In the design of imaging system, laser scanning system accounts for a considerable part. From simple one-dimensional linear scanning to two-dimensional plane scanning or three-dimensional scanning, these laser scanning systems have been widely used in many occasions. Such as laser marking, laser etching, three-dimensional contour scanner, laser bar code scanner, etc. The optical paths of these systems are not very complicated in design principle, and they are combined into a complete scanning system by cooperating with laser beam expander, beam splitter, scanning galvanometer and scanning motor. [pagebreak] Scan system parameters.

The scanning principle is shown in the following figure:

The scanning system can be divided into plane galvanometer scanning and drum scanning according to the types of reflection rotation, one-dimensional, two-dimensional and three-dimensional scanning according to the optical path, and scanning before and after the mirror according to the positions of galvanometer and scanning lens.

All the above scanning systems can be realized in ZEMAX, and the scanning effect can be dynamically demonstrated. Let's take the simplest one-dimensional linear scanning as an example to see the complete design process of the scanning system.

We need to design a lens, a plane mirror that rotates around its center, and the mirror focuses the laser on different positions on the image plane by rotating at different angles to form a scan. We know that a beam of light can only be focused at a certain position at a rotation angle. If we want to simulate the position of the optical path at different rotation angles at the same time, we need to use multiple configuration functions (which have been introduced in detail in the design of zoom system).

We use a Dan Toujing instead of the whole scanning lens group, Dan Toujing specification parameters:

Environmental protection department 10

EFFL 100

Glass BK7

Glass thickness 15

Wavelength 0.6328 micron

Here we quickly established the initial structure. For the detailed design process of Dan Toujing, please refer to the technical article: ZEMAX Basic Example-Dan Toujing Design.

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Open the general dialog box and enter the entrance pupil diameter 10mm:

Open the wavelength dialog box and enter the wavelength of 0.6328:

Insert two new standard surfaces in front of the image, input the material and glass thickness, set the F-number solution type on the back of the lens, and set the curvature radius of the front of the lens and the image space thickness variables:

Press F6 to open the evaluation function editor, set the default evaluation function and optimize the root mean square spot radius:

After setting, click the Opt button to optimize:

We need to add a vibrating mirror in front of the camera. If the distance from the lens is 50 mm, we will set the STO surface (the first surface at present) of the diaphragm to 50 mm. In order to see the incident beam, we will insert a virtual surface with the same thickness in front of the diaphragm:

We use a tool to quickly add a catadioptric mirror (explained in detail in the technical article Newton Telescope Design), and select: Tools & gt& gt coordinates & gt& gt to add a catadioptric mirror.

We see that in L3d view, the mirror becomes the global reference plane:

To set the incident beam (assuming the laser exit) as a global reference, you can directly right-click the first surface to open the surface properties dialog box and set it as a global coordinate reference surface:

Then double-click the L3d diagram to get the following view:

[pagebreak] Scanning angle setting under various structures.

We need to simulate the rotation of the mirror, and various rotations of the component can be realized by using the coordinate breakpoint surface. Here, we use the quick button method to rotate the component directly. Assume that the full scanning angle of the scanning system is 40 degrees, and the mirror rotation half angle is 10 degrees.

Open tools: tools >> coordinates & gt& gt tilt/deceleration, and make the following settings:

In the lens data editor, two coordinate breakpoint surfaces are automatically inserted to realize the rotation of a single mirror, while other elements remain unchanged:

We want to simulate the mirror rotating at different angles, so we need to use multi-configuration function. When designing the zoom system, we explained the multi-configuration tools in detail.

Press F7 to open the multi-configuration editor. If we want to simulate five different angles, then insert four more configurations and press Ctrl+Shift+Insert four times:

The mirror rotates at different angles to form a scanning state. We need to extract the parameters that control the rotation angle of the mirror into multiple configurations and let them change independently. Then the rotation angle is controlled by the current tilt parameter of the third surface around X, that is, the third parameter of the third surface:

Select the operand of this parameter in the multi-configuration editor, that is, Par3/3:

After selecting this operand, enter the angle values of five configurations:-10, -5, 0, 5, 10:

Open the L3d diagram, right-click on the diagram to open the Settings dialog box, and select Show all configurations. The light colors are differentiated according to the configuration:

Of course, we can also display each configuration individually and use the shortcut key: Ctrl+A to switch configurations.

So far, the structure of our simple one-dimensional line scanning system has been established. It can be clearly seen from the view that the aberration of the external field of view is very large due to the field curvature. Analyze the >: > speckle pattern > > configuration matrix to see the distribution size of each configuration spot:

The off-axis field of view is seriously separated from the on-axis field of view. We can imagine the main reason, because at first we only optimized the image quality of Dan Toujing's on-axis field of view.

Here we can make unified optimization, press F6 to open the evaluation function, and click OK in the default evaluation function dialog box to optimize again:

At this time, the design of our scanning system is all over. If you are interested in this kind of system, you can add a vibrating mirror to form a two-dimensional plane scan, or add an electric beam expanding system to form a three-dimensional scan. In the advanced application of ZEMAX, automatic scanning can be realized by programming language.