Ultrasonic tester

1. An ultrasonic device, comprising:

an ultrasonic sensor that applies ultrasound to a test object;

a casing that holds the ultrasonic sensor to be immersed in a contact medium that allows the ultrasound to propagate therethrough, the casing including a test object-facing opening; and

circuitry configured to, when the test object-facing opening of the casing is passing an opening of the test object in a test direction of the test object, control a moving speed of the casing such that a region of contact between the test object and the contact medium entering the opening of the test object is kept within the opening of the test object.

2. The ultrasonic device according to claim 1 , wherein:

the circuitry is configured to control a supply rate of the contact medium and the moving speed of the casing such that z×t satisfies 0<z×t<V, wherein z is a flow rate of the contact medium entering the opening of the test object, t is a time taken for the test object-facing opening of the casing to pass the opening of the test object in the test direction, and V is a volume of the opening of the test object.

3. The ultrasonic device according to claim 2 , further comprising:

a supply pipe through which the contact medium is supplied into the casing,

wherein the circuitry is configured to control the supply rate of the contact medium and the moving speed of the casing such that z×t satisfies 0<z×t<V+S, wherein S is a maximum volume of a portion of the contact medium that can bulge from the opening of the test object in a state where an interface between the portion of the contact medium and outside air is kept inside a perimeter of the opening of the test object under action of surface tension of the contact medium.

4. The ultrasonic device according to claim 3 , further comprising:

a discharge structure through which the contact medium is discharged out of the casing,

wherein the circuitry is configured to, when controlling the supply rate of the contact medium and the moving speed of the casing, calculate the flow rate z by subtracting a flow rate of the contact medium discharged through the discharge structure from the supply rate of the contact medium supplied through the supply pipe.

5. The ultrasonic device according to claim 4 , further comprising:

an actuator that presses a surface of the casing against the test object, the surface including the test object-facing opening,

wherein:

the discharge structure includes outlets through which the contact medium is discharged,

at least one of the outlets is a gap between the casing and the test object, and

the circuitry is configured to control the actuator to reduce the gap between the test object and the casing.

6. The ultrasonic device according to claim 3 , further comprising:

a valve that increases or decreases the supply rate of the contact medium supplied through the supply pipe,

wherein the circuitry is configured to control the supply rate of the contact medium by adjusting an opening degree of the valve.

7. The ultrasonic device according to claim 1 , wherein the casing has lower hardness than the test object.

8. The ultrasonic device according to claim 1 , wherein the casing is made of a resin.

9. The ultrasonic device according to claim 1 , further comprising:

a mover, controlled by the circuitry, to move the case in a test direction of the test object.

10. The ultrasonic device according to claim 9 , wherein the mover comprises:

an arm that holds the casing and an actuator.

11. The ultrasonic device according to claim 10 , wherein:

the actuator includes at least one of a linear actuator, an air cylinder, a ball screw, or a motor coupled to the arm.

12. A method, comprising:

sensing a test object through an opening of a casing, the casing holding a contact medium; and

controlling a moving speed of the casing such that a region of contact between the test object and the contact medium entering an opening of the test object is kept within the opening of the test object.

13. The method according to claim 12 , further comprising:

control a supply rate of the contact medium and the moving speed of the casing such that z×t satisfies 0<z×t<V, wherein z is a flow rate of the contact medium entering the opening of the test object, t is a time taken for the opening of the casing to pass the opening of the test object in a test direction of the test object, and V is a volume of the opening of the test object.

14. The method according to claim 13 , further comprising:

control the supply rate of the contact medium and the moving speed of the casing such that z×t satisfies 0<z×t<V+S, wherein S is a maximum volume of a portion of the contact medium that can bulge from the opening of the test object in a state where an interface between the portion of the contact medium and outside air is kept inside a perimeter of the opening of the test object under action of surface tension of the contact medium.

15. The method according to claim 14 , further comprising:

calculating the flow rate z by subtracting a flow rate of the contact medium discharged through the discharge structure from the supply rate of the contact medium supplied through a pipe, when controlling the supply rate of the contact medium and the moving speed of the casing.

16. The method according to claim 15 , further comprising:

controlling an actuator to reduce gap between the test object and the casing.

17. The method according to claim 14 , further comprising:

controlling the supply rate of the contact medium by adjusting an opening degree of a valve.

18. The method according to claim 12 , wherein:

the casing has lower hardness than the test object.

19. The method according to claim 12 , wherein the casing is made of a resin.

20. The method according to claim 12 , wherein:

the controlling the moving speed controls the moving speed to be greater than zero.