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Autofocus control method, autofocus controller, and image processor

A technology of automatic focusing and control method, applied in the direction of instrument, installation, optics, etc., can solve the problem of not being able to find the focus position stably, and achieve the effect of high-resolution observation

Inactive Publication Date: 2006-11-22
SONY CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Therefore, in the above-mentioned situation, the conventional technique of finding the focus position based on the maximum value of the focus evaluation value cannot stably find the best focus position

Method used

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  • Autofocus control method, autofocus controller, and image processor
  • Autofocus control method, autofocus controller, and image processor
  • Autofocus control method, autofocus controller, and image processor

Examples

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no. 1 example

[0042] figure 1 is a schematic structural diagram of an image processing device, on which the automatic focus control method and the automatic focus control device according to the embodiments of the present invention are adopted. Surface observation of an object sample (work) is performed with an image processing apparatus 1 specially constructed as a microscope for defect inspection of a device structure such as a semiconductor wafer by made by micromachining.

[0043] The image processing device 1 is equipped with a measurement platform 2 , an objective lens 3 , a lens driving part 4 , a lens barrel 5 , a CCD (charge coupled device) camera 6 , a controller 7 , a driver 8 , a monitor 9 and an illumination source 10 .

[0044] The measuring table 2 is constructed to support an object sample (for example, a semiconductor wafer) W and in the X-Y direction (in figure 1 , in the left-right direction and in the direction perpendicular to the drawing page).

[0045] Within the...

no. 2 example

[0107] Next, a second embodiment of the present invention will be described.

[0108] When miniaturization (processing rule) of the minimum mode width is performed, recent semiconductor wafers start to adopt more three-dimensional structures in their height direction. Light sources with shorter wavelengths require shallower depths of focus and are not conducive to reducing the number of focusable portions of objects with large height differences. If there are height differences in the screen, and different surfaces can be focused at different heights, an effective focusing operation must be performed to determine "where to focus", i.e. which surface of the sample to use as a reference surface. However, the conventional autofocus control method of finding the optimum focus position based on the focus estimation value has a disadvantage in that it cannot focus on a desired portion.

[0109] In order to solve this problem, a method will be described below which employs the auto...

no. 3 example

[0120] Next, a third embodiment of the present invention will be described. In describing this embodiment, a method of synthesizing a full-focus image of a subject sample based on the obtained image data and using the autofocus control method according to the present invention was cited.

[0121] In the case of a normal optical system, if a three-dimensional object beyond the focal depth of the optical system is observed through it, the overall focused image cannot be seen, and therefore, the purpose of inspection or observation cannot be achieved. Try to solve this problem with the following two methods, one of which is to use a special optical system such as a confocal optical system to obtain an overall focused full-focus image, and the other is to obtain an overall focus from images from different angles according to trigonometry A focused image, however, cannot be achieved cheaply by either of the above methods due to the need to use special optical systems.

[0122] On ...

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Abstract

An autofocus control method, an autofocus controller, and an image processor capable of eliminating influence originated from an optical system, realizing a stable autofocus function. In calculating a focus evaluation value of each sample image obtained at plural focus positions, dark and light patterns of brightness originated from the optical system is reduced by applying smoothing processing to the obtained sample image, and the focus evaluation value is calculated based on the smoothed sample image. Further, the focus evaluation value is standardized by average display brightness of the smoothed sample image to obtain an optimal evaluation value.

Description

technical field [0001] The present invention relates to, for example, an automatic focus control method, an automatic focus control device and an image processing device, all of which are suitable for use in a device for capturing images, observing and inspecting an object sample through a video camera, especially by eliminating the stable autofocus operation. Background technique [0002] Heretofore, automatic focus control of images has been performed using a focus estimated value obtained by estimating and quantifying the degree of focus from image data of a target sample (workpiece). That is, image data of the sample are collected at different distances between the lens and the subject and focus estimation values ​​are calculated for each image data in order to find an appropriate focus position. [0003] Figure 21 The relationship between lens-to-work distance (horizontal axis) and focus estimate (vertical axis) is shown. This relationship is obtained by loading imag...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G02B7/36
Inventor 江部宏树山内正弥菊地清幸黑田清隆高桥淳市
Owner SONY CORP
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