Image slicer pupil image detection device and method

Abstract

The present invention relates to an image splitter pupil image detection device, which comprises, in order along the optical path, a light source, a target plate, a simulation lens group, an image splitter to be detected, a spectroscope, and a pupil image receiving device; the light source is configured to illuminate the target plate; the target plate is configured to simulate the surface source target to be split by the image splitter and is uniformly illuminated by the light source; the simulation lens group is configured to form a real image of the target plate; the image splitter to be detected is placed at the real image of the target plate to form a pupil image; the spectroscope is configured to allow the light forming the real image to pass through and reflect the light from the image splitter to be detected to avoid blocking the optical path; the pupil image receiving device is configured to receive and record the size, position, and intensity information of the pupil image. The present invention also provides an image splitter pupil image detection method. The present invention is practical and easy to implement, does not rely on a front-end main telescope, a front optical system, or a rear-end pupil mirror, can evaluate the system performance of the image splitter, and can also provide a quantitative basis for the targeted registration of the pupil mirror.

Description

Technical Field

[0001] The present invention relates to the field of improved image slicer detection, and more particularly to an image slicer pupil image detection device and method. Background Art

[0002] An integral field spectrometer (IFS) is a crucial scientific terminal for astronomical spectral observations, commonly found on large telescopes worldwide. An IFS consists primarily of two main components: an integral field unit (IFU) and a spectrometer. The image splitter is the core component of the IFU, typically a series of closely spaced rectangular mirrors. The image splitter is placed on the image plane of the front telescope, with each mirror having a certain angle difference between them, reflecting the image plane in different directions. Early image splitters had a flat reflective surface, but later, spherical surfaces were adopted, generally referred to as improved image splitters. A pupil lens is typically used behind the image splitter to re-image the split image and align it onto the image plane of the IFU. After the image splitter's division and the pupil lens's re-imaging and alignment, the two-dimensional image plane formed by the front telescope is cut and aligned into a one-dimensional plane and fed into the spectrometer at the back of the IFU, thereby acquiring spectra from a two-dimensional surface source. This instrument is called an IFS.

[0003] Currently, performance testing of image splitters focuses on direct testing of specific device indicators such as curvature radius, surface shape, and angular error, or integrating them into an IFS system for system testing. The former method cannot accurately reflect the device's performance in the system (such as compatibility with the pupil lens), while the latter requires matching the entire system to achieve performance testing and verification, which is difficult to implement and will also superimpose the errors of other components, making it difficult to accurately evaluate the performance of the image splitter. Given these factors and the long and difficult development cycle of image splitters, it is necessary to conduct a performance evaluation that is closer to its actual use before system integration. Summary of the Invention

[0004] The present invention provides a device and method for detecting pupil images of a splitter. A front-end optical device is used to form a pupil image at the rear end of the image splitter. The performance of the image splitter is independently evaluated by detecting the pupil image.

[0005] The present invention provides an image slicer pupil image detection device, which comprises, in order along an optical path, a light source, a target plate, a simulation lens group, an image slicer to be detected, a spectroscope, and a pupil image receiving device; wherein the light source is configured to illuminate the target plate to form diffuse light; the target plate is configured to simulate a surface source target to be sliced ​​by the image slicer and is uniformly illuminated by the light source; the simulation lens group is configured to form a real image of the target plate; the image slicer to be detected is placed at the real image of the target plate to form a pupil image; the spectroscope is configured to allow light forming the real image to pass through and reflect light from the image slicer to be detected to prevent the pupil image detection device from blocking the optical path; and the pupil image receiving device is configured to receive the pupil image and record the size, position, and intensity information of the pupil image.

[0006] Furthermore, the light source is a monochromatic light source.

[0007] Furthermore, the target plate is a diffuse reflector.

[0008] Furthermore, the size of the target plate is greater than or equal to the working field of view of the image segmentor to be inspected.

[0009] Furthermore, the simulated lens group includes a front lens group, an aperture stop and a rear lens group in sequence along the optical path, and the front lens group, the aperture stop and the rear lens group are coaxial.

[0010] Furthermore, the front lens group is configured to collimate the light emitted from the target plate, and the rear lens group is configured to image the aperture to a preset size and position.

[0011] Furthermore, the front lens group and the rear lens group are positive power lenses or reflective mirrors.

[0012] Furthermore, the pupil image receiving device adopts CCD or CMOS.

