CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan Patent Application Serial Number 109122077, filed on Jun. 30, 2020, and Taiwan Patent Application Serial Number 110111970, filed on Mar. 31, 2021, and the full disclosures of which are incorporated herein by reference.

BACKGROUND

1. Field of the Disclosure

This disclosure generally relates to a time delay integration (TDI) sensor and, more particularly, to a TDI Complementary Metal-Oxide-Semiconductor (CMOS) image sensor that implements the rolling shutter operation by spatial compensation.

2. Description of the Related Art

The time delay integration (TDI) sensor uses an area array image sensor to capture images from an imaging platform that is moving relative to the imaged object or scene at a constant speed. The TDI sensor is conceptually considered as the stack of linear arrays, wherein each linear array moves across a same point of the scene at a time period that the image sensor moves a distance of one pixel.

Conventionally, the charge-coupled device (CCD) technology has been used for TDI applications because CCDs intrinsically operate by shifting charge from pixel to pixel across the image sensor to allow charges between pixels to integrate when the image sensor moves across a same point of the imaged scene.

However, CCD technology is relatively expensive to fabricate and CCD imaging devices consume relatively high power.

Although using a CMOS circuit can achieve lower power, higher degree of integration and higher speed, the existing designs suffer from higher noises. Although a 4-transistor (4T) structure can be used to minimize noises, the 4T pixels are clocked using a rolling shutter technique. Using the rolling shutter clocking can cause artifacts in the captured image since not all pixels are integrated over the same time period.

Therefore, U.S. Pat. No. 9,148,601 provides a CMOS image sensor for TDI imaging. Please refer toFIG. 1, the CMOS image sensor includes multiple pixel columns112, and each pixel column is arranged to be parallel to an along-track direction Da_t. For compensating the integration interval of the rolling shutter of the CMOS image sensor, a physical offset150is further arranged between two adjacent pixels of each pixel column112, wherein if the pixel column112has N rows, each physical offset150is equal to a pixel height divided by N.

Accordingly, the present disclosure further provides a TDI CMOS image sensor that implements the rolling shutter operation by spatial compensation.

SUMMARY

The present disclosure provides a TDI CMOS image sensor with a separation space determined according to the pixel height, the line time difference of a rolling shutter and the frame period.

The present disclosure further provides a TDI CMOS image sensor that changes the line time difference corresponding to different conditions with a fixed separation space.

To achieve the above objective, the present disclosure provides a TDI CMOS image sensor that captures an image frame using a rolling shutter and moves with respect to a scene in an along-track direction. The image sensor includes a pixel array having multiple pixel columns. Each of the pixel columns includes multiple pixels arranged in the along-track direction, and two adjacent pixels of each of the pixel columns have a separation space therebetween, wherein the separation space is a multiplication of a pixel height in the along-track direction by a time ratio of a line time difference of the rolling shutter and a frame period of capturing the image frame.

In addition, the present disclosure further provides a TDI CMOS image sensor that captures an image frame using a rolling shutter and moves with respect to a scene in an along-track direction. The image sensor includes a pixel array having multiple pixel columns. Each of the pixel columns includes multiple pixels arranged in the along-track direction, and two adjacent pixels of each of the pixel columns have a separation space therebetween, wherein the separation space is a summation of a pixel height in the along-track direction and a multiplication of the pixel height by a time ratio of a line time difference of the rolling shutter and a frame period of capturing the image frame.

The present disclosure further provides a TDI CMOS image sensor that captures an image frame using a rolling shutter and moves with respect to a scene in an along-track direction. The image sensor includes a pixel array having multiple pixel columns. Each of the pixel columns includes multiple pixels arranged in the along-track direction, and two adjacent pixel groups of the multiple pixels have a separation space therebetween to compensate a line time difference of using the rolling shutter, wherein each pixel group has a first pixel and a second pixel.

The present disclosure further provides a TDI CMOS image sensor that captures an image frame using a rolling shutter and moves with respect to a scene in an along-track direction. The image sensor includes a pixel array and multiple integrators. The pixel array includes multiple pixel columns. Each of the pixel columns includes multiple pixels arranged in the along-track direction, and two adjacent pixels of each of the pixel columns have a separation space therebetween, wherein the separation space is a multiplication of a pixel height in the along-track direction by a time ratio of a line time difference of the rolling shutter and a frame period of capturing the image frame. The multiple integrators respectively store pixel data in successive image frames corresponding to a same position of the scene. In one line time difference, each of the integrators is configured to integrate the pixel data in continuous image frames corresponding to the same position of the scene. In double line time difference, each of the integrators is configured to integrate the pixel data in non-continuous image frames corresponding to the same position of the scene.

The present disclosure further provides a TDI CMOS image sensor that captures an image frame using a rolling shutter and moves with respect to a scene in an along-track direction. The image sensor includes a pixel array and multiple integrators. The pixel array includes multiple pixel columns. Each of the pixel columns includes multiple pixels arranged in the along-track direction, and two adjacent pixel groups of the multiple pixels have a separation space therebetween to compensate a line time difference of using the rolling shutter, wherein each pixel group includes a first pixel and a second pixel. The multiple integrators respectively store pixel data in successive image frames corresponding to a same position of the scene. In one line time difference, each of the integrators is configured to integrate the pixel data in adjacent image frames corresponding to the same position of the scene. In double line time difference, each of the integrators associated with the first pixel is configured to integrate the pixel data in a next image frame corresponding to the same position of the scene, and each of the integrators associated with the second pixel is configured not to integrate the pixel data in the next image frame corresponding to the same position of the scene.

In the present disclosure, the separation space is not directly related to a size of the pixel array (i.e. a number of pixels), and the separation space can be determined as long as the frame period and the line time difference have been determined.

