Fluorescence imaging structure for specimen observation

Abstract

The utility model relates to a fluorescence imaging structure for specimen observation, and relates to the technical field of fluorescence imaging. Comprising a shell, a cover plate and a fluorescence imaging mechanism, and the fluorescence imaging mechanism is arranged in an internal cavity formed by the shell and the cover plate; the fluorescence imaging mechanism comprises an objective lens connecting plate, an objective lens fixing plate, an annular light source mounting bracket, a multi-channel optical filter fixing turntable, an optical filter and a driving assembly, the objective lens connecting plate is provided with a groove, and the objective lens fixing plate is detachably connected in the groove; the bottom end of the annular light source mounting bracket is connected with the objective lens fixing plate, and the top end is provided with a multicolor LED annular light source; the output end of the driving assembly is connected with the multi-channel optical filter fixing turntable; and the optical filters are circumferentially distributed at the edge of the multi-channel optical filter fixing turntable at equal intervals. According to a specimen marked by a dye, the rapid switching of a fluorescence imaging structure is realized through the millisecond-level rapid automatic switching of the multicolor LED annular light source and the control of the driving assembly on the multichannel optical filter fixing turntable.

Description

Technical Field

[0001] The utility model relates to the technical field of fluorescence imaging, in particular to a fluorescence imaging structure used for specimen observation. Background Art

[0002] As an important structural accessory in cell fluorescence imaging, the basic working principle of the fluorescence imaging structure is that when high-energy short-wavelength light irradiates the dye-labeled samples, these dye-labeled samples absorb energy and induce reflection of fluorescence with a wavelength lower than the energy of the excitation light. Based on this principle, fluorescence imagers are widely used to study the absorption, transportation, distribution and location of substances in cells. Some substances in cells, such as chlorophyll, can fluoresce after being irradiated with ultraviolet light; some other substances cannot fluoresce by themselves, but if they are stained with fluorescent dyes or fluorescent antibodies, they can also fluoresce after being irradiated with ultraviolet light. Fluorescence imagers are one of the tools for qualitative and quantitative research on such substances.

[0003] Most of the currently existing monochromatic fluorescence imaging structures are equipped with an LED excitation light source, a lens, a dichroic mirror, a fluorescence filter and a mounting support; the excitation light source and the lens are mounted on the support in parallel, the dichroic mirror and the excitation light source are fixed on the support at a 45° angle, and the fluorescence filter and the excitation light source are fixed on the support at a 90° angle; the light path is a short-wavelength excitation light source that is focused through a lens, directed parallel to the dichroic mirror to be reflected to the specimen to excite fluorescence, and then passes through the dichroic mirror to the fluorescence filter to reach the photosensitive element; the dichroic mirror provides different transmittance and reflectivity for incident light of different wavelengths, has a high reflectivity for light beams below the cut-off wavelength, and has a high transmittance for light beams above the cut-off wavelength; the filter is matched with the fluorescence wavelength band, and the lens ensures the collimation of the light beam.

[0004] The existing fluorescence imaging structure has the following problems: due to the overly complex application optical path of the dichroic mirror, the optical axis angles of various components require precision, resulting in extremely high manufacturing and installation precision of all components. If there is a slight deviation, fluorescence imaging cannot be achieved; the monochrome fluorescence imaging structure can no longer meet the current user needs, and the functionality is relatively single. To achieve multi-channel fluorescence imaging structure switching, either the entire module is switched manually or the entire module is switched automatically by electric. Manual switching has low efficiency, low repeatability, cumbersome operation, and is inconvenient to replace, wasting labor costs. Electric switching requires the preparation of multiple modules and the addition of a motion control system. The overall structure is complex and occupies a large space. In addition, the production cost of a single fluorescent imaging structure is high. The cost of the module directly increases due to the high processing precision, and the purchase cost of relatively more optical components directly increases. In the multi-channel fluorescent imaging structure, each optical component must be purchased according to the number of channels, which will be more expensive, and the utilization rate of optical components is low. If only one module works, the others will be idle, and the maximum value of the components will not be brought into play. Traditional modules have many internal components in the fluorescent unit, heavy mass, and large inertia. Electric switching cannot achieve millisecond-level rapid switching, and cannot be used in some special occasions, such as fluorescence resonance energy transfer technology (FRET), resulting in certain limitations in traditional fluorescent imaging structures. Utility Model Content