[0013] The present invention also provides a method for detecting pupil images of an image slicer, comprising:

[0014] Step S1, providing the image slicer pupil image detection device according to any one of claims 1 to 8;

[0015] Step S2, illuminating the target plate with a light source, wherein the light emitted by the target plate passes through a simulation lens group to form a real image of the target plate at the image plane of the target plate;

[0016] Step S3, placing the image cutter to be inspected at the theoretical position of the target plate image plane, the image cutter to be inspected cuts the target plate image plane to form a plurality of reflection channels, each channel reflects in a different direction, so as to form a pupil image at the theoretical position of the pupil image;

[0017] In step S4 , a pupil image receiving device receives the pupil image, measures the diameter, centroid position, axial position and energy distribution of the pupil image, and completes the performance evaluation of the image segmentor to be inspected.

[0018] The detection device of the present invention works independently and is practical and easy to use. It does not rely on the front-end main telescope, the front optical system and the rear-end pupil lens. It can evaluate the system performance of the image splitter and provide a quantitative basis for the targeted alignment of the pupil lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the image slicer pupil image detection device according to the present invention (top view).

[0020] Figure 2 Schematic diagram of an image splitter with 6 channels.

[0021] Figure 3 This is a schematic diagram showing the position and shape of the pupil image formed by each channel of the image divider. DETAILED DESCRIPTION

[0022] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0023] The image splitter pupil image detection device of the present invention utilizes a front-end optical path to form the field of view, pupil, and front-end image plane required for the image splitter's operation. The image splitter to be detected is placed on the front-end image plane, which is then split and reflected in different directions at the rear end, thereby achieving the image field segmentation function. Simultaneously, the image splitter forms an image of the front-end pupil, forming a pupil image in the rear-end optical path of the image splitter. By measuring the pupil image, quantitative detection of the angular deviation of each channel of the image splitter is achieved, as well as qualitative assessment of the deviation of the curvature radius of the image splitter and the consistency of the film layer.

[0024] Specifically, if Figure 1 As shown, the image splitter pupil image detection device provided by the present invention includes a light source 1, a target plate 2, a simulation lens group, an image splitter to be detected 6, a spectroscope 7 and a pupil image receiving device 8 in sequence along the light path.

[0025] The light source 1 is configured to provide illumination for illuminating the target plate 2 to form diffuse light. In this embodiment, the light source 1 is a monochromatic light source, such as light generated by a laser.

[0026] The target plate 2 is set as a surface source target required for the image slicer to be sliced. In this embodiment, the target plate 2 is a diffuse reflector, the size of which is greater than or equal to the working field of the image slicer, and is evenly illuminated by the light source 1.

[0027] The simulated lens assembly is configured to form a real image of the target plate 2 and includes, along the optical path, a front lens group 3, an aperture stop 4, and a rear lens group 5. The target plate 2, front lens group 3, aperture stop 4, and rear lens group 5 are all placed on an adjustment mount, which is adjusted to keep these four components coaxial.

[0028] The front lens group 3 is configured to collimate the light emitted from the target plate 2. In this embodiment, the front lens group 3 is a positive power lens or a reflector.

[0029] The aperture 4 can be formed by opening a circular hole of a certain diameter on a thin plate, which serves as the object plane of the rear lens group 5 and forms the working pupil of the image splitter after the rear lens group 5 forms an image.

[0030] The rear lens group 5 is configured to image the aperture 4 to a preset size and position, i.e., the size and position required for the image splitter to work. In this embodiment, the rear lens group 5 is a positive power lens or a reflector.

[0031] The front lens group 3 and target plate 2 define the image slicer's required field of view and corresponding magnification, while the aperture 4 and rear lens group 5 define the entrance pupil size and position necessary for the image slicer's operation. The following describes a method for determining the parameters of the front lens group 3, aperture 4, and rear lens group 5 in the inspection device of the present invention, using a specific image slicer to be inspected as an example.

[0032] Assume that the entrance pupil size corresponding to the image divider to be inspected is ENPD = Φ3mm, the distance between the entrance pupil and the image divider is ENPP = -300mm, the image divider linear field of view, i.e. the image divider size, is 2h′ = 8mm, and the image divider optical power is φ = 1 / 170mm -1 The above specific values ​​are given by the design of the integral field spectrometer system and are known quantities. The working area of ​​target plate 2 is represented by 2h, the focal length of the front lens group 3 is represented by f1, and the focal length of the rear lens group 5 is represented by f2. The specific values ​​of 2h and f2 are determined by the required resolution, target plate process, spatial layout, and other factors.

