SU1320663A1 - Device for measuring distance to reflecting surface - Google Patents

Abstract

The invention relates to a measuring and measuring technique and can be used for contactless measurement of the distance between optical components of lenses. The purpose of the invention is to improve the measurement accuracy by increasing the steepness of the information signal, which is achieved using a multi-gap diaphragm 2. The image of a multi-gap diaphragm 2, illuminated by the light source 1, is constructed by the aperture imaging unit 4 on the reflecting surface. The reflected signal is converted by the CCD 9 into a video signal, which is extracted by the sampling unit 10. The harmonic component of the video signal is extracted by the band-pass filter 11, the detector 12, the low-pass filter 13 and is detected by the display unit 14. The distance to the reflecting surface is recorded by the indicator 16 by the movement of the focusing lens 7 by the drive 8, which is controlled by the indicator 14 when the signal at its input reaches the maximum value. 1 hp ff, 3 ill. (O (L with to about Oi Oi WITH ipue .;

Description

I-isodpe reuHe is a test and measurement technique and can be used to measure the distance to a reflective surface without contact, for example, when measuring the air gap between the optical components of a lens.

The purpose of the invention is to improve the accuracy of measurements by using a multiple, spruce diaphragm.

FIG. 1 shows a functional diagram of the proposed device; in fig. 2 - multi-aperture; in fig. 3 — temporal diaphragms of signals formed at the outputs of individual blocks.

The device contains optically coupled light source 1, a multislit diaphragm 2, transparent windows 3 of which are located symmetrically with respect to the central opaque part, a diaphragm imaging unit 4 made in the form of a translucent element 5, a collimating lens 6 and a focusing lens 7, a drive 8, associated with a focusing lens 7, a phototransducer 9, made in the form of a linear position-sensitive photodetector based on a charge-coupled device (CCD), are connected in series e sampling unit 10, band-pass filter 11, detector 12, low-pass filter 13, indication unit 14, interrogation unit 15, the outputs of which are connected to control inputs of the CCD 9 and sampling unit 10, information input of the sampling unit 10 is connected to the output of the CCD 9. In addition, the device contains a position indicator 16 associated with the actuator 8. FIG. 1 also indicates an element 17 with reflective surfaces, the distance to which is measured.

The device works as follows.

The luminous flux generated by the light source 1 illuminates the multislit diaphragm 2. The image of the multislit diaphragm 2 with the help of the beam-splitting element 5, the collimating lens 6 and the focusing lens 7, is built on the reflective surface of the element 17 and during the reverse stroke with the help of the focusing lens and the collimating lens 6 on photosensitive surface of the CCD 9.

Interrogation unit 15 periodically generates interrogation pulses of a CCD 9. At the output of a CCD, pulses are periodically generated, the envelope of which is proportional to the illumination distribution over the photosensitive sites of the CCD 9. The pulses taken from the output of the CCD 9 arrive at the input of the sampling unit 10, the control input of which receives synchronizing signals. pulses from polling block 15.

At the output of block 10, the sample forms a video signal of a complex spectrum, the amplitude of which is proportional to the illumination distribution over the photosensitive sites of the CCD 9.

The video signal is fed to the input of the bandpass filter II, which separates the harmonic component, the frequency of which is determined by the distance between the image of the individual windows of the multi-slit diaphragm 2 and the polling time of the CCD 9.

The signal allocated by the band-pass filter 11 is detected by the detector 12, smoothed by the low-pass filter 13 and is indicated by the display unit 14.

When the planes of the image of the multislit diaphragm 2 and the reflecting surface of the element 17 coincide, the depth of modulation 5 of the image of the multislit diaphragm 2 built on the photosensitive surface of the CCD 9 is maximum (Fig. 3a). In this case, the harmonic component, allocated by the band-pass filter 11, has a maximum value and the display unit 14 indicates the maximum value.

When the image plane of the multislit diaphragm 2 is displaced relative to the reflecting surface of the element 17, the image modulation depth of the multislit g diaphragm 2 built on the photosensitive surface of the CCD 9 decreases (Fig. 36). In this case, the amplitude of the harmonic component allocated by the band-pass filter 11 is also reduced, and the display unit 14 indicates a smaller Q value.

By moving the focusing lens 7, the actuator 8 sets the position at which the display unit 14 indicates the maximum value. The position of the focusing lens 7 is indicated by a 5 position indicator 16, which indicates the distance to the reflecting surface.

The adjustment of the device is carried out by setting the reference element 17 with a reflective surface, i.e. 0 measurements are made relative to the reference distance.

The arrangement of the transparent windows 3 of the multislit diaphragm 2 symmetrically relative to the central opaque part of g (Fig. 2) increases the sensitivity of the device.

With a continuous positioning of the transparent windows 3 on the multislit diaphragm 2, the modulation depth in the central part of the image of the multislit diaphragm 2 0 varies less compared to the modulation depth from the side portions for the following reasons. The depth of field of the optical system, consisting of lenses 6 and 7, is higher in the center than in the field. The influence of the central beams 5 of the rays reflected from the subsequent reflecting surfaces of the element 17, which create an additional, slightly changing image modulation from the central part of the image of the multislit diaphragm 2 in the case of transparent windows in the central part of the multislit diaphragm 2, decreases. with a CCD 9 and a band-pass filter 11 increases the signal-to-sound ratio, which allows operation at higher spatial frequencies (less than the width of windows 3). This, in turn, increases the sensitivity and accuracy of measurements.

The use of the proposed device makes it possible to increase the accuracy of measuring the distance to the reflecting surface of an object by increasing the steepness of the information signal, which characterizes the moments of focusing the image of the multislit diaphragm on the reflecting surface of the object.

Claims (2)

Claim 1. Device for measuring the distance to the reflective surface, containing optically coupled light source, diaphDD and 9 eleven V-- L illllllllllllllHi ......... illllllliilllllliii ... eleven Editor A. Ogar Order 2649/44 Compiled by V. Chulkov Tehred I. Veres Corrector A. Ilyin Circulation 677 Subscription VNIIPI of the USSR State Committee on Inventions and Discoveries I 13035, Moscow, Zh-35. PayujCKaa nab. 4/5 Production and printing site, Uzhgorod, ul. Project 1a. four 0 five 0 ragma, diaphragm imaging unit, actuator associated with the diaphragm imaging unit, position indicator associated with the actuator, phototransducer, display unit, characterized in that it is equipped with a serially connected sampling unit, band-pass filter to improve measurement accuracy , a detector, a low-pass filter, the output of which is connected to the input of the display unit, a polling unit, the diaphragm is made multislit, the phototransducer is designed as a linear position-sensitive sensor th photodetector outputs interrogation unit connected with the control input of a linear position-sensitivity of the photodetector and the sampling unit, an information input of which is connected to the output of a linear position-a sensitive photodetector. 2. A device according to claim 1, characterized in that the transparent windows of the m, foot-slit diaphragm are arranged symmetrically with respect to the central opaque part. 3 2 / / FIG. 2 b FIG. 3