JP2006023275A - Droplet measuring device, measuring device, droplet measuring method, and measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance measurement precision concerning droplets in particular, concerning a measuring device and a measuring method. <P>SOLUTION: The measuring device comprises a laser generator 11 for generating one laser beam 12 having thickness thicker than a diameter of a droplet 16 of an object to be measured, a photodetector 14 for detecting the laser beam 12 generated from the laser generator 11 as a laser beam detection signal, and an ink jet head 15 for discharging the droplet 16 of the object to be measured so as to cross the laser beam 12 and applied to an ink jet printer. The photodetector 14 measures a speed and a volume concerning the droplet 16 on the basis of the laser beam detection signal when the droplet 16 passes the laser beam 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a measurement apparatus and a measurement method, and more particularly to a droplet measurement apparatus and a droplet measurement method suitable for increasing measurement accuracy related to a droplet.

  Conventionally, in an ink jet printing apparatus, ink droplets are ejected from each nozzle provided in an ink jet head toward the print medium while changing a relative position between the print medium such as paper and the ink jet head. Thus, printing is performed. Even if the same drive voltage waveform is applied to the inkjet head due to variations in processing and assembly during the manufacturing process, individual differences occur in the speed and volume of the ejected droplets. Moreover, even if it is a single inkjet head, the discharge amount differs for each nozzle.

  Here, conventionally, it is very important to accurately measure the velocity and volume of the droplets ejected from the inkjet head. That is, if the droplet velocity is inaccurate, the landing position on the print medium is shifted. On the other hand, when the volume of the liquid droplet is inaccurate, the liquid droplet that has landed on the print medium spreads too much, causing blurring or conversely fading.

  Therefore, conventionally, as disclosed in Patent Document 1, for example, in the droplet measurement method, for two parallel laser beams generated by passing laser beams from a light source through a slit, The ink droplets are vertically passed from the inkjet head, and the velocity of the droplets is obtained from the distance between the two laser beams and the passage time of the droplets in the two laser beams. Further, in the conventional droplet measurement method, the sectional shape of the droplet is obtained from the waveform of the photodetector that detects the laser light, and the sectional shape in the direction perpendicular to the track of the droplet is assumed to be a circle, The volume of the droplet is obtained.

JP 2003-127430 A

  By the way, in the conventional droplet measurement method, the resolution can be improved and the measurement accuracy of the droplet can be improved by narrowing the thickness of the laser beam in the traveling direction of the droplet to be smaller than the diameter of the droplet. It becomes. However, in the conventional droplet measuring method, the thickness of the laser beam is adjusted by passing the laser beam from the light source through the slit. However, the thickness of the laser beam is reduced to a desired size by diffraction. This makes it difficult to measure the liquid droplets.

  The reason for this will be described. As shown in FIG. 9, when a laser beam 2 (parallel light) having a wavelength λ passes through a pinhole 1 having a diameter d, the cross section of the laser beam 2 after passing is affected by diffraction and is concentrically bright. As a result, a so-called Airy disk is observed. The diameter of the Airy disk closest to the center is the diameter of the laser beam 2, and the angle θ of the edge of the laser beam 2 viewed from the edge of the pinhole 1 is the wavelength of the laser beam 2 and the diameter of the pinhole 1. When d, it is expressed by the following equation (1).

  Here, when the type is He—Ne laser light and the laser light 2 having a wavelength λ of 0.63 μm is used, the diameter of the pinhole 1 and the diameter of the laser light 2 at a position 1 mm away from the pinhole 1 are: It is represented by the following Table 1.

  In the conventional ink jet printing apparatus, the diameter of the droplet is about 15 to 34 μm (volume: about 2 to 20 pl), so in order to obtain sufficient measurement accuracy, it is desired to measure at least by dividing the droplet into five. Therefore, the diameter of the laser beam 2 that has passed through the pinhole 1 is preferably at least 3 μm or less. However, as can be seen from Table 1, it is impossible to obtain the above-described conditions by only 1 mm away from the pinhole 1. This calculation is for pinholes, but the above idea applies to slits as long as pinholes arranged in a horizontal row are slits. The distance between the position where the droplet passes the laser beam 2 and the position of the pinhole 1 is at least 1 cm, preferably 3 cm, for reasons of spatial constraints or for the purpose of preventing contamination due to droplet scattering. It is desirable to secure the above. That is, it is difficult to measure the velocity and volume of the droplet using a laser beam of 3 μm or less.

  In addition, the light intensity of the laser beam from the laser is not stable unless at least about 15 minutes have elapsed since the laser was turned on. Furthermore, the emission angle of the laser beam from the laser continues to change slightly over a period of several hours from when the laser is turned on. For this reason, even when all of a plurality of droplets having the same size and the same shape are measured, there is a possibility that the waveforms output from the detectors that have detected the laser light are not the same. Therefore, in the conventional measurement method, since the volume of the droplet is based on a value representing the intensity of the laser beam, the accuracy of volume measurement may be reduced if the influence of the thermal drift of the laser cannot be removed. .

