Same-focal-plane multi-focus lens focal length measuring device and method

Abstract

The invention relates to a device and method for measuring the focal length of a same-focal-plane multi-focus lens, and the device comprises a light source device, a sliding device, a combined lens device, and a detection device. The detection device comprises a CCD and a computer which are connected with each other; a to-be-detected multi-focus lens is arranged on the sliding device, the light source device is used for outputting single-wavelength divergent light rays, and the divergent light rays sequentially pass through the to-be-detected multi-focus lens and the combined lens device to be converged to a CCD of the detection device; the computer is connected with the sliding device and used for controlling the sliding device to move so as to adjust the distance between the to-be-measured multi-focus lens and the combined lens device and calculating the back focal length value of the to-be-measured multi-focus lens according to the distance corresponding to the minimum light spot size appearing on the CCD; the distance between the light source device and the to-be-measured multi-focus lens is more than 100 times of the back focal length value of the to-be-measured multi-focus lens. According to the invention, the focal length value of the to-be-measured multi-focus lens can be accurately measured.

Description

Technical Field

[0001] The invention relates to the technical field of short focal length optical element measurement, and in particular to a focal length measurement device and method for a same-focal-plane multi-focal-length lens. Background Art

[0002] Lenses with short focal lengths can form smaller optical systems, have the advantage of being easier to integrate, and are better used in integrated optical imaging, display, communication and other scenarios. Optical elements with multiple focal points on the same focal plane are mainly used in the fields of structured light, optical ranging, polarization imaging, etc. This type of optical element usually has a focal length of 1-10mm, with 2 or even more than 6 focal points on the same focal plane. For example, superlenses are used to achieve short-focal-length multi-focal-point optical ranging and polarization imaging. This type of element is a two-dimensional planar lens structure, compared to traditional lenses, superlenses. This optical element can adjust the shape, height and other parameters of the surface microstructure to achieve the regulation of light polarization, phase and other properties.

[0003] For focal length measurement of short focal length optical elements, the existing technology adopts the solution of combined lens, which can project the focus of the lens to be measured onto the rear CCD through the combined lens to achieve 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 of the multiple focal points are relatively divergent, and the parallel light field used in the existing technical solution is difficult to accurately project all the focal points onto the rear CCD through the combined lens. Summary of the invention

[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 multi-focal lens on the same focal plane, which can accurately measure the focal length value of the multi-focal lens to be measured.

[0005] The technical solution adopted by the present invention to solve its technical problems is as follows: a focal length measuring device for multi-focal lenses on 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 comprises a CCD and a computer connected to each other; the multi-focal lens to be tested is arranged on the sliding device, the light source device is used to output a single-wavelength divergent light, and the divergent light sequentially passes through the multi-focal lens to be tested and the combined lens device to converge on 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 multi-focal lens to be tested and the combined lens device, and calculate the back focal length value of the multi-focal lens to be tested according to the distance corresponding to the minimum spot size appearing on the CCD; the distance between the light source device and the multi-focal lens to be tested is more than 100 times the back focal length value of the multi-focal lens to be tested.

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

[0007] The combined lens device comprises a collimating lens and a focusing lens arranged in sequence, wherein the collimating lens is used to convert the light passing through the multi-focal lens to be tested into a parallel light beam; and the focusing lens is used to converge the parallel light beam onto the CCD of the detection device.

[0008] The sliding device comprises a stepping slider and a fixed base; the stepping slider is installed 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 to be tested.

[0009] The computer calculates the back focal length value of the multifocal lens to be tested by f0=Δ-f1, wherein f0 is the back focal length value of the multifocal lens to be tested, f1 is the front focal length of the collimating lens, and Δ is the distance between the multifocal lens to be tested and the combined lens device when the minimum spot size appears on the CCD.

