Method and device for measuring optical characteristics of lens unit

Abstract

Provided are a measurement method and device capable of appropriately and accurately acquiring the dynamic optical characteristics of a lens unit during lens vibration.　The measurement method according to the present invention comprises: lens vibration steps S3, S4 that alternately repeat a search mode in which a prescribed lens is vibrated for a prescribed duration by vibrating a vibrator by sweeping a vibration frequency within a prescribed range, and a drive mode in which the prescribed lens is vibrated for a prescribed duration longer than the prescribed duration in the search mode by vibrating the vibrator at a substantially constant frequency within a prescribed range; and a measurement step S6 in which the optical characteristics of the lens unit are measured only when the lens unit is in the drive mode during the lens vibration steps.

Description

Method and apparatus for measuring optical characteristics of a lens unit

[0001] The present invention relates to a measurement method and a measurement device for measuring the optical characteristics of a lens unit that constitutes an on-board camera mounted on a vehicle such as an automobile.

[0002] Conventionally, automobiles have been equipped with on-board cameras to assist with parking and prevent collisions through image recognition, and attempts have also been made to apply such cameras to autonomous driving. In addition, a camera module such as an on-board camera generally includes a lens unit having a lens group formed by a plurality of lenses arranged along an optical axis, a lens barrel that houses and holds the lens group, and an aperture member disposed between at least one of the lenses in the lens group (see, for example, Patent Document 1).

[0003] Furthermore, such lens units may be attached to a mounting portion such as the front grille of a vehicle (automobile), with the lens closest to the object exposed to the outside. In such cases, foreign matter such as water droplets, muddy water, ice, snow, and frost easily adheres to the surface of the lens. If this happens, it is necessary to remove the foreign matter to ensure a clear field of view for observation using the lens unit.

[0004] In recent years, foreign matter adhering to the surface of a lens (or lens cover) has been removed by vibrating the lens (or lens cover) with a vibrating body (ultrasonic vibration). For example, in Patent Document 2, a vibrating device for removing foreign matter such as water droplets and dust adhering to a dome-shaped cover (lens cover) is provided in a camera equipped with a lens unit.

[0005] Specifically, as shown in Figure 6, such a vibration device 2 is provided in a camera that has an imaging unit 5 with a lens 6 and a built-in circuit including an imaging element on the top of the camera body 3, and is equipped with a dome-shaped transparent cover 11, a cylindrical vibrating body 12 to which the cover 11 is fixed, and a piezoelectric element 13 that is fixed to the vibrating body 12 and vibrates the cover 11 via the vibrating body 12. The vibrating body 12 has a cylindrical portion 14 having a first end 14a located on the cover 11 side and a second end 14b located on the opposite side from the cover 11, a cylindrical first connecting portion 15 connected to the first end 14a of the cylindrical portion 14 and consisting of a cylinder with an inner diameter larger than that of the cylindrical portion 14, a first ring-shaped portion 16 interposed between the first connecting portion 15 and the cover 11 and having an inner diameter smaller than that of the first connecting portion 15, a second connecting portion 17 connected to the second end 14b of the cylindrical portion 14 and consisting of a cylinder with an outer diameter smaller than that of the cylindrical portion 14, and a second ring-shaped portion 18 interposed between the second connecting portion 17 and the piezoelectric element 13 and having an outer diameter larger than that of the second connecting portion 17.

[0006] In such a vibration device 2, by driving the piezoelectric element 13 and ultrasonically vibrating the cover 11 via the vibrating body 12, the movement and atomization of droplets can be more effectively achieved, or foreign matter adhering to the surface of the cover 11 can be removed.

[0007] JP 2013-231993 A Japanese Patent No. 6977784 A

[0008] The optical characteristics of the various types of lens units described above are generally measured and evaluated while the lens is fixed and stationary. That is, even in a configuration that includes a vibration device that can ultrasonically vibrate the lens as described above, the optical characteristics are measured and evaluated while the lens is in a static state without being vibrated (static optical characteristics are measured and evaluated).

