flow structure shedding from near the polygon mirror, which is considered as one of the causes of the jittering. In addition, this flow accompanies the complicated three-dimensional vortices on the outskirts of the alternative flow structure. The third is the sinking flow structure toward the polygon mirror contributing the frosted mirror trouble.

Banding Reduction in Electrophotographic Printer

The Banding is an image artifact that appears as light and dark bands periodically across a page. Banding can be classified into two categories: fine and rough ones.Fine banding artifact could be caused by the periodic vibration or motion of optical devices on the optical path with the excitation frequency of the polygon mirror motor. The periodic vibration is mainly related to excitation force due to an imbalance of the rotor part of polygon mirror motor or the structural weakness of laser scanning unit. The periodic motion is mainly caused by pyramidal errors of the polygon mirror motor.Rough banding artifact in printed images could be caused by the inaccurate motion or vibration of the OPC part or the fusing part driven by main driving unit. Printed image patterns have several frequencies, which can be obtained from the position of dots in a specific pattern of printed image and Fast Fourier Transform (FFT) result of the position data. The identified frequencies can be confirmed by referring to the tooth frequencies of the parts on the gearing table. This paper proposes a secure way to identify the causes of banding from FFT of the measured position data of dots in a specific pattern of printed images. The experiment was conducted to verify the identified causes of bandings.

Fast-Fourier-domain delay line for in vivo optical coherence tomography with a polygonal scanner.

We demonstrate in vivo optical coherence tomography using a Fourier-domain optical delay line constructed with a commercially available polygonal scanner. The 20-faceted polygonal mirror array, capable of scanning at rates up to 15 kHz, is implemented at 4 kHz to acquire 500 x 500 pixel images at 8 frames/s with a signal-to-noise ratio of 80 dB. Features of this delay line include scalability to high repetition rates, 98.6% linearity in group delay over 2 mm, and bandwidth support exceeding 150 nm. Images are obtained in an animal model (Xenopus laevis), and limitations due to phase-delay nonlinearity and polygon asymmetry are discussed.

2435 流体騒音を誘起するポリゴンミラーの流れ構造

2435 流体騒音を誘起するポリゴンミラーの流れ構造

Laser scanning for semiconductor mask pattern generation

The use of laser scanning to generate semiconductor masks is reviewed. Following a brief historical introduction that describes early pattern generator implementations, current and future industry mask requirements are described with the consequences for pattern generator design: the need for small features, tight CD control, and high pixel delivery rates. The system architecture of a current deep UV scanning system is described in detail along with important print strategies, such as grayscale printing and multipass error averaging. Several subsystem technologies are then explored with emphasis on the application to short wavelengths and multiple beams. Today, frequency-doubled lasers generate the 257-nm radiation used by DUV pattern generators; tomorrow, sum frequency generation will be required to reach the wavelengths at or below 200 nm. Acousto-optic modulation (AOM) technology is shown to scale favorably with shorter wavelengths and to have the bandwidth capability for future system. Acousto-optic beam deflection, polygonal mirror beam deflection, and the reduction of scan bow error through the use of an f /spl middot/ sin(/spl theta/) lens are examined. A section on scan optics and image formation presents the differences between partially coherent imaging as used by a wafer stepper and the incoherent superposition of Gaussian beams as used by a laser scanner. Partially coherent imaging is shown to have a sharper image slope but worse feature size linearity. This section also discusses the effect of finite AOM turn-on time on the aerial image in the scan direction.

Measurement of force sensory information in ultraprecision assembly tasks

Automation of assembly tasks has previously been tackled by many researchers. They mostly focused on the geometric constraints related to a considered task, e.g., relative configuration change between the peg and the hole. Such an approach, however, has a limited validity in the sense that, unlike ultraprecision assembly studied in the present study, it assumes that the dimensional tolerance is fairly large so that it allows change to the relative configuration of the two mating parts in an obvious fashion. The paper investigates what makes highly precise assembly tasks very difficult from the viewpoint of automation of the tasks. Tolerance considered in the present study is in the range of 3-9 /spl mu/m. We focus on force sensory information involved in a high-precision peg-in-a-hole task of a polygon mirror unit because a position-based analysis under such a narrow dimensional tolerance seems inappropriate. A variety of insertion experiments are conducted by skilled and unskilled subjects for comparison purposes in which associated force signals are measured and analyzed.

Fractal modes of unstable lasers with polygonal and circular mirrors

The lowest-loss modes of unstable lasers are fractals, emerging asymptotically in the limit of high Fresnel number. The fractality depends on the shape of the feedback mirror. An explicit asymptotic theory can be constructed for the lowest-loss mode, in terms of a superposition of successively magnified edge waves. For polygonal mirrors, the superposition is anisotropic, and gives rise to a mode | u( x, y)| whose graph is a surface with fractal dimension 3, consistent with previous analysis for strip (one-dimensional) mirrors. For circular mirrors, the lowest-loss mode is dominated by focusing of edge waves at the centre of the mirror; the resulting superposition of circular waves gives rise to a mode |u( r )| whose graph is a curve with fractal dimension 3/2.

Wide band laser heat treatment using pyramid polygon mirror

A wide laser beam optical system for laser heat treatment processing has been designed with a pyramid polygon mirror, which is able to adjust the amplitude and frequency. It consists of a rotating pyramid polygon mirror made of copper and a cooling part that protects the surface of the mirror from damage by heat. The system provides a linear laser heat source with the wide scanning width. This can increase the efficiency of production and quality of products. The CO 2 laser heat treatment has been processed on SNCM220 and SCM440 steels using the developed optical system. The width of specimens between 13 and 17 mm can be hardened for a single pass scanning.

真空ポンプ機能を持つレーザスキャナ用動圧型空気スラスト軸受に関する研究 静的特性

This paper proposes spiral grooved aerodynamic thrust bearings functioning as a viscous vacuum pump for a laser scanner motor in order to reduce the windage power loss of a polygon mirror. The proposed bearing can pump out air within the scanner housing by using the pumping effect of the spiral-grooved thrust bearing, and reduce the inner pressure of the housing. The pumping performances and the static characteristics of the proposed bearings are investigated numerically and experimentally. It was consequently found that the proposed bearing can reduce the inner pressure of the housing to less than 0.01 MPa and have the sufficient load carrying capacity to support the rotating shaft.