  The present invention has been made in view of the above, and one of its purposes is to provide a droplet measuring device and a droplet measuring method that improve the measurement accuracy of droplets.

  In order to solve the above-described problems and achieve the object, the present invention includes a laser beam generating means for generating one laser beam having a thickness larger than the diameter of a droplet to be measured, and the laser beam as a laser beam. Laser light detection means for detecting as a light detection result, droplet discharge means for discharging a droplet to be measured across the laser light, and the laser light detection result when the droplet passes through the laser light And a measuring means for measuring a droplet.

  According to an aspect of the present invention, the measurement unit includes a laser beam detection result when the droplet contacts the upper surface of the laser beam, and a laser beam when the droplet contacts the lower surface of the laser beam. Based on the detection result, the velocity of the droplet is measured.

  According to another aspect of the present invention, the measuring means is based on the detection result of the laser beam from when the droplet contacts the upper surface of the laser beam until the droplet completely enters the laser beam. The volume of the droplet is measured.

  According to still another aspect of the present invention, the measuring means is based on the laser light detection result from when the droplet contacts the lower surface of the laser beam until the droplet completely escapes from the laser beam. Then, the volume of the droplet is measured.

  The present invention also includes a laser light generation step for generating a single laser beam having a thickness larger than the diameter of the droplet to be measured, a laser beam detection step for detecting the laser beam as a laser beam detection result, A droplet discharge step of discharging a droplet to be measured so as to cross the laser beam, and a measurement step of measuring a droplet based on the laser light detection result when the droplet passes through the laser beam And including.

  According to the present invention as described above, a single laser beam having a thickness larger than the diameter of the droplet to be measured is detected as a laser beam detection result, and the droplet ejected across the laser beam is a laser beam. Since the measurement related to the droplet is performed based on the detection result of the laser beam when passing through the light, it is not necessary to reduce the diameter of the laser beam as in the conventional case, and the measurement accuracy regarding the droplet can be improved. There is an effect.

  The measurement apparatus of the present invention includes a light generator that emits a light beam, a sensor that receives the light beam, and a measurement unit that measures the light intensity of the light beam on the sensor. Here, the optical path of the light beam is arranged so that an object to be measured having a velocity component in a predetermined direction crosses the light beam at a predetermined portion. The width of the light beam in the predetermined portion along the predetermined direction is equal to or greater than the width of the object to be measured along the predetermined direction. Furthermore, the measurement unit derives a physical quantity of the object to be measured based on the change in the light intensity that appears in a period from when the object to be measured starts to cross the outer edge of the light beam to when the object has crossed.

  According to the measurement method of the present invention, a light generator that emits a light beam and a sensor that receives the light beam are provided, and a width along a predetermined direction of the light beam at a predetermined portion is the width of the object to be measured. A measuring device having a width equal to or larger than the predetermined direction is used. The measurement method includes a step (A) of flying the measurement object so that the measurement object having a velocity component in the predetermined direction crosses the light beam at the predetermined portion, and the sensor on the sensor. Based on the step (B) of measuring the light intensity of the light beam, and the change of the light intensity that appears within a period from when the object to be measured crosses the outer edge of the light beam to when it has crossed the object, (C) for deriving the physical quantity of

  According to the above feature, the derivation of the physical quantity (for example, volume) of the object to be measured is based on a change in light intensity that appears when the object to be measured crosses the outer edge of the light beam. For this reason, even if the width of the light beam is equal to or larger than the width of the object to be measured, the physical quantity of the object to be measured, for example, the volume can be derived. In other words, since it is not necessary to narrow the width of the light beam below the width of the object to be measured, there is a degree of freedom in designing the light source that generates the light beam or the optical components in the optical path, and this facilitates the measurement.

  The measurement apparatus of the present invention includes a light generator that emits a light beam, a sensor that receives the light beam, and a measurement unit that measures the light intensity of the light beam on the sensor. Here, the optical path of the light beam is arranged so that an object to be measured having a velocity component in a predetermined direction crosses the light beam at a predetermined portion. The width of the light beam in the predetermined portion along the predetermined direction is equal to or greater than the width of the object to be measured along the predetermined direction. Furthermore, the measurement unit detects, based on the light intensity, a first time when the measured object starts to enter the light beam and a second time when the measured object finishes escaping the light beam. , Along the predetermined direction of the object to be measured based on the difference between the first time and the second time, the magnitude of the velocity component, and the width of the light beam along the predetermined direction. The width value is derived.