[0009] However, in the presence of a camera equipped with the aforementioned vibration device that can remove foreign matter from the lens surface using ultrasonic vibration, there is also a need to measure and evaluate the optical characteristics of the lens unit (camera) while the lens is vibrating (the need to measure and evaluate dynamic optical characteristics).

[0010] When measuring dynamic optical characteristics in a camera equipped with a vibration device, a major issue is whether appropriate and accurate measurement results can be obtained. This will be explained below.

[0011] In order to effectively remove foreign matter from the lens surface in a camera equipped with a vibration device, it is desirable to vibrate the vibrating body (and therefore the lens) at the natural frequency of the foreign matter to resonate (amplify vibration) the foreign matter. Therefore, a search mode is used in which an AC output signal whose frequency is swept over a predetermined range is applied to a piezoelectric element (piezoelectric vibrator) to identify the natural frequency of the foreign matter (identify the type of foreign matter) from the measurement results of the frequency and current value at that time, and a drive mode is used in which an AC output signal whose frequency is swept around the natural frequency (resonance frequency) identified in the search mode is continuously applied to the piezoelectric element to continuously resonate (amplify vibration) the foreign matter (by continuing to vibrate at the resonant frequency) to effectively and efficiently remove the foreign matter from the lens surface (clean the foreign matter) by alternately repeating these modes. This allows foreign matter to be constantly and effectively removed (cleaned) in accordance with constantly changing conditions (for example, conditions in which the resonant frequency fluctuates due to changes in the foreign matter adhering thereto or temperature changes).

[0012] However, in the case of an ultrasonic cleaning method that alternates between these two modes, frequency drift may occur when vibrating the lens to measure its optical properties, or the mode may switch during the measurement of the optical properties, making it impossible to obtain appropriate and accurate measurement results.

[0013] The present invention has been made in view of the above circumstances, and has as its object to provide a measurement method and a measurement device that can appropriately and accurately obtain the dynamic optical characteristics of a lens unit during lens vibration.

[0014] In order to solve the above-mentioned problems, the present invention provides a measurement method for measuring optical characteristics of a lens unit including a predetermined lens while vibrating the predetermined lens via a vibrating body, the method comprising: a lens vibrating step that alternates between a search mode in which a vibration frequency is swept within a predetermined range to vibrate the vibrating body, thereby vibrating the predetermined lens for a predetermined duration (e.g., 0.5 seconds), and a drive mode in which the vibrating body is vibrated at a substantially constant frequency within the predetermined range, thereby vibrating the predetermined lens for a predetermined duration (e.g., 3 seconds) longer than the predetermined duration in the search mode; and a measurement step that, during the lens vibrating step, measures the optical characteristics of the lens unit using a predetermined measuring device only when the lens is in the drive mode.

[0015] According to the above-described configuration of the present invention, even in an irregular vibration form of the lens in which two vibration modes are alternately repeated, the optical characteristics of the lens unit are measured only in the drive mode in which the lens is in a stable vibration operating state in which the lens vibrates at a substantially constant frequency, making it possible to appropriately and accurately obtain the dynamic optical characteristics of the lens unit during lens vibration. Furthermore, because the optical characteristics are measured in the drive mode, which has a longer duration than the search mode, it is easy to ensure the time required to measure the optical characteristics using a measuring instrument.

[0016] Furthermore, such measurement of optical properties may be performed during an inspection process before shipment of the lens unit or a finished optical device (such as a camera) that includes the lens unit, or may be performed after the lens unit has been mounted, i.e., after an optical device such as a camera that includes a lens unit that includes a vibrating body that vibrates the lens has been installed in a predetermined installation location, while the lens is vibrating (for example, during an ultrasonic vibration cleaning process in which the lens is vibrated by a vibrating body to remove foreign matter adhering to the lens).

[0017] For example, when measuring optical characteristics during an inspection simulating the ultrasonic vibration cleaning process, the vibrating body (and therefore the lens) may be vibrated at the natural frequency of a specific foreign object in the drive mode. If multiple types of foreign objects are anticipated, the vibrating body (and therefore the lens) may be vibrated at multiple different natural frequencies corresponding to the foreign objects to obtain individual measurement results. Furthermore, when measuring optical characteristics during an actual ultrasonic vibration cleaning process, the vibrating body may be vibrated by sweeping the vibration frequency within a predetermined range in the search mode, and the natural frequency of the foreign object (the type of foreign object) may be identified from the measurement results of the frequency and current value at that time. Then, in the drive mode, the vibrating body may be vibrated at a substantially constant natural frequency (resonance frequency) identified in the search mode, causing the foreign object to continuously resonate (amplify vibration) (continue to vibrate at the resonant frequency).

