A full-band optical property measurement system

Abstract

This invention discloses a full-band optical characteristic measurement system. It includes: a transmitting device comprising a laser emitting unit and a visible light emitting unit; a collimating optical device comprising an integrator and a first collimating lens arranged sequentially along the light propagation direction; and a detection device comprising a detector, a first lens, and multiple attenuator wheels. The detector is suitable for the visible light band and a laser band within a preset range. The first lens is positioned at the front end of the detector. Each attenuator wheel is coaxially positioned at the front end of the first lens. Each attenuator wheel has multiple circular locking positions evenly distributed along its circumference, each locking position being used to fix attenuators with different attenuation ratios. During measurement, a target attenuator that meets the requirements is determined based on the intensity of the probe beam, so that the axis of the target attenuator coincides with the axis of the first lens. The optical characteristics of the object under test are then measured using the first lens and the detector. This application can measure full-band optical characteristics with high measurement efficiency.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and in particular to a full-band optical characteristic measurement system. Background Technology

[0002] Optical measurement is a non-contact measurement technique that uses some basic properties of light, such as reflection, interference, and scattering, to perform relevant precise measurements. Its main principle is to use the physical properties of light to detect the object being measured. Different measurement methods utilize different properties.

[0003] Currently, laboratory measurements of objects typically fall into two categories: visible light testing and laser testing. Because these two light sources operate on different principles, frequent switching between the detection and emission systems is necessary when using different light sources, impacting testing efficiency. In other words, a measurement system that can satisfy all optical characteristics across the entire wavelength range is not yet available.

[0004] Therefore, there is an urgent need for a full-band optical property measurement system to solve the above problems. Summary of the Invention

[0005] This invention provides a full-band optical characteristic measurement system that can meet the requirements of full-band optical characteristic measurement and improve measurement efficiency. The technical solution is as follows:

[0006] This invention provides a full-band optical characteristic measurement system, comprising:

[0007] The emitting device includes a laser emitting unit and a visible light emitting unit, wherein the laser emitting unit is used to emit laser light and the visible light emitting unit is used to emit visible light;

[0008] A collimating optical device includes an integrator and a first collimating lens arranged sequentially along the direction of light propagation; the integrator is used to adjust incident visible light or laser light into a uniform beam, and the first collimating lens is used to reflect the uniform beam onto the object being measured.

[0009] The detection device includes a detector, a first lens, and multiple attenuator rollers; the detector is suitable for the visible light band and a laser band within a preset range; the first lens is disposed at the front end of the detector; each attenuator roller is coaxially disposed at the front end of the first lens; each attenuator roller is provided with multiple circular slots evenly distributed along its circumference, and each slot is used to fix attenuators with different attenuation factors.

[0010] During measurement, the laser emitting unit or the visible light emitting unit is turned on according to the measurement requirements to emit the corresponding light beam; based on the intensity of the light beam, the target attenuator that meets the requirements is determined, and the position of each attenuator wheel is adjusted so that the axis of the target attenuator coincides with the axis of the first lens, and the optical characteristics of the object under test are measured using the first lens and the detector.

[0011] This invention provides a full-band optical characteristic measurement system. First, by setting up a collimating optical device, visible light or laser light can be reflected onto the object under test, making the measurement system applicable to various light sources and wavelengths. By setting multiple attenuator wheels and multiple attenuators with different attenuation ratios on each attenuator wheel, the target attenuator that meets the requirements can be determined according to the type and intensity of the light source. Finally, by adjusting the position of each attenuator wheel, the axis of the target attenuator is aligned with the axis of the first lens, thereby using the first lens and detector to measure the optical characteristics of the object under test, realizing the measurement of optical characteristics of various light sources and wavelengths. Therefore, the measurement system provided by this application is not only applicable to visible light but also to laser light, satisfying full-band measurement; furthermore, it eliminates the need to change the transmitting and detecting devices according to the type of light source, resulting in high measurement efficiency. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of a full-band optical characteristic measurement system provided in an embodiment of the present invention;

[0014] Figure 2 This is a schematic diagram of the combined transmitting device and collimating optical device provided in an embodiment of the present invention;

[0015] Figure 3 This is a schematic diagram of a laser emitting unit provided in an embodiment of the present invention;

[0016] Figure 4 This is a schematic diagram of a detection device provided in an embodiment of the present invention;

[0017] Figure 5 This is a schematic diagram of a background simulation device provided in an embodiment of the present invention.