  The measurement apparatus of the present invention includes a light generator that emits a light beam, a sensor that receives the light beam, and a measurement unit that measures the light intensity of the light beam on the sensor. Here, the optical path of the light beam is arranged so that an object to be measured having a velocity component in a predetermined direction crosses the light beam at a predetermined portion. The width of the light beam in the predetermined portion along the predetermined direction is equal to or greater than the width of the object to be measured along the predetermined direction. Furthermore, the measurement unit derives a first time when the measured object finishes entering the light beam and a second time when the measured object begins to escape the light beam based on the light intensity. , Along the predetermined direction of the object to be measured based on the difference between the first time and the second time, the magnitude of the velocity component, and the width of the light beam along the predetermined direction. The width value is derived.

  According to the measurement method of the present invention, a light generator that emits a light beam and a sensor that receives the light beam are provided, and a width along a predetermined direction of the light beam at a predetermined portion is the width of the object to be measured. A measuring device having a width equal to or larger than the predetermined direction is used. The measurement method includes a step (A) of flying the measurement object so that the measurement object having a velocity component in the predetermined direction crosses the light beam at the predetermined portion; A step (B) of measuring the light intensity of the light beam, a first time when the measured object starts to enter the light beam based on the light intensity, and the measured object finishes escaping the light beam. Based on the step (C) of deriving the second time, the difference between the first time and the second time, the magnitude of the velocity component, and the width of the light beam along the predetermined direction. And (D) deriving a value of the width along the predetermined direction of the object to be measured.

  According to the measurement method of the present invention, a light generator that emits a light beam and a sensor that receives the light beam are provided, and a width along a predetermined direction of the light beam at a predetermined portion is the width of the object to be measured. A measuring device having a width equal to or larger than the predetermined direction is used. The measurement method includes a step (A) of flying the measurement object so that the measurement object having a velocity component in the predetermined direction crosses the light beam at the predetermined portion; A step (B) of measuring the light intensity of the light beam, a first time when the measurement object finishes entering the light beam based on the light intensity, and the measurement object starts to escape the light beam. Based on the step (C) of deriving the second time, the difference between the first time and the second time, the magnitude of the velocity component, and the width of the light beam along the predetermined direction. And (D) deriving a value of the width along the predetermined direction of the object to be measured.

  According to the above feature, since the width of the object to be measured is not based on the value representing the magnitude of the light intensity, even if the light intensity of the light beam gradually changes due to the thermal drift of the light generator, the object to be measured can be accurately obtained. Can be derived. Here, if the shape of the object to be measured is a sphere, the volume can be derived.

  Embodiments of a droplet measuring apparatus and a droplet measuring method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

(A. Overall configuration of droplet measuring apparatus)
FIG. 1 is a schematic side view showing the configuration of an embodiment according to the present invention. In the figure, a droplet measuring device 10 for measuring the speed and volume of the droplet 16 discharged from the inkjet head 15 is shown. FIG. 2 is an enlarged perspective view showing a configuration in the vicinity of the measurement position P1 shown in FIG. 3 is an enlarged plan view and an enlarged side view showing a configuration in the vicinity of the measurement position P1 shown in FIG.

  The droplet measuring device 10 in FIG. 1 is disposed in the middle of the optical path of a laser beam generator 11 (for example, a He—Ne laser beam generator) that generates a laser beam 12 having a wavelength of 0.63 μm, for example. A cylindrical lens 13, a photodetector 14 that is disposed at a position facing the laser light generator 11 and detects the laser light 12, and a measurement positioned between the cylindrical lens 13 and the photodetector 14. And an inkjet head 15 that is disposed above the position P1 and that discharges the droplets 16. The ink jet head 15 is applied to an ink jet printing apparatus. The measurement position P1 corresponds to the focal line L1 in the cylindrical lens 13. In addition, the part except the inkjet head 15 among the droplet measuring devices 10 is described as “measuring device 10A”.

  The direction of the generatrix of the cylindrical lens 13 coincides with the Y-axis direction. By the way, the focal line L1 of the cylindrical lens 13 is not reduced below the diffraction limit due to the influence of light diffraction, and therefore has a certain finite thickness. In this embodiment, the cylindrical lens 13 is selected so that the thickness along the Z-axis direction of the focal line L1 (the width Lz described later) is equal to or greater than the width Dz of the droplet 16 in the Z-axis direction.

  In place of the cylindrical lens 13, for example, a plano-convex lens may be used. However, if the cylindrical lens 13 is configured to condense the laser light 12 onto the focal line L1, unlike the plano-convex lens, the measurement position P1 expands in the depth direction (the Y-axis direction described later). Therefore, the alignment of the inkjet head 15 is facilitated. Note that the cylindrical lens 13 may be omitted or a slit may be provided instead of the cylindrical lens 13 if a sufficiently high S / N ratio is realized when a signal value E (i) described later is obtained. .

