Modelling the focus error characteristic of a DVD player

Hnilicka, Bohumil; Besançon-Voda, Alina; Schroder, H.-J.; Filardi, Giampaolo

doi:10.1109/cca.2002.1038672

Cited by 5 publications

(6 citation statements)

References 3 publications

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“…The error is also increased when the velocity is fast. This is possible due to the high speed resulting in a loss of focus on the disk and the unstable easily [14]. Thus, an optimizing scratch can be obtained at low speed of disk rotation.…”

Section: Rotating Speed and Scratch Sizes Detected By CD And Dvd Pickmentioning

confidence: 99%

Utilization of CD and DVD Pick-Up Heads for Scratch Inspection of Magnetic Disk in Dynamic State Using Microcontroller

Polsawat

Tipcharoen²,

Siritaratiwat

2020

Applied Sciences

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A non-destructive technique to inspect a scratch on all magnetic disks in the beginning process of hard disk drive (HDD) manufacturing by using CD and DVD pick-up heads as the detector is proposed. It requires a 100% disk inspection of micrometer-sized scratches in a quick measurement with low cost inventing. Most of the previous studies were in static state but this is the first time to be done in dynamic study using the microcontroller in order to promptly serve for industrial utilization. The size, position, and shape characteristic of scratches are examined using light reflection technique. The results show that, when the laser beam is targeted on a magnetic disk in a position, either scratch or non-scratch, the reflected light intensity differs. The DVD pick-up head can detect the width and the surface characteristic of the scratches, which is similar to the results from scanning electron microscope (SEM) for all scratches sizes less than 100 µm. It is also found that using a DVD pick-up head provides a better resolution of shape characteristic and roughness of scratches surface than a CD pick-up head. Hence, the scratch size of 10s µm scale on the magnetic disk can be accurately characterized by this proposed technique, which can be further utilized for magnetic disk inspection in the hard disk drive manufacturing process.

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Section: Rotating Speed and Scratch Sizes Detected By CD And Dvd Pickmentioning

confidence: 99%

Utilization of CD and DVD Pick-Up Heads for Scratch Inspection of Magnetic Disk in Dynamic State Using Microcontroller

Polsawat

Tipcharoen²,

Siritaratiwat

2020

Applied Sciences

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“…In order to achieve a high surface decoding and reproduction density, it is of vital importance to converge the laser beam spot precisely to the prescribed data layer surface of the disk [2,3]. Focus error signal (FES), defined by the voltage value generated by a built-in four-quadrant detector (QD) versus the displacement of disk relative to the focal plane of the laser beam, is a non-linear function, which is also named as S-curve.…”

Section: Introductionmentioning

confidence: 99%

A sensitive optical probe for surface topography based on an optimized astigmatic method

Dong¹,

Xiao²,

Chen³

et al. 2014

SPIE Proceedings

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Surface topography is required to the function of many kinds of industrial products, and the number of applications keeps increasing, making the need for adequate control of surfaces and an understanding of surface topography measurements more important than ever. In this paper, we presented a sensitive and cost-effective optical probe for surface topography. The astigmatic method used in the optical probe is optimized for submicron/nanometer resolution and monotonic characterization of focus error signal (FES). A home-made system based on this optical probe was also presented, and the measurement results of surface topography indicate great potential of applications in many industrial fields.

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“…To overcome the disadvantage of the sharpness identification method, we develop the astigmatic auto-focus system which is very similar to the auto-focus function of the compact disk/digital versatile disk (CD/DVD) pickup head. There are many studies about the astigmatic optical system of the CD/DVD pickup head [4,5] and its applications [6][7][8]. The modeling of the astigmatic FES has been presented in works [4,5].…”

Section: Introductionmentioning

confidence: 99%

“…There are many studies about the astigmatic optical system of the CD/DVD pickup head [4,5] and its applications [6][7][8]. The modeling of the astigmatic FES has been presented in works [4,5]. In [4], an analytical formulation of the FES and its derivation with respect to the distance from the sample to the focal plane of the objective was defined.…”

Section: Introductionmentioning

confidence: 99%

Development of the fast astigmatic auto-focus microscope system

Hsu

Lee

Chen

et al. 2009

Meas. Sci. Technol.

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In this paper, a fast auto-focus microscope system was developed based on the astigmatic method. A collimated infrared laser beam was employed in the infinite-corrected microscope optical axis by the beam splitter and reflected by the sample surface. By embedding an astigmatic lens in the system, the reflected laser beam has different focal lengths in the sagittal and tangential planes. As the microscope's relative distance varies, the reflected laser beam shape also varies and can be detected by an embedded four-quadrant photodiode, i.e., the focus error signal (FES) can be found. Then, a fast auto-focus system can be realized by converting the FES to the microscope's defocus distance. We designed an astigmatic auto-focus system for a 20× objective lens with a ±50 µm working range, and this system could also be used for 10× and 5× objectives with ±200 µm and ±800 µm working ranges, respectively.

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Modelling the focus error characteristic of a DVD player

Cited by 5 publications

References 3 publications

Utilization of CD and DVD Pick-Up Heads for Scratch Inspection of Magnetic Disk in Dynamic State Using Microcontroller

Utilization of CD and DVD Pick-Up Heads for Scratch Inspection of Magnetic Disk in Dynamic State Using Microcontroller

A sensitive optical probe for surface topography based on an optimized astigmatic method

Development of the fast astigmatic auto-focus microscope system

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