JP7586477B2 - Apparatus and method for detecting damage to fruits and vegetables - Google Patents

Description

The present invention relates to a device for detecting damage to fruits and vegetables and a method for detecting damage to fruits and vegetables.

Fruits and vegetables are subject to impacts during harvesting, transportation, and packaging. Impacts can cause damage to the fruit and vegetables. Damage to fruit and vegetables can lead to the progression of spoilage and moisture loss, reducing the market value of the fruit and vegetables.

Fruits and vegetables with scratches are sorted out by visual inspection. However, the sorting accuracy of visual inspection is unstable, so there is a demand for automating the inspection.

As an apparatus for determining the condition of fresh produce, Patent Document 1 discloses a ripeness determination device that irradiates light onto the fruit to be inspected, measures the intensity of the light scattered from the fruit, and determines the ripeness of the fruit based on the measured intensity.

JP 2003-35669 A

The ripeness determination device in Patent Document 1 can determine the ripeness of fruits and vegetables, but cannot detect blemishes on the fruits and vegetables.

The present invention has been made to solve these problems, and aims to provide a fruit and vegetable damage detection device and a fruit and vegetable damage detection method that are capable of detecting damage to fruit and vegetables.

The device for detecting damage to fresh produce according to the present invention comprises a measurement unit that measures surface waves propagating on the surface of the fresh produce, and a detection unit that detects damage to the fresh produce based on the measured surface waves.If there is a position of reduced velocity on the surface where the propagation velocity of the surface wave is lower than the propagation velocity of the surface wave at other positions on the surface by a predetermined percentage or more, the detection unit determines that the fresh produce has damage .

The method for detecting damage to fresh produce of the present invention comprises the steps of measuring surface waves propagating on the surface of the fresh produce and detecting damage to the fresh produce based on the measured surface waves, and if, in the detection step, there is a position of reduced velocity on the surface where the propagation velocity of the surface wave is lower than the propagation velocity of the surface wave at other positions on the surface by a predetermined percentage or more, it is determined that the fresh produce has the damage.

The present invention provides a fruit and vegetable damage detection device and a fruit and vegetable damage detection method that can detect damage to fruit and vegetables.

1 is a block diagram of a fruit or vegetable damage detection device according to an embodiment. 4 is a flowchart showing the operation of the fruit or vegetable damage detection device according to the embodiment. 13 is a diagram showing an example of a correspondence relationship between a parameter corresponding to a position and time and a displacement of the surface of a fruit or vegetable obtained by the fruit or vegetable damage detection device according to the embodiment. FIG. 10A to 10C are diagrams for explaining a specific example of a damage-related determination process executed by the fruit or vegetable damage detection device according to the embodiment. 13 is a diagram showing an example of a measurement result of a displacement of a surface of fruit or vegetable using the fruit or vegetable damage detection device according to the first modified example. 13 is another example of the measurement result of the displacement of the surface of fruit or vegetable using the fruit or vegetable damage detection device according to the first modified example. 13 is an example of a waveform showing a change over time in the displacement of the surface of fruit or vegetable, which is used as a reference when the damage detection device of Modification 2 performs pattern recognition. FIG. 11 is a diagram showing an example of a correspondence relationship between a parameter corresponding to a position, time, and a displacement of the surface of a fruit or vegetable obtained by a fruit or vegetable damage detection device according to Modification 2. FIG. 2 is a schematic diagram showing a damage detection system used in Experiment 1 according to Example 1. FIG. 1 is a diagram illustrating the propagation of Rayleigh waves. FIG. 13 is a diagram for explaining excitation points and measurement points set in Experiment 1 according to Example 1. 1 shows an example of surface displacement measurements at several measurement points on an undamaged test material. FIG. 13 shows the relationship between a parameter corresponding to the position of the surface of the test material and the displacement of the surface of the test material versus time for an unbruised test material. FIG. 13 shows the relationship between a parameter corresponding to the position of the surface of the test material and the displacement of the surface of the test material versus time for a test material with a bruise applied thereto. FIG. 1 is a schematic diagram for explaining bruises on a test material. 4 shows the measurement results in Example 2, which are the surface displacement measurements at the measurement points of the test material on which a bruise has been made. 4 shows the measurement results in Example 2, which are the surface displacement measurements at different measurement points on the test material on which the bruise has been made. FIG. 13 is an experimental result of Example 2, showing the correspondence between the parameter corresponding to the position on the surface of the test material and the displacement of the surface of the test material over time for a test material that is not bruised. Figure 11A shows the experimental results of Example 2 under different conditions of the positional relationship between the excitation point and the measurement point, and is a diagram showing the correspondence between the parameters corresponding to the position of the surface of the test material for a test material that is not bruised, and the displacement of the surface of the test material versus time. Figures 11A and 11B are experimental results in Example 2 under different conditions of the positional relationship between the excitation point and the measurement point, and show the correspondence between the parameters corresponding to the position of the surface of the test material for a test material that is not bruised, and the displacement of the surface of the test material versus time. FIG. 13 is an experimental result of Example 2, showing the correspondence between a parameter corresponding to the position on the surface of a test material and time and the displacement of the surface of the test material for a test material having a bruise. Figure 12A shows the experimental results of Example 2 under different conditions of the positional relationship between the excitation point and the measurement point, and is a diagram showing the correspondence between the parameters corresponding to the position of the surface of a test material with a bruise and the displacement of the surface of the test material versus time. Figures 11A and 11B are experimental results of Example 2 under conditions with different positional relationships between the excitation point and the measurement point, and are figures showing the correspondence between parameters corresponding to the position on the surface of a test material with a bruise and the displacement of the surface of the test material versus time.

The fruit and vegetable damage detection device according to the present invention will be described in detail below, with reference to the drawings as appropriate. The embodiments and variations shown below are merely examples, and do not exclude the application of various modifications and techniques not explicitly stated in the embodiments and variations below. Furthermore, the configurations of the embodiments and variations can be modified in various ways without departing from the spirit of the embodiments and variations. Furthermore, the configurations of the embodiments and variations can be selected or combined as necessary.

In all the drawings used to explain the embodiments and modifications, the same elements are generally given the same reference numerals, and their description may be omitted. The fruit and vegetable damage detection device of the present invention detects damage to fruit and vegetable by measuring surface waves propagating on the surface of the fruit and vegetable. Damage includes bruises, abrasions, cuts, and other damage that impairs the skin and edible parts of the fruit and vegetable. Surface waves include Rayleigh waves and Love waves. In the following embodiments and modifications, the surface waves will be described as Rayleigh waves. In this specification, the surface of fruit and vegetable may be simply referred to as the "surface".

(Embodiment)
FIG. 1A is a block diagram of an apparatus 100 for detecting damage to fruit or vegetable 20 according to an embodiment of the present invention.

The damage detection device 100 detects damage to the fruit or vegetable 20 based on the Rayleigh waves on the surface of the fruit or vegetable 20. Thus, the fruit or vegetable 20 may be any fruit or vegetable as long as the surface vibrates. Examples of the fruit or vegetable 20 include apples, pears, loquats, tomatoes, apricots, grapes, cherries, plums, nectarines, prunes, plums, blueberries, papayas, persimmons, kiwis, peaches, mangoes, pawpaws, chestnuts, Akebia japonica, pomegranates, pineapples, durians, passion fruit, star fruit, quince, avocados, mangosteens, lychees, dragon fruit, bananas, figs, strawberries, raspberries, Satsuma mandarins, sweeties, grapefruits, hassaku citrus fruits, pomegranates, summer mandarins, watermelons, and melons.

When the fruit or vegetable 20 is a vegetable or fruit with a relatively thin and relatively soft skin or peel, i.e., a berry, stone fruit, pome fruit, or strawberry fruit, the damage detection device 100 can be of great benefit.

A berry is a fruit or vegetable that has a thin exocarp, a mesocarp and endocarp that are fleshy and made of soft, water-rich tissue, and produces seeds with a somewhat tough seed coat inside the mesocarp and endocarp. A drupe is a fruit or vegetable that has a thin exocarp, an enlarged mesocarp, a hard endocarp, and a lignified kernel. A pome is a fruit or vegetable that has an enlarged, fleshy receptacle or thalamus that encases the ovary, and has a core derived from the ovary inside. A strawberry is a fruit or vegetable that has an enlarged, liquid receptacle and numerous achenes on its surface. Berries, drupes, pome and strawberry vegetables or fruits are fruits or vegetables whose skin or skin is easily torn or broken by the teeth when eaten raw, and whose teeth reach the part of the fruit that is exposed to the food. Berry, stone, pome, and strawberry-like vegetables or fruits are easily damaged by external impacts on their thin and soft outer skin or pericarp, and damage to the outer skin or pericarp directly leads to pain in the part of the fruit that is eaten. Furthermore, spoilage easily progresses from the damage, so that the commercial value is easily lost. When the fruit or vegetable 20 is a berry, stone, pome, or strawberry-like vegetable or fruit, damage to the fruit or vegetable 20 can be detected using the damage detection device 100, so that only the fruit or vegetable 20 with high commercial value can be shipped. In addition, as will be described in detail later, the damage detection device 100 can detect damage to the fruit or vegetable 20 without directly contacting the fruit or vegetable 20. Therefore, damage to the fruit or vegetable 20 can be inspected without causing any new damage to fruit or vegetable that is easily damaged and whose commercial value is easily lost due to the damage, such as a berry, stone, pome, or strawberry-like vegetable or fruit. Therefore, the commercial value of the fruit or vegetable 20 can be maintained high before and after the inspection.

Berry, stone fruit, pome, and strawberry-like vegetables or fruits include apples, pears, pears, quince, loquats, tomatoes, apricots, grapes, cherries, plums, nectarines, prunes, plums, blueberries, papayas, persimmons, pawpaws, kiwis, peaches, mangoes, and strawberries.

The damage detection device 100 includes a mounting unit 30, a vibration generating device 40, a measuring unit 50, and a control device 60.

The placement unit 30 is a platform on which the fruit or vegetable 20 is placed. The placement unit 30 is equipped with a sensor (not shown) that detects that the fruit or vegetable 20 has been placed. When the sensor detects the fruit or vegetable 20, it transmits a detection signal to the control device 60.