[0018] In the above configuration, it is preferable that the duration of the drive mode is equal to or longer than the time required to measure the optical characteristics using a measuring device, and that the measurement step completes a predetermined measurement sequence of the optical characteristics within a single drive mode. This facilitates meaningful measurements and enables the optical characteristics to be measured simply, efficiently, and in a short time. In this case, the duration of the drive mode may be set based on the time required for measurement using the measuring device.

[0019] In the above configuration, the measurement step may be divided into a plurality of drive modes and measure the optical characteristics stepwise to complete the predetermined measurement sequence of the optical characteristics, thereby avoiding the duration of the drive modes being constrained by the measurement time of the optical characteristics (and vice versa), and also avoiding the type of measurement device that can be used being limited by the duration of the drive modes (and vice versa).

[0020] In the above configuration, it is also preferable that, in at least a plurality of drive modes involved in the measurement of optical characteristics, a trigger signal be output from the drive circuit that vibrates the vibrating body to the measuring instrument, and the measuring instrument measure the optical characteristics of the lens unit based on this trigger signal. This facilitates meaningful measurements and enables simple and efficient control of mode-dependent optical measurements.

[0021] In the above configuration, the measurement of optical characteristics is performed by obtaining a measurement value for any predetermined measurement item using a predetermined type of measuring instrument, and may be related to, for example, MTF (Modulation Transfer Function). Examples of measurement items include optical performance such as focal length, angle of view, image height characteristics, and peripheral illumination ratio, and imaging performance such as MTF and CTF. Examples of measurement methods include placing a test sample on a measuring instrument or measuring jig and performing measurement while the sample remains motionless during ultrasonic vibration.

[0022] The present invention also provides a measuring device for carrying out the measuring method.

[0023] According to the measuring method and measuring device of the present invention, the dynamic optical characteristics of a lens unit during lens vibration can be obtained appropriately and accurately.

[0024] 1 is a schematic cross-sectional view of a camera module as an example of an optical device whose optical characteristics are measured by a measurement device that performs a measurement method according to an embodiment of the present invention. FIG. 2 is a perspective view of the camera module of FIG. 1. FIG. 3 is a schematic block diagram of a measurement device that performs a measurement method according to an embodiment of the present invention. FIG. 4 is a timing chart showing frequency changes in a search mode and a drive mode. FIG. 5 is a flowchart of an example of steps of a measurement method according to an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of a lens unit equipped with a conventional vibrating body.

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present embodiments contribute to the achievement of "9. Industry, innovation and infrastructure" of the Sustainable Development Goals (SDGs) advocated by the United Nations, which states, "9.1 Develop quality, reliable, sustainable and resilient infrastructure, including regional and transborder infrastructure, to support economic development and human well-being, with a focus on affordable and equitable access for all."

[0026] Fig. 1 is a schematic cross-sectional view of a camera module equipped with a lens unit as an example of an optical device whose optical characteristics are measured by a measurement device that performs a measurement method according to an embodiment of the present invention, and Fig. 2 is a perspective view of this camera module. Note that the lens unit described below is particularly for a camera module such as an in-vehicle camera, and is installed, for example, fixed to the exterior surface of the automobile, with wiring drawn into the automobile and connected to a display or other device.

[0027] 1 and 2, the camera module 300 of this embodiment includes a lens unit 20. The lens unit 20 includes a cylindrical lens barrel 22 and a rectangular cylindrical first housing (housing) 23 in which the lens barrel 22 is provided.

[0028] The image-side (lower side in FIG. 1 ) ends of the lens barrel 22 and the first housing 23 are supported by a rectangular cylindrical second housing 24. The length of the second housing 24 in the optical axis direction is shorter than that of the first housing 23, but the outer and inner diameters are longer than those of the first housing 23. The optical axis is indicated by O, and the direction perpendicular to this optical axis O is the radial direction.

