RU189459U1 - Device for determining the modulation transfer function of optical-electronic systems - Google Patents

Abstract

The utility model relates to the field of monitoring parameters of optical-electronic systems and relates to a device for determining the modulation transfer function of optical-electronic systems. The device includes a radiation source and a test object of the type of a group of alternating light and dark bands. The test object is designed as a group of narrow slotted channels, whose inner surfaces have a high reflectance in the working spectral range. A light channel of rectangular cross section with a high reflectance of the inner surface and a diaphragm with a profile corresponding to the graph of the function representing the sum of nested sinusoids of different frequencies are installed between the radiation source and the test object along the rays. Diffusers are installed between the light channel and the diaphragm and at the output of the test object. The technical result is to improve the accuracy of determining the transfer function of the modulation of optical-electronic systems of the visible and infrared range in the low frequency region. 4 il.

Description

The invention relates to the field of measuring systems and can be used to determine the modulation transfer function (MTF) of the optical and electronic systems (ECO) of the visible and infrared range.

A device is known for forming an image of the worlds of a type of alternating light and dark bands for subsequent measurement with its help of the MTF of optical systems (Measurement of transfer functions of optical systems. / M. Shulman, LL: Mashinostroenie, 1980. 208 p.). This installation, however, has very large dimensions and is not intended for ECO research.

Closest to the proposed utility model to the technical nature and the achieved result is an installation for measuring the transfer function of the modulation of infrared ECO (US patent No. 6876443, IPC: H04N 17/002, publ. 05.04.2005). With the help of a radiation source, which is a black body and a diaphragm, having the form of a grid, a test object is formed of a group of alternating light and dark bands, the image of which is projected onto the studied ECO using a collimator, which converts it into a digital image, which is further processed on a personal computer (PC) in order to obtain the schedule of FPM.

The disadvantage of such a system is the unevenness of the test object over the area, the impossibility of controlling the frequency composition of the test object being formed, as well as the impossibility of calculating the MTF in the low-frequency region with sufficient accuracy.

The proposed device has a compact size and allows you to solve the technical problem of determining the FPM of the visible and infrared spectral range with the ability to more accurately calculate the FPM in the low frequency region.

To achieve this technical result, the proposed device includes a radiation source of the required spectral range, a test object of the form of a group of alternating light and dark bands, while the test object is made in the form of narrow slotted channels, whose inner surfaces have a high reflection in the working spectral range. A light channel of a rectangular cross section with a high reflectance of the inner surface, a diaphragm with a profile corresponding to the graph of the function representing the sum of nested sinusoids of different frequencies, as well as two diffusers: between the light channel and the diaphragm, and at the output of the test object.

The proposed invention is illustrated by the figures, which depict:

in FIG. 1 is a diagram of the proposed modulation transfer function measurement device;

in FIG. 2 -the image of the test object at the input and output of the system under test and the graphs of the brightness / illumination distribution along the line;

in FIG. 3 - Fourier transforms of the brightness / illumination distribution functions;

in FIG. 4 is a graph of the ECFFM.

The device (Fig. 1) consists of a radiation source of the required spectral range (1) located in front of the entrance end of the light

channel (2) of rectangular section. After the output end of the light channel, a diaphragm (3) is installed with a profile that corresponds to the graph of the function, which is the sum of nested sinusoids of different frequencies. After the diaphragm in the course of the rays is the test object (5), made in the form of a group of narrow slotted channels. Between the light channel (2) and the diaphragm (3), and at the output of the test object (5) there are diffusers (4). All components of the device are interconnected by screwing.

The device functions as follows:

From the source (1) the radiation of the required spectral range enters the light channel (2) of rectangular cross section, which creates a uniform illumination of the test object (5). The length of the light channel (2) to achieve the best result should be no less than 5 (five) times its transverse dimensions. To achieve greater uniformity of illumination of light bands, the test object (5) is designed as a group of narrow slotted channels, the inner surfaces of which have a high reflectance in the working spectral range. Diffusers (4) allow to increase the uniformity of illumination of the test object. Introduction to the path of the device before the test object of the diaphragm (3) with a profile corresponding to the graphics function, representing the sum of nested sinusoids of different frequencies, leads to the appearance of additional peaks in the frequency spectrum of the test object, allowing you to measure the FPM of the ECO under investigation. the number of measured values of the MTF in the low frequency range and in the frequency range corresponding to the frequency components of the test object, which leads to an increase in the measurement accuracy of the MTF in these areas. The ability to change the profile of the diaphragm by replacing it allows you to adjust the frequency composition of the test object. With the help of the ECO under test, an image of the test object is then formed, which is then processed on a PC in order to obtain an MTF schedule.

The values of MTF are determined by the formula

where M _in and M _out are the maximum values of the peaks of the Fourier transform of the brightness distribution along the line of the test object at the input and output of the optical-electronic system, respectively. Intermediate values of MTF can be determined by interpolation by cubic splines.

Thus, the proposed utility model allows for automated measurements of the FPM OES of the visible and infrared range with high accuracy and the ability to calculate the FPM at low frequencies.

Claims (1)

A device for determining the modulation transfer function of optical-electronic systems, including a source of radiation of the required spectral range and a test object of the form of a group of alternating light and dark bands, characterized in that the test object is made as a group of narrow slotted channels whose inner surfaces have a high rate reflections in the working spectral range, between the radiation source and the test object along the rays, a light channel of rectangular cross section is installed with a high reflectance of the internal surfaces, a diaphragm with a profile corresponding to the graph of the function, which is the sum of nested sinusoids of different frequencies, as well as two diffusers: between the light channel and the diaphragm, and at the output of the test object.

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