SU398910A1 - DEVICE FOR TRANSFORMING THE IMAGE STRUCTURE IN A SPATIAL-FREQUENCY IMAGE - Google Patents

Description

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Devices are known for converting an image structure into a spatial frequency image using optical coherent systems that contain, not a source of monochromatic radiation, a Fourier transform lens and a screen.

To simultaneously obtain a Fourier transform and its Hilbert transform, a diffraction grating is placed behind the Fourier transform lens, the central strokes of which are symmetrical about the optical axis are spaced apart by a distance equal to

-S- (2n +} a, where a is the lattice spacing, an is an integer.

In addition, to obtain a shadow instrument that is not critical to the direction of illumination, the radiation wavelength and the external climatic influence, the device is equipped with a reverse Fourier transform lens installed between the screen and the diffraction grating.

FIG. 1 and 2 schematically depict the described device and the shadow device.

The lens / Fourier transform is illuminated by a collimated monochromatic beam from source 2. Behind the transparency 3, a diffraction grating 4 is installed, the central strokes of which are separated by a distance equal to (1) a, where c is the diffraction grating

lattices, and n - an integer (n 0 or 1). The center of the array is located on the optical axis of the device. On screen 5, the diffraction pattern of the far field is displayed in zero order, and in the first order its Hilbert image is shown:

-w 1- / () (g) () J ()

where / (l :) is the amplitude of the floor that is formed by the transparency 3.

The shadow device (Fig. 2) consists of a source 2 of monochromatic light, a lens / Fourier transform, a screen 5 and a lens 6 of the inverse Fourier transform.

Diffraction grating 4, the central strokes of which are separated by a distance equal to - (2n + 1) a, where o is the diffraction pitch

lattice, an is an integer (n 0 or 1), is set in the spatial-frequency domain. On screen 5, the sample image is displayed in the zero diffraction order, and its Hilbert image in the first order. If the initial sample has a phase contrast, then in the central part of the field of view of the first order of this contrast, the limit is high.

Subject invention

Claims (2)

1. A device for converting an image structure into a spatial-frequency image containing a source of monochromatic radiation, a Fourier transform lens and a screen, characterized in that, in order to simultaneously obtain a Fourier transform and its Hilbert image, a diffraction grating is placed behind the Fourier transform lens, central strokes which are symmetric about the optical axis. separated by a distance equal to - (2n + 1} a, where a lattice spacing, an is an integer. 2. A device according to claim 1, characterized in that, in order to obtain a shadow instrument that is not critical to the direction of illumination, radiation wavelength and external climatic effects, 10, it is equipped with a Fourier transform lens installed between the screen and the diffraction grating. / J / Rig 2