[0029] The first housing 23 is disposed radially outward from the lens barrel 22, and the second housing 24 is disposed closer to the image (lower in FIG. 1 ) than the first housing 23. The lens barrel 22, first housing 23, and second housing 24 are disposed coaxially. A rectangular plate-shaped inner flange portion 24a is formed at the upper end of the second housing 24, and a convex portion 24b that protrudes toward the object side (upper in FIG. 1 ) is formed in the radial center of this inner flange portion 24a, and a through-hole 24c is formed in the radial center of this convex portion 24b.

[0030] Furthermore, a step 24d is formed on the upper surface of the inner flange 24a, and the lower end of the first housing 23 is fitted into this step 24d, thereby positioning the first housing 23 relative to the second housing 24 in the radial direction and the optical axis direction.

[0031] The lens unit 20 also includes a plurality of (e.g., six) lenses 31, 32, 33, 34, 35, and 36 arranged in order from the object side. The lens 31 is a first lens 31 located closest to the object side, and this first lens 31 is held by a lens holding portion 50 (described later) in the first housing 23. The five lenses 32, 33, 34, 35, and 36 arranged closer to the image side than the first lens 31 are provided inside the lens barrel 22.

[0032] Furthermore, a cylindrical protrusion 27 that protrudes toward the image side (downward in FIG. 1) is formed at the lower end of the lens barrel 22, and this protrusion 27 is inserted into and fits into the through-hole 24c provided in the second lens barrel 24. As a result, the lens barrel 22 and the second housing 24 are arranged coaxially and coincident with the optical axis O.

[0033] Furthermore, the first lens 31 located closest to the object is a glass lens, and the lenses 32 to 36 are resin lenses, but this is not limiting (for example, the lens 31 may be a resin lens). Furthermore, the surfaces of the lenses 31 to 36 may be provided with an anti-reflection film, a hydrophilic film, a water-repellent film, or the like, as needed.

[0034] The multiple lenses 31 to 36 fixed to and supported by the first housing 23 and the lens barrel 22 are arranged with their optical axes aligned, and the lenses 31 to 36 are lined up along a single optical axis O to form a group of lenses L used for imaging.

[0035] In this embodiment, the first housing 23 is disposed radially outward from the lens barrel 22. The first housing 23 is formed of a metal such as SUS and includes a rectangular cylindrical housing main body 23a, a rectangular plate-shaped top panel 23b integrally formed with the housing main body 23a at the upper end of the housing main body 23a, and a locking portion 23c integrally formed with the top panel 23b on the inner peripheral edge of the top panel 23b. That is, the top panel 23b in this embodiment has a shorter length extending from the upper edge of the housing main body 23a toward the inside than the top panel 105b shown in FIG. 6, and the locking portion 23c is formed on the inner peripheral edge of the top panel 23b. The thickness of the top panel 23b (thickness in the optical axis direction) is thinner than the thickness of the housing main body 23a (thickness in the radial direction).

[0036] The locking portion 23c includes a generally cylindrical protrusion 23d formed to protrude from the inner peripheral edge of the top plate portion 23b toward the object side (upper side in FIG. 1 ), and a pressing portion 23e bent radially inward from the upper end of the protrusion 23d. An inclined surface 23f inclined with respect to the optical axis O is formed along the circumferential direction on the pressing portion 23e. The inclined surface 23f presses the surface edge of the first lens 31, thereby fixing the first lens 31. In other words, when the lens group L is assembled and housed within the first housing 23 and the lens barrel 22, the inclined surface 23f of the pressing portion 23e presses the first lens 31, which is located closest to the object side of the lens group L, and fixes the first lens 31 to the object-side end of the first housing 23 in the optical axis direction.

[0037] Furthermore, an inner flange portion 26 having an opening with a diameter smaller than that of the sixth lens 36 is provided at the end (the lower end in FIG. 1) of the lens barrel 22 on the image side. The plurality of lenses 31 to 36 that make up the lens group L inside the first housing 23 and the lens barrel 22 are held and fixed in the optical axis direction by this inner flange portion 26 and the inclined surface 23 f of the pressing portion 23 e. Furthermore, a filter 99 such as an infrared cut filter is provided on the lower surface of the inner flange portion 26.

