Focal-length measurement device and method for common-focal-plane multi-focal lens

Abstract

The present invention relates to a focal-length measurement device and method for a common-focal-plane multi-focal lens. The measurement device comprises a light source device, a sliding device, a compound lens device and a detection device, wherein the detection device comprises a CCD and a computer, which are connected to each other; the sliding device is provided with a multi-focal lens waiting for measurement; the light source device is configured to output divergent light of a single wavelength, the divergent light passing through said multi-focal lens and the compound lens device in sequence and converging onto the CCD of the detection device; the computer is connected to the sliding device, is configured to control the movement of the sliding device so as to adjust the distance between said multi-focal lens and the compound lens device, and is configured to calculate the back focal length value of said multi-focal lens on the basis of the corresponding distance when the minimum spot size appears on the CCD; and the distance between the light source device and said multi-focal lens is at least 100 times the back focal length value of said multi-focal lens. The present invention can accurately measure the focal length value of said multi-focal lens.

Description

A device and method for measuring the focal length of a multifocal lens with the same focal plane. Technical Field

[0001] This invention relates to the field of short focal length optical element measurement technology, and in particular to a focal length measurement device and method for a multifocal lens with the same focal plane. Background Technology

[0002] Short focal length lenses can form smaller optical systems, offering advantages in integration and making them better suited for integrated optical imaging, display, and communication applications. Multifocal optical elements on the same focal plane are primarily used in structured light, optical ranging, and polarization imaging. These elements typically have focal lengths of 1-10mm and two, or even six or more, focal points on the same focal plane. For example, superlenses can be used to achieve short focal length multifocal optical ranging and polarization imaging. These elements are two-dimensional planar lens structures, unlike traditional lenses. Superlenses allow for adjustment of parameters such as the shape and height of their surface microstructures, enabling control over the polarization and phase properties of light.

[0003] For focal length measurement of short-focal-length optical elements, existing technologies employ a combined lens approach. This allows the focal point of the lens under test to be projected onto the rear CCD via the combined lens, enabling indirect measurement of different focal lengths. However, for short-focal-length optical elements with multiple focal points on the same focal plane, the light spots from these multiple focal points are quite divergent. The parallel light field used in existing technologies is insufficient to accurately project all focal points onto the rear CCD via the combined lens. Technical issues

[0004] The technical problem to be solved by the present invention is to provide a device and method for measuring the focal length of a multifocal lens with the same focal plane, which can accurately measure the focal length value of the multifocal lens under test. Technical solutions

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: A focal length measuring device for a multifocal lens with the same focal plane is provided, comprising a light source device, a sliding device, a combined lens device, and a detection device; the detection device includes a CCD and a computer connected to each other; the multifocal lens to be tested is disposed on the sliding device; the light source device is used to output single-wavelength divergent light, which sequentially passes through the multifocal lens to be tested and the combined lens device and converges onto the CCD of the detection device; the computer is connected to the sliding device and is used to control the movement of the sliding device to adjust the distance between the multifocal lens to be tested and the combined lens device, and to calculate the back focal length value of the multifocal lens to be tested based on the distance corresponding to the smallest spot size appearing on the CCD; the distance between the light source device and the multifocal lens to be tested is more than 100 times the back focal length value of the multifocal lens to be tested.

[0006] The light source device includes a light source, a filter, and a slit arranged in sequence.

[0007] The combined lens device includes a collimating lens and a focusing lens arranged in sequence. The collimating lens is used to convert the light rays passing through the multifocal lens under test into a parallel beam. The focusing lens is used to converge the parallel beam onto the CCD of the detection device.

[0008] The sliding device includes a stepping slider and a fixed base; the stepping slider is mounted on the fixed base and can slide along the fixed base under the control of the computer; the stepping slider is provided with a mounting position for mounting the multifocal lens under test.

[0009] The computer via Calculate the back focal length value of the multifocal lens under test, where, The value of the back focal length of the multifocal lens under test is given. The front focal length of the collimating lens. The distance between the multifocal lens under test and the combined lens device is the minimum spot size that appears on the CCD.

[0010] The technical solution adopted by this invention to solve its technical problem is: to provide a method for measuring the focal length of a multifocal lens with the same focal plane, using the above-mentioned multifocal lens focal length measuring device with the same focal plane, including the following steps:

[0011] The multifocal lens to be tested is mounted on the sliding device;

[0012] The light source device is turned on to generate single-wavelength divergent light. The divergent light passes through the multifocal lens under test and the combined lens device in sequence and then converges onto the CCD of the detection device to form multiple focused light spots.

[0013] The computer controls the sliding device to move the multifocal lens under test in the direction of propagation of the diverging light, thereby changing the spot size on the CCD of the detection device;

[0014] Whenever the size of the light spot on the CCD of the detection device changes, the size of the light spot and the corresponding distance between the multifocal lens under test and the combined lens device are recorded.

