CN109973858B

CN109973858B - Illuminator for underwater dark field imaging

Info

Publication number: CN109973858B
Application number: CN201711455647.3A
Authority: CN
Inventors: 李剑平; 章逸舟; 陈涛; 刘鹏; 陈良培
Original assignee: Shenzhen Institute of Advanced Technology of CAS
Current assignee: Shenzhen Institute of Advanced Technology of CAS
Priority date: 2017-12-28
Filing date: 2017-12-28
Publication date: 2022-03-08
Anticipated expiration: 2037-12-28
Also published as: CN109973858A

Abstract

The invention provides an illuminator for underwater dark field imaging, the illuminator is controlled by an imaging system, the illuminator is positioned in an imaging area of the imaging system, and the illuminator comprises a closed structural part and a plurality of illuminating units distributed on the structural part. The illumination unit may be composed of one, any two, or all three of three LEDs having central wavelengths of red, green, and blue, and include an ultraviolet LED of a UVC band. The plurality of lighting units constituting the illuminator must include visible light LEDs of three colors of red, green, and blue; wherein the uv LEDs form a "plug-in" distribution with other lighting units. The illumination direction of the light beam of the illumination unit is perpendicular to the central axis of the structural component and faces the direction of the central axis. The illuminator for underwater dark field imaging can improve the accuracy of an imaging result and delay underwater biological adhesion.

Description

Illuminator for underwater dark field imaging

Technical Field

The invention relates to the technical field of lighting equipment, in particular to an illuminator for underwater dark field imaging.

Background

Underwater microorganisms and particles are important components in water environments. The research on the micro organisms and the particles has important scientific significance and application value for subjects of water environment science, microbiology, oceanographic science, ecology and the like. The underwater dark field imaging technology is an important means for acquiring and researching underwater micro organism and particle information, and how to realize the illumination of the underwater dark field imaging is one of the key factors for obtaining high-quality underwater microscopic or microspur imaging. Due to the complex underwater environment and the refraction and scattering of light rays by the water body, the acquisition of the high-contrast and high-resolution color image puts high requirements on the whole dark field illumination technology.

Current dark field illumination devices typically use an annular light cone for dark field illumination, using circularly arranged LEDs as illuminators, with the direct direction of the LEDs being opposite to the imaging direction of the imaging lens and at a specific angle to the optical axis of the lens. The light emitted by the annular LED illuminator is converged in the imaging depth range of the imaging lens. The direct light of the LED directly irradiates the target object, but does not directly enter the lens. The lens images the scattered light formed on the target object by collecting the direct light, thereby forming dark field illumination.

However, the white light LED adopted by the current dark field illumination device is formed by combining blue light with a central wavelength of about 450nm and broad-spectrum yellow light emitted by phosphor excited by the blue light, and the response of the photosensitive chip of the camera of the imaging system to three bands of red, green and blue is usually equivalent, so that the image of the camera under the illumination of the white light LED will show a bluing effect, which seriously changes the color information of the imaging target itself, and makes the imaging result inaccurate.

Disclosure of Invention

The invention provides an illuminator for underwater dark field imaging, which can improve the accuracy of an imaging result.

In order to achieve the above object, the present application provides an illuminator for underwater dark field imaging, the illuminator being controlled by an imaging system, the illuminator being located in an imaging area of the imaging system, the illuminator comprising a closed structure and a plurality of illumination units distributed on the structure, the plurality of illumination units being distributed at equal angles around an axis of the structure, the illuminator comprising a plurality of visible light LEDs at different central wavelengths and ultraviolet light LEDs in a UVC band, wherein the central wavelengths of the plurality of visible light LEDs correspond one-to-one to photosensing peaks in a red, green, blue color photosensing curve of the imaging system; the illumination direction of the light beam of the illumination unit is perpendicular to the central axis of the structural component and faces the direction of the central axis.

