An Auto-level Star Simulator

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An Auto-level Star Simulator

An Auto-level Star Simulator

An auto-level star simulator is designed in this paper.The angle between the light simulated by the star simulator and the horizontal direction is fixed at a certain micro value.The key technical problems related to the star simulator are discussed and the solutions to the problems are suggested.Theauto-level star simulator has the quality of simple structure facilitating realization and easy handling.

 

Star simulator is an instrument used to provide simulated star targets for star sensors for calibration and testing. In practical applications, it is sometimes necessary to make the light emitted by simulated stars lie within the horizontal plane or form a small fixed angle with the horizontal plane, while ordinary star simulators cannot automatically and accurately provide such simulated starlight. This article proposes a design concept for an automatic Anping Star Simulator. In theory, this automatic Anping Star Simulator can provide simulated starlight with an angle accuracy of angular seconds with the horizontal plane, while coarse leveling the star model body. The principle experimental testing has also verified this.

The automatic Anping Star Simulator mainly consists of an automatic Anping optical path, a stable light source, and other lens groups. The design of the automatic Anping optical path mainly applies the principle of automatic compensation of the optical path.

  1. Design Plan and Principle

1.1 System optical path design

Based on a thorough study of the functions and accuracy indicators required for the automatic Anping Star simulator, we propose the following design scheme for the automatic Anping Star simulator. The optical system is shown in Figure 1.

Figure 1 Optical Path of the Automatic Anping Star Simulator System

In Figure 1, the light emitted by the stable light source illuminates the ground glass, forming a relatively uniform illumination field. The light beam passing through ground glass converges with lens 1 and lens 2, and then passes through a filter and attenuator group to converge on the star plate. A spectroscope has been added to the optical path to divide the light emitted by the light source into two parts: one part converges through the polarizing refraction path to form the required simulated starlight on the star plate; The other part propagates in the original direction and is received by the photoelectric detection device. After signal amplification processing, it serves as the feedback signal of the light source for stable control of light intensity.

The automatic leveling of the outgoing beam is mainly completed by an optical compensator, and its working principle is shown in Figure 2.

Figure 2 Working principle of compensator

When the optical axis of the star simulator tilts a small angle α At that time, due to the fixed connection between the star plate and the optical system, the position of the star on the star plate moved from A ‘to A. If there is no compensator, the simulated starlight beam will be aligned with the horizontal plane α Angular ejection star simulator.

In order to ensure that the light beam emitted from point A passes through the optical system of the star simulator and still shoots in the water plane direction, an optical compensator 4 needs to be installed at the distance l from the star plate to cause the beam to occur β Angle deflection.

The function of an optical compensator is to use certain optical principles to make the above angle relationship α And β Always holds true when the angles are not large. When the above conditions are met, even if the simulated optical axis has a slight tilt, it can still ensure that the emitted light is in the horizontal direction, achieving the purpose of automatic compensation. In this way, within a certain range, the star simulator can automatically simulate the starlight beam in the horizontal plane.

1.2 System stable light source design

As a star simulator system, the luminous intensity of its light source should be stable at a fixed value to simulate a specific magnitude. The stable control circuit of the light source is designed using the principle of optical power feedback, and the circuit schematic diagram is shown in Figure 3.

Figure 3 Stable Light Source Circuit Block Diagram

The beam emitted by the halogen tungsten lamp is received by a photodetector, converted into a voltage signal output, and compared with the voltage from the reference circuit through a comparison amplification circuit to obtain an error signal. This signal enters the power regulation circuit, known as the PID control circuit, and is adjusted to obtain a voltage output signal that meets the normal operation of the light bulb. This signal is then filtered and amplified to drive the halogen tungsten lamp to emit light. Through such optical power feedback control, the output power of the halogen tungsten lamp can be stabilized within the normal operating range required by the star simulator.

A stable light source was designed based on Figure 3. Test the light source and work continuously for 7 hours to obtain the data shown in Table 1.

Table 1 Light Source Stability Test Results

Analysis of the data in Table 1 shows that the long-term stability of the stable light source can reach 1%, which fully meets the requirements of the star simulator for light source stability.