[0015] Find the distance between the multifocal lens under test and the combined lens device when the spot size is the smallest, and calculate the back focal length value of the multifocal lens under test based on the distance between the multifocal lens under test and the combined lens device when the spot size is the smallest.

[0016] When the computer controls the sliding device to move the multifocal lens under test in the direction of propagation of the diverging light, it always ensures that the distance between the light source device and the multifocal lens under test is more than 100 times the back focal length of the multifocal lens under test. Beneficial effects

[0017] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: The present invention uses the imaging method instead of the parallel light method to measure the focal length of short focal length optical elements, and can accurately project all imaging information onto the CCD of the detection device through the combined lens, thereby accurately measuring the focal length value of the multifocal lens under test. Attached Figure Description

[0018] Figure 1 is a schematic diagram of the focal length measuring device of a multifocal lens with the same focal plane according to an embodiment of the present invention. Embodiments of the present invention

[0019] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0020] This invention relates to a focal length measuring device for multifocal lenses with the same focal plane. This device uses a combination of imaging and combined lens methods instead of the traditional parallel light field method to measure the focal length of multifocal optical elements on the same focal plane. For short focal length lenses, when the object distance is more than 100 times the focal length, it can be approximately equivalent to far-field parallel light. For example, for a lens with a focal length of 1mm, ZEMAX simulation is used. Under parallel light incident light, the simulated back focal length is 1mm. Using a point light source with an object distance of 300mm, the ZEMAX calculated back focal length is 1.003mm. The difference between the two simulated focal lengths is 0.3%. Since the difference between the two is negligible, this embodiment uses the imaging method instead of the parallel light method to measure the focal length of short focal length optical elements, enabling accurate projection of all imaging information onto the CCD through a combined lens.

[0021] As shown in Figure 1, the focal length measuring device for a multifocal lens with the same focal plane in this embodiment includes a light source device 1, a sliding device 4, a combined lens device 2, and a detection device 3. In this embodiment, the light source device 1, the combined lens device 2, and the detection device 3 are arranged in a straight line, and their optical centers are at the same height. The sliding device 4 is located between the light source device 1 and the combined lens device 2, and a multifocal lens 10 to be measured is mounted on it. The optical center of the multifocal lens to be measured is at the same height as the light source device 1, the combined lens device 2, and the detection device 3. The distance between the light source device 1 and the multifocal lens 10 to be measured is more than 100 times the back focal length value of the multifocal lens 10 to be measured.

[0022] In this embodiment, the light source device 1 includes a light source 5, a filter 6, and a slit 7 arranged sequentially, wherein the light source 5 can be a xenon lamp. The combined lens device 2 in this embodiment includes a collimating lens 11 and a focusing lens 12 arranged sequentially. The collimating lens 11 is used to convert the light passing through the multifocal lens 10 under test into a parallel beam; the focusing lens 12 is used to converge the parallel beam to the detection device 3. The detection device in this embodiment includes a CCD 13 and a computer 14 connected to each other. The sliding device 4 in this embodiment includes a stepping slider 8 and a fixed base 9; the stepping slider 8 is mounted on the fixed base 9 and can slide along the fixed base 9 under the control of the computer; the stepping slider 8 is provided with a mounting position for mounting the multifocal lens 10 under test.

[0023] When measuring focal length using the focal length measuring device for a multifocal lens with the same focal plane according to this embodiment, the following steps are included:

[0024] First, the multifocal lens 10 to be tested is mounted on the mounting position on the stepper slider 8;

[0025] Next, the light source 5 is turned on. The light emitted by the light source 5 passes through the filter 6 and the slit 7 to form single-wavelength diverging rays 15 and 16. Rays 15 and 16 pass through the multifocal lens 10 to be tested to form rays 17 and 18. Rays 17 and 18 converge onto the collimating lens 11. After passing through the collimating lens 11, rays 17 and 18 become parallel beams 19 and 20. After passing through the focusing lens 12, they converge onto the CCD 13 to form a focused spot.

[0026] Then, the computer 14 controls the movement of the stepping slider 8, causing the multifocal lens under test to move in the propagation direction of the diverging light, adjusting the distance between the multifocal lens under test 10 and the collimating lens 11, thereby changing the size of the light spot appearing on the CCD 13. It is worth mentioning that when controlling the movement of the stepping slider 8, it is necessary to always ensure that the distance between the light source device 1 and the multifocal lens under test 10 is at least 100 times the back focal length of the multifocal lens under test 10.

[0027] Subsequently, the software statistically analyzes the spot size data. Whenever the spot size on the CCD of the detection device changes, the spot size and the corresponding distance between the multifocal lens 10 and the collimating lens 11 are recorded.

