System for optical inspection

Abstract

This invention relates to an optical detection system for analyzing the image signal projected from the entrance pupil image of the objective lens's back focal plane onto an image capturing device to determine the tilt angle information of a measured point on an object under test, thereby simultaneously measuring the tilt angle and depth information of the measured point, improving the accuracy and stability of the depth and topography of the measured point. In one embodiment, the system includes an optical detection module responsible for projecting detection light and receiving reflected light from the object under test; a back focal plane module for capturing the optical image signal of the object under test on the back focal plane of the objective lens; a photosensitive module coupled to the photodetector module for generating optical information about the measured object light; and a computation module for calculating the surface topography of the object under test and the two-dimensional surface tilt angle of the measured point based on the optical image signal of the back focal plane and the optical information of the measured object light.

Claims

1. An optical detection system, comprising: An optical detection module includes an objective lens for projecting a detection light onto a test position on an object to be tested, and receiving a test object light reflected from the test position; A back-focusing module, coupled to the optical detection module, is used to capture optical information about the object light on one of the back focal planes of the objective lens to generate a first optical image signal; a light sensing module, coupled to the light detection module, is used to generate optical information about the object light; a calibration prism is disposed on one side of the objective lens, and the detection light passes through the calibration prism to form the object light; an optical displacement measurement module is used to generate a calibration test light projected onto the calibration prism, and the back-focusing module further captures a second optical image signal about the calibration test light; An image capturing unit is coupled to the optical detection module and the optical displacement measurement module. The image capturing unit is used to capture optical information about the object light on an image plane of the objective lens to generate a third optical image signal and a fourth optical image signal about the calibration test light. A computing module is used to receive the first optical image signal and the optical information, and determine the surface topography and surface tilt angle of the position to be measured based on the first optical image signal and the optical information. The computing module receives the first optical image signal and the second optical image signal, and determines an angular offset of the optical displacement measurement module based on the first optical image signal and the second optical image signal. It also receives the third optical image signal and the fourth optical image signal, and determines a lateral offset of the optical displacement measurement module based on the third optical image signal and the fourth optical image signal.

2. The optical detection system as described in claim 1, wherein the optical detection module is a confocal microscopy module, a white light interferometry microscopy module, a laser triangulation measurement module, a focal plane analysis measurement module, a projection shape-finding module, a structured light reconstruction module, a gradient light reconstruction module, an optical profilometer module, a digital holography module, an ellipsometry module, an optical scattering module, a spectral reflectometry module, an optical coherence scanning module, a differential interferometry module, a phase microscope module, or a microscopic imaging module.

3. The optical detection system as described in claim 1, wherein the back focus module further includes: a lens group for receiving the object light; and a Bertrand lens, which, in conjunction with the lens group, maps an entrance pupil image of the back focus plane within the objective lens onto an image capturing unit outside the objective lens to generate the first optical image signal.

4. The optical detection system as described in claim 3, wherein the Bertrand lens may be disposed in front of or behind the image plane of the back focus module.

5. The optical detection system as described in claim 1 further includes a light source module for generating the detection light, wherein the light source module is a collimated laser light or a diode light source with a divergence angle.

6. The optical detection system as claimed in claim 5, wherein a scanning module is further provided between the light source module and the objective lens for changing a reflection angle of the detection light.

7. The optical detection system as claimed in claim 5, wherein the computing module determines the tilt angle information and surface morphology of the location to be measured based on the center of the first optical image signal and a depth response curve of the optical information.

8. The optical detection system as described in claim 1, wherein the corrective prism comprises a penta prism, a right-angle mirror, a plane mirror, a right-angle prism, a roof prism, a Schmidt–Pechan prism, a Dove prism, or a beam splitter.

9. The optical detection system as claimed in claim 1 further includes a position adjustment module for adjusting the angle of the optical displacement measurement module according to the first optical image signal and the second optical image signal, and adjusting the lateral position of the optical displacement measurement module according to the first optical image signal, the third optical image signal and the fourth optical image signal.

10. The optical detection system as claimed in claim 9, wherein when the position adjustment module adjusts the angle of the optical displacement measurement module, when the first optical image signal and the second optical image signal are concentric, the position adjustment module eliminates the angular offset of the optical displacement measurement module; and when the position adjustment module adjusts the lateral position of the optical displacement measurement module, when the third optical image signal and the fourth optical image signal are concentric, the position adjustment module eliminates the lateral offset of the optical displacement measurement module.

11. The optical detection system as described in claim 1, the optical displacement measurement module further includes a first-axis optical displacement measurement module for generating an X-axis correction test light, a second-axis optical displacement measurement module for generating a Y-axis correction test light, and a third-axis optical displacement measurement module for generating a Z-axis correction test light, to correct the position of a measurement platform of the optical detection module. When the X-axis correction test light, the Y-axis correction test light, and the Z-axis correction test light are orthogonal to the detection optical axis of the optical detection module at the same point, the measurement platform achieves multi-axis zero Abbe error.

12. The optical detection system as described in claim 1, wherein the optical information is information about the depth of the location to be measured.

13. The optical detection system as described in claim 12, wherein the optical information is spectral information, phase difference information, image information, light intensity information, or interference information.

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