Focus Depth

With changing the aperture diaphragm (#8 in the right figer), the resolution and the depth of focus change.

The heigher the apearture, the better the resolution, but the depth of the field decreases with increasing apearture.

Thus we should find out the optimum apearture size to obtain the better resolution with the better focus depth.

The digital image processing for the continuous focus images is one of the possiblity to get the deep focus with preserving the better resolution.

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Sample Photos

These are the sample images of the same specimens, using 3 sizes of apearture.

The optimal size of pearture changes depending on the magnification (see. "FUJI HC2000 gallary").

Effect of Apearture Size on Field Depth

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The images of the lower preparation on the left side is getting sharp with decreasing the size of apearture.

Effect of Apearture Size on Resolution

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Digitally Processed Images (Extended Focus Image)

The digitally processed images, with higher resoliton and the deeper focus, have been synthesized from the serial focus images through the CCD camera.

1. Serial focus images with the maxium apeature, thus the maximum resolution, were recorded as "TIFF" format images.
   
2. The just in focus regions in each images have been picked up manually, then saved as a slice sectioned image.
   
3. All the slice images are summed as an extended focus image.
   

   Normal Focus	Extended Focus