2 Accuracy Verification Experiment of the auto-level Star Simulator

One of the key indicators of the design scheme of the automatic Anping Star Simulator proposed in this article is that the light emitted by the simulated star point can form a small fixed angle with the horizontal plane, which can remain stable even when only coarse leveling is performed on the main body of the star simulator. In order to verify the correctness of the technical solution, we designed experiments to test the accuracy of the principle prototype of the automatic Anping Star simulator. For the convenience of the experiment, the principle prototype adopts a visual structure. The actual angle between the line of sight and the true horizontal plane of the prototype of the automatic Anping Star Simulator was measured through experiments, and its stability was analyzed based on this. The accuracy of the angle between the starlight and the horizontal plane simulated by the automatic Anping Star Simulator was analyzed.

2.1 Main principles and steps of the experiment

In order to improve measurement accuracy, this article used a measuring microscope and conducted experiments in the laboratory with limited space and short distance. The experimental setup is shown in Figure 4.

Figure 4 Schematic diagram of experimental device

In Figure 4, the inner walls of the laboratory are located on the left and right sides. A scale with fine wire markings is placed on one side of the laboratory wall, and a measuring microscope is placed on the other side of the wall. The principle prototype of the automatic Anping Star simulator is supported on a tripod and placed near the measuring microscope and the scale for measurement. The measurement principle is shown in Figure 5.

Figure 5 Measurement principle diagram

Firstly, place the Automatic Anping Star Simulator at position 1 as shown in Figure 5, adjust the height of the Automatic Anping Star Simulator, and align it with a fixed fine line on the scale, that is, position A in Figure 5. Maintain the height and state of the automatic Anping Star Simulator unchanged, turn the objective lens of the automatic Anping Star Simulator to the measuring microscope, adjust the height of the measuring microscope, so that the cross hairs observed in the eyepiece of the automatic Anping Star Simulator coincide with the cross hairs image in the automatic Anping Star Simulator. Record the height direction reading of the measuring microscope at this time, which is a1 in Figure 5.

Move the Automatic Anping Star Simulator to position 2 as shown in Figure 5, adjust the height of the Automatic Anping Star Simulator, and align its objective lens with the fine line at position A. Maintain the height and state of the automatic Anping Star Simulator unchanged, turn the objective lens of the automatic Anping Star Simulator towards the measuring microscope, and make the crosshair of the measuring microscope coincide with the crosshair image in the automatic Anping Star Simulator. Record the height direction reading a2 of the measuring microscope at this time.

2.2 Experimental Data Analysis

We have conducted multiple repeated experiments on the basis of the above device. During multiple experiments, maintain the placement position of the experimental device and the height of the scale unchanged.

According to experimental data, the average angle between the actual line of sight and the true horizontal plane of the prototype of the automatic Anping Star simulator during operation is 2.3 ″, and the mean square error is σ= 0.5 ″, with a maximum error of 3.04 ″. The error of the experimental data includes the optical compensation error of the automatic Anping Star simulator and the error caused by the testing method. According to the principle of reversible optical path, the angle between the horizontal beam emitted by the automatic Anping Star simulator when actively emitting light and the true horizontal plane can also achieve the above accuracy.

This article proposes a design scheme for the automatic Anping Star Simulator. Through precision testing of its prototype, it can be seen that the angle accuracy between the light emitted by its star point and the horizontal plane can reach about 3 “, and the stability of this angle is σ= 0.5 ″.

The proposed automatic leveling star simulator can achieve automatic leveling of simulated starlight beams within a certain angle range of the optical axis tilt, making the angle between the simulated starlight and the real horizontal plane a small fixed angle. Through measurement methods in the laboratory, the preliminary design of the experimental principle prototype was tested, and it was shown that the simulated starlight beam intensity is stable, and the accuracy of the inclination angle with the horizontal plane can be controlled at the level of 3 “. It has the advantages of simple structure and easy operation, which can meet the special requirements of some use scenarios for star simulators and has good application prospects.

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