Further, the illumination unit may be formed of one, any two, or all three of LEDs having central wavelengths of red, green, and blue, and include an ultraviolet LED in the UVC band. The illuminating units forming the illuminator must include red, green and blue visible light LEDs, the red, green and blue light sensitivity curves of the imaging system have sensitivity peaks corresponding to the red, green and blue light bands, respectively, and the band and number of the visible light LEDs are determined by the requirements of the optical imaging system.

Further, the irradiation area of the ultraviolet light LED is positioned on the structural member between two adjacent lighting units, and the number of the ultraviolet light LED is determined by the ultraviolet radiation dosage requirement.

Further, the ultraviolet light LED has the following geometrical relationship with the irradiation area,

the first formula represents the relationship between the arc length of each ultraviolet illumination area and the corresponding central angle, wherein the whole illuminator is divided into n (n is more than or equal to 3) areas by the illumination unit; r is the curvature radius of the circumference where the light transmission window is located, L is the length of the light transmission window of the lighting unit, and alpha is a central angle corresponding to the half arc length; the second formula indicates that the uv LED must cover the light transmissive window area of the entire lighting unit; θ is the emission half-angle of the ultraviolet LED; d is the distance from the ultraviolet LED to the light-transmitting window; the third formula shows that the radius of curvature of a circle formed by the light-transmitting window must be larger than that of the imaging area; h is the horizontal dimension of the detector of the imaging system, v is the vertical dimension of the detector of the imaging system, and M is the magnification of the imaging lens of the imaging system; the fourth formula means that the triangle should conform to the sine theorem.

Further, the ultraviolet light LED emits light beams according to a specified time period and a specified duty cycle interval, and the wavelength band of the ultraviolet light LED is a UVC (ultraviolet radiation) band of 250-280 nanometers.

Further, the plurality of visible light LEDs operate in a pulse mode and are triggered by a camera in the imaging system, wherein a pulse width time of the visible light LEDs is shorter than an exposure time of the camera in the imaging system.

Furthermore, the structural member is a closed circle or a regular polygon, the plurality of lighting units are distributed on the structural member at equal intervals, and a central axis of the structural member coincides with an optical axis of the imaging system.

Further, the irradiation direction of the light beam of the illumination unit is also provided with an optical element for compressing the divergence angle of the light beam, so that the light beam emitted by the illumination unit forms a layered illumination area after passing through the optical element; wherein the layered illumination area is in an imaging area of the imaging system, and a thickness of the layered illumination area is less than or equal to a depth of field of an imaging lens in the imaging system.

Further, the optical element may be a cylindrical fresnel lens, or may be other optical elements such as a lens, a reflective cup, and a prism that can compress light beams.

Further, the illuminator further comprises a light-transmitting window and an encapsulation shell, wherein the shape of the light-transmitting window and the shape of the encapsulation shell are consistent with the shape of the structural part; the light-transmitting window is located on the inner side of the structural part, the packaging shell is located on the outer side of the structural part, and the light-transmitting window is connected with the packaging shell in a sealing mode so as to wrap the structural part and the lighting unit on the structural part.

From the above, the luminaire provided by the present application can distribute a plurality of lighting units on a closed structure, and the lighting units can cover visible light LEDs with different central wavelengths. The center wavelengths of the visible light LEDs are in one-to-one correspondence with the photosensitive peak values in the photosensitive curve of the imaging system, so that the color effect of each center wavelength can be balanced when the imaging system performs imaging, the imaging result can reflect the imaging target more truly, and the accuracy of the imaging result is improved. In addition, the illuminator provided by the application can also comprise an ultraviolet LED in the illuminating unit, and the ultraviolet LED can irradiate the areas, except for the illuminating device, on the structural member of the illuminator, so that the formation of various bacteria, viruses, parasites and algae biofilms can be inhibited. In addition, in the illuminating direction of the illuminating device, an optical element for compressing the divergence angle of the light beam is arranged, so that the light beam emitted by the illuminating unit is limited in the imaging depth of field of the imaging system, and the influence of stray light outside the depth of field on the dark field effect is prevented.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a front view of an illuminator for underwater dark field imaging;

FIG. 2 is a schematic diagram of an underwater dark field imaging optical system;

FIG. 3 is a view of an illumination unit consisting of red, green, and blue visible LEDs and ultraviolet LEDs;

fig. 4 is a schematic view of an irradiation region of ultraviolet rays in the illumination unit;

FIG. 5 is a schematic diagram of one-dimensional focusing of a cylindrical Fresnel lens;

fig. 6 is a geometric relationship between the ultraviolet ray emission angle and other structural parameters.