[0038] This embodiment also includes a ring-shaped lens holder 50 that holds the first lens 31. The lens holder 50 is manufactured by turning a metal such as stainless steel into a thin ring shape. The lens holder 50 has an inner peripheral surface 50a that is cylindrical and a toric surface 50b that is perpendicular to the inner peripheral surface 50a. The inner peripheral surface 50a and the toric surface 50b form an L-shaped cross section. The inner peripheral surface 50a is arranged coaxially with the optical axis O, and the toric surface 50b is arranged perpendicular to the optical axis O. The lens holder 50 also has an inner peripheral surface 50c that is perpendicular to the toric surface 50b and coaxial with the optical axis O. The inner peripheral surface 50c is arranged closer to the image (lower in FIG. 1 ) than the inner peripheral surface 50a and has a smaller inner diameter than the inner peripheral surface 50a.

[0039] The inner diameter of the inner peripheral surface 50c of the ring-shaped lens holder 50 is larger than the outer diameter of the lens barrel 22, so that the upper end of the lens barrel 22 is positioned inside the inner peripheral surface 50c of the lens holder 50. The lens holder 50 is also joined to the first housing 23. That is, the outer peripheral surface 50d and the upper surface 50e of the lens holder 50 each abut against the inner peripheral surface of the pressing portion 23e of the first housing 23 with almost no gap, so that the lens holder 50 fits into the top plate portion 23b of the first housing 23. In this way, the lens holder 50 is joined to the first housing 23, which has the top plate portion 23b. When the lens holder 50 is joined to the first housing 23, the axis of the lens holder 50 coincides with the optical axis O, and the lens holder 50 is positioned in the optical axis direction.

[0040] The lens holder 50 holds the first lens 31. That is, the inner peripheral surface 50a of the lens holder 50 abuts the outer peripheral surface of the first lens 31 with no gap, thereby positioning the first lens 31 in the radial direction and arranging it coaxially with the optical axis O. The annular surface 50b of the lens holder 50 abuts the flat bottom surface 31e of the first lens 31 facing the image side with no gap, thereby positioning the first lens 31 in the optical axis direction. The lenses 32 to 36 arranged on the image side of the first lens 31 are held by the lens barrel 22 so that their optical axes coincide, and the lens barrel 22 is arranged coaxially with the second housing 24 and the optical axis O, so that the first lens 31 and the lenses 32 to 36 arranged on the image side of the first lens 31 are arranged coaxially or with no more than a predetermined amount of eccentricity.

[0041] Furthermore, in this embodiment, a vibration mechanism 60 is provided that vibrates the first lens 31. The vibration mechanism 60 includes a vibrator 61 that ultrasonically vibrates, and a vibrating body 62 that transmits the ultrasonic vibration of the vibrator 61 to the first lens 31. Such a vibration mechanism 60 is disposed radially inward from the first housing 23 and radially outward from the lens barrel 22. The vibrator 61 is formed in the shape of an annular plate, and is provided inside the housing main body 23a of the first housing 23. The vibrator 61 is formed of, for example, a piezoelectric element.

[0042] The vibrating body 62 includes a donut-shaped disk-shaped mounting portion 62a, a main body 62b that extends from the mounting portion 62a toward the object side (upward in FIG. 1) and has a generally cylindrical shape with bulges and constrictions with an S-shaped cross section, with the outer and inner diameters varying continuously in the axial direction (optical axis direction), and a ring-shaped joint portion 62c formed at the upper end of the main body 62b. The vibrator 61 is attached and fixed to the lower surface of the mounting portion 62a, and the upper surface of the joint portion 62c is bonded with an adhesive to the lower surface (surface facing the image side) of the lens holding portion 50.