[0018] Figure label:

[0019] 1- Launching device;

[0020] 11-Laser emitting unit;

[0021] 111-Laser; 112-Second collimating mirror; 113-Fiber optic coupler; 114-Fiber optic patch cord; 115-Relay mirror; 116-Dichroic beam combiner; 117-Third collimating mirror; 118-Total reflection mirror; 119-Laser reflector;

[0022] 12 - Visible light emitting unit;

[0023] 2-Collimating optical device;

[0024] 21-Optical path reflector; 22-Integrator; 23-First collimating lens;

[0025] 3-Detection device;

[0026] 31-Detector; 32-First lens; 33-Attenuator wheel; 34-Attenuator; 35-Luminometer; 36-Second lens; 37-Box; 38-Light shield;

[0027] 4- Background simulation device;

[0028] 41-Background reflective surface; 42-Moving module; 43-Follow-up module; 44-Black background plate; 45-Cooling pipe;

[0029] 5-Control device; 6-Object being measured. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] The following describes the specific implementation of the above concept.

[0032] Please refer to Figures 1-4 This invention provides a full-band optical characteristic measurement system, comprising:

[0033] The emitting device 1 includes a laser emitting unit 11 and a visible light emitting unit 12. The laser emitting unit 11 is used to emit laser light, and the visible light emitting unit 12 is used to emit visible light.

[0034] The collimating optical device 2 includes an integrator 22 and a first collimating lens 23 arranged sequentially along the direction of light propagation; the integrator 22 is used to adjust the incident visible light or laser into a uniform beam, and the first collimating lens 23 is used to reflect the uniform beam onto the object 6 being measured.

[0035] The detection device 3 includes a detector 31, a first lens 32, and multiple attenuator rollers 33. The detector 31 is suitable for the visible light band and the laser band within a preset range. The first lens 32 is disposed at the front end of the detector 31. Each attenuator roller 33 is coaxially disposed at the front end of the first lens 32. Each attenuator roller 33 is provided with multiple circular slots evenly distributed along its circumference, and each slot is used to fix attenuators 34 with different attenuation factors.

[0036] During measurement, the laser emitting unit 11 or the visible light emitting unit 12 is turned on according to the measurement requirements to emit the corresponding light beam; according to the intensity of the light beam, the target attenuator 34 that meets the requirements is determined, and the position of each attenuator wheel 33 is adjusted so that the axis of the target attenuator 34 coincides with the axis of the first lens 32, and the optical characteristics of the object under test 6 are measured using the first lens 32 and the detector 31.

[0037] In this embodiment, firstly, by setting a collimating optical device 2, visible light or laser light can be reflected onto the object under test 6, making the measurement system applicable to various light sources and wavelengths. By setting multiple attenuator wheels 33 and multiple attenuators 34 with different attenuation ratios on each attenuator wheel 33, the target attenuator 34 that meets the requirements can be determined according to the type and intensity of the light source. Finally, by adjusting the position of each attenuator wheel 33, the axis of the target attenuator 34 is made to coincide with the axis of the first lens 32, thereby using the first lens 32 and the detector 31 to measure the optical characteristics of the object under test 6, realizing the measurement of optical characteristics of various light sources and wavelengths. It can be seen that the measurement system provided by this application is not only applicable to visible light, but also to laser light, satisfying full-band measurement; in addition, there is no need to change the emitting device 1 and the detector 3 according to the type of light source, resulting in high measurement efficiency.

[0038] It should be noted that this application does not impose specific limitations on the specific form of the visible light emitting unit 12, as long as it can emit visible light that meets the user's requirements.