  In the present embodiment, the principal ray of the laser beam 12 at the measurement position P1 propagates on a plane determined by the X axis direction and the Y axis direction perpendicular to each other. Further, the propagation direction of the laser beam 12 is parallel to the X-axis direction. Furthermore, the optical path of the laser beam 12 is arranged so that the droplet 16 having a velocity component in the Z-axis direction perpendicular to both the X-axis direction and the Y-axis direction crosses the laser beam 12 at the measurement position P1. .

  Here, as shown in FIG. 4A, the thickness D (width Lz) of the laser beam 12 at the measurement position P1 is larger than the width Dz with respect to the drop direction of the droplet 16. . Further, it is assumed that the intensity distribution of the laser beam 12 is uniform on a cross section perpendicular to the direction in which the laser beam 12 propagates.

  Thus, at the measurement position P1, the width Lz along the Z-axis direction of the laser beam 12 is equal to or greater than the width Dz along the Z-axis direction of the droplet 16. In addition, in this embodiment, the width Ly in the Y-axis direction of the laser beam 12 at the measurement position P1 is equal to or larger than the width of the droplet 16 along the Y-axis direction. For these reasons, when the droplet 16 passes through the laser beam 12, the droplet 16 is completely covered by the laser beam 12.

  Returning to FIG. 1, the photodetector 14 includes a sensor 21 having a photodiode and a current / voltage conversion circuit, and a measurement unit 22. The sensor 21 is arranged so that the entire cross section of the laser beam 12 is incident thereon. The sensor 21 outputs a detection signal E according to the light intensity of the incident laser beam 12. The sensor 21 sets the voltage of the detection signal E to a reference level (for example, 0) when the cross section of the laser light 12 is completely incident, and the light intensity of the laser light 12 decreases when the light intensity of the laser light 12 decreases. The voltage of the detection signal E is increased in proportion to the decrease. On the other hand, the measurement unit 22 measures the light intensity of the laser light 12 on the sensor 21 according to the detection signal E output from the sensor 21. Further, the measurement unit 22 calculates a physical quantity of the droplet 16 such as the volume or velocity of the droplet 16 based on the measured light intensity.

  When the droplet 16 does not pass through the laser beam 12, the entire area of the cross section of the laser beam 12 emitted from the cylindrical lens 13 enters the sensor 21. In this case, the potential (intensity) of the detection signal E becomes the reference level. On the other hand, when the droplet 16 crosses the laser beam 12, a part of the laser beam 12 is reflected, absorbed, or refracted by the droplet 16. Since a part of the laser beam 12 cannot enter the sensor 21, the light intensity of the laser beam 12 at the sensor 21 decreases, and as a result, the potential (intensity) of the detection signal E increases. . Therefore, when the droplet 16 passes through the laser beam 12, a convex waveform appears upward in the profile representing the time change of the detection signal E. In this embodiment, such a waveform accompanying the passage of the droplet 16 is denoted as “droplet passage waveform PW” (FIG. 4B).

(B. Method for measuring droplet velocity)
Next, a method for measuring the velocity of the droplet 16 in this embodiment will be described with reference to FIGS. 4 (a) and 4 (b). In FIG. 1, when a droplet 16 is ejected from the inkjet head 15, the droplet 16 falls while drawing a locus K1, as shown in FIGS. Then, as shown in FIG. 4B, when the lower end of the droplet 16 comes into contact with the upper surface (or the upper outer edge) of the laser beam 12 near the measurement position P1 (focal line L1) at time t1, the photodetector 14 changes in the intensity of the detection signal E of the sensor 21. Specifically, in this case, the detection signal E rises from the reference level. When the droplet 16 completely enters the laser beam 12, the intensity of the detection signal E of the sensor 21 in the photodetector 14 becomes substantially constant. This is because the droplet 16 is completely covered with the laser beam 12. Furthermore, when the lower end of the droplet 16 comes into contact with the lower surface (or lower outer edge) of the laser light 12 at time t2, the intensity of the detection signal E of the sensor 21 in the photodetector 14 changes. Specifically, in this case, the detection signal E starts to decrease.

  As a result, the photodetector 14 divides the thickness D (width Lz) of the laser light 12 by the time τ between the time t1 and the time t2 when the detection signal E changes, thereby obtaining the droplet 16. Vm (= D / τ) is obtained.

(C. Method of measuring droplet volume)
Next, a method for measuring the volume of the droplet 16 in one embodiment will be described with reference to FIGS. 4 and 5. First, the droplet 16 is blown so that the droplet 16 having a velocity component in the Z-axis direction crosses the laser beam 12 at the measurement position P1. Specifically, the droplet 16 is ejected from the inkjet head 15 in the Z-axis direction.