[0005] The purpose of the utility model is to provide a novel fluorescent module to solve the problems existing in the prior art proposed in the above background technology, such as complex module structure, inconvenient switching, difficult later maintenance, high manufacturing cost, and usage limitations.

[0006] To achieve the above-mentioned purpose, the utility model provides a fluorescence imaging structure for specimen observation, comprising: a shell, a cover plate and a fluorescence imaging mechanism, wherein the fluorescence imaging mechanism is arranged in an internal cavity formed by the shell and the cover plate;

[0007] The fluorescence imaging mechanism comprises an objective lens connecting plate, an objective lens fixing plate, an annular light source mounting bracket, a multi-channel filter fixing turntable, a filter and a driving assembly; a groove is arranged on one side of the objective lens connecting plate, and the objective lens fixing plate is detachably connected in the groove; the bottom end of the annular light source mounting bracket is connected to the objective lens fixing plate, and a multi-color LED annular light source is arranged on the top; the driving assembly is mounted on the other side of the objective lens connecting plate, and the output end of the driving assembly is connected to the multi-channel filter fixing turntable located below the objective lens connecting plate; the filters are fixedly connected to the inner edge of the multi-channel filter fixing turntable in equidistant circular distribution.

[0008] Furthermore, a plurality of slots corresponding to the positions of the filters are circumferentially provided at the bottom end of the multi-channel filter fixing turntable, the inner walls of the slots are installed with spring plates, and the bottom ends of the spring plates are installed with positioning beads; a positioning groove cooperating with the positioning beads is provided on the inner bottom wall of the shell, a pressure sensor is installed in the positioning groove, and the pressure sensor is electrically connected to the controller of the drive assembly.

[0009] Furthermore, when the multi-channel filter fixing turntable rotates until the slot hole corresponds to the positioning groove, the positioning bead extends out of the slot hole under the thrust of the spring and abuts against the pressure sensor in the positioning groove.

[0010] Furthermore, elastic members are arranged around the inner wall of the groove, and clamping plates are connected to the elastic members for clamping the objective lens fixing plate.

[0011] Furthermore, the driving assembly comprises a stepper motor, a power wheel, a transmission belt, a rotating shaft and a driven wheel, wherein the stepper motor is fixed to the top of the objective lens connecting plate, and the power wheel is fixedly connected to the outer side of the lower end of the output shaft of the stepper motor; the top of the rotating shaft (10) is rotatably connected to the center of the objective lens connecting plate (3) through a bearing, and the bottom end is fixedly connected to the multi-channel filter fixing turntable, and a driven wheel is fixed on the rotating shaft, and the driven wheel is transmission-connected to the power wheel through a transmission belt.

[0012] Furthermore, mounting holes of equal arc are opened at the inner edge of the multi-channel filter fixing turntable, the outer side of the filter is fixedly connected to the inner side of the mounting hole, and the filters in the mounting holes are filters of different wavelength bands. A mounting hole is left in the multi-channel filter fixing turntable with a filter not fixedly connected to the inner side.

[0013] Furthermore, the multi-color LED annular light source (6) is composed of lamp beads of different light waves, and there are a total of 8 groups of light of 7 wavelengths plus bright field white light. Each light segment is evenly distributed along the circumferential direction to form a multi-color evenly distributed annular light source.

