Image processing method and image processing system

1. An image processing method comprising the steps of:

imaging an inspection object moving in a predetermined direction a plurality of times with an imaging unit disposed in a predetermined position while a visual field of the imaging unit is lighted by a lighting source disposed in a constant relative position with respect to the imaging unit;

aligning a plurality of images with the inspection object as a reference by searching sequentially for a region indicating at least part of the inspection object between two images in the plurality of images of the moving inspection object acquired by a series of imagings with the imaging unit; and

producing a composite image from the plurality of aligned images,

wherein the producing the composite image comprises a step of computing image information representing a unit region from pieces of image information possessed by regions in the plurality of aligned images,

wherein the step of computing is performed to compute image information corresponding to each unit region constituting the composite image.

2. The image processing method according to claim 1 , wherein the step of computing image information further comprises:

acquiring a luminance of the image information possessed by the region of each of the plurality of aligned images and

computing one of a minimum value, a maximum value, an average value, and a median of the image information representing the unit region with respect to the acquired luminance.

3. The image processing method according to claim 1 , wherein the step of producing the composite image further comprises the steps of:

providing a plurality of different computation rules to compute the image information representing the unit region and producing a plurality of kinds of composite images according to each of the plurality of different computation rules;

displaying the plurality of kinds of composite images; and

receiving selection from the plurality of different computation rules that should be used to produce the composite image in the plurality of computation rules.

4. The image processing method according to claim 1 , wherein the step of producing the composite image further comprises the steps of:

providing a plurality of different computation rules to compute the image information representing the unit region and producing a plurality of kinds of composite images according to each of the plurality of different computation rules;

computing an index indicating a discrimination degree with respect to the plurality of kinds of composite images; and

selecting a computation rule that should be used to produce the composite image in the plurality of computation rules according to the computed index.

5. The image processing method according to claim 1 , wherein the aligning step further comprises the steps of:

extracting a first region indicating the inspection object from a first image that is acquired by imaging the inspection object and searching a region that is matched with the first region in a second image that is acquired subsequent to the first image; and

extracting a second region having a size independently of a size of the first region from the second image, the second region indicating the inspection object, and searching a region that is matched with the second region in a third image that is acquired subsequent to the second image.

6. The image processing method according to claim 1 , wherein all the images including a whole or part of the inspection object in the images that are acquired with the imaging unit are aligned in the aligning step.

7. The image processing method according to claim 1 , wherein a composite image having a range broader than a visual field range of the imaging unit is produced in the composite image producing step.

8. The image processing method according to claim 1 , wherein the lighting source is disposed such that a longitudinal direction of the lighting source is substantially orthogonal to a moving direction of the inspection object.

9. The image processing method according to claim 1 , wherein the step of producing the composite image further includes the steps of:

displaying the plurality of images that are acquired by performing a series of imagings to a first inspection object with the imaging unit;

receiving selection of the image that is used to produce the composite image in the plurality of displayed images;

producing the composite image using the image corresponding to imaging timing of an image selected with respect to the first inspection object in a plurality of images that are acquired by performing a series of imagings to a second inspection object with the imaging unit.

10. An image processing system comprising:

an imaging unit that is disposed in a predetermined position;

a lighting source that is disposed in a constant relative position with respect to the imaging unit; and

a control unit,

wherein the control unit is configured for

causing the imaging unit to image an inspection object moving in a predetermined direction a plurality of times while a visual field of the imaging unit is lighted;

aligning a plurality of images with the inspection object as a reference by searching sequentially for a region indicating at least part of the inspection object between two images in the plurality of images of the moving inspection object acquired by a series of imagings with the imaging unit; and

producing a composite image by computing image information representing a unit region from pieces of image information possessed by regions in the plurality of aligned images, the computation being performed to compute image information corresponding to each unit region.

11. The image processing method according to claim 2 , wherein the step of producing the composite image further comprises the steps of:

providing a plurality of different computation rules to compute the image information representing the unit region and producing a plurality of kinds of composite images according to each of the plurality of different computation rules;

displaying the plurality of kinds of composite images; and

receiving selection from the plurality of different computation rules that should be used to produce the composite image in the plurality of computation rules.

12. The image processing method according to claim 2 , wherein the step of producing the composite image further comprises the steps of:

providing a plurality of different computation rules to compute the image information representing the unit region and producing a plurality of kinds of composite images according to each of the plurality of different computation rules;

computing an index indicating a discrimination degree with respect to the plurality of kinds of composite images; and

selecting a computation rule that should be used to produce the composite image in the plurality of computation rules according to the computed index.