Next, as shown in (1) in FIG. 5, the photodetector 14 obtains the projection area S ₂ when the droplet 16 contacts the laser beam 12 from the detection signal E of the laser beam 12. In (2), the photodetector 14 obtains a difference S ′ ₂ between the projected area S ₁ obtained in the previous sample and the projected area S ₂ obtained in (1). Here, since the difference S ′ ₂ is obtained, even if the light intensity of the laser beam 12 varies due to the thermal drift of the laser beam generator 11, the error due to the variation is canceled. This is because the period of variation in light intensity due to thermal drift is sufficiently longer than the period (sampling period) for obtaining the projection area S _i .

In (3) of FIG. 5, the photodetector 14 assumes that the difference S ′ ₂ obtained in (2) is a rectangle whose height is Vm / f and whose horizontal width is y, and from the area to the horizontal width Find y. Vm is the velocity of the droplet 16, and f is the sampling frequency of the sampling unit 24 described later.

  Next, in (4), the photodetector 14 assumes that the rectangle is a projection of a cylinder having a bottom diameter y and a height Vm / f, and obtains the volume of the cylinder. Thereafter, the light detector 14 detects from the time t1 when the lower end of the droplet 16 contacts the upper surface (or upper outer edge) of the laser light 12 to the time t3 when it completely enters the laser light 12 (sampling period). The calculation from 1) to (4) is performed to determine the volume of each cylinder. And the photodetector 14 calculates | requires the volume value Iv of the droplet 16 by integrating | accumulating the volume of these cylinders.

  In this embodiment, in this way, the increase amount of the volume of the portion where the laser beam 12 and the droplet 16 overlap each other is derived for each of a plurality of sampling times in the sampling period. Then, the volume values Iv are derived by adding the obtained increases to each other. The sampling period described here is a period from when the droplet 16 starts to cross the upper outer edge of the laser light 12 to when it finishes crossing. That is, the sampling period is a period from time t1 to time t3.

  The sampling period may be a period from when the droplet 16 starts to cross the lower outer edge of the laser light 12 to when it finishes crossing. That is, the sampling period may be a period from time t2 to time t4. When the sampling period is defined as described above, the volume reduction amount of the portion where the laser beam 12 and the droplet 16 overlap each other may be derived for each of a plurality of sampling times in the sampling period. The volume value Iv can be derived by adding the absolute values of the obtained reduction amounts to each other.

  As described above, according to the measurement method, the change in the light intensity that appears when the droplet 16 crosses the upper outer edge or the lower outer edge of the laser light 12 is measured. For this reason, even if the width Lz of the laser beam 12 is equal to or larger than the width Dz of the droplet 16, the volume of the droplet 16 can be derived.

  A set of a plurality of diameters y obtained in a period from time t1 to time t3 (or from time t2 to time t4) represents the shape of one droplet 16 on the YZ cross section. For this reason, the shape of the droplet 16 can be determined based on the set of the plurality of diameters y. Further, when the volume value Iv is 0 (zero) even though the inkjet head 15 is driven, this corresponds to the fact that the droplet 16 has not been ejected. That is, by determining whether the volume value Iv is zero or a value other than zero, the presence / absence of the droplet 16 (success / failure of ejection) can be detected.

(D. Measurement unit)
Hereinafter, the structure and function of the measurement unit 22 for deriving the velocity or volume of the droplet 16 will be described in more detail with reference to FIG.

  The measurement unit 22 shown in FIG. 6 connects the sampling unit 24 that samples the detection signal E, the memory 25, the CPU 33, the ROM 34, the RAM 35, and the external interface unit 36 so that they can communicate with each other. And a bus 37. In this embodiment, the CPU 33, the ROM 34, and the RAM 35 function as the “volume calculation unit 26”.

  The sampling unit 24 is a circuit that converts an analog signal into a digital signal. In the present embodiment, the sampling unit 24 samples the detection signal E with a period Δt, and generates a signal value E (i) corresponding to the voltage value of the detection signal E. Here, “i” is an integer from 1 to n, and corresponds to the sampled order. The memory 25 stores each of the signal values E (i) generated by the sampling unit 24. Then, each of the signal values E (i) stored in the memory 25 is sequentially output in a predetermined cycle according to a command from the CPU 33. The volume calculation unit 26 receives a plurality of signal values E (i) output from the memory 25 and derives the velocity or volume of the droplet 16 according to (1) to (4) above.

  Next, the function of the volume calculation unit 26 will be described in more detail with reference to FIG. The function of the volume calculation unit 26 is realized by the CPU 33 executing a computer program stored in the RAM 35 or 34 in FIG.

  As shown in FIG. 7, when the process is started in step S1, the CPU 33 initializes a variable “i” and a variable “Iv”. Here, the variable “i” and the variable “Iv” are both contents in a predetermined storage area in the RAM 35. The variable “i” is an integer in the range of 1 to n, and is a specifier that specifies one of a plurality of signal values E (i) corresponding to one ejection. Therefore, “n” is equal to the number of signal values E (i). On the other hand, the volume value of the droplet 16 is stored in the variable “Iv”. In this embodiment, 2 is set to the variable “i” in step S1. On the other hand, 0 (zero) is set in the variable “Iv”.

