CN112161208A

CN112161208A - Light emitting device

Info

Publication number: CN112161208A
Application number: CN202011040360.6A
Authority: CN
Inventors: 李虎; 黄成�; 陈国平
Original assignee: Guangzhou Guanglian Electronic Technology Co ltd
Current assignee: Guangzhou Guanglian Electronic Technology Co ltd
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2021-01-01
Also published as: WO2022062542A1

Abstract

The invention relates to the technical field of stage lamps, and provides a light-emitting device which comprises an LED array, a light-emitting module and a light-emitting module, wherein the LED array comprises a plurality of LED unit modules, each LED unit module comprises at least one LED chip, and a light-emitting area of each LED unit module is substantially circular; the collimating lens array is used for collimating the light rays emitted by the LED unit module; and the condenser lens is used for focusing the light rays collimated by the collimating lens array on a preset focal plane to form a light spot which is substantially circular. The light emitting area of the LED unit module is set to be generally circular, and under the condition that the light is homogenized without the adoption of the fly-eye lens arranged oppositely, the generally circular and uniform light spots are formed on the focal plane, so that the cost is greatly reduced, and the light spots with better light emitting effect are obtained; the invention also improves the photoelectric efficiency, the luminous efficiency, the service life and the stability of the LED chip, improves the wafer utilization rate of the LED chip manufacture, and reduces the junction temperature and the production cost of the LED chip.

Description

Light emitting device

Technical Field

The invention relates to the technical field of stage lamps, in particular to a light-emitting device.

Background

The light source adopted by the traditional stage lamp is a gas discharge bulb light source (commonly known as HID), and the light emitted by the light source is collected by a reflecting cup and is projected by an imaging lens, so that the illumination of the stage is realized or various stage effects are manufactured. In general, lamps using such light sources have high energy consumption, low luminous efficiency and short product life, and the lamp liner of the lamps is filled with high-voltage metal halide, so that certain danger coefficient exists.

In recent years, the Light Emitting Diode (LED) light source is developed rapidly, is a clean energy-saving light source without pollution and has long service life. With the continuous development of the technology, the luminous flux generated by each watt of electric power is increased year by year, and the process is mature day by day, so that the method provides conditions for the large-scale popularization and application of the LED.

However, the LED used in the stage lighting industry is required to have the characteristics of high power, large luminous flux output, strong directivity, good uniformity, and circular light spot of its emergent light spot, and in the prior art, the high-power light source system used in the stage lighting field mostly adopts the array-type LED light source, and the LED chip of the LED light source is rectangular. As shown in fig. 1, multiple light beams emitted by the LED light sources are collimated into near-parallel light by the corresponding collimating lens arrays one by one, then homogenized by the opposite fly-eye lenses, and converged by the condensing lenses on the focal plane thereof to form uniform light spots having a certain illumination area.

Specifically, as shown in fig. 1 and 2, the opposed fly-eye lens in the related art includes a first fly-eye lens 301 and a second fly-eye lens 302, which are two identical fly-eye lens units, and each of the two fly-eye lens units has the same hexagonal arrangement shape, the same size, and the same focal length. The light collimated by the collimating lens array is divided into a plurality of hexagonal areas in the shape of the fly-eye lens unit by the first fly-eye lens in the light outgoing direction, and then focused on a focal plane of the light by the second fly-eye lens and the condensing lens to form hexagonal light spots in the shape of the fly-eye unit, wherein the hexagonal light spots are shown in fig. 3; then, a circular diaphragm is arranged on the focal plane of the condensing lens, so that a circular light spot required by the stage lamp is obtained.

However, in the scheme, the LED chip with the rectangular effective light emitting surface is used, the LED chip and the collimating lens array corresponding to the LED chip in one-to-one correspondence form an axis-to-axis optical system, and on the basis of the hexagonal light spot obtained by performing optical integration by using the compound eye unit in the hexagonal arrangement shape, the circular light spot is cut by using the diaphragm, so that the light utilization efficiency of the whole optical system is not high, and the optical system is complex and expensive.

Disclosure of Invention

The invention aims to overcome the defect of low light utilization efficiency in the prior art and provides a light-emitting device which is used for improving the light utilization efficiency and reducing the cost.