[0010] The technical solution adopted by the present invention to solve the technical problem is: to provide a method for measuring the focal length of a cofocal plane multi-focal lens, using the above-mentioned cofocal plane multi-focal lens focal length measuring device, comprising the following steps:

[0011] Install the multifocal lens to be tested on a sliding device;

[0012] Turning on the light source device to generate a single-wavelength divergent light, the divergent light sequentially passes through the multi-focal lens to be tested and the combined lens device, and then converges onto the CCD of the detection device to form a plurality of focused light spots;

[0013] The computer controls the sliding device to move the multi-focal lens to be tested in the propagation direction of the divergent light, so that the spot size on the CCD of the detection device changes;

[0014] Whenever the spot size on the CCD of the detection device changes, the spot size and its corresponding distance between the multi-focal lens to be tested and the combined lens device are recorded;

[0015] The distance between the multifocal lens to be tested and the combined lens device when the spot size is the smallest is found, and the back focal length value of the multifocal lens to be tested is calculated according to the distance between the multifocal lens to be tested and the combined lens device when the spot size is the smallest.

[0016] The computer controls the sliding device so that when the multifocal lens to be tested moves in the propagation direction of the divergent light, the distance between the light source device and the multifocal lens to be tested is always ensured to be more than 100 times the back focal length value of the multifocal lens to be tested.

[0017] Beneficial Effects

[0018] Due to the adoption of the above-mentioned technical scheme, the present invention has the following advantages and positive effects compared with the prior art: the present invention adopts the imaging method instead of the parallel light method to measure the focal length of the short-focal-length optical element, and can accurately project all imaging information onto the CCD of the detection device through the combined lens, thereby being able to accurately measure the focal length value of the multi-focal lens to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of a focal length measuring device for multi-focal lenses on the same focal plane according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0021] The embodiment of the present invention relates to a focal length measuring device for a multi-focal lens on the same focal plane, which uses a combination of an imaging method and a combined lens method to replace the traditional parallel light field solution to measure the focal length of a multi-focal optical element on the same focal plane. For a short focal length lens, 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 incidence, the simulated back focal length is 1mm, and the point light source simulation with an object distance of 300mm is used, and the back focal length calculated by ZEMAX is 1.003mm. The difference between the simulated calculated focal lengths of the two is 0.3%. Since the difference between the two can be ignored, the present embodiment uses an imaging method instead of a parallel light method to measure the focal length of a short focal length optical element, and all imaging information can be accurately projected onto a CCD through a combined lens.

[0022] like Figure 1 As shown, the focal length measuring device of the same focal plane multi-focal lens of this embodiment comprises 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 the 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 multi-focal lens 10 to be tested is arranged thereon, and the optical center of the multi-focal lens to be tested 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 multi-focal lens 10 to be tested is more than 100 times the back focal length value of the multi-focal lens 10 to be tested.

[0023] The light source device 1 in this embodiment includes a light source 5, a filter 6 and a slit 7 arranged in sequence, 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 in sequence, wherein the collimating lens 11 is used to convert the light passing through the multi-focal lens 10 to be tested into a parallel light beam; the focusing lens 12 is used to converge the parallel light 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 installed 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 multi-focal lens 10 to be tested.

[0024] When the focal length measurement device for multi-focal lens with the same focal plane of the present embodiment is used to measure the focal length, the following steps are included:

[0025] First, the multifocal lens 10 to be tested is mounted on the mounting position on the stepping slider 8;

[0026] 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 divergent light 15 and light 16. The light 15 and light 16 pass through the multi-focal lens 10 to be tested to form light 17 and light 18. The light 17 and light 18 converge on the collimating lens 11. After passing through the collimating lens 11, the light 17 and light 18 become parallel light beams 19 and 20. After passing through the focusing lens 12, the light converges on the CCD 13 to form a focused light spot.

[0027] Then, the stepping slider 8 is controlled to move by the computer 14, so that the multifocal lens to be tested moves in the propagation direction of the divergent light, and the distance between the multifocal lens 10 to be tested and the collimating lens 11 is adjusted, so that the size of the light spot appearing on the CCD 13 changes. It is worth mentioning that when the stepping slider 8 is controlled to move, it is necessary to always ensure that the distance between the light source device 1 and the multifocal lens 10 to be tested is more than 100 times the back focal length value of the multifocal lens 10 to be tested.

[0028] Afterwards, the spot size data is counted by software, and whenever the spot size on the CCD of the detection device changes, the spot size and its corresponding distance between the multi-focal lens 10 to be tested and the collimating lens 11 are recorded.