[0014] The beneficial effects of the utility model are:

[0015] The utility model only needs a switchable multi-color LED ring light source, a set of multi-channel filter fixing turntable and a driving component. According to the specimen marked with the dye, the multi-color LED ring light source is quickly and automatically switched in milliseconds, and the multi-channel filter fixing turntable equipped with the filter is controlled by the power output transmission of the driving motor. The rapid switching of the fluorescence imaging structure can be achieved, and fluorescence imaging marking of various bands can be achieved by exciting fluorescence with the minimum cost, the optimal space and the simplest epi-illumination. The fluorescence resonance energy transfer technology can also be used to study the interaction between molecules under the physiological conditions of living cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the utility model;

[0017] Figure 2 This is a structural schematic diagram of the fluorescent imaging mechanism of the utility model from a first viewing angle;

[0018] Figure 3 It is a structural schematic diagram of the second viewing angle of the fluorescent imaging mechanism of the utility model;

[0019] Figure 4 It is a structural schematic diagram of the third viewing angle of the fluorescent imaging mechanism of the utility model;

[0020] Figure 5 It is a structural schematic diagram of the housing of the utility model;

[0021] Figure 6 This is the adaptation diagram of the positioning bead and the positioning groove of the utility model;

[0022] Figure 7 This is the adaptation diagram of the positioning bead and the positioning groove of the utility model;

[0023] Figure 8 This is the fluorescent molding circuit diagram of the utility model;

[0024] Fig. 9 This is the fluorescent molding circuit diagram of the utility model;

[0025] Fig.10 This is the fluorescent molding circuit diagram of the utility model;

[0026] Fig.11 This is a principle block diagram of the fluorescence microscopy imaging of the present utility model.

[0027] Among them, in the figure:

[0028] 1. Shell; 2. Cover plate; 3. Objective lens connecting plate; 4. Objective lens fixing plate; 5. Ring light source mounting bracket; 6. Multi-color LED ring light source; 7. Stepper motor; 8. Power wheel; 9. Transmission belt; 10. Rotating shaft; 11. Driven wheel; 12. Multi-channel filter fixing turntable; 13. Filter; 14. Slot hole; 15. Positioning bead; 16. Positioning groove; 17. Pressure sensor; 18. Groove. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the utility model are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0031] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0032] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0033] In addition, the terms "installed", "set", "provided with", "connected", "connected", and "socketed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0034] like Figure 1-11As shown, the utility model provides a fluorescence imaging structure for specimen observation, comprising: a shell 1, a cover plate 2 and a fluorescence imaging mechanism, wherein the fluorescence imaging mechanism is arranged in an internal cavity formed by the shell and the cover plate; the fluorescence imaging mechanism comprises an objective lens connecting plate 3, an objective lens fixing plate 4, an annular light source mounting bracket 5, a multi-channel filter fixing turntable 12, a filter 13 and a driving assembly, wherein a groove 18 is arranged on one side of the objective lens connecting plate 3, and the objective lens fixing plate 4 is detachably connected in the groove 18; the bottom end of the annular light source mounting bracket 5 is connected to the objective lens fixing plate 4, and a multi-color LED annular light source 6 is arranged on the top; the driving assembly is installed on the other side of the objective lens connecting plate 3, and the output end of the driving assembly is connected to the multi-channel filter fixing turntable 12 located below the objective lens connecting plate 3; the filter 13 is fixedly connected to the inner edge of the multi-channel filter fixing turntable 12 in an equidistant circular distribution.