The technical scheme adopted by the invention is that the light-emitting device comprises an LED array, a plurality of LED unit modules and a plurality of LED chips, wherein each LED unit module comprises at least one LED chip, and a light-emitting area of each LED unit module is substantially circular; the collimating lens array comprises a plurality of collimating lenses, and each collimating lens is aligned to one LED unit module and is used for collimating the light rays emitted by the LED unit modules; and the condenser lens is used for focusing the light rays collimated by the collimating lens array on a preset focal plane so as to form a substantially circular and uniform light spot.

In the scheme, the light rays emitted by the LED array are collimated into nearly parallel light beams by the collimating lens array and emitted, the nearly parallel light beams are focused on a preset focal plane of the condensing lens through the condensing lens, images of the LED array are formed on the focal plane and are overlapped together, and light spots which are approximately circular are formed, namely the light spots formed on the focal plane are overlapped and accumulated by the images formed on the light emitting surfaces of the light sources. Because the light emitting surfaces of the LED chips are uniform, and the whole light emitting surfaces of the LED chips emit light uniformly, the superposition of the mirror images of the LED chips on the focal plane of the condensing lens is uniform light spots. The substantially circular shape means that the light emitting area of the LED unit module is circular or approximately circular.

Compared with the prior art, the LED array uses a rectangular chip, and the opposite fly-eye lens is used for optically homogenizing the LED array so as to form a hexagonal light spot on a focal plane of the condensing lens; this scheme sets up the luminous region of LED unit module into being substantially circular, and under the condition that does not adopt opposition fly-eye lens to carry out dodging to it, this scheme has formed the facula that becomes circular and even on the focal plane roughly, and this compares prior art, and this scheme has reduced opposition fly-eye lens in order to reduce the cost greatly, and obtains the facula that the illuminating effect is better.

Preferably, the light emitting surface of the LED chip includes a non-light emitting area and a light emitting area, and the non-light emitting area is distributed on the periphery of the light emitting area of the LED chip; the LED unit module comprises an LED chip, and a light emitting area of the LED chip is substantially circular; or the LED unit module comprises more than two LED chips, and the light emitting area of each LED chip is combined to form the light emitting area of the LED unit module. In the scheme, under the condition that the LED unit module is provided with only one LED chip, the light emitting area of the LED chip is the light emitting area of the LED unit module, and the non-light emitting area is distributed on the periphery of the light emitting area of the LED chip, so that light emitted by the light emitting area of the LED chip is more concentrated. Compared with the prior art that the LED arrays are arranged in a nearly circular shape to obtain nearly circular light spots, the scheme is directly improved on the LED chips, the light emitting areas of the LED chips are set to be nearly circular on the whole, and the light spots formed on the focal plane of the condensing lens are more nearly circular or circular.

Under the condition that the LED unit module is provided with at least two LED chips, the light emitting areas of the LED unit module are formed by the combination of the light emitting areas of the chips in the LED unit module, and the LED unit module is arranged in such a way to accord with the place with higher illumination intensity. Moreover, the light emitting areas of the LED chips are concentrated together, so that uniform light spots are favorably formed, and the phenomenon that the light rays emitted by the LED unit module are in the dark lines of the light spots formed on the focal plane of the focusing lens due to the fact that the LED chips and the LED chips have large gaps is avoided. Moreover, the light-emitting area and the non-light-emitting area in the LED unit module can be distinguished, so that the non-light-emitting area has adverse effect on the light emitting effect of the light-emitting area.

Preferably, the LED unit module includes two LED chips, each of which has a light emitting area in a substantially semicircular shape; or, the LED unit module comprises four LED chips, and the shape of the light emitting area of each LED chip is substantially in a fan shape with a central angle of 90 degrees.

Preferably, the area of the light emitting area of the LED chip occupies at least 70% of the area of the light emitting surface of the LED chip. In this scheme, the proportion that the area of the luminous region of LED chip accounts for the area of LED chip light emitting area is higher, and the wafer utilization ratio of LED chip is higher, and the parameter setting of this scheme can obtain higher wafer utilization ratio of LED chip to improve LED chip's luminous efficacy.