Next, in step S2, the signal value E (i) and the signal value E (i-1) are extracted from the memory 25, and based on the signal value E (i) and the signal value E (i-1), The CPU 33 derives the cross-sectional areas S _i and S _(i−1) . Here, the correlation between the signal value E (i) and the cross-sectional area S (i) is known by prior calibration. In this embodiment, the signal value E (i) and the cross-sectional area S _i are associated with each other by a linear expression.

Next, in step S3, the CPU 33 obtains a difference S ′ _i between the sectional area S _i and the sectional area S _(i−1) . In step S4, the CPU 33 derives the partial volume value Iv (i) of the droplet 16 based on the difference S ′ _i as described in the above (4).

  In step S5, the CPU 33 adds the partial volume value Iv (i) and the variable “Iv”, and stores the resultant value in the variable “Iv” again. In addition, in step S6, the CPU 33 determines whether or not the variables “i” and “n” are equal to each other. When “i” and “n” are equal to each other (step S6 is Yes), the variable “Iv” at that time represents the volume value Iv of the droplet 16. Therefore, in this case, in step S8, the CPU 33 extracts the variable “Iv” as the volume value Iv. On the other hand, if “i” and “n” are not equal (No in Step S6), 1 is added to the variable “i” in Step S7, and Steps S2 to S6 are repeated.

  According to the measurement method or measurement apparatus as described above, one laser beam 12 having a thickness larger than the diameter of the droplet 16 to be measured is detected as the laser beam detection signal E, and crosses the laser beam 12. Since the velocity or volume of the droplet 16 is measured based on the laser beam detection signal E when the ejected droplet 16 passes through the laser beam 12, the diameter of the laser beam 12 is reduced as in the prior art. There is no need to reduce the size, and the measurement accuracy for the droplet 16 can be increased.

  Conventionally, two laser beams are required to measure the velocity of the droplet 16, but according to the above embodiment, only one laser beam is required, so that the configuration of the apparatus can be simplified. I can do it.

  Another embodiment of the method for measuring the volume of the droplet 16 will be described with reference to FIGS. The method for measuring the volume of the droplet 16 of this embodiment is effective when the shape of the droplet 16 is close to a sphere. In addition, since the droplet measuring apparatus 10 used in the present embodiment is basically the same as the droplet measuring apparatus 10 of the first embodiment, detailed description of the configuration and functions thereof will be omitted. Further, “light beam B” in the present embodiment is a term including the laser beam 12 shown in the first embodiment. However, the light beam B may be a light beam that is not in phase instead of the laser light 12.

  As shown in FIG. 8A, in this embodiment as well, the propagation direction of the light beam B at the measurement position P1 is parallel to the X-axis direction as in the first embodiment. Further, the width (beam width Lz) of the light beam B along the Z-axis direction is equal to or larger than the width (width Dz) of the droplet 16 along the Z-axis direction. In this embodiment, the value W of the beam width Lz and the velocity Vm of the droplet 16 are known.

  First, the measurement unit 22 detects a time t1 (FIG. 8B) at which the droplet 16 starts to enter the light beam B. Time t1 is the time when the lower end of the droplet 16 contacts the upper outer edge of the light beam B. In the present embodiment, the measurement unit 22 detects the time when the droplet passage waveform PW in the detection signal E rises from the reference level as time t1. Specifically, the measurement unit 22 detects the time when the value of the droplet passage waveform PW becomes equal to or greater than the threshold th as time t1.

  When the droplet 16 finishes entering the light beam B, the droplet 16 is completely covered by the light beam B. This is because the beam width Lz is greater than or equal to the width Dz. After the droplet 16 is completely covered by the light beam B, the droplet 16 begins to escape the light beam B and exits from the lower outer edge of the light beam B. Thereafter, the droplet 16 finishes escaping the light beam B.

  Therefore, the measurement unit 22 detects time t4 when the droplet 16 finishes escaping the light beam B. Time t4 is a time when the upper end of the droplet 16 contacts the lower outer edge of the light beam B. In this embodiment, the measurement unit 22 detects the time when the droplet passage waveform PW substantially returns to the reference level as time t4. Specifically, the measurement unit 22 detects the time when the value of the droplet passage waveform PW is equal to or less than the threshold th as time t4.

  When detecting times t1 and t4, a differential value PWD of the droplet passage waveform PW shown in FIG. 8C may be used. Specifically, the time when the differential value PWD becomes less than the threshold value td1 to the threshold value td1 or more may be detected as the time t1. Similarly, the time when the differential value PWD becomes less than the threshold value td2 to the threshold value td2 or more may be detected as the time t4. Then, the times t1 and t4 can be detected more accurately.