[0035] Further optimization, the bottom end of the multi-channel filter fixing turntable 12 is circumferentially provided with a plurality of slots 14 corresponding to the positions of the filters 13, the inner wall of the slots 14 is provided with springs, and the bottom end of the springs is provided with positioning beads 15; the inner bottom wall of the housing 1 is provided with positioning grooves 16 cooperating with the positioning beads 15, and a pressure sensor 17 is installed in the positioning groove 16, and the pressure sensor 17 is electrically connected to the controller of the driving assembly. When the multi-channel filter fixing turntable 12 rotates until the slots 14 correspond to the positioning grooves 16, the positioning beads 15 extend from the slots 14 under the thrust of the springs and abut against the pressure sensor 17 in the positioning groove 16. The shrapnel in the utility model is always in a compressed state. When the slot hole 14 and the positioning slot 16 are not opposite to each other, the positioning bead is completely located in the slot hole. As the driving component drives the multi-channel filter fixing turntable 12 to rotate until the slot hole 14 corresponds to the positioning slot 16, the positioning bead 15 is extended from the slot hole 14 under the thrust of the shrapnel and abuts against the pressure sensor 17 in the positioning slot 16. The pressure sensor transmits a signal to the controller of the driving component, and the driving component stops moving, thereby realizing the precise positioning of the filter 13.

[0036] As a further optimization, elastic members are arranged around the inner wall of the groove 18 , and clamping plates are connected to the elastic members for clamping the objective lens fixing plate 4 , thereby facilitating the installation and removal of the objective lens fixing plate 4 .

[0037] The driving assembly includes a stepper motor 7, a power wheel 8, a transmission belt 9, a rotating shaft 10 and a driven wheel 11. The stepper motor 7 is fixed to the top of the objective lens connecting plate 3, and the power wheel 8 is fixedly connected to the outer side of the lower end of the output shaft of the stepper motor 7; the top of the rotating shaft 10 is rotatably connected to the center of the objective lens connecting plate 3 through a bearing, and the bottom is fixedly connected to the multi-channel filter fixing turntable 12. A driven wheel 11 is fixed on the rotating shaft 10, and the driven wheel 11 is transmission-connected to the power wheel 8 through a transmission belt 9. The power wheel 8 and the driven wheel 11 are transmission-connected through a transmission belt, so that after the stepper motor 7 is started, the output shaft thereof rotates to drive the power wheel 8 at its lower end to rotate, so that the driven wheel 11 rotates to drive the rotating shaft 10 to rotate, so that the multi-channel filter fixing turntable 12 at the lower end of the outer side of the rotating shaft 10 rotates, so that the filters 13 of different wavelength bands are driven to the lower end of the objective lens fixing plate 4, and a stepper motor 7 provides a power source to achieve precise control switching. In addition, the utility model improves the meshing transmission mode of the power wheel 8 and the driven wheel 11, changes it to a transmission belt transmission, and under the positioning effect of the positioning beads 15, further improves the positioning accuracy.

[0038] Further optimization, the inner edge of the multi-channel filter fixing turntable 12 is provided with mounting holes of equal arc, the outer side of the filter 13 is fixedly connected to the inner side of the mounting hole, and the filter 13 in the mounting hole is a filter 13 of different wavelengths, and the multi-channel filter fixing turntable 12 has a mounting hole with the inner side of the filter 13 not fixedly connected. Filters 13 of different wavelengths are evenly installed on the multi-channel filter fixing turntable 12, and the fluorescent dye provided by the specimen is observed as needed. According to the optical principle of short-wave excitation of long-wave, the LED lamp beads with short wavelengths are illuminated, and the lamp beads of other wavelengths are all turned off, and the filter 13 of the current wavelength is switched to accordingly, so as to realize the fluorescence imaging mark of the specimen. In the case of no filter 13, there is no fluorescence, and bright field imaging is performed, and the LED lamp also corresponds to white light.

[0039] Further optimization, the multi-color LED ring light source 6 is composed of lamp beads of different light waves, and there are a total of 8 groups of light with 7 bands plus bright field white light. Each segment of light is evenly distributed along the circumferential direction to form a multi-color evenly distributed ring light source, thereby ensuring that there is light on all sides, so that the specimen placed above the multi-color LED ring light source 6 can receive uniform light energy, and the lamp beads are fixed on a substrate at the upper end of the ring light source mounting bracket 5 with a certain inclination angle to the main optical axis of the objective lens, and the angle size is designed synchronously according to the focal length of the objective lens.