[0033] The optical path magnification ratio M of the front lens group 3 and rear lens group 5 is 2h' / 2h = -f2 / f1, where h' represents the size of the aperture image formed by the rear lens group 5. If 2h = -1mm and f2 = 200mm are selected as needed, then M = 8 / (-1) = -8. The focal length f1 of the front lens group 3 is -f2 / M = -200 / (-8) = 25mm. The distance from the aperture image to the rear lens group 5 is l' = ENPP - (-f2) = -300 + 200 = -100mm. The distance l from the aperture 4 to the rear lens group 5 satisfies 1 / l = 1 / l' - 1 / f2, resulting in l = -200 / 3 ≈ -66.7mm. The magnification ratio M2 of the rear lens group 5 is l' / l = -100 / (-66.7) = 1.5, and the aperture 4 has a diameter Φ = ENPD / M2 = 3 / 1.5 = 2mm.

[0034] The image splitter 6 is placed at the image plane of the target plate 2 and is used to form a pupil image at a conjugate position of the aperture 4. Specifically, based on the operating principle of the image splitter, the image splitter 6 comprises multiple channels, each of which is a rectangular reflective surface. The image splitter 6 splits and reflects the real image of the target plate 2 in different directions, forming multiple sub-channels. Each sub-channel reflects light to its rear end, forming a pupil image at its exit pupil, i.e., at a conjugate position of the aperture 4.

[0035] Beam splitter 7 is an optical path deflection device, designed to transmit light forming a real image and reflect light from image splitter 6 to one side to prevent the pupil image detection device from blocking the optical path. Beam splitter 7 is placed appropriately between image splitter 6 and the pupil image, with the principle of not blocking the optical path and facilitating device layout.

[0036] The pupil image receiving device 8 is configured to receive and record the size, position and intensity information of the pupil image. The pupil image receiving device 8 is placed at the image plane of the pupil image. In this embodiment, it can be a device such as CCD or CMOS.

[0037] In this embodiment, the image splitter 6, the beam splitter 7 and the pupil image receiving device 8 are all mounted on an adjustment frame to adjust their relative positions with respect to the optical axis.

[0038] The position and size of the pupil image are determined by the optical power of the image splitter to be inspected and the position of the entrance pupil. In this embodiment, the theoretical position of the pupil image EXPP = (φ + 1 / ENPP) -1 =[1 / 170+1 / (-300)] -1 =392.3mm. Figure 1 As shown, the positions of the beam splitter 7 and the pupil image receiving device 8 are determined according to the following formula: d1 + d2 = EXPP, where d1 represents the horizontal distance along the optical axis between the image splitter 6 and the center of the beam splitter 7, and d2 represents the horizontal distance along the optical axis between the pupil image receiving device 8 and the center of the beam splitter 7. The pupil image size EXPD = ENPD × (EXPP / ENPP) = 3 × (392.3 / 300) = 3.92 mm.

[0039] The present invention also provides a method for detecting pupil images of an image segmentor, the method comprising the following steps:

[0040] Step S1: providing the above-mentioned image slicer pupil image detection device.

[0041] In step S2, light source 1 illuminates target plate 2. Light from target plate 2 passes through front lens group 3, aperture 4, and rear lens group 5, forming a real image of target plate 2 on the target plate image plane. The size of the real image of target plate 2 is equal to or larger than the working field of view of image splitter 6.

[0042] Step S3, placing the image cutter 6 at the theoretical position of the target plate image surface, the image cutter 6 cuts the target plate image surface to form multiple reflection channels, each channel reflects to a different direction to form a pupil image at the theoretical position of the pupil image.

[0043] In step S4, pupil image receiving device 8 receives the pupil image and measures its diameter, centroid position, axial position, and energy distribution to evaluate the performance of image slicer 6 or assist in system adjustment. The pupil image diameter and axial position allow for a qualitative assessment of the consistency of the curvature radius R of each channel of the image slicer, while the energy distribution allows for a qualitative assessment of the consistency of the film reflectivity of each channel.