Preferably, the light emitting area of the LED unit module is located in the central area of the LED unit module, and the non-light emitting areas of the LED chips are uniformly distributed on the periphery of the light emitting area of the LED unit module. This scheme so sets up, can concentrate LED chip's light emitting area. When the LED unit module has a plurality of LED chips, the LED chips in the LED unit module are concentrated together, so that light rays of a light emitting area of the LED unit module can be more concentrated.

Preferably, the LED array is disposed on the ceramic substrate, and the ceramic substrate is provided with a first electrode; the LED unit module is provided with a second electrode, the second electrode is distributed in a non-luminous area of the LED chip, and the first electrode is electrically connected with the second electrode. This scheme so sets up, can avoid the second electrode produces the influence to the light-emitting effect of luminous region.

Preferably, the first electrodes are provided with two electrodes which are symmetrically distributed on two sides of the LED unit module and have a certain distance with the LED unit module; the LED unit module is approximately square, and the second electrodes are distributed in the areas of four corners of the LED unit module; the second electrodes positioned on the same side of the LED unit module are connected to the same first electrode. This scheme so sets up, can make the drive current who passes through the LED chip distribute in whole LED chip uniformly to reduce the pressure drop of electric current through the LED chip, thereby improved the photoelectric efficiency of LED chip and reduced the junction temperature of LED chip, meanwhile, improved the luminous efficacy, life-span and the stability of LED chip in addition, still improved the wafer utilization ratio that whole LED chip was made even, thereby reduction in production cost. The temperature is the temperature of the PN junction.

Preferably, one first electrode is arranged on one side of the LED unit module, and a certain distance is reserved between the first electrode and the LED unit module; the LED unit module is substantially square, corresponds to the first electrode, and the second electrodes are distributed in the non-light-emitting area on the same side of the LED unit module and are connected to the first electrode.

Preferably, the LED unit modules with one LED chip are disposed in the center of the LED array and/or symmetrically and uniformly distributed in the edge area of the LED array, and every two adjacent three LED unit modules with at least two LED chips are arranged in an equilateral triangle. In the scheme, two adjacent three LED unit modules provided with at least two LED chips are in an equilateral triangle, so that the arrangement between the collimating lenses in the corresponding collimating lens array is more compact, the optical invariance is reduced, and the optical illumination and the luminous density of the LED array are improved.

Preferably, the collimating lens comprises a first collimating lens and a second collimating lens which are sequentially arranged in the light emitting direction of the LED array, the first collimating lens and the second collimating lens are respectively in one-to-one correspondence with the LED unit modules, and light rays emitted by the LED unit modules sequentially pass through the first collimating lens and the second collimating lens to be emitted in a collimating mode.

Compared with the prior art, the invention has the beneficial effects that: the LED array, the collimating lens array and the condensing lens are arranged, wherein the light emitting area of the LED unit module is set to be substantially circular, and under the condition that opposite compound eye lenses are not adopted for carrying out light uniformization on the LED unit module, substantially circular and uniform light spots are formed on a focal plane, so that the cost is greatly reduced, and the light spots with better light emitting effect are obtained; the LED chip and the LED unit module are optimized, so that the photoelectric efficiency, the luminous efficiency, the service life and the stability of the LED chip and the wafer utilization rate of the LED chip are improved, and the junction temperature and the production cost of the LED chip are reduced.

Drawings

Fig. 1 is a structural view of a related art light emitting device.

Fig. 2 is a structural view of a conventional opposed fly-eye lens.

Fig. 3 is a diagram of the effect of simulated light spots in the prior art.

Fig. 4 is a structural view of a light emitting device of the present invention.

Fig. 5 is a structural diagram of the LED light source module 100 provided with one LED chip.

Fig. 6 is a structural diagram of the LED light source module 100 having two LED chips.

Fig. 7 is a structural diagram of the LED light source module 100 having four LED chips.

Fig. 8 is a schematic view illustrating an arrangement of the LED light source module 100 and the first electrode 121.

Fig. 9 is a second schematic view of the arrangement of the LED light source module 100 and the first electrode 121.

Fig. 10 is a third schematic view illustrating an arrangement of the LED light source module 100 and the first electrode 121.

FIG. 11 is an LED array layout of the present invention.

Fig. 12 is a diagram of the simulated light spot effect of the invention.