The mounting unit 30 is configured to adjust the position of the fruit or vegetable 20 in each of three mutually perpendicular axes, the X-axis, the Y-axis, and the Z-axis, depending on the size and shape of the fruit or vegetable 20. This allows the center of the fruit or vegetable 20 to be aligned with the center of the track of the measuring unit 50. The track center is the reference position for the movement of the measuring unit 50, and is located above the mounting unit 30.

The center of the fruit or vegetable 20 refers to the position that is the center position of the fruit or vegetable 20 in the X-axis direction, the center position of the fruit or vegetable 20 in the Y-axis direction, and the center position of the fruit or vegetable 20 in the Z-axis direction.

The vibration generating device 40 is a device that applies pressure waves to the surface of the fruit or vegetable 20. In this embodiment, the vibration generating device 40 includes a laser device 41 and a lens 43.

The laser device 41 emits a laser beam under the control of the control device 60. The lens 43 is, for example, a plano-convex lens. The lens 43 focuses the laser beam emitted from the laser device 41. This forms a laser induced plasma (LIP) in the air. The LIP is a plasma formed when a high-power laser beam is emitted into the air and the laser fluence (i.e., energy density) exceeds a certain value (specifically, 10 ¹⁵ W/m ² ). The laser device 41 is controlled by the control device 60 in at least one of the laser pulse energy, the irradiation range of the laser beam, and the irradiation time of the laser beam so that the laser fluence exceeds 10 ¹⁵ W/m ² .

The LIP expands at high speed. When the LIP expands, a pressure wave is generated that travels through the air and hits the fruit or vegetable 20. An impact is then applied to the fruit or vegetable 20 at the location where the pressure wave hits. In other words, the vibration generator 40 uses the impact of the pressure wave as a vibration force for the fruit or vegetable 20 to vibrate the fruit or vegetable 20. In the following description, a position on the surface of the fruit or vegetable 20 where the pressure wave hits is referred to as a vibration point.

When the pressure waves generated by the vibration generator 40 hit the fruit or vegetable 20, Rayleigh waves are generated on the surface of the fruit or vegetable 20. The Rayleigh waves propagate along the surface of the fruit or vegetable 20.

The measurement unit 50 is, for example, a laser Doppler vibrometer. The measurement unit 50 measures the Rayleigh waves that have propagated to a measurement point on the surface of the fruit or vegetable 20. More specifically, the measurement unit 50 measures the response of the fruit or vegetable 20 to the pressure wave. The response here is the displacement of the surface of the fruit or vegetable 20. The measurement unit 50 transmits the measured displacement to the control device 60. The measurement point is the position where the displacement of the surface of the fruit or vegetable 20 is measured, and is a position on the surface of the fruit or vegetable 20.

The measuring unit 50 moves around the fruit or vegetable 20 around the orbit center under the control of the control device 60. The orbit along which the measuring unit 50 moves describes a circle with the orbit center as the center.

More specifically, the measurement unit 50 can move in a circular motion around the center of the orbit, at a position a certain distance away from the center of the orbit, along a plane (hereinafter sometimes referred to as the orbit plane) that includes the center of the orbit and is inclined at an angle θ with respect to a horizontal plane that also includes the center of the orbit. θ is an angle greater than or equal to 0 degrees and less than 180 degrees.

When measuring the Rayleigh wave, the measuring unit 50 moves as shown in (1) to (4) below.
(1) Starting from a position on the orbital plane of θ = 0 degrees (i.e., a horizontal plane including the center of the orbit), the robot moves around the fruit or vegetable 20 at a constant angle Δη (here, Δη = 7.5 degrees) until it has completed one revolution around the fruit or vegetable 20.
(2) Along an orbital plane with θ of 7.5 degrees, the robot starts from a position on the orbital plane and moves in increments of Δη (=7.5 degrees) until it has completed one revolution around the fruit or vegetable 20 .
(3) Repeat (2) while increasing θ by 7.5 degrees each time.
(4) Starting from a position on the orbital surface as a starting point, the robot moves in increments of Δη (=7.5 degrees) along the orbital surface with θ being 172.5 degrees (=180 degrees-7.5 degrees) until it has completed one revolution around the fruit or vegetable 20.

This allows the measurement points to be set anywhere on the entire surface of the fruit or vegetable 20, except for the positions that become the excitation points. In other words, depending on the shape of the fruit or vegetable 20, the measurement unit 50 can measure Rayleigh waves at substantially all positions on the surface of the fruit or vegetable 20, except for the positions that become the excitation points.

In this embodiment, in principle, 48 measurement points can be set around the circumference of the fruit or vegetable 20, and the angle θ from the horizontal plane can take 24 values from 0 degrees to 172.5 degrees. Also, considering that positions that become vibration points cannot be set as measurement points, a maximum of 1151 (= 48 x 24 - 1) measurement points can be set on the surface of the fruit or vegetable 20.

The control device 60 controls the entire damage detection device 100. The control device 60 includes a memory unit 61 and a CPU (Central Processing Unit) (not shown).

The memory unit 61 includes a read only memory (ROM) and a random access memory (RAM). The memory unit 61 stores a predetermined program for detecting damage to the fruit or vegetable 20.

The CPU reads out a specific program stored in the ROM, expands it into the RAM, and executes the expanded program to function as the control unit 62 and the detection unit 63.

The control unit 62 controls the emission of laser light from the laser device 41. The control unit 62 transmits an output signal to the laser device 41 when a detection signal is received or when a predetermined condition is met. The predetermined condition will be described in detail later.

The control unit 62 controls the position of the measurement unit 50 by sending a movement signal to the measurement unit 50 indicating the position where the measurement unit 50 should be located.

The detection unit 63 detects damage to the fruit or vegetable 20 based on the Rayleigh waves measured by the measurement unit 50. The detection unit 63 determines the correspondence between the measurement points and the propagation speed of the Rayleigh waves at the measurement points based on the measurement results from the measurement unit 50. The measurement unit 50 then detects damage to the fruit or vegetable 20 based on the determined correspondence.

Figure 1B is a flowchart showing the operation of the device 100 for detecting damage to fruit or vegetable 20 according to the first embodiment of the present invention.

First, the control unit 62 determines whether or not the fruit or vegetable 20 has been placed on the placement unit 30 (step S1). Here, if the control unit 62 receives a detection signal from the placement unit 30, it determines that the fruit or vegetable 20 has been placed on the placement unit 30, and if the control unit 62 does not receive the detection signal, it determines that the fruit or vegetable 20 has not been placed on the placement unit 30.

First, if the control unit 62 determines that no fruit or vegetable 20 is placed on the placement unit 30 (NO in step S1), the control unit 62 repeats the process in step S1.

If fruit or vegetable 20 is placed on the placement unit 30 (YES in step S1), the control unit 62 controls the vibration generating device 40 to emit laser light (step S2).

Next, the measurement unit 50 measures the Rayleigh waves on the surface of the fruit or vegetable 20 (step S3). The measurement in step S3 is performed for a predetermined time, for example, about 3 milliseconds from the time the pressure wave hits the fruit or vegetable.

The measurement unit 50 starts measuring the displacement of the surface of the fruit or vegetable 20 a certain time (e.g., 10 milliseconds) before the control unit 62 sends an output signal to the vibration generating device 40. Rayleigh waves are generated when the pressure waves generated by the processing in step S2 hit the fruit or vegetable 20, so the measurement of the Rayleigh waves is performed after step S2.

Next, the control unit 62 determines whether a predetermined condition is met (step S4). The predetermined condition is that the number of measurements of the Rayleigh wave for one fruit or vegetable 20 has reached a predetermined number. The predetermined number is a predetermined number of measurements of the Rayleigh wave for one fruit or vegetable 20. The predetermined number is, for example, 1151 times. 1151 times corresponds to the maximum number of measurement points that can be set by the damage detection device 100 of this embodiment.

If the predetermined condition is not met (NO in step S4), the control device 60 changes the measurement point of the Rayleigh wave (step S5). In step S5, the control unit 62 moves the measurement unit 50.

The damage detection device 100 repeats the processes of steps S2 to S5 until the number of measurements reaches a predetermined number. Each time a measurement is performed on one fruit or vegetable 20, the Rayleigh waves are measured at a different measurement point. In other words, the damage detection device 100 measures Rayleigh waves at multiple measurement points on one fruit or vegetable 20.

If the predetermined condition is met (YES in step S4), the damage detection device 100 performs damage detection processing on the fruit or vegetable 20 (step S6).

In step S6, the following process is executed. First, the detection unit 63 determines the correspondence between the position on the surface and the propagation speed of the Rayleigh wave based on the measurement results by the measurement unit 50. The detection unit 63 then refers to this correspondence, and if there is a position on the surface where the propagation speed of the Rayleigh wave is lower than the propagation speed of the Rayleigh wave at other positions on the surface of the fruit or vegetable 20 by a predetermined percentage or more (hereinafter referred to as a speed reduction position), the detection unit 63 determines that the fruit or vegetable 20 is damaged. On the other hand, if there is no speed reduction position on the surface, the detection unit 63 determines that the fruit or vegetable 20 is not damaged. The predetermined percentage is a criterion for determining the speed reduction rate, and is, for example, 40%.

In addition, if it is determined that the fruit or vegetable 20 is damaged, the detection unit 63 calculates the distribution of speed reduction positions on the surface, and identifies the extent of the damage on the surface of the fruit or vegetable 20 based on the calculated distribution.

A specific example of the process performed in step S6 will be described below with reference to Figures 1C and 1D. It is assumed that the fruit or vegetable 20 is an apple, and the vibration point is set at the equator of the apple. The equator is located on the surface of the apple, and is a portion that is located in a position that approximately halves the distance between the upper end of the rachis depression and the lower end of the calyx depression in the direction along the apple's core.

Based on the measurement results by the measurement unit 50, the detection unit 63 determines the correspondence between parameters corresponding to positions on the surface of the fruit or vegetable 20 (i.e., measurement points), time, and the displacement of the surface of the fruit or vegetable 20.