[0043] In such vibration mechanism 60, vibrator 61 ultrasonically vibrates at a predetermined frequency, causing vibration body 62 to ultrasonically vibrate. When vibration body 62 vibrates, first lens 31 ultrasonically vibrates at the same frequency via lens holder 50, since vibration body 62 is joined to lens holder 50, thereby removing foreign matter such as water droplets, muddy water, ice, snow, and frost from lens surface 31 a of first lens 31.

[0044] The lens holder 50 is fitted to the top plate 23b of the first housing 23, but the thickness of the top plate 23b is thinner than the thickness of the housing main body 23a, and the top plate 23b functions as a damper, so that vibrations of the lens holder 50 are less likely to be transmitted to the housing main body 23a. This makes it less likely that vibrations will be transmitted to the second housing 24 fitted to the housing main body 23a, and as a result, vibrations are less likely to be transmitted to the lens barrel 22 fitted to the second housing 24, and therefore to the lenses 32 to 36, thereby preventing a deterioration in optical performance caused by displacement of the lenses 32 to 36 due to vibrations.

[0045] In this embodiment, the lens unit 20 is made up of the first housing 23, the first lens 31 held in the first housing 23, the lens barrel 22, the lenses 32 to 36 held in the lens barrel 22, the lens holder 50, the vibration mechanism 60, etc. The camera module 300 of this embodiment is made up of the lens unit 20 and the second housing 24 fitted into the first housing 23 of the lens unit 20. The second housing 24 has a package sensor (image sensor) 304 inside.

[0046] The package sensor 304 is disposed inside the second housing 24 opposite the filter 99, and is positioned to receive the image of the object formed by the lens unit 20. The package sensor 304 includes a CCD, a CMOS, or the like, and converts the light that is collected through the lens unit 20 and reaches the package sensor 304 into an electrical signal. The converted electrical signal is then converted into analog data or digital data, which are components of the image data captured by the camera.

[0047] The second housing 24 also includes a drive circuit board 305 therein. The drive circuit board 305 is a board having a drive circuit 4 (see FIG. 3) that applies a voltage of a predetermined frequency to the piezoelectric element 61 of the vibration mechanism 60 to drive it. The drive circuit board 305 and the vibrator (piezoelectric element) 61 are formed of an FPC or the like and are connected by wiring 306 that passes through a wiring hole 24f formed in the inner flange portion 24 of the second housing 24.

[0048] The optical characteristics of a camera module configured as described above are measured by a measuring device 1 that performs a measurement method according to one embodiment of the present invention. The measuring device 1 measures the optical characteristics of the lens unit 20 that includes the first lens 31 while vibrating the first lens 31 via a vibrating body 62. As shown in Figure 3, the measuring device 1 includes a driving circuit 4 that is provided on a driving circuit board 305 and vibrates the vibrating body 62 (applying a voltage of a predetermined frequency to the piezoelectric element 61), a measuring device 6 that measures the optical characteristics of the lens unit 20, and a control circuit 2 that controls the operation of the driving circuit 4 and the measuring device 6.

[0049] In this case, the control circuit 2 controls the operation of the drive circuit 4 to alternate between a search mode in which the vibration frequency is swept within a predetermined range to vibrate the vibrating body 62, thereby vibrating the first lens 31 for a predetermined duration, and a drive mode in which the vibrating body 62 is vibrated at an approximately constant frequency within the predetermined range, thereby vibrating the first lens 31 for a predetermined duration longer than the predetermined duration in the search mode, and also controls the operation of the measuring instrument 6 to measure the optical characteristics of the lens unit 20 only when in the drive mode.

[0050] Specifically, as an example, during inspection before shipping of the camera module 300, as shown in the timing chart of FIG. 4, the period of the search mode (t ＣＹＣＬＥ In this period (for example, a duration of 0.5 seconds), the drive circuit 4 sets the drive voltage Vdr to a predetermined voltage and the frequency f to f ＭＩＮ ~f ＭＡＸThe AC output signal s1 swept to the frequency t is applied to the piezoelectric element 61. Therefore, the vibrating body 62 vibrates at the swept frequency, and the first lens 31 rotates for a predetermined duration t ＣＹＣＬＥ The vibration is vibrated over a period of time.