Reference numerals: the LED unit module 100, the non-light-emitting region 111, the light-emitting region 112, the ceramic substrate 120, the gold wire 122, the first electrode 121, the first collimating lens 201, the second collimating lens 202, the condensing lens 400, and the focal plane 500.

Detailed Description

The drawings are only for purposes of illustration and are not to be construed as limiting the invention. For a better understanding of the following embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

Example 1

As shown in fig. 4, the present embodiment provides a light emitting device including an LED array, a collimating lens array, and a condensing lens 400.

To facilitate understanding of the light emitting device provided in this embodiment 1, the following first describes its application. The LED array is arranged on the ceramic substrate 120, the ceramic substrate 120 is provided with a first electrode 121, a second electrode is arranged in the LED array, and the first electrode 121 and the second electrode are electrically connected to realize the electrification of the LED array. After the LED array is powered on, the LED array emits light, and the light emitted by the LED array is collimated by the collimating lens array, then enters the condensing lens 400, and is focused by the condensing lens 400 onto the preset focal plane 500, so as to form a substantially circular and uniform light spot.

As shown in fig. 5, 6, and 7, the LED array includes a plurality of LED unit modules 100, each LED unit module 100 includes at least one LED chip, and a light emitting area of the LED unit module 100 is substantially circular. The substantially circular shape means that the light emitting area of the LED unit module 100 is circular or approximately circular.

In particular, the LED chip is substantially rectangular, but is not limited to being rectangular. The LED chip is provided with a light-emitting surface, the light-emitting surface comprises non-light-emitting areas 111 and light-emitting areas 112, and the non-light-emitting areas 111 are distributed on the periphery of the light-emitting areas 112. In order to make the light of the LED unit module 100 more concentrated, the light emitting area of the LED unit module 100 is located in the central area of the LED unit module 100, and the non-light emitting areas of the LED chips are uniformly distributed on the periphery of the light emitting area 112 of the LED chips. Specifically, the area of the LED chip light emitting area 112 occupies at least 70% of the area of the LED chip light emitting surface.

Specifically, the light emitting region 112 of the LED chip is provided with a PN junction, which is a basic principle of light emission of the LED chip. In detail, the LED chip is a light emitting diode, and the core part of the light emitting diode is a wafer composed of a P-type semiconductor and an N-type semiconductor, and there is a transition layer between the P-type semiconductor and the N-type semiconductor, which is called a P-N junction. In the PN junction of some semiconductor materials, the injection of minority carriers and majority carriers when they are recombined releases excess energy in the form of light, thereby directly converting electrical energy into light energy.

As shown in fig. 5, when the LED unit module 100 has only one LED chip, a light emitting area of the LED chip is substantially circular. That is, the light emitting region 112 of the LED chip is the light emitting region of the LED unit module 100, and the light emitting region 112 of the LED chip is disposed in the central region of the light emitting region of the LED chip, and meanwhile, the non-light emitting region 111 of the LED chip is distributed at the periphery of the LED unit module 100.

As shown in fig. 6 and 7, when the LED unit module 100 includes more than two LED chips, the light emitting regions 112 of each LED chip are combined to form the light emitting region of the LED unit module 100, and the light emitting region of the LED unit module 100 formed by combining the light emitting regions 112 of the LED chips is substantially circular and located in the central region of the LED unit module 100, and the non-light emitting regions 111 of the LED chips are uniformly distributed on the periphery of the light emitting region of the LED unit module 100. In this case, the light emitting area of the LED unit module 100 being substantially circular can be understood as: the light emitting region of the LED unit module 100 is formed by splicing and combining the light emitting regions 112 of two or more LED chips to form a light emitting region with a circular or near-circular outline. In detail, the LED chips in the LED unit module 100 are closely arranged and tightly packed with each other.

In one embodiment, as shown in fig. 6, the LED unit module 100 is provided with two LED chips, and the light emitting region 112 of each LED chip is substantially semicircular. In detail, a partial edge of the light emitting region 112 of each LED chip may be flush with a partial edge of the light emitting surface of the LED chip, and thus, the light emitting region 112 of the LED chip may maximally occupy the area of the light emitting surface of the LED chip.