[0040] The utility model only needs a switchable multi-color LED ring light source, a set of multi-channel filter fixing turntable and a driving component. According to the specimen marked with the dye, the multi-color LED ring light source is quickly and automatically switched in milliseconds, and the multi-channel filter fixing turntable equipped with the filter is controlled by the power output transmission of the driving motor. The rapid switching of the fluorescence imaging structure can be achieved, and fluorescence imaging marking of various bands can be achieved by exciting fluorescence with the minimum cost, the optimal space and the simplest epi-illumination. The fluorescence resonance energy transfer technology can also be used to study the interaction between molecules under the physiological conditions of living cells.

[0041] When the utility model is in use, the excitation light is incident obliquely, does not enter the main optical axis, is not coaxial with the emission light, the excitation and emission light will not interfere with each other, the excitation light is incident obliquely, the emission light is perpendicular to the specimen, and reaches the eyepiece or the imaging original through the objective lens, and the excitation light is incident from different directions at two or more different angles, which can effectively avoid the condition of uneven excitation. The single-angle oblique injection and multi-angle oblique injection are compared. In the single-angle oblique injection, the energy of the specimen close to the light source is strong, and the excitation energy obtained at the specimen far away from the light source is weak, which leads to uneven excitation energy and affects the fluorescence effect. The multi-angle oblique injection can effectively avoid this kind of poor fluorescence effect caused by uneven excitation energy, and the emission light A filter wheel is added through the objective lens, behind the objective lens, in the optical path between the objective lens and the eyepiece or the imaging element. There are different filters 13 on the wheel. Excitation lights of different colors correspond to corresponding emission light filters 13. Through program control, the excitation light module is preferably a monochrome LED. The excitation light includes but is not limited to 370nm, 470nm, 530nm, 620nm, etc. The filters 13 include 460nm, 530nm, 605nm, 690nm, etc. The excitation light and the filter 13 correspond one to one. In the fluorescence mode, when the user selects a certain wavelength of excitation light, the program automatically cuts the corresponding filter 13 into the optical path.

[0042] When studying the interaction between two proteins a and b, a fusion protein fluorescent dye can be constructed based on the FRET principle. This fusion protein fluorescent dye consists of two parts: cyan fluorescent protein (CFP) and yellow fluorescent protein (YEP). According to the optical principle of short-wave excitation of long-wave, 433nm in the multi-color LED ring light source 6 is used as the excitation wavelength, and then the stepper motor 7 is started. The rotation of its output shaft can drive the power wheel 8 at its lower end to rotate, so that the driven wheel 11 rotates and drives the rotating shaft 10 to rotate, so that the multi-channel filter 13 at the lower end of the outer side of the rotating shaft 10 The fixed turntable 12 rotates, and the 476nm filter is repeatedly switched back and forth at high speed. The film 13 and the 527nm filter 13 capture the corresponding fluorescence energy. When proteins a and b do not interact, CFP and YFP are far apart and fluorescence resonance energy transfer cannot occur. Therefore, what is detected is the fluorescence energy of CFP with an emission wavelength of 476nm. However, when proteins a and b interact, protein b is displaced by protein a, making CFP and YFP close enough to each other for fluorescence resonance energy transfer. At this time, what is detected is the fluorescence energy of YFP with an emission wavelength of 527nm. In this way, protein-protein interactions can be studied under the physiological conditions of living cells.

[0043] The control system in the utility model is composed of LEDs of 8 different colors, a single-chip main control circuit, a motor drive circuit, a stepping motor, a host computer and a camera.

[0044] When the utility model needs to excite fluorescence, the host computer sends a command to the single-chip microcomputer to turn on the LED of the corresponding color, and controls the stepper motor to drive the turntable to rotate. There are seven corresponding filters on the multi-channel filter fixed turntable. The single-chip microcomputer controls the corresponding filters on the multi-channel filter fixed turntable to rotate to the camera, so that the fluorescence excited by the LED reaches the camera through the filter to realize fluorescence imaging. The same applies to fluorescence of other colors.