[0051] During ultrasonic cleaning after actual mounting, in this search mode, for example, a signal processing circuit (not shown) performs a predetermined sweep range f based on the measurement results of the resonance frequency and the current value in the search mode. ＭＩＮ ~f ＭＡＸ For example, the signal processing circuit determines that the foreign matter adhering to the surface of the first lens 31 is water, that is, the resonant frequency (the natural frequency of the foreign matter) is f ０１ It is determined that this is the case.

[0052] Following this search mode, the first lens 31 is vibrated for a predetermined duration (t ＣＹＣＬＥ ) for a predetermined duration (t ＤＲＩＶＥ Specifically, as an example, the drive circuit 4 vibrates at a resonance frequency f ０１ In drive mode A, the AC output signal s1 swept between the resonant frequency f and the resonant frequency f is applied to the piezoelectric element 61. More specifically, in relation to the above-mentioned actual ultrasonic cleaning after mounting, in drive mode A, the drive circuit 4 sweeps the AC output signal s1 between the resonant frequency f and the resonant frequency f for a period ΔT. ０１ Range before and after f ＦＳ is applied to the piezoelectric element 61 (in actual ultrasonic cleaning, the resonant frequency f ０１ By continuing the vibration at this frequency, it is possible to prevent the temperature of the first lens 31 from rising excessively, and to atomize the water (droplets) adhering to the surface of the first lens 31. In this example, the frequency of the AC output signal applied to the piezoelectric element 61 changes in a stepwise manner. Specifically, the AC output signal changes in frequency at every period Δt. ＳＴＥＰ Of course, the sweep form is not limited to this.

[0053] Thereafter, the search mode and the drive mode are alternately repeated. As another example of the drive mode, FIG. 4 shows a drive mode B following the search mode after the drive mode A. In this drive mode B, the drive circuit 4 operates at a resonant frequency f ０２ and apply the AC output signal s1 to the piezoelectric element 61 (resonance frequency f ０２ (The piezoelectric element 61 is fixed to the surface of the substrate 60 and driven by the piezoelectric element 61.) In actual ultrasonic cleaning after mounting, such modes are alternately repeated to ensure that foreign matter is always effectively removed (cleaned) in accordance with the ever-changing conditions (for example, conditions in which the resonance frequency fluctuates due to changes in the foreign matter adhering thereto or temperature changes).

[0054] In the measuring device 1 according to this embodiment, the optical characteristics of the lens unit 20 are measured only when the device is in the drive mode, based on the control signal s4 sent from the control circuit 2 to the measuring device 6. In this case, the duration of the drive mode (t ＤＲＩＶＥ The length of the time s3 may be equal to or longer than the time required for the measuring instrument 6 to measure the optical characteristics of the lens unit 20, in which case the measuring instrument 6 completes a predetermined measurement sequence of the optical characteristics within a single predetermined drive mode. Alternatively, the measuring instrument 6 may complete the predetermined measurement sequence of the optical characteristics by measuring the optical characteristics of the lens unit 20 in stages across multiple drive modes. In this case, a trigger signal s3 may be output to the measuring instrument 6 from the driving circuit 4 that vibrates the vibrating body 62 in at least the multiple drive modes involved in measuring the optical characteristics, and the measuring instrument 6 may measure the optical characteristics of the lens unit 20 based on this trigger signal s3.

[0055] An example of the method steps for stepwise measurement based on the trigger signal s3 is shown in a flowchart in FIG. 5. As shown in the figure, in this example, first, the lens unit 20 is placed in the measurement device 1 (step S1). Then, the measurement conditions are set by the operator or the like (step S2). Thereafter, as described above, the search mode (lens vibration step S3) and the drive mode (lens vibration step S4) are alternately repeated. When the trigger signal s3 is received by the measurement device 6 in the drive mode (YES in step S5), the measurement device 6 measures the optical characteristics of the lens unit 20 (measurement step S6). Then, it is determined (e.g., by the control circuit 2) whether the measurement is complete (step S7). If the measurement is complete (YES in step S7), the measurement results are output (e.g., from the measurement device 6) (step S8).

