Double-line sensor automatic focusing system

Abstract

The invention relates to the technical field of semiconductors, in particular to an automatic focusing system of a double-line sensor, which can enable the focusing action to be smooth, improve the focusing efficiency and shoot a clear and non-skew picture, and the focusing process is as follows: a light source irradiates a stripe-shaped pattern, and the stripe-shaped pattern is transmitted to an object after passing through a reflector, a half-reflector and a lens; a graph of an object is divided into two paths after passing through the lens, the half-reflecting mirror, the imaging lens and the beam splitter, one path directly enters the image taking device, the other path is divided into two paths again after passing through the light path difference system, one path passes through the line sensor A to enable light to be focused on the front side of the line sensor A, and the other path passes through the line sensor B to enable light to be focused on the rear side of the line sensor B; the line sensor A and the line sensor B send signals to the focusing controller, the focusing controller takes the signal of the line sensor A and the signal of the line sensor B which are equal in strength as a focusing signal, and the focusing controller continuously controls the driver to adjust the distance between the lens and an observed object so as to adjust the optical path distance and maintain the state of the focusing signal.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a dual-route sensor automatic focusing system. Background Art

[0002] At present, in order to achieve high precision in process defects, most of the focusing methods use low-cost, point-shaped infrared light to create the focusing optical path. The disadvantage is that there is only one point-shaped standard to distinguish the focus from the objective lens to the sensor area. The instability of the light spot and halo is mostly related to the misjudgment of unstable light decay. In addition, for multi-level process, there may be problems in the image acquisition. In addition, the single-line sensor infrared reflection conversion method has a large reflection time error and a large depth of field difference. Figure 1 The point-shaped and single-line infrared focusing systems currently on the market are low-priced, but for wafer stacking or other product stacking processes, the height difference of the 2D defect types imaged is very large. During high-speed imaging, when targeting discontinuous high-low height difference surfaces, misjudgment and the software system disconnection and shutdown are unstable, resulting in poor focusing effect. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a dual-route sensor automatic focusing system, which can make the tracking focus action smooth, improve the focusing efficiency, and take clear and non-skewed photos.

[0004] The technical scheme is as follows: a dual-path sensor automatic focusing system, characterized in that it includes a light source, a stripe pattern, a reflector, a semi-reflective mirror, a lens, a beam splitter, an optical path differential system, a line sensor, and an imaging device; the focusing process is: the light source irradiates the stripe pattern, which is transmitted to the object after passing through the reflector, the semi-reflective mirror, and the lens. The object image is divided into two paths after passing through the lens, the semi-reflective mirror, the imaging lens, and the beam splitter. One path directly enters the imaging device, and the other path is divided into two paths again after passing through the optical path differential system. One path passes through the line sensor A to focus the light on the front side of the line sensor A, and the other path passes through the line sensor B to focus the light on the back side of the line sensor B. The line sensor A and the line sensor B send signals to the focus controller. The focus controller uses the equal signal strength of the line sensor A and the line sensor B as the quasi-focus signal. The focus controller continuously controls the driver to adjust the distance between the lens and the observed object, thereby adjusting the optical path distance and maintaining the quasi-focus signal state.

[0005] After adopting the present invention, line sensor A and line sensor B are used to align the front and rear positions, and the driver is continuously controlled to adjust the optical path distance to maintain the quasi-focus signal state. Smoother movements can be achieved in the focus tracking action. Since it works continuously, the impact of vibration is reduced, the focusing efficiency is improved, and clear and non-skewed photos can be taken. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1It is a schematic diagram of an existing single-line infrared focusing system; Figure 2 It is a schematic diagram of the system of the present invention; Figure 3 This is a schematic diagram of the optical path difference system splitting; Figure 4 It is a single-line sensor signal curve diagram of the prior art; Figure 5 It is a signal curve diagram of the line sensor A and the line sensor B in the present invention; Figure 6 It is a schematic diagram of STEP and FP mode actions; Figure 7 This is a schematic diagram of an example of detecting the height difference of focus tracking. DETAILED DESCRIPTION

[0007] See Figure 2 , Figure 3 As shown, a dual-path sensor automatic focusing system includes a light source, a stripe pattern, a reflector, a semi-reflector, a lens, a beam splitter, an optical path differential system, a line sensor, and an imaging device; the focusing process is: an infrared light source 1 irradiates a stripe pattern 2, which is transmitted to an object after passing through a reflector 1 3, a semi-reflector 1 4, a semi-reflector 2 5, and a lens 6; an illumination source 7 provides the required brightness and is arranged above the semi-reflector 1 4; the image of the object passes through a lens 6, a semi-reflector 2 5, an imaging lens 7, and a beam splitter 8 and is divided into two paths, one of which directly enters an imaging device 9 (such as a CCD camera, etc.) ), the other path is divided into two paths again through the optical path differential system 10, the optical path differential system 10 is composed of a beam splitter and a reflector, one path passes through the line sensor A to focus the light on the front side of the line sensor A, and the other path passes through the line sensor B to focus the light on the back side of the line sensor B. The line sensor A and the line sensor B send signals to the focus controller 11, and the focus controller 11 uses the signal intensity of the line sensor A and the signal intensity of the line sensor B as the quasi-focus signal. The focus controller 11 continuously controls the driver 12 to adjust the distance between the lens and the observed object, thereby adjusting the optical path distance and maintaining the quasi-focus signal state.

[0008] See Figure 4 As shown, when using 1 line sensor: the principle is to track the peak value as the basis for accurate focus. When the system is out of focus, the signal returns a single value and cannot determine whether the tracking direction is near or far, thus slowing down the speed.

[0009] See Figure 5 As shown, when two line sensors are used: when the system is out of focus, the required tracking direction can be obtained by calculating the signals of line sensor A and line sensor B, thereby improving the tracking performance.

[0010] During the focusing process, there are two action modes. One is the STEP mode. The focusing process is interrupted, and the action and stop are repeated, which is the cause of Z-axis vibration and skewed pictures. The other is the FP action, which is the action mode of the present invention. The Z-axis is controlled to move continuously according to the signals of the two line sensors, which reduces the vibration and does not produce skewed pictures. Figure 6 shown.

[0011] by Figure 7 For example, as the surface of the object continues to change, the focusing operation is continued without vibration. The upper Line Scan is 200µm, the lower Line Scan is 200µm, and the Z-axis movement is always increased to increase the height difference range of 400µm to reflect the focusing action.

Claims

1. A dual-path sensor autofocus system, characterized in that: It includes a light source, a stripe pattern, a reflector, a half-reflector, a lens, a beam splitter, an optical path differential system, a line sensor, and an imaging device; the focusing process is: the light source irradiates the stripe pattern, which is transmitted to the object after passing through the reflector, the half-reflector, and the lens; the object image is divided into two paths after passing through the lens, the half-reflector, the imaging lens, and the beam splitter, one of which directly enters the imaging device, and the other is divided into two paths again after passing through the optical path differential system, one of which passes through the line sensor A to focus the light on the front side of the line sensor A, and the other passes through the line sensor B to focus the light on the back side of the line sensor B. The line sensor A and the line sensor B send signals to the focus controller, and the focus controller uses the equal signal strength of the line sensor A and the line sensor B as the quasi-focus signal, and the focus controller continuously controls the driver to adjust the distance between the lens and the observed object, thereby adjusting the optical path distance and maintaining the quasi-focus signal state.

Images