[0045] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A fluorescence imaging structure for specimen observation, characterized in that: include: A housing (1), a cover plate (2) and a fluorescent imaging mechanism, wherein the fluorescent imaging mechanism is arranged in an internal cavity formed by the housing and the cover plate; The fluorescence imaging mechanism comprises an objective lens connecting plate (3), an objective lens fixing plate (4), an annular light source mounting bracket (5), a multi-channel optical filter fixing turntable (12), an optical filter (13) and a driving assembly. A groove (18) is arranged on one side of the objective lens connecting plate (3), and the objective lens fixing plate (4) is detachably connected in the groove (18); the bottom end of the annular light source mounting bracket (5) is connected to the objective lens fixing plate (4), and a multi-color LED annular light source (6) is arranged on the top end; the driving assembly is mounted on the other side of the objective lens connecting plate (3), and the output end of the driving assembly is connected to the multi-channel optical filter fixing turntable (12) located below the objective lens connecting plate (3); and the optical filter (13) is fixedly connected to the inner edge of the multi-channel optical filter fixing turntable (12) in an equidistant circular distribution.

2. A fluorescent imaging structure for specimen observation as claimed in claim 1, characterized in that: The bottom end of the multi-channel filter fixing turntable (12) is provided with a plurality of slots (14) corresponding to the positions of the filters (13) in the circumferential direction, the inner wall of the slot (14) is provided with a spring sheet, and the bottom end of the spring sheet is provided with a positioning bead (15); the inner bottom wall of the housing (1) is provided with a positioning groove (16) matching with the positioning bead (15), a pressure sensor (17) is installed in the positioning groove (16), and the pressure sensor (17) is electrically connected to the controller of the drive assembly.

3. A fluorescent imaging structure for specimen observation as claimed in claim 2, characterized in that: When the multi-channel filter fixing turntable (12) rotates until the slot hole (14) corresponds to the positioning slot (16), the positioning bead (15) extends out of the slot hole (14) under the thrust of the spring and abuts against the pressure sensor (17) in the positioning slot (16).

4. A fluorescent imaging structure for specimen observation as claimed in claim 1, characterized in that: Elastic parts are arranged around the inner wall of the groove (18), and clamping plates are connected to the elastic parts for clamping the objective lens fixing plate (4).

5. A fluorescent imaging structure for specimen observation as claimed in claim 1, characterized in that: The driving assembly comprises a stepping motor (7), a power wheel (8), a transmission belt (9), a rotating shaft (10) and a driven wheel (11); the stepping motor (7) is fixed to the top end of the objective lens connecting plate (3); the power wheel (8) is fixedly connected to the outer side of the lower end of the output shaft of the stepping motor (7); the top end of the rotating shaft (10) is rotatably connected to the center of the objective lens connecting plate (3) through a bearing, and the bottom end is fixedly connected to the multi-channel filter fixing turntable (12); a driven wheel (11) is fixed on the rotating shaft (10), and the driven wheel (11) is transmission-connected to the power wheel (8) through a transmission belt (9).

6. A fluorescent imaging structure for specimen observation as claimed in claim 5, characterized in that: The inner edge of the multi-channel filter fixing turntable (12) is provided with mounting holes of equal arc, the outer side of the filter (13) is fixedly connected to the inner side of the mounting hole, and the filters (13) in the mounting holes are filters (13) of different wavelength bands, and the multi-channel filter fixing turntable (12) has a mounting hole with the inner side of the mounting hole not fixedly connected to the filter (13).

7. A fluorescent imaging structure for specimen observation according to claim 1 or 6, characterized in that: The multi-color LED annular light source (6) is composed of lamp beads of different light waves, and there are a total of 8 groups of light of 7 wavelengths plus bright field white light. Each light segment is evenly distributed along the circumferential direction to form a multi-color evenly distributed annular light source.

Images