[0039] It should also be noted that when light intensity attenuation is not required, the attenuator 34 does not need to be installed on the attenuator wheel 33. In this case, the axis of the slot without the attenuator 34 can be aligned with the axis of the first lens 32. Furthermore, when multiple attenuation is required, an attenuator 34 can be selected on each of the multiple attenuator wheels 33, and the axes of all the attenuators 34 can be aligned with the axis of the first lens 32 simultaneously to achieve the effect of multiple attenuation. Additionally, a laser wavelength of 1000nm to 1600nm can be used; of course, other wavelengths are also possible, and this application does not impose specific limitations.

[0040] like Figure 3 As shown, in some embodiments, the laser emitting unit 11 includes at least one laser 111 and a beam-shaping and expanding optical module;

[0041] Each laser 111 is used to emit lasers of different powers, and the shaping and beam expanding optical module is used to adjust the laser emitted by each laser 111 into a laser beam with a preset divergence angle.

[0042] In this embodiment, measuring the reflection characteristics of the object under test 6 does not place high requirements on the mode of the laser 111. Therefore, one or two high-power, multimode, continuous semiconductor lasers 111 are selected. The operating envelopes of each laser 111 are 1.06±0.03µm and 1.55±0.03µm, respectively. Of course, other types of lasers 111 can also be used, and this application does not make specific limitations.

[0043] It should be noted that the components of the shaping and beam-expanding optical module will differ depending on the number of lasers 111 used.

[0044] In some embodiments, when there is only one laser 111, the shaping and beam expanding optical module includes a second collimating mirror 112, a fiber optic coupler 113, a fiber optic jumper 114, a repeater mirror 115, and a laser reflector 119 arranged sequentially along the laser propagation direction.

[0045] The second collimating mirror 112 is used to collimate the elliptical spot output by the laser 111 into a parallel circular spot; the fiber optic coupler 113 is used to couple the incident parallel beam; the fiber optic jumper 114 is used to homogenize the incident laser; the repeater mirror 115 is used to adjust the divergence angle of the emitted laser so that the emitted laser beam meets the preset divergence angle; and the laser reflector 119 is used to introduce the laser beam into the collimating optical device 2.

[0046] In this embodiment, since the divergence angle of the laser emitted from the optical fiber usually does not meet the divergence angle requirements of actual experiments, a repeater 115 is needed to adjust the divergence angle of the emitted laser. The inventors discovered that the laser can cover the object under test 6 when the divergence angle is no greater than 13°. Therefore, a preset divergence angle of no greater than 13° is chosen. In addition, the core diameter of the optical fiber patch cord 114 is 0.6 mm, and the numerical aperture NA is 0.22. Of course, other sizes can also be used, and this application does not make specific limitations.

[0047] In some embodiments, when there are two lasers 111, the shaping and expanding optical module further includes a dichroic beam combiner 116, a third collimating mirror 117 and a total reflection mirror 118, with the dichroic beam combiner 116 disposed between the second collimating mirror 112 and the fiber optic coupler 113.

[0048] The third collimating mirror 117 is used to collimate the elliptical light spot output by another laser 111 into a parallel circular light spot, which is incident on the total reflection mirror 118. The total reflection mirror 118 is used to reflect all the incident laser light onto the dichroic beam combiner 116. The dichroic beam combiner 116 is used to reflect the laser light incident from the total reflection mirror 118 onto the fiber coupler 113 and transmit the laser light incident from the second collimating mirror 112 onto the fiber coupler 113.

[0049] In this embodiment, the second collimating lens 112 and the third collimating lens 117 collimate the elliptical beam output from the laser 111 into a parallel circular beam, ensuring that the interface of the two laser beams remains essentially consistent after beam combining, thus improving coupling into the optical fiber. The dichroic beam combiner 116 provides high reflectivity for one wavelength of laser light and high transmittance for another, facilitating low-loss beam combining of the two laser beams. The fiber optic patch cord 114 makes the emitted laser more uniform, effectively suppressing laser speckle. Laser speckle is formed by laser self-generated interference, creating granular patterns within the laser beam cross-section, severely affecting the uniformity of the emitted laser.

