SU821989A1 - Device for determining image plane - Google Patents

Description

The invention relates to an instrumentation technique and can be used to determine the plane of the best installation in any part of the spectral range when monitoring cinema and photographic devices during their manufacture and adjustment.

Autocollimating devices for determining the image plane are known, containing autocollimators, in the focal plane of the lenses of which test objects are installed, test systems consisting of an objective with an adjustment mirror, and analyzing systems with a 1J photodetector.

However, due to the sensitivity of these devices to the mutual decentering of the analyzing and test systems, they are not used in the production of film and photographic equipment.

Closest to the invention is a device for determining the image plane, containing a collimator, in the focal plane of the lens of which a test object is installed, a beam splitter, a test system including a lens with a seating mirror, an analyzing system with focusing keys

and photo registration system 2. In addition, this device is equipped with a second test object located in the plane optically conjugated with the focal one and the photoelectric receiver.

The image of the first test object is projected through the beam splitter with an autocollimator lens and the objective of the system under study onto the alignment mirror. Reflected from the mirror, the light rays pass in the opposite direction through both lenses, the beam splitter, the second test5 object and fall on the photodetector. Since both test objects are the same in area, with the full combination of test objects, which corresponds to the best sharpness, to the photodetector

0 passes maxim; m or minimum of light, depending on the pattern and the relative position of the test objects.

However, in this device, the focusing plane depends on the accuracy of the position of the test object, in addition to that. The centering of the test system causes the image of the first test object to shift relative to the second one, which leads to the appearance of a false signal on the photodetector. Besides. the system does not allow defining the defocus sign, i.e. the signal taken from the photodetector does not indicate in which direction the lens of the system under test should be mixed relative to the adjustment mirror in order to eliminate the defocusing. These shortcomings lead to the fact that the device does not provide the required accuracy and reliability of work. The purpose of the invention is to improve the accuracy and reliability of device operation. This goal is achieved by inserting a reference channel from the reflector and a modulator of the splitter into the device for determining the image plane, and a beam splitter between the volumes of the collimator and the system under test is optically aligned position-sensitive element of the photo-recording system, the modulator being designed with the possibility of alternately overlapping the reference channel and the channel of the system under test. Photo registrar's system is executed by Yen in the form of series-connected position-sensitive element, synchronous detector, and actuator. Elimination of the effect of the decentering of the system under test makes it possible to increase the accuracy and reliability of the device, which is facilitated and achieved by the proposed design of the indissolubility of the analyzing system. Fig. 1 is a schematic diagram of the device in Fig. 2 — a circuit for turning on a photodetector; on fig.Z view of the signal of the photodetector. A device for determining the plane of the isobritus contains a colpimeter 1 test object 2 located in; the lens focal plane (2 and images of the test object in the plane of the position-sensitive photodetector, formed by the first and second focusing wedges, respectively), the reflector element of the beam splitter 4, the lens 5 of the tested device, the alignment mirror b, the modulator 7, the anchoring system 8, focusing wedges 9, lens 10 of an analyzing system, collective 11, a wrapping lens 1 aperture diaphragm 13, a position-sensitive photodetector condenser 15 (PFC), a selective amplifier 16, synchronous detection 17, the actuator 18, the collimator 1 forms a parallel beam of rays from an object test 2.1 located on its objective lens 2.1 This beam of rays reflected from the splitter 4 is partially directed to the reflecting element 3. Reflected from the reflecting element the rays go back in the same direction and, forming the reference channel, enter the analyzing system. The remainder of the beams, forming the main channel, passes the beam splitter 4 and is focused by the lens 5 to the alignment mirror 6, is reflected from it and returns back through the lens 5, is reflected from the beam splitter 4 and is directed to the analyzing system 8. The lens 10 focuses the beams of the main and reference channels and the plane of the focusing wedges 9. The image of the test object, taken in the plane of the wedges, is transferred by the wrapping lens 12 and the condenser 14 to the IFP 15, while the aperture diaphragm 13 cuts off parasitic beams. The modulator 7 is driven at constant speed by an electric motor and alternately overlaps the beams of the reference channel and the system under test. The PFR signal is amplified by a selective amplifier 16 and fed to a synchronous detector 17, the reference voltage of which is synchronized with the angular position of the modulator. For example, the voltage of a modulator motor can be used as a reference voltage. The device works as follows. In the case when the beams of the beams of the reference channel are blocked by the modulator and the adjustment mirror 6 is located in the focal plane of the object, va 5, in the plane conjugated with the plane of the focusing wedges, the images 2 and 2 are aligned. In order to eliminate the effect of possible displacement of the images 2 relative to the photodetector and to register. the signal is proportional only. their mutual displacement, diagonally located pads of the photodetector are connected in parallel, and the electrodes connecting the pairs of plots in this way form the output circuit of the photoreceiver (Fig. 2), in which the recording device or amplifier input is included as load resistance. Thus, in the absence of mutual shift of the images 2 and 2, the signal at the output of the PFR is zero. In this case, it is assumed that the sensitivities of the individual PFR sites are the same. The defocusing of lens 5 leads to the mutual displacement of images 2 and 2 and the appearance of an electrical signal at the output of the PFC, which is proportional to the defocus value. The direction of the current PFR is determined by the defocus sign. If there is no defocusing, but the different sensitivity of the pads (drift zero PFR), a false signal takes place in its output circuit. The same effect leads to misalignment of the optical elements of the analyzing system. Thus, there is a likelihood of a false component in the signal corresponding to the system under test. In order to eliminate a spurious signal, a reference channel is inserted in the device, which in the PFF plane Zi of the test system is switched off by the modulator 7. When the zero drift or disconnection of the analyzing system, the Uee reference signal takes place in the PFF output circuit. The signal in the absence of defocusing of the system under test is equal to a false signal. This paled-eHCTBO can be easily achieved by selecting the reflection coefficient — element of the reflecting or diaphragming beams of the reference channel. When the modulator is rotated and the system under test is defocused, a variable information signal is observed at the output of the PFC, and (Fig. 3), the equal difference of signals Unct, -UOH. the position of the modulator. The constant voltage at the output of the synchronous detector corresponds to the defocusing value of the system under test, and its polarity corresponds to the defocusing sign. one

The signal removed from the output of the synchronous detector can be used to register the presence of the defocus value or to control the feedback system that eliminates the defocus.

Claims (2)

1. A device for determining the plane of the invention, containing a collimator, in the focal plane of the lens of which the test object is installed, a beam splitter, the test object 5 a system comprising an adjustment mirror lens / analyzing system with focusing wrenches and a photo-registration system, characterized in that  In order to increase the accuracy and reliability of controlling the position of the image plane, a reference channel from a reflector and a modulator was inserted into it, a beam splitter installed between the lenses of the collimator and the system under test, and the plane of analysis of the focusing wedges is optically coupled to 0 system, moreover, the modulator is made with the possibility of alternately overlapping the reference channel and the channel of the system under test. 2. Device POP.1, OTLI-, r that the photoregistration system is designed as a series-connected position-sensitive element, a synchronous detector, and an actuator. 0 Sources of information taken into account in the examination 1. Kreopalov G.V., Purev D.T. Research and control of optical systems. M., Mechanical Engineering, 1978 5 pp.4-63. 2. Kreopalov G.V., Purev D.T. Research and control of optical systems. M., Mechanical Engineering, 1978, p.48 (prototype). / UK UUUHUUU J