CN205940927U - Testing device for characteristic parameters of swing mirror - Google Patents

Abstract

The utility model discloses a testing device for the characteristic parameters of a swing mirror, which comprises a light source component, a developing screen, a facula center acquisition system and a swing mirror arranged on the emergent light path of the light source component; the exit port of the light source component is provided with a diaphragm, and the diaphragm is provided with a plurality of circular light through holes with different sizes; the display screen is positioned on the reflection light path of the swing mirror and can receive the reflection light of the swing mirror at each position, and the reflection light of the swing mirror forms light spots on the display screen; and the light spot center acquisition system is used for recording the light spot image on the developing screen and the center coordinates thereof. The utility model has the advantages of angle measurement scope is big, measurement of efficiency is high.

Description

Oscillating mirror characteristic parameter test device

technical field

The utility model belongs to the technical field of optical precision measurement, and relates to a test device for characteristic parameters of an oscillating mirror, which is suitable for general oscillating mirrors, especially for testing the characteristic parameters of high-frequency oscillating mirrors. The characteristic parameters of the oscillating mirror include scanning resolution, scanning angular velocity, scanning uniformity, scanning angle repeatability, scanning linear segment time, effective scanning field of view, scanning frequency and the like.

Background technique

Optical imaging payloads carried by satellites, reconnaissance and mapping aircraft, and UAVs are often affected by relative image motion, resulting in blurred image quality of the acquired images. The swing mirror is a key component used to compensate for image motion in the camera, which can overcome relative image motion. The effect of shifting can improve the image quality. Limited by the relative motion speed between the carrier of the optical system and the ground target, the motion period of the swing mirror may reach millisecond level. Therefore, the characteristic parameters of the oscillating mirror, especially the characteristic parameters of the high-frequency oscillating mirror, directly affect the success or failure of the task. In addition, in the field of laser processing, the oscillating mirror is used to control the laser beam to realize the processing of different positions of the workpiece. The characteristic parameters of the oscillating mirror directly determine the processing quality of the processed workpiece. In order to improve the processing efficiency, the frequency of the oscillating mirror high.

At present, the commonly used measurement methods for the characteristic parameters of the pendulum mirror include: circular grating goniometric method, laser interferometry goniometric method, internal reflection high-precision differential small swing angle goniometric method and self-collimation goniometric method, etc. The circular grating angle measurement method uses moiré fringes to measure the turning angle of the pendulum mirror. It has fast measurement speed, high precision and strong ability to resist environmental interference. However, this method needs to install a circular grating structure on the pendulum mirror, which cannot realize non-contact measurement. The range is greatly limited; the laser interferometric goniometric method uses the optical path difference between the measurement beam and the reference beam caused by the rotation angle of the swing mirror to measure the rotation angle of the swing mirror. The measurement accuracy is high, but an auxiliary device needs to be installed on the swing mirror , which will affect the dynamic performance of the pendulum mirror; the internal reflection high-precision differential small pendulum angle goniometric method places two mirrors in the transmission and reflection directions of the beam splitter, and uses the change in reflectivity of the two mirrors to measure Measure the size of the incident angle, this method can realize non-contact measurement and high-speed measurement, but because the linear relationship between reflectivity and incident angle is only established near the critical angle, the measuring range is limited, and other angle measuring equipment is required for rough measurement in use , the measurement efficiency is low, and the optical path structure is complex when measuring two-dimensional angles. The autocollimation goniometric method uses the object-image relationship characteristics of the optical system to measure the angle of the incident light. It can measure two-dimensional angles and is a non-contact measurement. However, its angle measurement range is small and the frequency response is low, so it is difficult to apply in the swing mirror test. .

The patent [CN 101609250 B] proposes a testing device for characteristic parameters of an oscillating mirror that combines a circular grating angle measurement system and a small-angle high-precision angle measurement system, which can perform dynamic non-contact high-precision measurement of the characteristic parameters of the oscillating mirror. However, the The method needs to use the tracking device to track the oscillating mirror in real time, which has high requirements on the tracking stability and precision of the tracking device, and it is difficult to measure the characteristic parameters of the high-frequency oscillating mirror.

Patent [CN 103884491 A] proposes a pendulum mirror two-dimensional dynamic angle measurement device including three parts: an infinite target generation system, a two-dimensional dynamic angle measurement system and a synchronous acquisition system. It has high speed, wide range and non-contact However, since the incident light of the pendulous mirror has a relatively large angle in space after being reflected, the device needs to use a large-sized beam splitter, and the processing technology of a large-sized beam splitter is difficult and expensive.

Utility model content

Based on the above background, the utility model provides a testing device for the characteristic parameters of the oscillating mirror, which can realize the non-contact measurement of the characteristic parameters of the high-frequency oscillating mirror, and has a large angle measurement range, high measurement efficiency and low cost.