[0050] In some embodiments, the collimating optical device 2 further includes at least one optical path reflector 21; the optical path reflector 21 is disposed at the front end of the integrator 22;

[0051] The optical path reflector 21 is used to reflect the visible light emitted by the visible light emitting unit 12 or the laser light reflected by the laser reflector 119 to the integrator 22.

[0052] In this embodiment, since the visible light emitted by the visible light emitting unit 12 and the laser reflected by the laser reflector 119 need to meet a certain optical path with the integrator 22, the entire system occupies a large area. However, this application can achieve multiple reflections of the light beam by setting at least one optical path reflector 21, thereby meeting the optical path requirement while reducing the overall planar unfolded volume of the system.

[0053] In some embodiments, the collimating optical device 2 further includes a rotation module, on which a first collimating lens 23 is mounted. The rotation module is used to adjust the azimuth and elevation angles of the first collimating lens 23. By adjusting the azimuth and elevation angles of the first collimating lens 23, the light beam can be directed onto the object 6 being measured. Furthermore, the first collimating lens 23 is a large-aperture collimating lens.

[0054] like Figure 4 As shown, in some embodiments, the detection device 3 further includes a luminance meter 35 and a second lens 36 disposed at the front end of the luminance meter 35;

[0055] When measuring ambient brightness, the axis of the attenuator 34 that meets the requirements is adjusted to coincide with the axis of the second lens 36 so that the brightness of the environment can be measured using the luminance meter 35.

[0056] In this example, by setting the luminance meter 35, the on-site environment can be calibrated, and the impact of the environment on the measurement can be measured in real time.

[0057] In addition, in some embodiments, each attenuator wheel 33 is equipped with a motor, a driver, a motion controller and a position measuring device, thereby facilitating the electric drive of each attenuator wheel 33 and the accurate positioning of the attenuator 34.

[0058] In some embodiments, both the first lens 32 and the second lens 36 include focusing functionality and both comprise two-stage lens groups; wherein the first-stage lens group is a positive lens group and the second-stage lens group is a negative lens group. Furthermore, the effective optical aperture of the first-stage lens can be Φ125mm, and the focal length can be designed to be 95mm; the effective optical aperture of the second-stage lens group can be Φ50.8mm, and the focal length can be designed to be -50.8mm; the combination of the first-stage lens and the second-stage lens group provides a 30° field of view.

[0059] In this embodiment, each lens is achromatic and primarily responsible for receiving weak echo signals, including focusing functionality. The overall design resembles a Galilean telescope system. Furthermore, the use of a negative lens group in the second-stage lens group effectively compresses the size of the optical system, and the Galilean telescope system produces an upright image, making it easier for the human eye to observe through a display.

[0060] like Figure 4 As shown, in some embodiments, it also includes a housing 37 and two light shields 38;

[0061] The detector 31, the first lens 32, the luminance meter 35, the second lens 36, and each attenuation wheel 33 are all housed inside the housing 37. Two through holes are provided on the wall of the housing 37 near the attenuation wheel 33. The axis of one through hole coincides with the axis of the first lens 32, and the axis of the other through hole coincides with the axis of the second lens 36. Each light shield 38 is provided outside each through hole.

[0062] The inventors also discovered that, due to the varying size and detection angle of the object being measured 6, a large black background plate 44 was required, and the position of the black background was constantly adjusted according to the changes in the position of the object being measured 6 and the detection angle. This not only occupied laboratory space but also affected measurement efficiency.

[0063] To solve the above problems, the inventors proposed a background simulation device 4.

[0064] like Figure 5 As shown, the background simulation device 4 includes a background reflective surface 41, a moving module 42, a follow-up module 43, and a black background plate 44;

[0065] The detection device 3 is mounted on the moving module 42, and the background reflective surface 41 is mounted on the follower module 43. The moving module 42 and the follower module 43 are located on both sides of the object under test 6, and can rotate synchronously around the object under test 6. The black background plate 44 is suspended directly above the object under test 6.