In the figure, 1 is an illumination unit, 2 is an optical element, 3 is a light-transmissive window, 4 is a package housing, 5 is an imaging system, 6 is an illuminator, 7 is a red LED, 8 is a green LED, 9 is a blue LED, 10 is an ultraviolet LED, and 11 is a structural member.

Detailed Description

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.

Referring to fig. 1 and 2, the present application provides an illuminator 6 for underwater dark field imaging, the illuminator 6 is controlled by an imaging system 5, the illuminator 6 is located in an imaging area of the imaging system 5, in the present embodiment, the illuminator 6 includes a closed structural member 11 and a plurality of illumination units 1 distributed on the structural member 11. The plurality of lighting units are equiangularly distributed about the axis of the structure. The plurality of lighting units 1 include a plurality of visible light LEDs with different central wavelengths, wherein the central wavelengths of the plurality of visible light LEDs correspond to the photosensitive peaks in the photosensitive curve of the imaging system 5 one by one. The light beam of the lighting unit 1 is irradiated in a direction perpendicular to and facing the central axis of the structural member 11.

Referring to fig. 3, in one embodiment, the plurality of visible light LEDs may include a red LED (r)7, a green LED (g)8, and a blue LED (b) 9. In a practical application scenario, the illumination unit may be composed of one, any two, or all three of red, green, and blue LEDs with central wavelengths, and include an ultraviolet LED in the UVC band. The plurality of lighting units constituting the illuminator must include visible light LEDs of three colors of red, green, and blue. Specifically, the lighting unit may be one of a red light LED, a green light LED, and a blue light LED, or two or three of a red light LED, a green light LED, and a blue light LED, which form all lighting units of the luminaire, and must include visible light bands of three colors, red, green, and blue. Accordingly, the photosensitive peak in the photosensitive curve of the imaging system may correspond to a red light band, a green light band, and a blue light band, respectively. Therefore, when the photosensitive system performs imaging, the LEDs with different central wavelengths can be controlled through current, so that each color is balanced, and the imaging effect is more real.

In this embodiment, the illumination unit may further include an ultraviolet led (u) 10. The ultraviolet LED can be used for inhibiting the formation of various bacteria, viruses, parasites and algae biofilms on the structural member. Specifically, the UltraViolet light LED may be located in a UVC (ultra violet C) band. The wavelength of UVC wave band ultraviolet light is 250 nm-280 nm, and the ultraviolet light with the wavelength can destroy the molecular structure of DNA or RNA in microbial organism cells to cause the death of growing cells and regenerative cells, so as to achieve the effects of sterilization and disinfection, thereby inhibiting the formation of various bacteria, viruses, parasites and algae biofilms.

In this embodiment, the visible LEDs may all be operated in a pulsed mode, with the illumination being triggered by means of a camera in the imaging system, with the pulse width time of the pulses being shorter than the exposure time of the camera. According to the image collected by the camera, the luminous intensity of the visible light LED is adjusted by adjusting the current, so that the color temperature and the intensity of illumination are changed, and the image imaging quality is improved. Certainly, in practical application, the visible light LED can also continuously illuminate, but compared with continuous illumination, the pulse mode can reduce the energy consumption of the light source on one hand, and on the other hand, can prevent underwater organisms from losing the meaning of in-situ measurement due to aggregation caused by phototaxis.