Basic principle of the utility model is:

First, a three-dimensional Cartesian coordinate system is established in combination with the parallel beams emitted by the light source assembly; the beam emitting system emits parallel beams with a certain caliber, and the parallel beams are reflected by the pendulum mirror to form a spot on the developing screen; the spot center acquisition system extracts the center of the spot The coordinates in the three-dimensional rectangular coordinate system; combined with the vector coordinate direction of the incident light beam of the pendulum mirror, the normal vector direction of the reflective surface of the pendulum mirror at different times is reversed; the characteristic parameters of the pendulum mirror are calculated through the time-varying characteristic curve of the normal vector.

The technical scheme of the utility model is:

The swing mirror characteristic parameter test device includes a light source component and a swing mirror arranged on the light source component’s outgoing light path; an aperture is installed at the exit port of the light source component; its special feature is that the aperture includes a plurality of different sizes Light-through holes, the light-through holes are round holes; the test device also includes a developing screen and a light spot center acquisition system; the developing screen is located on the reflection light path of the pendulum mirror and can receive reflections from the pendulum mirror at various positions. The reflected light of the oscillating mirror forms a light spot on the developing screen; the light spot center acquisition system is used to record the light spot image on the developing screen and acquire the center coordinates of the light spot image.

There are two above-mentioned light-through holes, which are denoted as the first light-through hole and the second light-through hole.

The diameter of the first light hole is at least twice the diameter of the second light hole, which is convenient for the spot center acquisition system to identify the corresponding target point.

The utility model has the advantages of:

(1) The utility model utilizes the light spot center acquisition system to obtain the precise position of the center of the light spot formed on the developing screen after the parallel light beam is reflected by the pendulum mirror, and deduces the three-dimensional direction of the normal line of the pendulum mirror reflection surface at different times, and at different times The three-dimensional pointing integration realizes the non-contact measurement of the characteristic parameters of the high-frequency oscillating mirror, the angle measurement range is large, the measurement efficiency is high, and the cost is low.

(2) The utility model can realize the dynamic non-contact measurement of the characteristic parameters of the oscillating mirror, and has a large angle measurement range; the whole set of testing device has no moving parts, and does not need to track the oscillating mirror in real time, and can test the characteristic parameters of the high-frequency oscillating mirror; The specially designed aperture realizes the function of obtaining multiple spot centers at the same time, and the measurement efficiency is high;

(3) By adjusting the distance between the developing screen and the oscillating mirror, the test error caused by the drift of the light source, the error of the spot center acquisition algorithm and other factors can be effectively suppressed, and the high-precision measurement of the characteristic parameters of the high-frequency oscillating mirror can be realized.

Description of drawings

Fig. 1 is the schematic diagram of the testing device of the present utility model;

Fig. 2 is the structural representation of the diaphragm of the present utility model;

Fig. 3 is a schematic diagram of the scheme of calibrating the positional relationship of each component in the present invention.

detailed description

Below in conjunction with accompanying drawing and specific embodiment, the utility model is further elaborated.

As shown in FIG. 1 , the device for testing characteristic parameters of the oscillating mirror provided by the present invention includes a light source assembly 1 , a oscillating mirror 2 , a developing screen 3 and a spot center acquisition system 4 .

A diaphragm is installed at the exit port of the light source assembly 1; a plurality of light holes of different sizes are provided on the diaphragm, and all light holes are round holes (the center of the round hole is easy to extract, and the parallel holes emitted by the round hole After the light beam is reflected by the swing mirror, the spot image displayed on the developing screen is still symmetrical, the center of the spot is easy to extract, and the test error is small). Here, the number and distribution of the light holes will affect the linear equation of the central ray of the parallel light beam emitted from each light hole and the coordinates of the intersection of the central ray and the reflective surface of the pendulum mirror 2 . There are two light holes in the diaphragm of this embodiment, which are respectively recorded as the first light hole 5 and the second light hole 6; and in order to facilitate the identification of the corresponding target point by the spot center acquisition system, the The diameter is at least twice the diameter of the second light through hole 6 .

The swing mirror 2 is arranged on the outgoing light path of the light source assembly 1 .

The developing screen 3 is arranged on the reflection light path of the oscillating mirror 2 and can receive the reflected light of the oscillating mirror 2 at various positions; the reflected light of the oscillating mirror 2 forms light spots on the developing screen 3 .