In one embodiment, as shown in fig. 7, the LED unit module 100 is provided with four LED chips, and the light emitting region 112 of each LED chip is substantially shaped like a sector with a central angle of 90 degrees. In detail, as described above, a partial edge of the light emitting region 112 of each LED chip may be flush with a partial edge of the light emitting surface of the LED chip, and thus, the light emitting region 112 of the LED chip may maximally occupy the area of the light emitting surface of the LED chip.

Specifically, as shown in fig. 8, 9, and 10, in order to energize the LED array, a second electrode is provided in the non-light emitting region 112 of the LED chip. The second electrode may be connected to the first electrode 121 disposed on the ceramic substrate 120 by a gold wire 122. The first electrode 121 is disposed corresponding to one LED unit module 100, and the number of the first electrodes 121 corresponding to one LED unit module 100 may be one or two, but is not limited to one or two first electrodes 121.

In one particular embodiment, the LED chip is square, as shown in fig. 8. One first electrode 121 is disposed at one side of the LED unit module 100, and has a certain distance from the LED unit module 100. Corresponding to the position of the first electrode 121, a plurality of first electrodes 121 are distributed on the non-light emitting region 111 on the same side of the LED unit module 100, and three first electrodes 121 may be provided. In detail, the first electrodes 121 are connected to the same first electrode 121 through gold wires 122, respectively.

In a specific embodiment, as shown in fig. 9, the LED unit module 100 is provided with a square LED chip. The two first electrodes 121 are symmetrically distributed on two sides of the LED unit module 100, and have a certain distance from the LED unit module 100. In order to enable the driving current of the LED chip to be uniformly distributed on the entire chip, which is beneficial to improving the efficiency or improving the lifetime and stability of the chip, the regions where the four corners of the LED unit module 100 are located are the non-light-emitting regions 111, and the second electrodes are distributed in the regions where the four corners of the LED unit module 100 are located. In detail, the second electrodes located on the same side of the LED unit module 100 are connected to the same first electrode 121.

In one specific embodiment, as shown in fig. 10, the LED unit module 100 is substantially the same as that shown in fig. 9 except that at least two LED chips are provided.

In a specific embodiment, the application of the LED array is that the LED array comprises a plurality of LED unit modules 100, each LED unit module 100 has one LED chip, and the light emitting area 112 of the LED chip is circular.

In a specific embodiment, the application of the LED array is that the LED array comprises a plurality of LED unit modules 100, each LED unit module 100 comprises at least two LED chips, the light emitting areas 112 of each LED chip are combined to form the light emitting area of the LED unit module 100, and the light emitting area of the LED unit module 100 is substantially circular.

In a specific embodiment, the application of the LED array is that the LED array is substantially in a hexagonal arrangement. The LED array comprises a plurality of LED unit modules 100, wherein part of the LED unit modules 100 are provided with one LED chip, and part of the LED unit modules 100 comprise at least two LED chips. The LED unit module 100 having one LED chip may be mixed with the LED unit module having at least two LED chips, specifically, as shown in fig. 11, the LED unit module 100 provided with one LED chip is provided in plurality, and the LED unit module 100 provided with at least two LED chips is provided in plurality, specifically arranged as: the LED unit modules 100 with one LED chip are disposed in the center of the LED array and/or symmetrically and uniformly distributed in the edge area of the LED array, and the center of the LED array is the geometric center of the LED array, so that there may be one or more unit modules 100 with one LED chip disposed in the center of the LED array. In the LED array, two adjacent LED unit modules 100 having at least two LED chips are arranged in an equilateral triangle to improve the light emitting density of the LED array, and in detail, two adjacent LED unit modules 100 having two LED chips are arranged in an equilateral triangle.

The collimating lens array includes a plurality of collimating lenses, and each collimating lens is aligned with one LED unit module 100 and is used for collimating the light emitted from the LED unit module 100. Specifically, the collimating lens includes a first collimating lens 201 and a second collimating lens 202 sequentially disposed in the light emitting direction of the LED array, the first collimating lens 201 and the second collimating lens 202 respectively correspond to the LED unit modules 100 one to one, and the light emitted by the LED unit modules 100 sequentially passes through the first collimating lens 201 and the second collimating lens 202 to be collimated and emitted. It can also be said that the first collimating lenses 201 are arranged in an array and correspond to the LED unit modules 100 in the LED array one to one, and the second collimating lenses 202 are also arranged in an array and correspond to the LED unit modules 100 in the LED array one to one. In detail, the second collimating lenses 202 are seamlessly spliced.