Figure 1C is a diagram showing an example of the correspondence relationship between parameters corresponding to position, time, and the displacement of the surface of the fruit or vegetable 20. The measurement unit 50 measures the change in the displacement of the surface of the fruit or vegetable 20 over time for each measurement point. The detection unit 63 determines the correspondence relationship shown in Figure 1C by arranging the measurement results at measurement points located at the equator. GR1 in Figure 1C will be explained later.

In Figure 1C, angle is shown as a parameter corresponding to position. The angle refers to the angle indicated by the direction from the center of fruit or vegetable 20 toward each measurement point, when the direction from the center of fruit or vegetable 20 toward the vibration point at the equator of fruit or vegetable 20 is set to 0 degrees. The displacement in Figure 1C is shown changing from white to black as its value decreases from +1 μm to -1 μm. The displacement is the amount of movement of the surface of fruit or vegetable 20 from its position when it is not vibrated. The time on the horizontal axis is the elapsed time from the time when measurement of the displacement of the surface of fruit or vegetable 20 began.

In FIG. 1C, the line RW01, which extends so that the angle increases as time increases, and the line RW02, which extends so that the angle decreases as time increases, are lines that indicate Rayleigh waves. When the excitation point is fixed and the measurement unit 50 is moved as in the embodiment, the length from the excitation point to the measurement point during measurement changes each time the measurement unit 50 moves. Therefore, as shown in FIG. 1C, the lines RW01 and RW02 that indicate Rayleigh waves extend diagonally. The lines RW01 and RW02 are composed of lines that connect parts that show relatively large displacements in an approximately linear manner. The lines that connect parts that show relatively large displacements in an approximately linear manner are lines that connect white parts in FIG. 1C in an approximately linear manner, or lines that connect black parts in an approximately linear manner. In FIG. 1C, the lines RW01 and RW02 are shown as lines that connect white parts in an approximately linear manner. The absolute value of the slope of the lines RW01 and RW02 is the propagation speed of the Rayleigh waves.

The detection unit 63 determines the propagation velocity of the Rayleigh wave at the measurement point based on the absolute value of the slope of one of the lines indicating the Rayleigh wave, for example, line RW01. The detection unit 63 then determines whether there is a measurement point (i.e., a position of velocity reduction) where the propagation velocity is 40% or more lower than the propagation velocity at the other measurement points. If there is a position of velocity reduction, the detection unit 63 determines the measurement point corresponding to the position of velocity reduction.

Figure 1D is a diagram for explaining a specific example of the damage determination process executed by the damage detection device 100. As shown in Figure 1D, the line RW01 (the white line portion in Figure 1D) is composed of three straight line portions RPT1, RPT2, and RPT3.

The detection unit 63 determines that the propagation velocity of the Rayleigh wave is V11 at all measurement points located in the range on the surface corresponding to the straight line portion RPT1. Similarly, the detection unit 63 determines that the propagation velocity of the Rayleigh wave is V12 at all measurement points located in the range on the surface corresponding to the straight line portion RPT2. The detection unit 63 also determines that the propagation velocity of the Rayleigh wave is V13 at all measurement points located in the range on the surface corresponding to the straight line portion RPT3. Note that V11, V12, and V13 are determined based on the absolute values of the slopes of the straight line portions RPT1, RPT2, and RPT3. In this way, the detection unit 63 determines the correspondence between the measurement points on the equator and the propagation velocity of the Rayleigh wave.

V12 is at least 40% smaller than both V11 and V13. Therefore, the detection unit 63 determines that there is a speed reduction position, and further determines all measurement points located at positions on the surface corresponding to the straight line portion RPT2 (measurement points within a range of 75 degrees or more and 112.5 degrees or less) as speed reduction positions. The detection unit 63 then identifies the position range on the surface corresponding to the determined speed reduction positions as the range in which damage exists.

In FIG. 1D, line RW01, one of the straight lines representing a Rayleigh wave, is made up of three straight line segments, but if the fruit or vegetable 20 is not damaged, it is often made up of a single straight line segment. In this case, it can be said that the Rayleigh wave propagates at a nearly constant propagation speed regardless of its position on the surface.

As described above, the damage detection device 100 according to the embodiment measures Rayleigh waves at multiple points on the surface of the fruit or vegetable 20. Then, based on the measurement points and the magnitude of the propagation speed of the Rayleigh waves, if a point of reduced speed is present, it is determined that damage exists on the surface of the fruit or vegetable 20. Thus, damage to the fruit or vegetable 20 can be detected.

In addition, the damage detection device 100 determines the correspondence between the measurement points and the propagation speed of the Rayleigh waves, and determines the distribution of the speed reduction positions from the determined correspondence. Therefore, the damage detection device 100 can identify the range of damage on the surface of the fruit or vegetable 20.

The damage detection device 100 generates Rayleigh waves on the surface of the fruit or vegetable 20 by applying pressure waves generated when a LIP is formed to the fruit or vegetable 20, without irradiating the fruit or vegetable 20 with laser light or striking it. This makes it possible to detect damage without damaging the fruit or vegetable 20. Therefore, as described above, even if the fruit or vegetable 20 is a berry, stone fruit, pome fruit, or strawberry fruit, that is, a fruit or vegetable that is easily damaged, damage can be inspected without compromising the commercial value of the fruit or vegetable 20.

(Variation 1)
The damage detection device 100 according to the first modification will be described below, focusing mainly on the differences from the above-described embodiment.

The placement unit 30 of the damage detection device 100 according to the modified example functions as a position change unit. The placement unit 30 changes the position of the fruit or vegetable 20 relative to the measurement unit 50 under the control of the control device 60.

The placement unit 30 rotates the fruit or vegetable 20 around three mutually perpendicular axes, the X-axis, the Y-axis, and the Z-axis. Here, in this modified example, the X-axis, the Y-axis, and the Z-axis are rotation axes that pass through the fruit or vegetable 20 and intersect with each other at one point in the fruit or vegetable 20 (hereinafter, this one point may be referred to as the center of rotation).

As in the embodiment, the placement unit 30 is configured to adjust the position of the fruit or vegetable 20 in the X-axis, Y-axis, and Z-axis directions according to the size and shape of the fruit or vegetable 20. This allows the center of the fruit or vegetable 20 to coincide with the center of rotation.

The measurement unit 50 in the first modification is disposed at a position where the angle formed by a line (hereinafter referred to as a first line) connecting the position where the LIP is formed (i.e., the position where the pressure wave is generated) and one rotation axis, and a line (hereinafter referred to as a second line) that intersects with the first line and connects the measurement unit 50 and the one rotation axis is a predetermined angle (e.g., 15 degrees). Here, the one rotation axis is a rotation axis perpendicular to a plane including the first line and the second line. The predetermined angle may be any angle greater than 0 degrees and less than or equal to 15 degrees. Note that the measurement unit 50 does not move around the fruit or vegetable 20, unlike the above-described embodiment.

The control unit 62 according to the first modification controls the placement unit 30 instead of controlling the position of the measurement unit 50. More specifically, the control unit 62 transmits a posture control signal to the placement unit 30 to change the posture of the fruit or vegetable 20. The posture control signal includes, for example, information indicating the angle to be rotated around the mutually orthogonal X-axis, Y-axis, and Z-axis.

In this way, the damage detection device 100 according to variant example 1 changes the measurement point of the Rayleigh wave by changing the orientation of the fruit or vegetable 20 relative to the measurement unit 50, instead of moving the measurement unit 50.

The operations performed by the damage detection device 100 in the first modified example are the same as those performed by the damage detection device 100 in the embodiment, except for the processing contents of steps S5 and S6.

In the first modification, in step S5, the control unit 62 controls the placement unit 30 to change the orientation of the fruit or vegetable 20 relative to the measurement unit 50. As a result, the measurement point is changed.

A specific example of the process performed in step S6 in Modification 1 will be described below with reference to Figures 1E and 1F. Note that the damage in the following description is assumed to be present over a relatively wide area on the surface. Also, it is assumed that the measuring unit 50 is positioned so that the specified angle is 15 degrees. Furthermore, it is assumed that the fruit or vegetable 20 is an apple.

Figures 1E and 1F are examples of measurement results obtained by the damage detection device 100 for the fruit or vegetable 20 according to the first modification, and are graphs showing the change in displacement of the surface of the fruit or vegetable 20 over time.

Figures 1E and 1F show the measurement results at different measurement points. The time on the horizontal axis indicates the elapsed time from the time when measurement of the displacement of the surface of the fruit or vegetable 20 was started. PT1 and PT2 in Figures 1E and 1F will be explained later. Below, the graphs in Figures 1E and 1F will be explained as being the measurement results at measurement points M1 and M2 located on the equator of the fruit or vegetable 20.

First, the detection unit 63 determines a velocity parameter corresponding to the propagation velocity of the Rayleigh wave in the range on the surface from the excitation point to the measurement point based on a graph showing the change over time in the displacement of the surface at each measurement point on the equator. This velocity parameter is the reciprocal of the time it takes for the Rayleigh wave to reach the measurement point after it is generated at the excitation point.

For example, in the graphs of Figures 1E and 1F, the times from when the Rayleigh wave is generated until it reaches measurement points M1 and M2 are TAR1 and TAR2, respectively. Therefore, the speed parameters from the excitation point to measurement points M1 and M2 can be found by calculating the reciprocals of TAR1 and TAR2, respectively.

The detection unit 63 compares the obtained speed parameters to determine whether there is a range on the surface where the speed parameter is 40% or more smaller than the speed parameters in other ranges (hereinafter referred to as a speed reduction range).

In variant 1, the length from the excitation point to the measurement point is kept almost constant, so the length from the excitation point to the measurement point is constant regardless of the position of the measurement point. Therefore, the propagation speed of the Rayleigh wave in the range from the excitation point to the measurement point is inversely proportional to the time it takes for the Rayleigh wave to reach the measurement point after it is generated, and is proportional to the speed parameter in the range from the excitation point to the measurement point.