Utilize the method that the utility model tests the swing mirror characteristic parameter as follows:

First define a three-dimensional rectangular coordinate system, the origin O of the coordinate system is located at the midpoint of the line connecting the centers of the first light through hole 5 and the second light through hole 6, and the direction of the Z axis is the same as the direction of the outgoing light beam of the light source assembly 1, The Y axis is perpendicular to the plane where the developing screen 3 is located (as shown in Figure 1); then test the swing mirror characteristic parameters according to the following steps:

1) Calibrate the positional relationship between the light source assembly 1, the developing screen 3 and the spot center acquisition system 4:

1.1) A pentaprism 7 is arranged on the outgoing light path of the light source assembly 1, and the parallel light beam emitted by the light source assembly 1 is deflected by 90° by the pentaprism 7;

1.2) Calibrate the inner orientation element of the spot center acquisition system 4;

1.3) directly collect the parallel rays emitted by the pentaprism 7 with the spot center acquisition system 4, and adjust the position of the spot center acquisition system 4 until the star point image coordinates of the parallel rays acquired by it are at the calibration pixel of the inner orientation element;

1.4) The developing screen 3 is moved into the optical path between the pentaprism 7 and the light spot center acquisition system 4, and the position of the developing screen 3 is adjusted so that the outgoing light beam of the pentaprism 7 is at the central position of the developing screen 3;

1.5) Paste a double-sided reflector on the surface of the developing screen 3, and adjust the position of the developing screen 3 until the reflected beam of the double-sided reflector completely enters the light source assembly 1;

1.6) The double-sided reflector is removed, and the pentaprism 7 is replaced by the pendulum mirror 2 to be tested.

2) Turn on the light source assembly 1, and the parallel light emitted by it forms a light spot on the developing screen 3 after being reflected by the swing mirror 2;

3) Open the spot center acquisition system 4, record the spot image and its center coordinates on the developing screen 3;

4) Perform data processing on the acquired spot image to obtain the characteristic parameters of the swing mirror 2:

4.1) Calculate the unit normal vector of the reflective surface of the pendulum mirror:

The parametric equation of the central ray of the parallel light beam emitted by the light source assembly 1 through the first light through hole 5 is The parametric equation of the central ray of the parallel beam emitted by the light source assembly 1 through the second light hole 6 is In the formula, a is the distance between the centers of the first light-through hole 5 and the second light-through hole 6;

The intersection coordinates of the central ray and the reflective surface of the pendulum mirror are respectively denoted as M ₁ (0,-a/2,z ₇ ) and M ₂ (0,a/2,z ₈ );

After the central ray is reflected by the pendulum mirror 2, the intersection coordinates with the developing screen 3 are respectively marked as N ₁ (x ₅ , L, z ₅ ) and N ₂ (x ₆ , L, z ₆ ), where x ₅ , z ₅ , the values of x ₆ and z ₆ are obtained through the spot center acquisition system 4;

The plane equation of the reflective surface of the pendulum mirror is Ax+By+Cz=D (3), in the formula, parameter A, B, C vector (A, B, C) is the unit normal vector of the reflective surface of the pendulum mirror;

The plane equation of the developing screen 3 is y=L (4), where L is the distance from the developing screen 3 to the Z axis, which is a known value calibrated through the step 1);

Combining the formulas (1) to (4) and the coordinates N ₁ (x ₅ , L, z ₅ ) and N ₂ (x ₆ , L, z ₆ ) for derivation, it can be obtained that:

In the formula, k ₁ and k ₂ are the parameters introduced in the derivation.

Formula (5) is equivalent to solving nonlinear equations F(A,B,C,D,z ₇ ,z ₈ ,k ₁ ,k ₂ )=0(6), and its solution can be solved by quasi-Newton method or Broyden method . Obtain the values of parameters A, B, and C from the solution vector of formula (6), that is, obtain the unit normal vector of the reflective surface of the pendulum mirror at different moments

4.2) Normal vectors of the reflective surface of the pendulum mirror at different times Integrate as follows to obtain the normal vector of the pendulum mirror reflection surface at different times t _i Relative to the reflective surface of the pendulum mirror at the initial time t ₀ unit normal vector angle of

In the formula: is the unit normal vector of the reflective surface of the pendulum mirror at time t ₀ ; is the unit normal vector of the reflective surface of the pendulum mirror at time t _i ;

according to The swinging angle of the swinging mirror at different times t _i relative to the initial time t ₀ can be obtained, so as to obtain the time-varying characteristic curve of the swinging mirror motion, and realize the non-contact dynamic test of the swinging mirror characteristic parameters.

Claims (3)

1. A pendulum mirror characteristic parameter testing device, comprising a light source assembly and a pendulum mirror placed on the exit light path of the light source assembly; an aperture is installed at the exit port of the light source assembly; it is characterized in that: The diaphragm includes a plurality of light holes of different sizes, and the light holes are all round holes; The test device also includes a developing screen and a light spot center acquisition system; the developing screen is located on the reflected light path of the swing mirror, and can receive the reflected light of the swing mirror at various positions, and the reflected light of the swing mirror forms a light spot on the developing screen; The light spot center acquiring system is used for recording the light spot image on the developing screen, and acquiring the center coordinates of the light spot image. 2. The device for testing the characteristic parameters of the oscillating mirror according to claim 1, characterized in that: there are two light holes, which are denoted as the first light hole and the second light hole. 3 . The device for testing characteristic parameters of an oscillating mirror according to claim 2 , wherein the diameter of the first light-through hole is at least twice the diameter of the second light-through hole. 4 .