After detecting the time t1 and the time t4, the diameter value φ of the droplet 16 is obtained according to the following formula (2).
φ = Vm (t4-t1) -W (2)
That is, the diameter value φ of the droplet 16 is derived based on the difference between the time t4 and the time t1, the velocity Vm of the droplet 16, and the value W of the beam width Lz. The velocity Vm of the droplet 16 is the same as the velocity component in the Z-axis direction of the droplet 16.

Instead of detecting the times t1 and t4, as shown in FIG. 8B, the time t3 when the droplet 16 finishes entering the light beam B and the time t2 when the droplet 16 starts to escape the light beam B. And may be detected. However, when the times t3 and t2 are detected, the diameter value φ of the droplet 16 is obtained from the following equation (3).
φ = W−Vm (t2−t3) (3)
That is, the diameter value φ of the droplet 16 is derived based on the difference between the time t2 and the time t3, the velocity Vm of the droplet 16, and the value W of the beam width Lz. As described above, the velocity Vm of the droplet 16 is the same as the velocity component in the Z-axis direction of the droplet 16.

When the diameter value φ of the droplet 16 is derived, the volume Iv of the droplet 16 is obtained from the following formula (4) according to the formula of the volume of the sphere.
^{Iv = πφ 3/6 ... (} 4)

  According to the measurement method as described above, since the value of the light intensity is not used when the volume Iv (or diameter φ) of the droplet 16 is derived, the light intensity of the light beam B is caused by the thermal drift of the laser light generator 11. Even if it gradually changes, the volume Iv (or diameter φ) of the droplet 16 can be accurately derived.

(Modification)
As described above, the droplet measuring apparatus and the droplet measuring method according to the present invention are suitable for measuring physical quantities such as the velocity or volume of droplets ejected from an inkjet head. However, the object to be measured whose physical quantity is measured by the measuring device 10 </ b> A in the droplet measuring device 10 is not limited to the droplet 16. Specifically, the measuring device 10A can measure the volume of an object to be measured having a rotationally symmetric shape with respect to an axis parallel to the flight path or trajectory. Furthermore, even if the object to be measured does not have a rotationally symmetric shape, the presence or absence of the object to be measured is determined according to the time transition (time change) of the light intensity received by the sensor 21, or the light beam B It is possible to detect a cross-sectional width (or shape) of an object to be measured in a vertical cross-section.

  Examples of the measurement object other than the liquid droplet 16 are a ball bearing and a gap agent used in a liquid crystal display device. Ball bearings are required to have high precision roundness. Further, the gap agent is also required to have high dimensional accuracy at a high level. Therefore, it is advantageous to measure the shape or volume of the ball bearing and the gap agent with the measuring method according to the present invention. Here, the ball bearing and the gap agent are solid objects unlike the droplets 16. In such a case, for example, the ball bearing or the gap agent may be dropped from the funnel so that the ball bearing or the gap agent passes through the measurement position P1 of the light beam B. Then, the measuring device 10A can measure the volume and shape of the ball bearing or the gap agent.

It is a schematic side view which shows the structure of one Example concerning this invention. It is an expansion perspective view which shows the structure of measurement position P1 vicinity shown in FIG. (A) is an enlarged plan view showing a configuration near the measurement position P1, and (b) is an enlarged side view. (A) And (b) is a figure explaining the measuring method of the speed of the droplet 16 in the same Example. It is a figure explaining the measuring method of the volume of the droplet 16 in the same Example. It is a functional block diagram which shows the measurement part of a present Example. It is a flowchart explaining operation | movement of the measurement part of a present Example. (A) is a schematic diagram showing a state where a droplet starts to enter the light beam and a state where the droplet finishes escaping the light beam, (b) is a graph showing a droplet passage waveform, (C) is a graph of the differential value of a droplet passage waveform. It is a figure explaining the problem of the conventional droplet measuring method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Droplet measuring device, 11 ... Laser light generator, 12 ... Laser light, 13 ... Cylindrical lens, 14 ... Photo detector, 15 ... Inkjet head, 21 ... Sensor, 22 ... Measuring part.

Claims (11)