Therefore, by making a judgment based on the value of the speed parameter, the detection unit 63 determines whether or not there is a range on the surface where the propagation speed is 40% or more lower than the propagation speed in other ranges on the surface. Furthermore, the speed reduction range includes a speed reduction position. Therefore, as described above, by making a judgment based on the value of the speed parameter, the detection unit 63 determines whether or not there is a speed reduction position.

The speed parameter from the excitation point to measurement point M2 is approximately 53% smaller than the speed parameter from the excitation point to measurement point M1. Therefore, the detection unit 63 determines that there is a speed reduction range, i.e., a speed reduction position, and further determines that there is damage to the fruit or vegetable 20. The detection unit 63 then identifies the range of damage on the surface based on the distribution of the speed reduction positions, i.e., the speed reduction range on the surface.

If it is determined that there is no speed reduction position, the detection unit 63 determines that there is no damage to the fruit or vegetable 20.

The above-mentioned process is effective when the length from the excitation point to the measurement point is equal to or shorter than the length of the damage range. When the damage range is small enough that the length of the damage range is shorter than the length from the excitation point to the measurement point, only the velocity parameters that propagate between the range where the damage exists and the range where the damage does not exist can be calculated. In other words, the velocity parameters of the Rayleigh wave that propagates only through the range where the damage exists cannot be calculated. Therefore, when the criterion for the rate of decrease in the propagation velocity (velocity parameter) is set to 40%, the detection unit 63 may determine that there is no damage even though there is damage. For this reason, the shorter the length from the excitation point to the measurement point is, that is, the smaller the above-mentioned specified angle is, the higher the accuracy of damage detection. In addition, the damage range can be identified with high accuracy.

As described above, the damage detection device 100 according to the first modified example changes the measurement point by changing the attitude of the fruit or vegetable 20 relative to the measurement unit 50. By making such changes multiple times, it is possible to perform Rayleigh wave measurements at various positions on the surface of the fruit or vegetable 20 without moving the measurement unit 50. This allows the measurement point to be changed in a shorter time, and ultimately makes it possible to more efficiently inspect the fruit or vegetable 20 for damage using the damage detection device 100.

The damage detection device 100 according to the first modification changes the attitude of the fruit or vegetable 20 relative to the measurement unit 50, so the positional relationship between the position of the measurement unit 50 and the position where the LIP is formed does not change. In addition, since the excitation point is also changed in conjunction with the change in the measurement point, the measurement point can be changed one after another without changing the positional relationship between the measurement point and the excitation point.

That is, even if the measurement point is changed, the distance between the measurement point and the vibration point is maintained approximately constant. Furthermore, the measurement unit 50 is positioned at a position where the angle formed by the line connecting the position where the LIP is formed and the rotation axis and the line that intersects with the line connecting the measurement unit 50 and the rotation axis is greater than 0 degrees and is less than or equal to 15 degrees. This improves the accuracy of detecting damage to the fruit or vegetable 20. Specifically, it is possible to more accurately determine whether or not damage is present in the fruit or vegetable 20, and to more accurately identify the extent of the damage.

(Variation 2)
The damage detection device 100 according to the second modification will be described below, focusing mainly on the differences from the first modification described above.

The difference from Modification 1 is the processing performed in step S6. In Modification 2, in step S6, the detection unit 63 performs pattern recognition on the measurement results of the measurement unit 50 to determine whether or not there is damage to the fruit or vegetable 20. The detection unit 63 also performs pattern recognition on the measurement results of the measurement unit 50 to identify the extent of damage on the surface. An example of pattern recognition performed by the damage detection device 100 of Modification 2 is described below. The following description is an example in which the fruit or vegetable 20 is an apple, and processing is performed on the measurement results at a measurement point located on the equator.

<Pattern Recognition Example 1>
A waveform (hereinafter referred to as the reference waveform) that is used as a reference for pattern recognition is stored in advance in the memory unit 61. The reference waveform is a waveform that indicates the change over time in the surface displacement at a position on the surface of the fruit or vegetable 20 when a Rayleigh wave propagates through that position where there is no damage on the surface of the fruit or vegetable 20. FIG. 2A is an example of a waveform that indicates the change over time in the surface displacement of the fruit or vegetable, which is used as a reference when the detection unit 63 performs pattern recognition. The time range PT in FIG. 2A is the time range in which a partial waveform (hereinafter referred to as the reference partial waveform) that is to be compared in the pattern recognition is located. The reference partial waveform includes a waveform portion that indicates a Rayleigh wave component. The time on the horizontal axis indicates the elapsed time from the time when measurement of the surface displacement of the fruit or vegetable 20 was started.

The detection unit 63 determines the correspondence between the surface displacement and time for each position (i.e., measurement point) on the surface of the fruit or vegetable 20 based on the measurement results by the measurement unit 50. The correspondence determined here indicates the time history waveform of the displacement of the surface of the fruit or vegetable 20 at the measurement point.

In the following description, it is assumed that the relationship between displacement and time obtained based on the measurement results by the measurement unit 50 includes the relationship between displacement and time shown in Figures 1E and 1F.

The detection unit 63 performs pattern recognition on the time history waveform of each measurement point based on the reference partial waveform. First, the detection unit 63 extracts a predetermined waveform portion (hereinafter referred to as the extracted waveform) from the time history waveform at each measurement point so that the waveform portion showing the Rayleigh wave component is included. For the time history waveforms of Figures 1E and 1F, the detection unit 63 extracts the waveform portion of time range PT1 and the waveform portion of time range PT2, respectively, as the extracted waveform. The detection unit 63 then compares the extracted waveforms corresponding to all measurement points with the reference partial waveform to determine whether the extracted waveform and the reference partial waveform have the same shape.

For example, if the extracted waveform has a displacement that is more than twice the maximum displacement in the reference partial waveform, the detection unit 63 determines that the extracted waveform and the reference partial waveform are different waveforms. Also, if the extracted waveform does not have a displacement that is more than twice the maximum displacement, the detection unit 63 determines that the extracted waveform and the reference partial waveform are the same waveform.

The maximum displacement of the extracted waveform in FIG. 1E is approximately 0.5 μm, and the maximum displacement of the extracted waveform in FIG. 1F is approximately 3.7 μm. Therefore, the detection unit 63 determines that the extracted waveform in FIG. 1E is the same waveform as the reference partial waveform, and determines that the extracted waveform in FIG. 1F is a waveform different from the reference partial waveform.

When the detection unit 63 determines that the extracted waveforms corresponding to all measurement points are the same as the reference partial waveform, it determines that there is no damage to the fruit or vegetable 20. When the extracted waveforms corresponding to all measurement points include even one extracted waveform that is determined to be different from the reference partial waveform, the detection unit 63 determines that there is damage to the fruit or vegetable 20.

In addition, the detection unit 63 identifies the extent of damage on the surface of the fruit or vegetable 20 based on the positions of the measurement points corresponding to the extracted waveform that is determined to be different from the reference partial waveform.

The memory unit 61 may store only the reference partial waveform, i.e., the waveform of the portion to be compared. The standard for the magnitude of displacement does not necessarily have to be twice the maximum displacement of the reference partial waveform. Furthermore, when determining whether the extracted waveform and the reference partial waveform have the same shape, the detection unit 63 may make the determination based on a characteristic part of the waveform other than the magnitude of displacement, such as the wavelength.

<Pattern Recognition Example 2>
A second example of pattern recognition will now be described with reference to Fig. 2B. In the following description, it is assumed that the fruit or vegetable 20 is an apple.

Based on the measurement results by the measurement unit 50, the detection unit 63 determines the correspondence between parameters corresponding to positions on the surface of the fruit or vegetable 20 (i.e., measurement points), time, and the displacement of the surface of the fruit or vegetable 20, and generates an image showing this correspondence.

Figure 2B is a diagram showing an example of the correspondence relationship between parameters corresponding to position, time, and the displacement of the surface of the fruit or vegetable 20. The detection unit 63 determines the correspondence relationship shown in Figure 2B by arranging the measurement results (i.e., a graph of the change in displacement over time) at measurement points located at the equator.

In Figure 2B, the angle on the vertical axis, the time on the horizontal axis, and the color of the displacement have the same meanings as the angle, time, and displacement in Figure 1C, so a detailed explanation will be omitted.

As with variant 1, variant 2 utilizes a measurement method in which the measurement point is switched by changing the orientation of the fruit or vegetable 20. Therefore, even if the measurement point is changed, the length from the excitation point to the measurement point remains almost the same. Therefore, line RW03 indicating the Rayleigh wave is a line that extends approximately parallel to the direction in which the straight line indicating the same time extends. Line RW03 is composed of lines that connect in an approximately linear manner parts that indicate relatively large displacements. Lines that connect in an approximately linear manner parts that indicate relatively large displacements are lines that connect in an approximately linear manner white parts in Figure 2B or lines that connect in an approximately linear manner black parts. In Figure 2B, line RW03 is shown as a line that connects in an approximately linear manner white parts.

GR2 in Figure 2B (the area within the dashed double-dashed line frame) is the image generated by the detection unit 63.

The detection unit 63 performs pattern recognition on the generated image. First, the detection unit 63 searches for lines indicative of Rayleigh waves in the image GR2. Then, if the detection unit 63 determines that the lines indicative of Rayleigh waves are not divided from 0 degrees to 360 degrees, it determines that there is no damage to the fruit or vegetable 20. If the detection unit 63 determines that the lines indicative of Rayleigh waves are divided into multiple lines, it determines that there is damage to the fruit or vegetable 20.

The detection unit 63 performs pattern recognition on the image GR2 and finds the line RW03. The detection unit 63 then determines that the line RW03 is divided by the dividing portion SPT. The detection unit 63 then determines that the fruit or vegetable 20 is damaged.

The detection unit 63 further identifies the angle range of the divided portion SPT. Then, based on the identified angle range, the detection unit 63 identifies the range in which damage exists on the surface of the fruit or vegetable 20. For example, the detection unit 63 identifies an angle range of 75 degrees or more and 112.5 degrees or less as the range in which damage exists.

The pattern recognition performed in variant example 2 is not limited to the two examples described above. Any method can be used that can determine whether the propagation state of the Rayleigh waves is different from the propagation state of the Rayleigh waves in other parts.