In addition, in the present embodiment, since the ultraviolet light irradiation for a long time causes accelerated deterioration of the device, it is desirable to avoid direct irradiation of the device such as the visible light LED with the ultraviolet light LED. Referring to fig. 4 and 6, the light emitting angle of the ultraviolet light emitted by a single uv LED with UVC band may be slightly smaller than the included angle formed between two adjacent lighting units, so that the light emitted by the uv LED may just irradiate the structural member between two adjacent lighting units, but not the lighting units, thereby forming a "plug-in" type ultraviolet light irradiation layout, and avoiding accelerated aging of the optoelectronic device.

In conjunction with fig. 6, in particular, the uv LED has the following geometrical relationship with its irradiation area,

the first formula represents the relationship between the arc length of each ultraviolet illumination area and the corresponding central angle, wherein the whole illuminator is divided into n (n is more than or equal to 3) areas by the illumination unit; r is the curvature radius of the circumference where the light-transmitting window is located, L is the length of the light-transmitting window of the lighting unit, namely BC in figure 6, and alpha is a central angle corresponding to the half arc length, namely FOE in figure 6; the second formula indicates that the uv LED must cover the light transmissive window area of the entire lighting unit; theta is the emission half angle of the ultraviolet light LED, namely ≈ GAC in fig. 6; d is the distance from the ultraviolet LED to the light transmissive window, AG in fig. 6; the third formula shows that the radius of curvature of a circle formed by the light-transmitting window must be larger than that of the imaging area; h is the horizontal dimension of the detector of the imaging system, v is the vertical dimension of the detector of the imaging system, and M is the magnification of the imaging lens of the imaging system; the fourth formula means that the triangular AOG should conform to the sine theorem. For example, when the divergence half-angle of the uv LED is 22.82 °, the length of the light transmissive window is 10mm, the distance between the uv LED and the light transmissive window is 11.57mm, and the radius of curvature of the circle around which the light transmissive window is located is 40mm, the "plug-in" design just described above is met.

In this embodiment, the uv LEDs may also be operated at intervals to emit light beams at specified time periods and specified duty cycle intervals. For example, the light power of the ultraviolet light LED is 1mW, the duty ratio of the emitted light is 50%, and the cycle period is 10 minutes.

In this embodiment, the structural member 11 may be a closed circle or a regular polygon, the plurality of lighting units 1 may be distributed on the structural member at equal intervals, and a central axis of the structural member coincides with an optical axis of the imaging system, so as to improve uniformity and intensity of illumination.

In this embodiment, the wavelength band and the number of the visible LEDs can be determined by the requirement of the imaging system, and the number of the ultraviolet LEDs can be determined by the requirement of the ultraviolet radiation dose.

Referring to fig. 1, the illumination direction of the light beam of the illumination unit 1 may be further provided with an optical element 2 for compressing the divergence angle of the light beam, so that the light beam emitted by the illumination unit 1 forms a layered illumination area after passing through the optical element 2. In this embodiment, the optical element may include at least one of a cylindrical fresnel lens, a reflective cup, and a prism. Referring to fig. 5, taking a fresnel lens as an example, the fresnel lens is a common optical element in lighting applications. A common fresnel lens uses a series of concentric grooves cast on a plastic substrate. Each concentric groove corresponds to a separate refractive surface. Such a lens is very thin and therefore the light loss due to absorption by the material is small. A cylindrical fresnel lens is an optical element used to focus only a single dimension. Each lighting unit is preceded by a 10mm x 10mm square cylindrical fresnel lens, the lighting unit being placed in the focal plane of the fresnel lens. The light beams from either the red, green, blue, visible or ultraviolet LEDs are constrained within the imaging depth of field to form a layered illumination field. The layered illumination area formed by the cylindrical Fresnel lens is perpendicular to the optical axis of the imaging system. In this embodiment, the layered illumination area is in an imaging region of the imaging system, and a thickness of the layered illumination area is smaller than or equal to a depth of field of an imaging lens in the imaging system, so as to prevent stray light outside the depth of field from affecting a dark field effect.