[0066] When testing the infrared radiation characteristics of the object under test 6, the angle between the background reflective surface 41 and the horizontal plane is adjusted so that the black background plate 44 fills the field of view of the detection device 3, thus providing a black background for the object under test 6.

[0067] In this embodiment, suspending the black background plate 44 directly above the object 6 being measured saves laboratory space. By designing the background reflective surface 41 and adjusting its angle with the horizontal plane, the black background plate 44 can fill the field of view of the detection device 3, thus providing a black background for the object 6 being measured. Furthermore, by setting up the moving module 42 and the follow-up module 43, when the measurement angle needs to be adjusted, only the moving module 42 and the follow-up module 43 need to be rotated synchronously to quickly reach the required measurement angle without moving the black background plate 44. Therefore, this application not only saves space but also improves measurement efficiency.

[0068] It should be noted that the detection device 3 preferably forms a 180° angle with the background reflective surface 41 and is respectively set opposite to the object being measured 6, so as to facilitate the change of the angle of the detection device 3.

[0069] It should also be noted that the full band includes the visible light band, the laser band, and the infrared band. When using visible light and laser for optical testing, there is no need to cool the black background plate 44. However, when using the infrared band for optical testing, it is necessary to cool the black background plate 44 to create a temperature difference between it and the object being tested 6.

[0070] Therefore, in some embodiments, when using infrared bands for optical testing, it is also necessary to lay cooling pipes 45 on the top surface of the black background plate 44. Low-temperature liquid flows in the cooling pipes 45. The preset temperature is lower than the temperature of the object being tested, and the difference between the preset temperature and the temperature of the object being tested is not less than 5°C.

[0071] In this step, by controlling the flow rate of the refrigerant in the pipe, the temperature of the black background plate 44 can be controlled, creating a significant temperature difference between the black background plate 44 and the object being measured 6. This eliminates environmental influences during measurement, allowing the detection device 3 to obtain data with a uniform background and low noise, thus improving testing accuracy.

[0072] In some embodiments, the black background plate 44 is made of anodized black aluminum plate, and the cooling pipes 45 are arranged in a spiral on the top surface of the black background plate 44.

[0073] By laying spiral pipes above the aluminum plate, the temperature of the aluminum plate can be reduced rapidly, thus improving the heat exchange effect.

[0074] In some embodiments, the angle between the background reflective surface 41 and the horizontal plane is 30° to 60°, preferably 45°. Of course, users can also choose other angles, as long as the electromagnetic waves emitted by the black background plate 44 are reflected to the detection device 3.

[0075] In some embodiments, a control device 5 is also included for controlling the laser emitting unit 11, the visible light emitting unit 12, the detector 31, the first lens 32, each attenuator wheel 33, the luminance meter 35, the second lens 36, the movement module 42, and the follow-up module 43.

[0076] By setting up control device 5, the above-mentioned equipment can be electrically driven, thereby enabling rapid control.

[0077] It should be noted that, in this document, relational terms such as first, second, third, and fourth are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0078] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A full-band optical characteristic measurement system, characterized in that, include: The emitting device (1) includes a laser emitting unit (11) and a visible light emitting unit (12), wherein the laser emitting unit (11) is used to emit laser light and the visible light emitting unit (12) is used to emit visible light. The collimating optical device (2) includes an integrator (22) and a first collimating lens (23) arranged sequentially along the direction of light propagation; the integrator (22) is used to adjust the incident visible light or laser into a uniform beam, and the first collimating lens (23) is used to reflect the uniform beam onto the object under test (6). The detection device (3) includes a detector (31), a first lens (32), and multiple attenuator rollers (33); the detector (31) is suitable for the visible light band and the laser band within a preset range; the first lens (32) is disposed at the front end of the detector (31); each attenuator roller (33) is coaxially disposed at the front end of the first lens (32); each attenuator roller (33) is provided with multiple circular slots evenly distributed along its circumference, and each slot is used to fix attenuators (34) with different attenuation ratios; During measurement, the laser emitting unit (11) or the visible light emitting unit (12) is turned on according to the measurement requirements to emit the corresponding light beam; according to the intensity of the light beam, the target attenuator (34) that meets the requirements is determined, and the position of each attenuator wheel (33) is adjusted so that the axis of the target attenuator (34) coincides with the axis of the first lens (32), and the optical characteristics of the object under test (6) are measured using the first lens (32) and the detector (31).