As described above, the damage detection device 100 according to the second modification can identify the presence or absence of damage and the extent of the damage by performing pattern recognition on the measurement results of the Rayleigh waves. Furthermore, the damage detection device 100 according to the second modification can achieve the same effects as the damage detection device 100 according to the first modification.

(Variation 3)
The damage detection device 100 according to the third modification will be described below, focusing mainly on the differences from the above-described embodiment.

The difference from the embodiment is the process performed in step S6. In the third modification, in step S6, the detection unit 63 performs pattern recognition on the measurement results of the measurement unit 50 to determine whether or not there is damage to the fruit or vegetable 20. The detection unit 63 also performs pattern recognition on the measurement results of the measurement unit 50 to identify the extent of the damage on the surface.

<Pattern Recognition Example 3>
As in the above-described pattern recognition example 1, the detection unit 63 determines whether or not a reference partial waveform in a reference waveform previously stored in the storage unit 61 is the same waveform as an extracted waveform in the time history waveform at each measurement point, thereby determining the presence or absence of damage. Furthermore, the detection unit 63 identifies the extent of damage on the surface of the fruit or vegetable 20 based on the position of the measurement point corresponding to the extracted waveform determined to be a waveform different from the reference partial waveform.

In addition, in the third modification, the excitation point is fixed while the measurement unit 50 moves it, so that the length from the excitation point to the measurement point changes each time the measurement point is switched. Therefore, the time at which the Rayleigh wave arrives at each measurement point is different. For this reason, the time range corresponding to the extracted waveform in the time history waveform at each measurement point shifts to a later time depending on the length from the excitation point to the measurement point. Apart from this, the detection unit 63 determines whether or not damage exists and identifies the range in which the damage exists in the same way as in the first pattern recognition example.

<Pattern Recognition Example 4>
1C and 1D, a fourth example of pattern recognition executed by the damage detection device 100 of the third modification will be described below. Differences from the second example of pattern recognition described above will be mainly described.

Based on the measurement results from the measurement unit 50, the detection unit 63 determines the correspondence between parameters corresponding to positions on the surface of the fruit or vegetable 20 (i.e., measurement points), time, and surface displacement, and generates an image showing this correspondence. In the following description, it is assumed that the image GR1 (portion within the two-dot chain line frame) shown in Figures 1C and 1D was generated by the detection unit 63.

The detection unit 63 performs pattern recognition on the generated image GR1.

The detection unit 63 searches for a line indicative of a Rayleigh wave in the image GR1. If the detection unit 63 determines that the line indicative of a Rayleigh wave is made up of approximately one straight line segment, it determines that there is no damage to the fruit or vegetable 20. If the detection unit 63 determines that the line indicative of a Rayleigh wave is made up of multiple straight line segments, it determines that there is damage to the fruit or vegetable 20.

The detection unit 63 performs pattern recognition on the image GR1 and finds the line RW01 (the white line portion in FIG. 1D). The detection unit 63 then determines that the line RW01 is composed of three straight line portions RPT1, RPT2, and RPT3. The detection unit 63 then determines that the fruit or vegetable 20 is damaged.

The detection unit 63 further identifies the angle range of the straight line portion PRT2, which is a portion whose inclination is significantly different from that of the straight line portions RPT1 and RPT3. The detection unit 63 then identifies the range in which damage exists on the surface of the fruit or vegetable 20 based on the identified angle range. The detection unit 63 identifies, for example, an angle range of 75 degrees or more and 112.5 degrees or less as the range in which damage exists.

The pattern recognition performed in variant example 3 is not limited to the two examples described above. Any method can be used that can determine whether the propagation state of the Rayleigh waves is different from the propagation state of the Rayleigh waves in other parts.

As described above, the damage detection device 100 according to the third modification can identify the presence or absence of damage and the extent of the damage by performing pattern recognition on the measurement results of the Rayleigh waves. Furthermore, the damage detection device 100 according to the third modification can achieve the same effects as the damage detection device 100 according to the first modification.

(Other Modifications)
When damage detection device 100 moves measuring unit 50 around fruit or vegetable 20, damage detection device 100 only needs to include measuring unit 50 and control device 60, and does not necessarily need to include mounting unit 30 and vibration generating device 40. In other words, mounting unit 30 and vibration generating device 40 may be devices prepared separately from damage detection device 100.

The method of applying pressure waves to the fruit or vegetable 20 is not limited to the method of forming a LIP using laser light, and any method that can vibrate the surface of the fruit or vegetable 20 may be used. Thus, for example, a Rayleigh wave may be generated (i.e., vibration may be applied) in the fruit or vegetable 20 using an acoustic device such as a speaker. However, it is preferable that the pressure wave is applied to the excitation point of the fruit or vegetable 20 in a small area that can be considered as a point. Alternatively, a vibration device such as a vibrator may be used to generate a Rayleigh wave (i.e., vibration) by contacting the fruit or vegetable 20. However, from the viewpoint of detecting damage without causing any additional damage to the fruit or vegetable 20, it is preferable to use a device that vibrates the fruit or vegetable 20 without contacting the fruit or vegetable 20.

The number of measurements of the Rayleigh wave for one fruit or vegetable 20 is not limited to 1151. From the viewpoint of determining only the presence or absence of damage, the number of measurements may be less than 1151. In this case, the above-mentioned constant angle Δη is set to be greater than 7.5 degrees, and the angle θ is changed to a value greater than 7.5 degrees.

From the viewpoint of identifying the extent of the damage more accurately, the number of measurements may be greater than 1151. In this case, the above-mentioned constant angle Δη is set to be smaller than 7.5 degrees, and the angle θ is changed to a value smaller than 7.5 degrees.

The placement unit 30 in the first and second variants does not necessarily have to be configured to rotate the fruit or vegetable 20 around three axes, but only needs to be configured to rotate it around at least one rotation axis.

In the above-mentioned embodiment and each modified example, the measuring unit 50 measures the displacement of the surface of the fruit or vegetable 20 as the response of the fruit or vegetable 20 to the pressure wave. However, the measured response may be the velocity or acceleration corresponding to the vibration of the surface of the fruit or vegetable 20. When the velocity or acceleration is measured, the displacement value can be obtained by integrating the measurement result. In addition, since the measuring unit 50 only needs to measure the vibration of the surface of the fruit or vegetable 20, a laser displacement meter or the like may be used instead of a laser Doppler vibrometer. In addition, a camera capable of measuring the vibration of the surface of the fruit or vegetable 20 may be used as the measuring unit 50. When such a camera is used, the vibration at each position of the entire range of the surface of the fruit or vegetable 20 can be measured by measuring the fruit or vegetable 20 from at least two directions. Therefore, the number of movements of the measuring unit 50 according to the embodiment and modified example 3 and the number of changes in posture by the mounting unit 30 according to modified examples 1 and 2 can be reduced.

In the first and second variants, the measuring unit 50 is positioned so that the predetermined angle is greater than 0 degrees and less than or equal to 15 degrees, but from the viewpoint of determining whether or not damage has occurred, the predetermined angle may be greater than 15 degrees and less than or equal to 90 degrees.

The lens 43 of the vibration generating device 40 may be any lens capable of focusing laser light. For example, the lens 43 may be an objective lens, a focusing lens, a cylindrical lens, or a combination of these lenses.

In the embodiment and the second variant, the measurement unit 50 moves around the fruit or vegetable 20 in increments of Δη degrees from the starting point, but the measurement unit 50 may move in increments of Δη degrees from the starting point in one direction to a point on the opposite side of the starting point with respect to the center of the trajectory, and then move from the starting point in the other direction to the opposite point.

Example 1
The inventors have demonstrated through Experiment 1 that bruises on fruits and vegetables can be detected by measuring Rayleigh waves, which are an example of surface waves on fruits and vegetables. Experiment 1 conducted by the inventors will be described below.

<Test materials>
In this experiment, four apples were used as test materials, i.e., fruits and vegetables. More specifically, the apples were fresh "Sun Fuji" apples produced in Aomori Prefecture, with a diameter of about 10 cm. In the following description, the four apples will be referred to as Sample 1, Sample 2, Sample 3, and Sample 4, respectively.

<Damage detection system>
Fig. 3 is a schematic diagram showing a damage detection system 200 used in Experiment 1 according to Example 1. In Fig. 3, reference numeral 110 denotes an apple.

The damage detection system 200 includes a lab jack 130, a vibration generator 140, a laser Doppler vibrometer (LDV) 150, and an analyzer 170.

The lab jack 130 is a platform on which the apple 110 is placed. The height of the lab jack 130 is adjustable. The lab jack 130 has a cushion provided at the position where the apple is placed.

The vibration generating device 140 includes a laser device 141, a mirror 142, and a plano-convex lens 143.

A high-power Nd:YAG pulsed laser (Continum Inc. Surelite III-10, wavelength 1064 nm, beam diameter 9.5 mm, pulse width 5 ns, maximum output 850 mJ, divergence angle 0.5 mrad) was used as the laser device 141.

The mirror 142 changes the direction of the laser light LS emitted from the laser device 141 toward the position where the LIP is to be formed.

A plano-convex lens with a focal length of 100 mm was used as the plano-convex lens 143. The plano-convex lens 143 focuses the laser light LS whose direction of travel has been changed by the mirror 142. This forms a LIP, and as the LIP expands, a pressure wave is generated that propagates through the air. The impact of this pressure wave was used as a vibration force for the apple 110, causing the surface of the apple 110 to vibrate.

In this experiment, the laser pulse energy of the laser light was set to 850 mJ.

The laser fluence (i.e., energy density) I [W/ ^m2 ] required to form LIP in air is expressed as I=E/(ST) using the laser pulse energy E [J], the laser light irradiation time T [s], and the area S [ ^m2 ] of the region irradiated with the laser light LS. The threshold value of LIP in air is I≧ ¹⁰¹⁵ W/ ^m2 . In this experiment, the area S of the region in air irradiated with the laser light LS was adjusted so that the energy density I was ¹⁰¹⁵ W/m2 or ^more .