[0044] like Figure 2 and Figure 3 As shown, the image splitter to be inspected consists of 6 channels, namely channels 6-1 to 6-6. It should be noted that for clarity, each channel is shown in a separate view, and the upper and lower surfaces of adjacent channels are actually in close contact. The rectangular curved surface on the left end is its reflective working surface, which receives the light incident from the rear lens group 5 and is reflected on this surface. Each channel forms a pupil image with an aperture of EXPD at the theoretical position of the pupil image EXPP, that is, 8-1 is the pupil image of channel 6-1, 8-2 is the pupil image formed by channel 6-2, and so on. Assume Figure 3 The distance error between the measured pupil image centroid of channel 8-2 and the reference channel centroid is Δd. Therefore, the angular error of this channel relative to the reference channel is Δθ = Δd / EXPP / 2. By sequentially measuring the centroid error of each channel relative to the reference channel, we can calculate its angular error and evaluate the performance of the image divider.

[0045] Similarly, this device can be used to obtain the contour and intensity information of the pupil image. After extraction and processing, the consistency of the curvature radius of the image divider and the uniformity of the film reflectivity can be qualitatively evaluated. After the pupil image contour is extracted, the pupil image diameter of each channel is obtained. According to the pupil image diameter and the diameter of the aperture 4, the curvature radius of the image divider is calculated using the imaging formula. The consistency of the pupil image sizes of each channel can also be compared with each other, as well as with the theoretical values ​​simulated by the optical software. The intensity information of the pupil image reflects the reflectivity of the divider film layer, and the reflectivity consistency of each channel film layer can be compared with the collected intensity information. If the target plate 2 is set as a small hole to form a point light source, and the small hole is moved by the translation stage, the reflectivity test can be performed on each point on the working surface of the image divider by scanning.

[0046] The detection device of the present invention works independently and is practical and easy to use. It does not rely on the front-end main telescope, the front optical system and the rear-end pupil lens. It can evaluate the system performance of the image splitter and provide a quantitative basis for the targeted alignment of the pupil lens.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Various modifications are possible. In other words, any simple, equivalent changes and modifications made in accordance with the claims and description of the present invention are within the scope of protection of the patent claims. Anything not fully described in this invention constitutes conventional technology.

Claims

1. An image splitter pupil image detection device, characterized in that: Along the optical path, it includes light source, target plate, simulation mirror group, image splitter to be inspected, spectroscope and pupil image receiving device; wherein, The light source is configured to illuminate the target plate to form diffuse light; The target plate is configured to simulate a surface source target to be cut by the image cutter and is evenly illuminated by the light source; The simulation mirror group is configured to form a real image of the target plate; The image to be inspected splitter is placed at the real image of the target plate to form a pupil image; The spectroscope is configured to transmit the light forming the real image and reflect the light from the image splitter to be inspected, so as to prevent the pupil image detection device from blocking the light path; The pupil image receiving device is configured to receive the pupil image and record size, position and intensity information of the pupil image; The simulated lens group includes a front lens group, an aperture stop and a rear lens group in sequence along the optical path, and the front lens group, the aperture stop and the rear lens group are coaxial; The front lens group is configured to collimate the light emitted from the target plate, and the rear lens group is configured to image the aperture to a preset size and position.

2. The image slicer pupil image detection device according to claim 1, characterized in that: The light source is a monochromatic light source.

3. The image slicer pupil image detection device according to claim 1, wherein: The target plate is a diffuse reflector.

4. The image slicer pupil image detection device according to claim 1, wherein: The size of the target plate is greater than or equal to the working field of view of the image segmentor to be inspected.

5. The image slicer pupil image detection device according to claim 1, wherein: The front lens group and the rear lens group are positive power lenses or reflecting mirrors.

6. The image slicer pupil image detection device according to claim 1, characterized in that: The pupil image receiving device adopts CCD or CMOS.

7. A method for detecting pupil images of an image splitter, characterized in that: include: Step S1, providing the image slicer pupil image detection device according to any one of claims 1 to 6; Step S2, illuminating the target plate with a light source, wherein the light emitted by the target plate passes through a simulation lens group to form a real image of the target plate at the image plane of the target plate; Step S3, placing the image cutter to be inspected at the theoretical position of the target plate image plane, the image cutter to be inspected cuts the target plate image plane to form a plurality of reflection channels, each channel reflects in a different direction, so as to form a pupil image at the theoretical position of the pupil image; In step S4 , a pupil image receiving device receives the pupil image, measures the diameter, centroid position, axial position and energy distribution of the pupil image, and completes the performance evaluation of the image segmentor to be inspected.

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