2. The system according to claim 1, characterized in that, The laser emitting unit (11) includes at least one laser (111) and a beam-shaping and expanding optical module; Each of the lasers (111) is used to emit lasers of different powers, and the shaping and beam expanding optical module is used to adjust the laser emitted by each of the lasers (111) into a laser beam with a preset divergence angle.

3. The system according to claim 2, characterized in that, When the number of lasers (111) is one, the shaping and beam expanding optical module includes a second collimating mirror (112), an optical fiber coupler (113), an optical fiber jumper (114), a repeater mirror (115), and a laser reflector (119) arranged sequentially along the laser propagation direction. The second collimating lens (112) is used to collimate the elliptical spot output by the laser (111) into a parallel circular spot; the fiber optic coupler (113) is used to couple the incident parallel beam; the fiber optic jumper (114) is used to homogenize the incident laser; the repeater (115) is used to adjust the divergence angle of the emitted laser so that the emitted laser beam meets the preset divergence angle; the laser reflector (119) is used to introduce the laser beam into the collimating optical device (2).

4. The system according to claim 3, characterized in that, When there are two lasers (111), the shaping and expanding optical module further includes a dichroic beam combiner (116), a third collimating mirror (117), and a total reflection mirror (118). The dichroic beam combiner (116) is disposed between the second collimating mirror (112) and the fiber optic coupler (113). The third collimating mirror (117) is used to collimate the elliptical spot output by another laser (111) into a parallel circular spot, which is incident on the total reflection mirror (118); the total reflection mirror (118) is used to reflect all the incident laser onto the dichroic beam combiner (116); the dichroic beam combiner (116) is used to reflect the laser incident from the total reflection mirror (118) onto the fiber optic coupler (113), and transmit the laser incident from the second collimating mirror (112) onto the fiber optic coupler (113).

5. The system according to claim 1, characterized in that, The detection device (3) also includes a luminance meter (35) and a second lens (36) disposed at the front end of the luminance meter (35); When measuring ambient brightness, the axis of the attenuator (34) that meets the requirements is adjusted to coincide with the axis of the second lens (36) so that the brightness of the environment can be measured using the luminance meter (35).

6. The system according to claim 5, characterized in that, It also includes a background simulation device (4); the background simulation device (4) includes a background reflective surface (41), a moving module (42), a follow-up module (43) and a black background plate (44); The detection device (3) is mounted on the moving module (42), the background reflective surface (41) is mounted on the follower module (43), the moving module (42) and the follower module (43) are located on both sides of the object under test (6) and can rotate synchronously around the object under test (6); the black background plate (44) is suspended directly above the object under test (6); When the infrared radiation characteristics of the object under test (6) are tested, the angle between the background reflective surface (41) and the horizontal plane is adjusted so that the black background plate (44) fills the field of view of the detection device (3) to provide a black background for the object under test (6).

7. The system according to claim 6, characterized in that, The top surface of the black background plate (44) is covered with a cooling pipe (45), and a low-temperature liquid flows in the cooling pipe (45). The low-temperature liquid is used to reduce the temperature of the black background plate (44) to a preset temperature, which is lower than the temperature of the object being tested (6).

8. The system according to claim 7, characterized in that, The difference between the preset temperature and the temperature of the object being tested (6) is not less than 5°C.

9. The system according to claim 6, characterized in that, The black background plate (44) is made of anodized black aluminum plate.

10. The system according to claim 6, characterized in that, It also includes a control device (5) for controlling the laser emitting unit (11), the visible light emitting unit (12), the detector (31), the first lens (32), each of the attenuation wheel (33), the luminance meter (35), the second lens (36), the moving module (42) and the follow-up module (43).

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