[0056] As described above, according to this embodiment, in an irregular vibration form of the first lens 31 in which two vibration modes (i.e., search mode and drive mode) are alternately repeated, the optical characteristics of the lens unit 20 are measured only in the drive mode in which the first lens 31 is in a stable vibration operating state in which it vibrates at a substantially constant frequency, making it possible to appropriately and accurately obtain the dynamic optical characteristics of the lens unit 20 during lens vibration. Furthermore, because the optical characteristics are measured in the drive mode, which has a longer duration than the search mode, it is easy to ensure the time required to measure the optical characteristics using the measuring device 6.

[0057] The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the present invention, the shapes of the lens, housing, lens barrel, etc. are not limited to those of the above-described embodiments. Furthermore, the vibration patterns in the drive mode and search mode are not limited to those of the above-described embodiments. Furthermore, without departing from the spirit of the present invention, some or all of the above-described embodiments may be combined, or part of the configuration of one of the above-described embodiments may be omitted.

[0058] REFERENCE SIGNS LIST 1 Measuring device 2 Control circuit 4 Drive circuit 6 Measuring instrument 20 Lens unit 31 First lens 60 Vibration mechanism 61 Piezoelectric element 62 Vibrating body

Claims

1. A measurement method for measuring the optical characteristics of a lens unit including a predetermined lens while vibrating the predetermined lens through a vibrating body, the method comprising: a search mode in which the vibrating body is vibrated by sweeping a vibration frequency within a predetermined range to vibrate the predetermined lens over a predetermined duration; and a drive mode in which the vibrating body is vibrated at a substantially constant frequency within the predetermined range to vibrate the predetermined lens over a predetermined duration longer than the predetermined duration in the search mode, the lens vibration step of alternately repeating these modes; and a measurement step of measuring the optical characteristics of the lens unit using a predetermined measuring instrument only when in the drive mode during the lens vibration step.

2. The measurement method according to claim 1, wherein the length of the duration of the drive mode is equal to or longer than the time required to measure the optical characteristics by the measuring instrument, and the measurement step is characterized by completing a predetermined measurement sequence of the optical characteristics within a single predetermined drive mode.

3. The measurement method according to claim 1, wherein the measurement step is characterized by completing a predetermined measurement sequence of the optical characteristics by measuring the optical characteristics step by step in a divided manner over a plurality of the drive modes.

4. The measurement method according to claim 3, wherein in at least the plurality of drive modes involved in the measurement of the optical characteristics, a trigger signal is output from a drive circuit that vibrates the vibrating body to the measuring instrument, and based on this trigger signal, the measuring instrument measures the optical characteristics of the lens unit.

5. A measuring device for measuring the optical characteristics of a lens unit including a predetermined lens while vibrating the predetermined lens via a vibrating body, the measuring device comprising: a drive circuit that vibrates the vibrating body; a measuring instrument for measuring the optical characteristics of the lens unit; and a control circuit that controls the operations of the drive circuit and the measuring instrument, wherein the control circuit causes the vibrating body to vibrate by sweeping a vibration frequency within a predetermined range, thereby vibrating the predetermined lens over a predetermined duration, and a search mode; and a drive mode in which the vibrating body is vibrated at a substantially constant frequency within the predetermined range, thereby vibrating the predetermined lens over a predetermined duration longer than the predetermined duration in the search mode, and alternately repeats the operations of the drive circuit so as to alternately repeat the operations of the drive circuit, and controls the operation of the measuring instrument so as to measure the optical characteristics of the lens unit only when in the drive mode. A measuring device characterized by the above.

6. The length of the duration of the drive mode is equal to or longer than the time required for the measuring instrument to measure the optical characteristics. The measuring instrument is characterized in that a predetermined measurement sequence of the optical characteristics is completed within a single predetermined drive mode. The measuring device according to claim 5.

7. The measuring instrument is characterized in that a predetermined measurement sequence of the optical characteristics is completed by measuring the optical characteristics step by step in a divided manner over a plurality of the drive modes. The measuring device according to claim 5.

8. The drive circuit outputs a trigger signal to the measuring instrument in at least the plurality of drive modes involved in the measurement of the optical characteristics, and the measuring instrument measures the optical characteristics of the lens unit based on the trigger signal. The measuring device according to claim 7, characterized by the above.

Images