The positions of the laser device 141, mirror 142, and plano-convex lens 143, as well as the height of the lab jack 130, were adjusted so that the LIP was formed 3 mm from the surface of the apple 110.

Figure 4 is a diagram explaining the propagation of Rayleigh waves. Note that points P and BP are points on the surface of apple 110.

When the pressure wave generated when the LIP is formed hits point P, which is the excitation point of apple 110, an impact is applied to point P, causing it to vibrate. This generates a Rayleigh wave on the surface of apple 110. The Rayleigh wave propagates across the surface of apple 110 from point P as its starting point. The Rayleigh wave also propagates to point BP, which is located on the opposite side of point P.

Return to the explanation of Figure 3.

The laser Doppler vibrometer 150 is an instrument that measures the response of the apple 110 to pressure waves. In this experiment, an LDV (Polytec Inc. NLV-2500-5) was used as the laser Doppler vibrometer 150 to measure the displacement of the surface of the apple 110.

The dashed line in FIG. 3 is a curve (hereinafter referred to as a movement curve) that indicates a position a certain distance away from the center O of the apple 110. In this experiment, the laser Doppler vibrometer 150 was moved along the dashed line, and the displacement of the surface of the apple 110 was measured at multiple measurement points on the equator EQ of the apple 110. The measurement points set in this experiment will be described in detail later. The center O is the position that is the center position of the apple 110 in the X-axis direction, the center position of the apple 110 in the Y-axis direction, and the center position of the apple 110 in the Z-axis direction, when the three mutually perpendicular axes are the X-axis, Y-axis, and Z-axis.

In this experiment, a spectrum analyzer (NI PXI-4462) was used as the analyzer 170 to record the measurement results from the laser Doppler vibrometer 150.

<Excitation points and measurement points>
Fig. 5 is a diagram for explaining the excitation point IP and the measurement points MP1 to MP47 in Experiment 1. Fig. 5 shows the state of an apple 110 as viewed from above. BR in Fig. 5 indicates a bruise.

In this experiment, the excitation point IP and measurement points MP1 to MP47 were set on the equator EQ of the apple 110.

The excitation point IP is the position where the pressure wave caused by the LIP is applied. In this experiment, the excitation point IP was set on the equator EQ of the apple 110.

In explaining this experiment, the line connecting points O and IP is taken as the reference line, and the direction from point O to point IP along this reference line is referred to as the 0 degree direction. The position of point IP is also sometimes referred to as the 0 degree position.

In this experiment, 47 measurement points (measurement points MP1 to MP47) were set at equal intervals. Measurement points MP1 to 47 are the positions that are the subject of measurement by the laser Doppler vibrometer 150. Measurement points MP1 to 47 are each located in a direction rotated 7.5n degrees counterclockwise from the 0 degree direction, where n is an integer between 1 and 47. For example, measurement point MP1 is located at the 7.5 degree position, measurement point MP12 is located at the 90 degree position, measurement point MP24 is located at the 180 degree position, and measurement point MP36 is located at the 270 degree position.

＜Bruises＞
Samples 1 to 4 were stored in a refrigerator at a temperature of 0°C and a humidity of 50%, and were then left at room temperature for 1 hour. Then, the Rayleigh wave measurement described below was performed on Samples 1 to 4 without the bruise BR, and Samples 1 to 4 were then allowed to freely fall from a height of 15 cm and collided with a steel surface plate to leave a bruise BR at the equator EQ. In this experiment, the bruise BR was left on Samples 1 to 4 so that the bruise BR was located near the measurement point MP12.

In the case of an apple 110 with a bruise BR, although the flesh of the apple 110 is damaged, it is difficult to visually distinguish between the skin covering the damaged flesh and the skin covering the undamaged flesh. In other words, it is difficult to identify the location of the bruise BR just by looking at the skin of the apple 110.

<Rayleigh wave measurement>
In this experiment, each time a Rayleigh wave was measured, the laser Doppler vibrometer 150 was moved in the direction of the arrow Y1 in Fig. 3 from the 7.5 degree direction to the 180 degree direction in increments of 7.5 degrees. This allowed the Rayleigh waves at measurement points MP1 to MP24 to be measured one after another. The laser Doppler vibrometer 150 was also moved in the direction of the arrow Y2 in Fig. 3 from the 352.5 degree direction to the 187.5 degree direction in increments of 7.5 degrees. This allowed the Rayleigh waves at measurement points MP47 to MP25 to be measured one after another.

The laser device 141 emits laser light LS each time a Rayleigh wave is measured at one measurement point. For example, when the measurement of the Rayleigh wave at measurement point MP1 is completed, the laser device 141 emits laser light LS when measuring the Rayleigh wave at measurement point MP2.

＜Other＞
The inventors measured the Rayleigh waves for Samples 1 to 4 in an environment with a temperature of 20° C. and a humidity of 60%. The inventors measured the Rayleigh waves for Samples 1 to 4 both in a state in which the bruise BR was not made and in a state in which the bruise BR was made. The inventors also measured the Rayleigh waves for Samples 1 to 4 with the bruise BR made within 6 hours after the bruise BR was made on each of the samples.

For each measurement point, the displacement of the surface of the apple 110 was continuously measured using the laser Doppler vibrometer 150 for a fixed period of time, here about 13 milliseconds. Note that the laser Doppler vibrometer 150 started measuring the displacement of the surface of the apple 110 about 10 milliseconds before the Rayleigh waves were generated, and the displacement of the surface of the apple 110 was measured for about 3 milliseconds after the Rayleigh waves were generated on the surface of the apple 110.

<Results of Experiment 1>
Fig. 6 is an example of the measurement results of the surface displacement at several measurement points of the sample 4, and is a graph showing the change in the surface displacement over time. The graph in Fig. 6 shows the measurement results of the Rayleigh wave of the sample 4 in a state in which the contusion BR is not formed, and shows the change in the surface displacement over time at the measurement points MP6, MP12, and MP18.

Note that the displacement is the amount of movement of the surface of apple 110 from its position when it is not vibrating. When the surface moves in a direction from the center O of apple 110 toward the surface of apple 110 (hereinafter referred to as the radial direction), the sign of the displacement is positive, and when the surface moves in the opposite direction to the radial direction, the sign of the displacement is negative. The time is the elapsed time from the time when the laser Doppler vibrometer 150 started measuring the displacement of the surface of apple 110. The time when the Rayleigh wave was generated on the surface of apple 110 was 10 milliseconds.

Then, by arranging the graphs of the time change in the surface displacement at the measurement points MP1 to MP47 for each position of the measurement points MP1 to MP47, the correspondence between the parameter (here, angle) corresponding to the surface position of the sample 4, time, and displacement was generated.

Figure 7 shows the experimental results for sample 4, which does not have a bruise BR, and shows the relationship between the parameter (here, angle) corresponding to the position on the surface of sample 1, time, and the displacement of the surface of sample 4.

The angle on the vertical axis in Figure 7 corresponds to the position on the surface of sample 4. When n is an integer between 1 and 47, the integer 7.5n degrees corresponds to the position of measurement point MPn. In addition, the magnitude of the angle from 0 degrees to 360 degrees corresponds to the length of the circumference along the equator EQ of sample 4.

The displacement in Figure 7 is shown going from white to black as its value decreases from +1 μm to -1 μm.

In this experiment, the excitation point IP was fixed, while the measurement points MP1 to MP47 were switched in succession. Therefore, the time at which the Rayleigh wave reached the measurement points MP1 to MP47 became slower in proportion to the distance from the excitation point IP. Therefore, as shown in Figure 7, the Rayleigh wave is represented as a straight line RW1 whose angle value increases in proportion to time, and a straight line RW2 whose angle value decreases in proportion to time. Furthermore, the slopes of these straight lines RW1 and RW2 were almost constant without changing significantly along the way.

The straight line RW1 shows the Rayleigh wave propagating from the excitation point IP to the measurement points MP1, MP2, .... On the other hand, the straight line RW2 shows the Rayleigh wave propagating from the excitation point IP to the measurement points MP47, MP46, ....

The fact that the slope of the straight lines RW1 and RW2 does not change significantly along the way and is shown as a straight line with an almost constant slope means that the Rayleigh waves propagate at almost the same speed through measurement points MP1 to MP47 of sample 4. The propagation speed of the two Rayleigh waves is the absolute value of the slope of the straight lines RW1 and RW2, and its value was approximately 84 m/s.

Figure 8 shows the experimental results for Sample 4 with bruises BR, and is a diagram showing the correspondence between the parameter (here, angle) corresponding to the position on the surface of Sample 4 and the time and the displacement on the surface of Sample 4. The correspondence in Figure 8 is obtained by arranging the graphs of the time change in the surface displacement at measurement points MP1 to MP47 for Sample 4 with bruises BR for each position of measurement points MP1 to MP47.

In line RW3, which shows the Rayleigh wave, the absolute value of the slope in the angle range of 75 degrees or more and 112.5 degrees or less is smaller than the absolute value of the slope in the angle range of 0 degrees or more and less than 75 degrees, and the absolute value of the slope in the angle range of more than 112.5 degrees and less than 360 degrees. This result means that the propagation speed of the Rayleigh wave is smaller in the angle range of 75 degrees or more and 112.5 degrees or less.

The absolute value of the slope of line RW3 in the angle range of 0 degrees or more and less than 75 degrees, and in the angle range of more than 112.5 degrees and less than 360 degrees, was approximately the same as the absolute value of the slope of straight lines RW1 and RW2. Therefore, it can be said that the propagation speed of the Rayleigh wave propagating on the surface of sample 4 with dents BR is approximately the same as the propagation speed of the Rayleigh wave propagating on the surface of sample 4 without dents BR in the angle range of 0 degrees or more and less than 75 degrees, and in the angle range of more than 112.5 degrees and less than 360 degrees.