The condenser lens 400 is a lens with a positive focal length, and is used for focusing the light collimated by the collimating lens array on a predetermined focal plane 500, as shown in fig. 10, so as to form a substantially circular and uniform light spot. Specifically, the plurality of nearly parallel light beams are focused on the focal plane 500 of the condenser lens 400 through the condenser lens 400, and images of the LED unit modules 100 are formed on the focal plane 500 and overlapped together to form a substantially circular and uniform light spot.

It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific embodiments of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention claims should be included in the protection scope of the present invention claims.

Claims

1. A light-emitting device, comprising

The LED array comprises a plurality of LED unit modules (100), each LED unit module (100) comprises at least one LED chip, and the light emitting area of each LED unit module (100) is substantially circular;

the collimating lens array comprises a plurality of collimating lenses, and each collimating lens is aligned to one LED unit module (100) and is used for collimating the light rays emitted by the LED unit modules (100);

and the condenser lens (400) is used for focusing the light rays collimated by the collimating lens array on a preset focal plane (500) so as to form a substantially circular and uniform light spot.

2. The light-emitting device according to claim 1, wherein the light-emitting surface of the LED chip comprises non-light-emitting areas (111) and light-emitting areas (112), the non-light-emitting areas (111) are distributed at the periphery of the light-emitting areas (112) of the LED chip;

the LED unit module (100) comprises an LED chip, and a light emitting area (112) of the LED chip is substantially circular;

or the LED unit module (100) comprises more than two LED chips, and the light emitting areas (112) of the LED chips are combined to form the light emitting areas of the LED unit module (100).

3. A light emitting device according to claim 2, wherein the LED unit module (100) comprises two LED chips, each having a light emitting area in a substantially semicircular shape;

or, the LED unit module (100) comprises four LED chips, and the shape of a light emitting area of each LED chip is substantially in a fan shape with a central angle of 90 degrees.

4. A light emitting device according to any one of claims 2 or 3, wherein the area of the LED chip light emitting area (112) is at least 70% of the area of the LED chip light emitting surface.

5. The light-emitting device according to claim 1, wherein the light-emitting area of the LED unit module (100) is located in the central area of the LED unit module (100), and the non-light-emitting areas (111) of the LED chips are uniformly distributed on the periphery of the light-emitting area of the LED unit module (100).

6. A light emitting device according to claim 5, wherein said LED array is arranged on said ceramic substrate (120), said ceramic substrate (120) being provided with a first electrode (121); the LED unit module is provided with a second electrode, the second electrode is distributed in a non-light-emitting area of the LED chip, and the first electrode (121) is electrically connected to the second electrode.

7. The light-emitting device according to claim 6, wherein two first electrodes (121) are symmetrically disposed on two sides of the LED unit module (100) and spaced from the LED unit module; the LED unit module (100) is approximately square, and the second electrodes are distributed in the areas of four corners of the LED unit module (100); the second electrodes on the same side of the LED unit module (100) are connected to the same first electrode (121).

8. A light emitting device according to claim 6, wherein one first electrode (121) is disposed on one side of the LED unit module (100) and is spaced from the LED unit module (100); the LED unit module (100) is substantially square, corresponds to the first electrode (121), and the second electrodes are distributed in the non-light-emitting area (111) on the same side of the LED unit module (100) and are connected to the first electrode (121).

9. The lighting device according to claim 1, wherein the LED unit modules (100) having one LED chip are disposed at the center of the LED array and/or symmetrically and uniformly distributed at the edge area of the LED array, and two adjacent LED unit modules (100) having at least two LED chips are arranged in an equilateral triangle.

10. The lighting device according to claim 1, wherein the collimating lens comprises a first collimating lens (201) and a second collimating lens (202) sequentially disposed in the light emitting direction of the LED array, the first collimating lens (201) and the second collimating lens (202) respectively correspond to the LED unit modules (100) one by one, and the light emitted from the LED unit modules (100) is collimated and emitted sequentially through the first collimating lens (201) and the second collimating lens (202).