[0029] Finally, find the distance Δ between the multifocal lens 10 to be tested and the collimating lens 11 when the spot size is minimum. At this time, subtract the front focal length f1 of the collimating lens 11 from the distance Δ between the multifocal lens 10 to be tested and the back focal length f0 of the multifocal lens 10 to be tested, that is, f0=Δ-f1.

[0030] The present invention is further explained below by taking the measurement of the focal length value of a certain metasurface sample as an example.

[0031] In this embodiment, the light source 5 uses 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, and the distance between the xenon lamp and the metasurface sample is greater than 2000mm. The focal length of the designed metasurface sample is about 9mm, which can form four focuses with different polarizations in the same focal plane, and can be used 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, so that four imaging spots appear 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. The size data of the four imaging spots is recorded by software, and the spot size is matched one by one with the distance between the metasurface sample and the collimating lens 11. The distance Δ between the metasurface sample and the collimating lens 11 corresponding to the minimum spot size is found from the recorded data, and the focal length value of the metasurface sample is calculated by f0=Δ-f1.

[0032] It is not difficult to find that the present invention adopts the imaging method instead of the parallel light method to measure the focal length of the short focal length optical element, 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 multi-focal lens to be tested.

Claims

1. A focal length measuring device for a multi-focal lens on the same focal plane, characterized in that: It comprises a light source device, a sliding device, a combined lens device and a detection device; the detection device comprises a CCD and a computer connected to each other; a multifocal lens to be tested is arranged on the sliding device, the light source device is used to output a single-wavelength divergent light, and the divergent light sequentially passes through the multifocal lens to be tested and the combined lens device and converges on 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 calculate the back focal length value of the multifocal lens to be tested according to the distance corresponding to the minimum 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.

2. The focal length measuring device for multi-focal lens on the same focal plane according to claim 1, characterized in that: The light source device comprises a light source, a filter and a slit which are arranged in sequence.

3. The focal length measuring device for multi-focal lens on the same focal plane according to claim 1, characterized in that: The combined lens device comprises a collimating lens and a focusing lens arranged in sequence, wherein the collimating lens is used to convert the light passing through the multi-focal lens to be tested into a parallel light beam; and the focusing lens is used to converge the parallel light beam onto the CCD of the detection device.

4. The focal length measuring device for multi-focal lens on the same focal plane according to claim 1, characterized in that: The sliding device comprises a stepping slider and a fixed base; the stepping slider is installed 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 to be tested.

5. The focal length measuring device for multi-focal lens on the same focal plane according to claim 3, characterized in that: The computer calculates the back focal length value of the multifocal lens to be tested by f0=Δ-f1, wherein f0 is the back focal length value of the multifocal lens to be tested, f1 is the front focal length of the collimating lens, and Δ is the distance between the multifocal lens to be tested and the combined lens device when the minimum spot size appears on the CCD.

6. A method for measuring the focal length of a multi-focal lens on the same focal plane, characterized in that: The focal length measuring device for a multi-focal lens on the same focal plane as claimed in any one of claims 1 to 5 comprises the following steps: Install the multifocal lens to be tested on a sliding device; Turning on the light source device to generate a single-wavelength divergent light, the divergent light sequentially passes through the multi-focal lens to be tested and the combined lens device, and then converges onto the CCD of the detection device to form a plurality of focused light spots; The computer controls the sliding device to move the multi-focal lens to be tested in the propagation direction of the divergent light, so that the spot size on the CCD of the detection device changes; Whenever the spot size on the CCD of the detection device changes, the spot size and its corresponding distance between the multi-focal lens to be tested and the combined lens device are recorded; The distance between the multifocal lens to be tested and the combined lens device when the spot size is the smallest is found, and the back focal length value of the multifocal lens to be tested is calculated according to the distance between the multifocal lens to be tested and the combined lens device when the spot size is the smallest.

7. The method for measuring focal length of a cofocal multi-focal lens according to claim 6, characterized in that: The computer controls the sliding device so that when the multifocal lens to be tested moves in the propagation direction of the divergent light, the distance between the light source device and the multifocal lens to be tested is always ensured to be more than 100 times the back focal length value of the multifocal lens to be tested.

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