In FIG. 8, the magnitude of the propagation velocity of the Rayleigh wave in the angle range of 75 degrees or more and 112.5 degrees or less was calculated to be about 45 m/s from the absolute value of the slope of the line RW3 in the angle range of 75 degrees or more and 112.5 degrees or less. This value is about 46% smaller than the propagation velocity of the Rayleigh wave in sample 4 without the contusion BR (i.e., about 84 m/s). In other words, in sample 4 with the contusion BR, the propagation velocity of the Rayleigh wave in the angle range of 75 degrees or more and 112.5 degrees or less is about 46% smaller than the values in the angle range of 0 degrees or more and less than 75 degrees, and in the angle range of more than 112.5 degrees and less than 360 degrees.

Table 1 shows data on samples 1 to 4 obtained from this experiment. Note that the propagation velocity Vbf is data on samples 1 to 4 without the contusion BR, and is the average value of the propagation velocity of the Rayleigh wave at the equatorial region EQ. The propagation velocity Vaf is data on samples 1 to 4 with the contusion BR, and is the average value of the propagation velocity of the Rayleigh wave in the region where the propagation velocity of the Rayleigh wave is small. The velocity reduction rate indicates the rate of reduction of the propagation velocity Vaf relative to the propagation velocity Vbf, and can be expressed as (Vbf-Vaf) x 100/Vbf.

Table 1 shows that the masses of samples 1 to 4 are between 313.3g and 347.5g. Therefore, it can be said that samples 1 to 4 do not contain any extremely large or small apples.

Table 1 shows that the propagation velocity Vaf of samples 1 to 4 is at least 44% smaller than the propagation velocity Vbf of samples 1 to 4.

The inventors evaluated the size of the bruises BR in samples 1 to 4.

Figure 9 is a diagram for explaining the bruise BR on the apple 110. The upper part of Figure 9 shows a schematic diagram of the bruise BR when the apple 110 is viewed from a direction directly facing the bruise BR, and the lower part of Figure 9 shows a schematic diagram of the bruise BR when viewed from a direction perpendicular to the direction directly facing the bruise BR.

W1 and W2 are values relating to a plane (hereinafter referred to as the extension plane) that includes the extension direction of the bruise BR. W1 and W2 are the dimensions in the directions along two mutually perpendicular axes included in the extension plane.

y and b are the values of the bruise BR in the radial direction of the apple 110. y is the length of the depression of the surface of the apple 110 toward the center O due to the bruise BR. b is the length from the surface of the apple 110 before the bruise BR is made to the point of the bruise BR on that surface closest to the center O.

When using the enclosed volume method, the size of the bruise BR, or the bruise volume E, is expressed by the following formula:

The inventors used formula (1) to calculate the amount of bruising E for the four apples 110 used as test materials.

Table 2 shows the bruise BR values (W1, W2, y, and b), bruise volume, and range of bruise BR for samples 1 to 4.

Table 2 shows that the range of the bruise BR in sample 4 is 75 degrees or more and 112.5 degrees or less. This range corresponds to the angle range in which the propagation speed in sample 4 with the bruise BR is smaller than the surrounding area (i.e., the angle range from 75 degrees or more to 112.5 degrees or less).

The range where the Rayleigh wave propagation velocity is low in Samples 1 to 3 did not completely coincide with the range where the contusion BR exists in Samples 1 to 3 (see Table 2). However, the range where the Rayleigh wave propagation velocity is low in Samples 1 to 3 and the range where the contusion BR exists in each of Samples 1 to 3 (see Table 2) overlapped over a wide angular range. In other words, it was found that the range where the contusion BR exists corresponds to the range where the Rayleigh wave propagation velocity is low.

In this way, it was found that in the area where the bruise BR exists on the surface of the apple 110, the propagation speed is more than 40% slower than in the area where the bruise BR does not exist.

Therefore, it was found that by measuring the Rayleigh waves on the apple 110 and determining whether there is a position where the propagation speed of the Rayleigh waves is smaller than the propagation speed of other positions by a predetermined percentage or more, it is possible to determine whether the apple 110 has a bruise BR. It was also found that by identifying the range where the propagation speed of the Rayleigh waves is smaller than the propagation speed of other positions by a predetermined percentage or more, it is possible to identify the range where the bruise BR exists.

In addition, when the apple 110 does not have a bruise BR, in the correspondence relationship between the parameters corresponding to the surface position of the apple 110 and the surface displacement over time, the lines RW1 and RW2 indicating the Rayleigh waves were lines that could be considered to be approximately one straight line. On the other hand, when the apple 110 has a bruise BR, in the correspondence relationship between the parameters corresponding to the surface position of the apple 110 and the surface displacement over time, the absolute value of the slope of the line RW3 indicating the Rayleigh waves changed in the angle range corresponding to the presence range of the bruise BR compared to the absolute value of the slope of the line indicating the Rayleigh waves outside that angle range. In other words, the line RW3 was composed of multiple straight line segments. Therefore, it was found that it is possible to determine whether the apple 110 has a bruise BR by determining whether the line indicating the Rayleigh waves can be considered to be approximately one straight line in the correspondence relationship between the parameters corresponding to the surface position of the fruit or vegetable and the surface displacement over time. Furthermore, it was found that the range in which the bruise BR exists can be identified by identifying the angle range of the straight line portion that has a different slope compared to other straight line portions in the line showing the Rayleigh wave.

Example 2
The inventors carried out Experiment 2 in which the Rayleigh wave on the surface of fruit or vegetable was measured while keeping the distance between the excitation point IP and the measurement point constant. Hereinafter, Experiment 2 will be described, focusing mainly on the differences from Experiment 1.

<Test materials>
As in Experiment 1, Samples 1 to 4 were used as test materials.

＜Bruises＞
The storage conditions of sample 4 and the method of applying the bruise BR were the same as in experiment 1.

<Damage detection system>
The damage detection system used in Experiment 2 includes a rotating platform instead of the lab jack 130. The rotating platform is a platform that can rotate around the vertical direction. That is, the axis of rotation is along the vertical direction. The inventors placed the apple 110 on the rotating platform so that the axis of rotation passes through the center of the apple.

The laser Doppler vibrometer 150 is positioned so that the angle formed by the line connecting the position where the LIP is formed and the axis of rotation and the line that intersects with the line connecting the laser Doppler vibrometer 150 and the axis of rotation is a constant angle (hereinafter referred to as angle α).

<How to measure Rayleigh waves>
In this experiment, the position of the laser Doppler vibrometer 150 was set so that the angle α was 15 degrees, 45 degrees, and 90 degrees for samples 1 to 4 without the bruise BR and samples 1 to 4 with the bruise BR, and measurements of Rayleigh waves propagating to 48 measurement points (measurement points MP1 to MP48) on the equator EQ were performed under each set condition. Measurement points MP1 to MP47 correspond to measurement points MP1 to MP47 in experiment 1. Measurement point MP48 is a measurement point located in the 0 degree direction.

First, the position of the laser Doppler vibrometer 150 relative to the position where the LIP is formed was set so that the angle α was 15 degrees. Then, a measurement was performed of the Rayleigh wave that had propagated to one measurement point. Each time a Rayleigh wave was measured, the turntable was rotated 7.5 degrees around the rotation axis to successively change the measurement point and excitation point IP. In this way, 48 measurement points and excitation points IP were set at approximately equal intervals on the equator EQ of sample 4. Note that even if the measurement point and excitation point are changed, the length from the excitation point IP to the measurement point remains approximately constant.

After completing the measurement of the Rayleigh waves at the 48 measurement points, the position of the laser Doppler vibrometer 150 was changed so that the angle α was 45 degrees. Then, the Rayleigh waves were measured at the 48 measurement points in the same way as when the angle α was 15 degrees.

Furthermore, the position of the laser Doppler vibrometer 150 was changed so that the angle α was 90 degrees, and the Rayleigh waves were measured at 48 measurement points.

<Results of Experiment 2>
(1) Change in displacement over time Figure 10A shows the measurement results of the surface displacement at the measurement point of sample 4, which has a bruise. The measurement results in Figure 10A are graphs showing the change in displacement over time of measurement point MP1 when angle α is 15 degrees. As described above, measurement point MP1 is located at a position of 7.5 degrees. Since angle α is 15 degrees, the excitation point is located at a position of 352.5 degrees. In other words, neither measurement point MP1 nor the excitation point is located in the range of existence of the bruise BR in sample 4 (see Table 2).

TAR11 in FIG. 10A is the time from when the Rayleigh wave is generated in sample 4 until the Rayleigh wave reaches measurement point MP1. TAR11 was approximately 0.15 milliseconds. The perimeter (hereinafter referred to as the circumference) of sample 4 at the equator EQ was 28 cm. The measurement points were shifted by 7.5 degrees each time, and the angle α of 15 degrees corresponds to two shifts. Therefore, the length from the excitation point to measurement point MP1 is 2/48 times the circumference. Therefore, the propagation speed of the Rayleigh wave in the range from the excitation point to measurement point MP1 was calculated as 28 cm x 2/48 x 1/(0.15 milliseconds) to be approximately 78 m/s.

Figure 10B shows the measurement results of the surface displacement at another measurement point on sample 4, which has a bruise. The measurement results in Figure 10B are a graph showing the change in displacement over time of measurement point MP14 when angle α is 15 degrees. Measurement point MP14 is located at a position of 105 degrees. Since angle α is 15 degrees, the excitation point is located at a position of 90 degrees. In other words, both measurement point MP14 and excitation point IP are located within the range of existence of bruise BR on sample 4 (see Table 2).

TAR12 in Figure 10B is the time from when a Rayleigh wave is generated in sample 4 until the Rayleigh wave reaches measurement point MP14. TAR12 was approximately 0.32 milliseconds. Since the circumference of sample 4 is 28 cm and the length from the excitation point to measurement point MP14 is 2/48 times the circumference, the propagation speed of the Rayleigh wave in the range from the excitation point to measurement point MP14 was calculated as 28 cm x 2/48 x 1/(0.32 ms) to be approximately 36 m/s.

Therefore, in sample 4, it was found that the propagation velocity of the Rayleigh wave in the area where the contusion BR exists (approximately 36 mm/s) was reduced by approximately 53% compared to the propagation velocity of the Rayleigh wave in the area where the contusion BR does not exist (approximately 78 m/s).