Referring to fig. 1, in the present embodiment, the illuminator further includes a light-transmissive window 3 and an enclosure 4, and the shapes of the light-transmissive window 3 and the enclosure 4 are consistent with the shape of the structural member 11. The light-transmitting window 3 is located on the inner side of the structural member 11, the packaging shell 4 is located on the outer side of the structural member 11, and the light-transmitting window 3 is hermetically connected with the packaging shell 4 to wrap the structural member 11 and the lighting unit 1 on the structural member 11. Specifically, the material of the light-transmitting window is fused silica glass which has high transmittance and high strength in both visible light band and ultraviolet band. The light-transmitting window and the packaging shell are tightly packaged to prevent water leakage. The packaging shell is made of high-heat-conductivity and corrosion-resistant materials. Of course, in practical application, the light-transmitting window may also be made of other materials according to practical situations, and the comparison of the present application is not limited.

In a practical application scenario, the illuminator provided by the application comprises three visible light LEDs of red, green and blue, an ultraviolet LED in a UVC band, an optical element, a light-transmitting window and a package housing. The illuminator has an annular or polygonal shape. The plurality of lighting units are distributed on the illuminator in an equal angle, so that the uniformity and the illumination intensity of illumination are improved. The illuminating units can be formed by combining three visible light LEDs (red, green and blue) and an ultraviolet light LED, and the light beam irradiation directions of the illuminating units are perpendicular to the axis of the annular illuminator and face inwards; or a single visible light LED and ultraviolet light LED are combined, and the direction irradiated by the light beams of the plurality of lighting units with different wave bands is inwards perpendicular to the axis of the annular illuminator. The wave band and the number of the visible light LEDs are determined by the requirements of an optical imaging system, and the number of the ultraviolet light LEDs is determined by the requirements of ultraviolet radiation dose. An optical element is added in front of each lighting unit to compress the divergence angle of the LED in the direction of the optical axis to form a layered lighting area, and the layered lighting area is positioned in the imaging area of the imaging lens. The thickness of the illumination layer is smaller than or equal to the depth of field of the imaging lens, so that stray light outside the imaging area is reduced, and the contrast of a dark field image is improved. The emission center wavelengths of the red, green and blue LEDs are matched with the induction wavelength peak values of the red, green and blue colors of the camera photosensitive chip, the luminous intensity of the LEDs is adjusted through current, and the luminous intensity of different visible light LEDs is adjusted to change the color temperature and the light intensity of dark field illumination. The visible light LEDs are operated in a pulsed mode and triggered by the camera, with the pulse width of the visible light LEDs being shorter than the camera exposure time. Compared with continuous illumination, the pulse mode can reduce the energy consumption of a light source on one hand, and can avoid the phenomenon that underwater organisms lose the significance of in-situ measurement due to aggregation caused by phototaxis on the other hand.

The wavelength of UVC wave band ultraviolet light is 250 nm-280 nm, and the ultraviolet light with the wavelength can destroy the molecular structure of DNA or RNA in microbial organism cells to cause the death of growing cells and regenerative cells, so as to achieve the effects of sterilization and disinfection, thereby inhibiting the formation of various bacteria, viruses, parasites and algae biofilms. However, since the long-term uv irradiation causes accelerated aging of the device, it is desirable to avoid direct irradiation of the uv LED to the visible LED or the like. The light emitted by the ultraviolet LED and other lighting units form a space layout of a plug-in type, and the irradiation direction of the ultraviolet LED is perpendicular to the optical axis inwards. The number of uv LEDs may be determined according to the uv radiation requirements. The emission half-angle of the uv LED is determined according to the spatial distribution pattern of the visible LEDs. In order to save energy, the ultraviolet light LED works not in a normally bright mode but in a timing illumination mode with equal time intervals. In addition, the packaging structure material of the darkfield illuminator is selected according to the requirements of high heat conduction, corrosion resistance and the like.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. An illuminator for underwater dark field imaging, the illuminator controlled by an imaging system, the illuminator located in an imaging region of the imaging system, the illuminator comprising a closed structure and a plurality of illumination units distributed on the structure, the plurality of illumination units being equiangularly distributed around an axis of the structure, the illuminator comprising a plurality of visible light LEDs at different central wavelengths and ultraviolet LEDs in the UVC band, wherein the central wavelengths of the plurality of visible light LEDs are in one-to-one correspondence with photosensing peaks in a red, green and blue color photosensing curve of the imaging system; the irradiation direction of the light beam of the lighting unit is perpendicular to the central axis of the structural part and faces to the direction of the central axis; the ultraviolet light LED has the following geometrical relationship with the irradiation area,

