Optics: measuring and testing – By polarized light examination – With light attenuation
Reexamination Certificate
1999-03-22
2001-05-15
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
By polarized light examination
With light attenuation
C382S154000
Reexamination Certificate
active
06233049
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a three-dimensional measurement apparatus that measures the shape of an object in noncontacting fashion by irradiating the object with a reference beam such as a slit ray or a spot beam.
BACKGROUND OF THE INVENTION
A three-dimensional measurement apparatus that employs a slit ray projection method (also known as a light chopping method) is known in the prior art, as disclosed, for example, in Japanese Patent Unexamined Publication No. 9-196632. The slit ray projection method is a method for obtaining a three-dimensional image (range image) by optically scanning an object, and is a form of active measurement method that photographs an object by projecting a specific reference beam on it. The slit ray projection method uses a slit ray whose cross section is a straight line.
When performing a three-dimensional measurement, the purpose of the measurement can vary in different ways. There are many situations according to the purpose; for example, one may want to make the measurement at high speed and in the shortest possible time, or may want a high resolution measurement at some sacrifice of the measuring speed, or may want to measure an object having a large depth.
However, according to the prior art three-dimensional measurement apparatus, it has only been possible to make measurements for the purpose that matches the specification of the three-dimensional measurement apparatus. For example, the measuring speed, the measurable dimension in the depth direction, the resolution, etc. have been predetermined as specifications, and it has not been possible to cope with situations that require significant changes in the measuring conditions, such as when one wants to make measurements at higher speed or with a higher resolution. Accordingly, in the prior art, it has been necessary to purchase different three-dimensional measurement devices for different measurement purposes.
The present invention has been devised in view of the above problem, and it is an object of the invention to provide a three-dimensional measurement apparatus which can accommodate multiple different measurement conditions to address various measurement purposes.
SUMMARY OF THE INVENTION
A three-dimensional measurement apparatus according to the invention comprises means for irradiating a measurement target with a reference beam, means for scanning the reference beam, a photosensor for receiving light reflected from the measurement target irradiated with the reference beam, and means for repeatedly driving the photosensor during the scanning of the reference beam and thereby reading out signals output therefrom. The apparatus measures a three-dimensional shape of the measurement target based on the output signals from the photosensor. The apparatus further includes, in one embodiment, means for selecting an operation mode, and means for switching the scanning speed of the reference beam and a readout operation of the photosensor in accordance with the selected operation mode.
A three-dimensional measurement apparatus according to a second embodiment of the invention is characterized by the provision of means for selecting an operation mode, and means for switching a line width for the readout of the photosensor in accordance with the selected operation mode.
A three-dimensional measurement apparatus according to a third embodiment of the invention is characterized by means for selecting an operation mode, and means for switching line spacing for the readout of the photosensor in accordance with the selected operation mode.
A three-dimensional measurement apparatus according to yet another embodiment of the invention is characterized by means for selecting an operation mode, means for switching the scanning speed of the reference beam in accordance with the selected operation mode, means for switching a line width for the readout of the photosensor in accordance with the selected operation mode, and means for switching line spacing for the readout of the photosensor in accordance with the selected operation mode.
A three-dimensional measurement apparatus according to a further aspect of the invention is characterized by means for selecting an operation mode, means for switching the line width of an effective light receiving region of the photosensor, as well as line spacing for the readout, in accordance with the selected operation mode, and means for switching the number of lines shifted per frame for the readout of the photosensor in accordance with the selected operation mode.
A three-dimensional measurement apparatus according to another aspect of the invention is characterized by the provision of means for switching the readout operation between skipping intermediate lines and adding together the readout output signals when the number of lines shifted is more than one.
Factors describing the performance of the three-dimensional measurement apparatus include: measuring speed QS, measurement range QR which is the dynamic range in the depth direction (Z direction), resolution QD, sensitivity QB, and measurement area QE which is the dynamic range in the vertical direction (Y direction).
Parameters determining the above performance factors include: the number of lines (the number of readout lines) GL of the effective light receiving region Ae of the photosensor, the entire line width (readout line width) GW of the effective light receiving region Ae, line spacing GT which is a value obtained by dividing the line width GW by the number of lines GL, the number of shifts GS, and slit ray width GP (the width, w, of the slit ray U).
Usually, as the number of lines, GL, decreases, for example, the readout speed increases, increasing the measuring speed QS. When the line width GW is increased, the dynamic range in the depth direction (Z direction) increases, resulting in a wider measurement range QR. The resolution QD increases as the number of shifts, GS, decreases.
Depending on which performance factor is given priority, the operation mode is selected from among a standard mode, high speed mode, wide-Z mode, high sensitivity mode, high resolution mode, and high-speed wide-Z mode. Each operation mode has variations of its own. Various measurement purposes can be addressed by setting the operation mode in various ways.
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Ide Eiichi
Kondo Takashi
Miyazaki Makoto
Norita Toshio
Tanabe Hideki
Burns, Doane, Swekcer & Mathis, LLP
Minolta Co. , Ltd.
Pham Hoa Q.
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