For this reason, it was found that even when measuring Rayleigh waves while keeping the length from the excitation point to the measurement point constant, as in Experiment 2, it is possible to identify the area on the surface of the fruit or vegetable where the propagation speed of the Rayleigh wave is reduced based on the correspondence between the displacement of the fruit or vegetable surface at each measurement point and time. Therefore, even when measuring Rayleigh waves while keeping the length from the excitation point to the measurement point constant, if the length from the excitation point to the measurement point is relatively short, it can be said that it is possible to determine the presence or absence of damage based on whether or not there is an area on the surface of the fruit or vegetable where the propagation speed of the Rayleigh wave is reduced. It can also be said that it is effective to use a value of 40% as the criterion for determining the speed reduction rate.

In addition, by identifying the area where the propagation speed of the Rayleigh wave is decreasing, it is possible to roughly identify the area where the bruise BR exists.

PT11 and PT12 in Figures 10A and 10B are time ranges in which extracted waveforms containing Rayleigh wave components are located. Comparing the extracted waveforms in Figures 10A and 10B, it was found that the waveforms have clearly different amplitudes and wavelengths. In other words, depending on whether the measurement point is located in the range where the bruise BR is present, the waveforms showing the time change in displacement of the surface of the fruit or vegetable that contain Rayleigh wave components are clearly different.

Therefore, when measuring Rayleigh waves while keeping the length from the excitation point to the measurement point constant, it can be said that the presence or absence of bruises BR on fruit or vegetables can be determined based on the waveform showing the correspondence between displacement and time at each measurement point. It can also be said that the range in which bruises BR exist can be roughly identified based on the waveform showing the correspondence between displacement and time at each measurement point.

When measuring Rayleigh waves using a method in which only the measurement point is changed while the excitation point is fixed, the time range in which the Rayleigh wave components are located in the correspondence relationship between surface displacement and time varies depending on the length from the excitation point to the measurement point. Therefore, as long as the Rayleigh wave components can be accurately extracted from the correspondence relationship between surface displacement and time, it can be said that the presence or absence of a bruise BR can be determined by processing the measurement results at each measurement point in the same way as with the method in which the length from the excitation point to the measurement point is constant. It can also be said that the range in which the bruise BR exists can be roughly identified.

(2) Corresponding Relationship Between Parameters Corresponding to Surface Position and Time and Displacement Figures 11A, 11B, and 11C are experimental results in Example 2, showing the corresponding relationship between parameters (i.e., angles) corresponding to surface positions and time and surface displacement for Sample 4 without bruises BR. Figures 11A, 11B, and 11C are experimental results when angles α are 15 degrees, 45 degrees, and 90 degrees, respectively. The angles on the vertical axes in Figures 11A, 11B, and 11C correspond to the surface positions of Sample 4.

In this experiment, unless the angle α is changed, the length from the excitation point IP to the measurement point remains almost constant, so the Rayleigh wave arrives at each measurement point at almost the same time. For this reason, as shown in Figures 11A, 11B, and 11C, the Rayleigh wave is represented as a straight line extending almost parallel to the vertical axis. These results mean that the Rayleigh wave propagates at almost the same propagation speed at all 48 measurement points.

Although not shown, in samples 1 to 3, which do not have bruises BR, when α is 15 degrees, 45 degrees, or 90 degrees, the line showing the Rayleigh wave in the correspondence relationship between the parameter corresponding to the surface position (i.e., the angle) and the time and surface displacement is a straight line extending almost parallel to the vertical axis. Therefore, it can be said that in all of samples 1 to 3, the Rayleigh wave propagated at almost the same propagation speed regardless of the position of the measurement point.

Next, the measurement results for sample 4 with bruise BR will be described with reference to Figures 12A, 12B, and 12C.

12A, 12B, and 12C are experimental results for Example 2, showing the relationship between the parameter (i.e., angle) corresponding to the surface position on Sample 4 with a bruise and the surface displacement over time. 12A, 12B, and 12C are experimental results for angles α of 15 degrees, 45 degrees, and 90 degrees, respectively.

QR in Figures 12A, 12B, and 12C indicates a specific range. The specific range QR is an angle range that has a displacement that is significantly different from the displacement in angle ranges other than the specific range, and is an angle range in which a dividing portion that divides the lines RW21, RW22, and RW23 that indicate the Rayleigh wave is located. In the following description, angle ranges other than the specific range will be referred to as other ranges.

Figure 12A shows that the specific range QR is the angle range of 75 degrees or more and 112.5 degrees or less, and the other ranges are the angle range of 0 degrees or more and less than 75 degrees, and the angle range of more than 112.5 degrees and less than 360 degrees. This specific range QR coincided with the range of the bruise BR in sample 4 (see Table 2). The size of the specific range QR shown in Figure 12A is approximately 37.5 degrees (= 112.5 degrees - 75 degrees).

12B and 12C each show a specific range QR that is wider than the specific range QR shown in FIG. 12A. The size of the specific range QR shown in FIG. 12B is approximately 90 degrees, and the size of the specific range QR shown in FIG. 12C is approximately 105 degrees. Thus, the smaller the angle α, that is, the shorter the length from the excitation point to the measurement point, the smaller the specific range QR. Also, looking at FIGS. 12B and 12C and Table 2, it can be seen that in sample 4, the specific ranges QR with angles α of 90 degrees and 45 degrees each overlap over a wide range with the range of the bruise BR on the surface of apple 110.

A similar trend was observed in samples 1 to 3, which had bruises BR. That is, in samples 1 to 3, the specific range QR became smaller as the angle α became smaller, from 90 degrees, to 45 degrees, to 15 degrees. Furthermore, in samples 1 to 3, the specific range QR where the angle α was 90 degrees, 45 degrees, and 15 degrees overlapped over a large area with the range of the bruises BR on the surface of the apple 110 (see Table 2).

From these results, it was found that even when measuring Rayleigh waves while keeping the length from the excitation point to the measurement point constant as in variant example 2, it is possible to determine the presence or absence of a bruise BR on apple 110 based on the presence or absence of a specific range QR, that is, based on whether or not the line representing the Rayleigh wave is interrupted in the correspondence between the parameter corresponding to the surface position and the time and the surface displacement.

In addition, it was found that even if the distance from the excitation point to the measurement point is relatively long, at least within a certain distance, it is possible to determine the presence or absence of a bruise BR based on an image showing the correspondence between the parameters corresponding to the surface position and the time and the surface displacement.

It was also found that the shorter the distance from the excitation point to the measurement point, the more accurately the extent of the bruise BR can be identified. Furthermore, it was found that the extent of the bruise BR can be identified with high accuracy by determining the position of the laser Doppler vibrometer 150 relative to the position where the LIP is formed so that the certain angle α is 15 degrees or less.

The present invention can be suitably used in a damage detection device for detecting damage to fruits and vegetables, and a damage detection method for fruits and vegetables. Therefore, its industrial applicability is extremely high.

20 Fruit or vegetable 30 Placement section 40 Vibration generator 41 Laser device 43 Lens 50 Measurement section 60 Control device 61 Memory section 62 Control section 63 Detection section 100 Damage detection device 110 Apple 130 Lab jack 140 Vibration generator 141 Laser device 142 Mirror 143 Plano-convex lens 150 Laser Doppler vibrometer 170 Analyzer 200 Damage detection system EQ Equatorial section LS Laser light BR Bruise

Claims (12)

a measuring unit for measuring a surface wave propagating on the surface of the fruit or vegetable;
a detection unit that detects damage to the fruit or vegetable based on the measured surface wave ,
When a velocity reduction position is present on the surface, the velocity reduction position being a position where the propagation velocity of the surface wave is lower than the propagation velocity of the surface wave at another position on the surface by a predetermined percentage or more, the detection unit determines that the fruit or vegetable is damaged.
A device for detecting damage to fresh produce. The fruit and vegetable damage detection device according to claim 1, wherein the measurement unit measures the surface waves at multiple positions on the surface. The device for detecting damage to fruits or vegetables according to claim 1 , wherein the detection unit identifies an area where the damage exists on the surface based on a distribution of the speed reduction positions on the surface. The present invention further includes a vibration generating device for applying a pressure wave to the fruit or vegetable.
the surface wave is a Rayleigh wave,
The fruit or vegetable damage detection device according to claim 1 , wherein the measurement unit measures the Rayleigh wave generated due to the pressure wave. The device for detecting damage to fruits and vegetables according to claim 4 , wherein the detection unit determines whether or not the damage is present in the fruits and vegetables by performing pattern recognition on a waveform or an image based on the Rayleigh wave . The fruit or vegetable damage detection device according to claim 5 , wherein the detection unit identifies an area where the damage exists on the surface by performing pattern recognition on a waveform or an image based on the Rayleigh wave . The fruit or vegetable damage detection device according to claim 4 , further comprising a position changer that changes the position of the fruit or vegetable relative to the measuring unit. The fruit or vegetable damage detection device according to claim 7 , wherein the attitude changing unit rotates the fruit or vegetable about a rotation axis passing through the fruit or vegetable. The fruit and vegetable damage detection device of claim 8, wherein an angle formed by a line connecting the position where the pressure wave is generated and the rotation axis and a line that intersects with the line connecting the measuring unit and the rotation axis is 15 degrees or less. The device for detecting damage to fruits and vegetables according to claim 1 , wherein the fruits and vegetables are fruits or vegetables belonging to any one of a berry, a stone fruit, a pome fruit, and a strawberry fruit. 11. The device for detecting damage to fruits and vegetables according to claim 10, wherein the fruits and vegetables are any of apples, pears, European pears, quince, loquats, tomatoes, apricots, grapes, cherries, plums, nectarines, prunes, plums, blueberries, papayas, persimmons, pawpaws, kiwis, peaches, mangoes, and strawberries . Measuring a surface wave propagating on a surface of the fruit or vegetable;
detecting damage to the fruit or vegetable based on the measured surface waves;
Equipped with
In the detecting step, when a velocity reduction position is present on the surface, the velocity reduction position being a position where the propagation velocity of the surface wave is lower than the propagation velocity of the surface wave at another position on the surface by a predetermined percentage or more, the fruit or vegetable is determined to have the damage.
A method for detecting damage in fresh produce.