[0028] Finally, the distance between the multifocal lens 10 and the collimating lens 11 when the light spot size is minimized is found. At this time, the distance between the multifocal lens 10 to be tested and the collimating lens 11 is... Subtract the front focal length of collimating lens 11 The back focal length value of the multifocal lens 10 under test can then be obtained. ,Right now .

[0029] The present invention will be further illustrated below by taking the measurement of the focal length of a metasurface sample as an example.

[0030] In this embodiment, the light source 5 is a xenon lamp, the wavelength of the filter 6 is set to 532nm, and the slit 7 is set to 0.5mm. When measuring the metasurface sample, the metasurface sample is first placed on the stepping slider 8, with a distance greater than 2000mm between the xenon lamp and the metasurface sample. The metasurface sample is designed with a focal length of approximately 9mm, enabling it to form four focal points with different polarizations on the same focal plane, suitable for multi-polarization imaging lenses. During measurement, the xenon lamp is turned on, and the stepping slider 8 is moved and controlled by the computer 14 to adjust the distance between the metasurface sample and the collimating lens 11, resulting in four imaging spots appearing on the CCD 13. As the distance between the metasurface sample and the collimating lens 11 changes, the size of the four imaging spots changes accordingly. Software records the size data of the four imaging spots and correlates these spot sizes with the distance between the metasurface sample and the collimating lens 11. The distance between the metasurface sample and the collimating lens 11 corresponding to the smallest spot size is found from the recorded data. ,pass The focal length of the metasurface sample was calculated.

[0031] It is easy to see that the present invention uses the imaging method instead of the parallel light method to measure the focal length of short focal length optical elements. It can accurately project all imaging information onto the CCD of the detection device through the combined lens, thereby accurately measuring the focal length value of the multifocal lens under test.

Claims

1. A focal length measuring device for a multifocal lens with the same focal plane, characterized in that, The device includes a light source, a sliding device, a combined lens device, and a detection device. The detection device includes a CCD and a computer connected to each other. A multifocal lens to be tested is mounted on the sliding device. The light source is used to output single-wavelength divergent light, which passes sequentially through the multifocal lens to be tested and the combined lens device before converging onto the CCD of the detection device. The computer is connected to the sliding device and is used to control the movement of the sliding device to adjust the distance between the multifocal lens to be tested and the combined lens device, and to calculate the back focal length value of the multifocal lens to be tested based on the distance corresponding to the smallest spot size appearing on the CCD. The distance between the light source and the multifocal lens to be tested is more than 100 times the back focal length value of the multifocal lens to be tested.

2. The focal length measuring device for a multifocal lens with the same focal plane according to claim 1, characterized in that, The light source device includes a light source, a filter, and a slit arranged in sequence.

3. The focal length measuring device for a multifocal lens with the same focal plane according to claim 1, characterized in that, The combined lens device includes a collimating lens and a focusing lens arranged in sequence. The collimating lens is used to convert the light rays passing through the multifocal lens under test into a parallel beam. The focusing lens is used to converge the parallel beam onto the CCD of the detection device.

4. The focal length measuring device for a multifocal lens with the same focal plane according to claim 1, characterized in that, The sliding device includes a stepping slider and a fixed base; the stepping slider is mounted on the fixed base and can slide along the fixed base under the control of the computer; the stepping slider is provided with a mounting position for mounting the multifocal lens under test.

5. The focal length measuring device for a multifocal lens with the same focal plane according to claim 3, characterized in that, The computer via Calculate the back focal length value of the multifocal lens under test, where, Here is the back focal length of the multifocal lens under test. The front focal length of the collimating lens. The distance between the multifocal lens under test and the combined lens device is the minimum spot size that appears on the CCD.

6. A method for measuring the focal length of a multifocal lens with the same focal plane, characterized in that, The focal length measuring device for a multifocal lens with the same focal plane as described in any one of claims 1-5 includes the following steps: The multifocal lens to be tested is mounted on the sliding device; The light source device is turned on to generate single-wavelength divergent light. The divergent light passes through the multifocal lens under test and the combined lens device in sequence and then converges onto the CCD of the detection device to form multiple focused light spots. The computer controls the sliding device to move the multifocal lens under test in the direction of propagation of the diverging light, thereby changing the spot size on the CCD of the detection device; Whenever the size of the light spot on the CCD of the detection device changes, the size of the light spot and the corresponding distance between the multifocal lens under test and the combined lens device are recorded. Find the distance between the multifocal lens under test and the combined lens device when the spot size is the smallest, and calculate the back focal length value of the multifocal lens under test based on the distance between the multifocal lens under test and the combined lens device when the spot size is the smallest.

7. The method for measuring the focal length of a multifocal lens with the same focal plane according to claim 6, characterized in that, When the computer controls the sliding device to move the multifocal lens under test in the direction of propagation of the diverging light, it always ensures that the distance between the light source device and the multifocal lens under test is more than 100 times the back focal length of the multifocal lens under test.

Images