Laser beam generating means for generating one laser beam having a thickness equal to or larger than the diameter of the droplet to be measured;
Laser light detection means for detecting the laser light as a laser light detection result;
A droplet discharge means for discharging a droplet to be measured so as to cross the laser beam;
Measuring means for measuring the droplet based on the detection result of the laser beam when the droplet passes through the laser beam;
A droplet measuring apparatus comprising:   The measuring means is configured to detect the liquid based on a laser light detection result when the liquid droplet contacts the upper surface of the laser light and a laser light detection result when the liquid droplet contacts the lower surface of the laser light. The droplet measuring apparatus according to claim 1, wherein the droplet velocity is measured.   The measuring means measures the volume of the droplet based on the detection result of the laser beam from when the droplet contacts the upper surface of the laser beam until the droplet completely enters the laser beam. The droplet measuring device according to claim 1 or 2.   The measuring means measures the volume of the droplet based on the detection result of the laser beam from when the droplet contacts the lower surface of the laser beam until the droplet completely escapes from the laser beam. The droplet measuring device according to claim 1 or 2. A laser beam generation step for generating one laser beam having a thickness equal to or greater than the diameter of the droplet to be measured;
A laser beam detection step of detecting the laser beam as a laser beam detection result;
A droplet discharge step of discharging a droplet to be measured so as to cross the laser beam;
A measurement step for measuring a droplet based on the detection result of the laser beam when the droplet passes through the laser beam;
A droplet measuring method comprising: A light generator for emitting a light beam;
A sensor for receiving the light beam;
A measurement unit for measuring the light intensity of the light beam on the sensor;
A measuring device comprising:
An optical path of the light beam is arranged so that an object to be measured having a velocity component in a predetermined direction crosses the light beam at a predetermined portion,
The width along the predetermined direction of the light beam at the predetermined portion is not less than the width along the predetermined direction of the object to be measured,
The measurement unit derives a physical quantity of the measurement object based on a change in the light intensity that appears in a period from when the measurement object starts to cross the outer edge of the light beam to when the measurement object finishes crossing.
Measuring device. A light generator that emits a light beam; and a sensor that receives the light beam, wherein a width of the light beam in a predetermined portion along a predetermined direction is greater than or equal to a width of the object to be measured along the predetermined direction. A measuring method using a certain measuring device,
Step (A) of flying the object to be measured so that the object to be measured having a velocity component in the predetermined direction crosses the light beam at the predetermined part;
Measuring the light intensity of the light beam on the sensor (B);
A step (C) of deriving a physical quantity of the object to be measured based on a change in the light intensity that appears within a period from when the object to be measured starts traversing the outer edge of the light beam to when the object has been traversed;
A measurement method that includes A light generator for emitting a light beam;
A sensor for receiving the light beam;
A measurement unit for measuring the light intensity of the light beam on the sensor;
A measuring device comprising:
An optical path of the light beam is arranged so that an object to be measured having a velocity component in a predetermined direction crosses the light beam at a predetermined portion,
The width along the predetermined direction of the light beam at the predetermined portion is not less than the width along the predetermined direction of the object to be measured,
The measurement unit detects, based on the light intensity, a first time when the measured object starts to enter the light beam and a second time when the measured object finishes escaping the light beam, and The width of the object to be measured along the predetermined direction based on the difference between the first time and the second time, the magnitude of the velocity component, and the width of the light beam along the predetermined direction. Derive the value of
Measuring device. A light generator for emitting a light beam;
A sensor for receiving the light beam;
A measurement unit for measuring the light intensity of the light beam on the sensor;
A measuring device comprising:
An optical path of the light beam is arranged so that an object to be measured having a velocity component in a predetermined direction crosses the light beam at a predetermined portion,
A width along the predetermined direction of the light beam at the predetermined portion is equal to or greater than a width along the predetermined direction of the object to be measured;
The measurement unit derives, based on the light intensity, a first time when the measurement object finishes entering the light beam and a second time when the measurement object starts to escape the light beam, and The width of the object to be measured along the predetermined direction based on the difference between the first time and the second time, the magnitude of the velocity component, and the width of the light beam along the predetermined direction. Derive the value of
Measuring device. A light generator that emits a light beam; and a sensor that receives the light beam, wherein a width of the light beam in a predetermined portion along a predetermined direction is greater than or equal to a width of the object to be measured along the predetermined direction. A measuring method using a certain measuring device,
A step (A) of flying the object to be measured so that the object to be measured having a velocity component in the predetermined direction crosses the light beam at the predetermined part;
Measuring the light intensity of the light beam on the sensor (B);
A step (C) of deriving, based on the light intensity, a first time at which the measured object starts to enter the light beam and a second time at which the measured object finishes escaping the light beam;
Based on the difference between the first time and the second time, the magnitude of the velocity component, and the width of the light beam along the predetermined direction, the measurement object along the predetermined direction. Deriving a width value (D);
A measurement method that includes A light generator that emits a light beam; and a sensor that receives the light beam, wherein a width of the light beam in a predetermined portion along a predetermined direction is greater than or equal to a width of the object to be measured along the predetermined direction. A measuring method using a certain measuring device,
A step (A) of flying the object to be measured so that the object to be measured having a velocity component in the predetermined direction crosses the light beam at the predetermined part;
Measuring the light intensity of the light beam on the sensor (B);
A step (C) of deriving, based on the light intensity, a first time at which the measurement object finishes entering the light beam and a second time at which the measurement object begins to escape the light beam;
Based on the difference between the first time and the second time, the magnitude of the velocity component, and the width of the light beam along the predetermined direction, the measurement object along the predetermined direction. Deriving a width value (D);
A measurement method that includes

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