wherein the first formula represents that the whole illuminator is divided into n areas by the lighting unit, wherein n is more than or equal to 3; the relation between the arc length of each ultraviolet illumination area and the corresponding central angle; r is the curvature radius of the circumference where the light transmission window is located, L is the length of the light transmission window of the lighting unit, and alpha is a central angle corresponding to the half arc length; formula 2 the second formula indicates that the uv LED must cover the light transmissive window area of the entire lighting unit; θ is the emission half-angle of the ultraviolet LED; d is the distance from the ultraviolet LED to the light-transmitting window; formula 3 the third formula shows that the radius of curvature of the circle formed by the light-transmitting window must be larger than that of the imaging area; h is the horizontal dimension of the detector of the imaging system, v is the vertical dimension of the detector of the imaging system, and M is the magnification of the imaging lens of the imaging system; the fourth formula means that the triangle should conform to the sine theorem.

2. A luminaire as claimed in claim 1, characterized in that the illumination unit is constituted by one, any two or all three LEDs with a central wavelength in the three colors red, green and blue, while containing uv LEDs in the UVC band; the plurality of lighting units constituting the illuminator include visible light LEDs of three colors of red, green, and blue; correspondingly, the light sensing peak value in the red, green and blue color light sensing curve of the imaging system respectively corresponds to a red light wave band, a green light wave band and a blue light wave band, and the wave band and the number of the visible light LEDs are determined by the requirements of the optical imaging system.

3. A luminaire as claimed in claim 1 or 2, characterized in that the irradiation area of the uv LEDs is on the structure between two adjacent lighting units, the number of uv LEDs being determined by the uv radiation dose requirement.

4. A luminaire as claimed in claim 3, wherein the ultraviolet LED emits a beam of light for a specified period of time and at specified duty cycle intervals.

5. An illuminator according to claim 1, wherein the plurality of visible light LEDs are operated in a pulsed mode and are triggered by a camera in the imaging system, wherein the pulse width time of the visible light LEDs is shorter than the exposure time of the camera in the imaging system.

6. A luminaire as claimed in claim 1, wherein the structure is a closed circle or a regular polygon, the plurality of illumination units being equally spaced on the structure, a central axis of the structure coinciding with an optical axis of the imaging system.

7. A luminaire as claimed in claim 1, characterized in that the irradiation direction of the light beam of the illumination unit is further provided with an optical element for compressing the divergence angle of the light beam, so that the light beam emitted by the illumination unit forms a laminar illumination zone after passing through the optical element; wherein the layered illumination area is in an imaging area of the imaging system, and a thickness of the layered illumination area is less than or equal to a depth of field of an imaging lens in the imaging system.

8. A luminaire as claimed in claim 7, characterized in that the optical element is a cylindrical Fresnel lens, or other lenses, reflectors, prisms, which are able to achieve beam compression.

9. A luminaire as claimed in claim 7 or 8, further comprising a light transmissive window and an enclosure, both of which conform in shape to the structure; the light-transmitting window is located on the inner side of the structural part, the packaging shell is located on the outer side of the structural part, and the light-transmitting window is connected with the packaging shell in a sealing mode so as to wrap the structural part and the lighting unit on the structural part.