Methods for investigating an object by means of a reflectable radiation beam and devices suitable for carrying out the methods having an image sensor rigidly interconnected with an optical detector

• US 5,401,979 A
• Filed: 11/08/1993
• Issued: 03/28/1995
• Est. Priority Date: 11/09/1992
• Status: Expired due to Fees

• Current Assignee: Assembleon B.V.
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Gieles, Antonius C. M., Kooijman, Cornelis S.
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): LE, QUE TAN
• Application Number:
  US08/148,807
• Time in Patent Office: 505 Days
• Field of Search: 250/561, 250/560, 250/562, 250/557, 250/572, 356/376, 348/126, 348/140, 348/87, 348/94
• US Class Current: 250/559.29
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures

Abstract

Methods, devices and an image sensor for investigating an object (13) by means of a reflectable radiation beam (25) which forms a spot (24) on the object which can be moved relative to the object (13), whereby the actual position of the spot on the object is determined by means of the reflected portion of the radiation beam detected by an optical detector (23), while the desired position of the spot relative to the object is determined by means of a multidimensional image sensor (21). The radiation beam can subsequently be moved relative to the object until the actual position of the spot corresponds to the desired position of the spot, or differences between the actual and the desired position of the spot may be determined as a measure for differences in the distance between the object and a reference plane (62).

Claims

1. A method of investigating an object by means of a reflectable radiation beam which forms a spot on the object which is movable relative to the object, while a portion of the radiation beam reflected by the object is detected by an optical detector and subsequently the radiation beam is moved relative to the object until the optical detector detects a predetermined desired reflection of the radiation beam, characterized in that the actual position of the spot on the object is determined from the reflected portion of the radiation beam detected by means of the optical detector, while the desired position of the spot relative to the object is determined by means of a multidimensional image sensor, after which the radiation beam is moved relative to the object until the actual position of the spot determined by means of the optical detector corresponds to the desired position of the spot determined by means of the image sensor.

2. A method as claimed in claim 1, characterized in that the spot is moved relative to the object by means of a pivotable deflection mirror which is pivoted in dependence on the difference between the actual and the desired position of the spot detected by the optical detector and the image sensor, respectively.

3. A method of investigating an object by means of a reflectable radiation beam which forms a spot on the object which is movable relative to the object, while a portion of the radiation beam reflected by the object is detected by an optical detector, characterized in that the optical detector and a multidimensional image sensor have a common optical axis which is perpendicular to a reference plane through the object, while the positions of the spot on the object projected onto the reference plane are determined from the reflected portion of the radiation beam detected by means of the optical detector during the displacement of the radiation beam over a predetermined track, the desired positions of the spot relative to the object projected onto the reference plane being determined by means of the image sensor, after which differences between the actual and the desired positions of the spot are determined as a measure for differences in distance from the objects to the reference plane along the predetermined track.

4. A method as claimed in claim 3, in which the object is a component provided with connection legs which are soldered to contact pads by means of a laser acting as a heat radiation source, characterized in that the detection of a comparatively great difference in distance between a connection leg and the reference plane compared with other connection legs leads to the conclusion that there is a contact failure between the connection leg and the contact pad, in which case the laser is switched off in order to prevent burning of the detached connection leg.

5. A method as claimed in claim 3, characterized in that the spot of the radiation beam is positioned until the actual position corresponds to a desired position and in that the spot of the radiation beam is also used for determining differences in distance between an object and a reference plane.

6. A device for investigating an object which device is provided with a radiation source, an optical detector and a displacement device for displacing a spot thrown onto an object by a radiation beam to be emitted by the radiation source, characterized in that the device is further provided with a multidimensional image sensor cooperating with the optical detector and with a positioning circuit for controlling the radiation beam in dependence on the difference between an actual position of the spot detectable by the optical detector and a desired position of the spot detectable by the image sensor.

7. A device as claimed in claim 6, characterized in that the optical detector is provided with a position detection element.

8. A device as claimed in claim 6, characterized in that the image sensor is provided with a solid-state matrix array camera.

9. A device as claimed in claim 8, characterized in that the optical detector is mounted in the image sensor, the solid-state matrix array camera and the optical detector being rigidly connected to one another and having the same image field obtained through a common, semi-transparent mirror.

10. A device for investigating an object which device is provided with a radiation source, an optical detector and a displacement device for displacing a spot thrown onto an object by a radiation beam to be emitted by the radiation source, characterized in that the device is further provided with a multidimensional image sensor cooperating with the optical detector, the optical detector and the image sensor having a common optical axis which is perpendicular to a reference plane, and is provided with a measuring circuit for determining differences in the distance between the object and the reference plane from differences between actual positions of the spot on the reference plane detectable by the optical detector and desired positions of the spot on the reference plane detectable by the image sensor during the displacement of the radiation beam along a predetermined track.

11. A device as claimed in claim 10, characterized in that a common control circuit is provided with the positioning circuit and the measuring circuit.

12. A device as claimed in claim 11, characterized in that the displacement device controllable by the control circuit is provided with a pivotable deflection mirror.