TWI403691B - The method of taking the telemetry instrument - Google Patents

Abstract

An image taking method for push-broom type remote sensing instrument includes doubling the clock rate to increase the sampling time of said sensing device, saving the first half of image signals taken by said sensing device during said sampling time into a first buffer, discarding the second half of image signals taken by said sensing device, processing the data in the first buffer so as to generate the image.

Description

Image pickup method of push-broom telemetry instrument

The present invention relates to a push-broom telemetry satellite, and more particularly to an image capture method for a telemetry instrument on a push-broom telemetry satellite.

The sensors of the passive on-board optical sensing system are mainly divided into two types: the Whisk-broom and the Push-broom. The sensing elements of the sweep sensor, such as the CCD, are arranged in a direction parallel to the flight direction. When the satellite is flying, the mirror is continuously rotated and scanned back and forth. Currently, the optical telemetry system mostly uses a push-scan sensor, and its CCD The alignment direction is perpendicular to the flight direction, so the imaging geometry is approximately parallel projection in the flight direction and perspective projection in the vertical flight direction, also referred to as semi-perspective projection.

Referring to FIG. 1, the sensor of the camera of the push-broom telemetry satellite is in a single direction and the forward direction of the vertical satellite, and the satellite continuously captures the image during the forward motion to capture the ground 2D image. However, because the sensor is not stationary in the sensor's sampling period, there is relative motion, which causes smearing effects. The blur effect is related to the integration time of the sensor. The short integration time can reduce the blur effect. When the integration time is infinite, it can be imagined that the ground is completely stationary relative to the satellite, but photography requires a certain integration time to obtain enough light for imaging.

According to the current analysis of the telemetry payload modulation transfer function (MTF; Modulation Transfer Function) curve design budget table, to improve the precision of the resolution with assembly calibration technology, the maximum improvement can be obtained by about 20%. However, the cost of improving the calibration technique is high, and the blurring effect reduces the definition by 36%. If the blurring effect is reduced, the sharpness can be improved at a low cost.

The object of the present invention is to provide an image capturing method of a push-broom telemetry instrument.

According to the present invention, a method for capturing a push-broom telemetry apparatus includes (A) increasing the clock speed to shorten the sampling time of the sensing element; (B) sensing the sensing element during the sampling time. The first half of the image capture signal is stored in the first buffer; (C) the latter half of the sensing component is discarded; and (D) the data is processed in the first buffer to generate an image.

The image taking method proposed by the invention is simple to implement, and only needs to slightly modify the existing system and operation, and the cost is low.

The blur effect is related to the integration time of the sensor. The short integration time can reduce the blur effect. When the integration time is infinite, it can be imagined that the ground relative satellite is completely still.

The fuzzy effect formula is as follows:

Taking Instantaneous Field Of View (IFOV)=2m as an example, Equation 1 can be used to obtain Int_period=1, (for e.g. 0.3 ms @ 2m GSD)

The clock of each scan of the conventional CCD is equal to the ground resolution divided by the satellite ground speed. FIG. 2 is a schematic diagram of an embodiment of the present invention, and the present invention provides an image capturing mode to maintain the original RSI telemetry imager ( Telescope), designed with the same optomechanical design, provides a multiplier FPA read sensor clock rate, also calculated in Equation 1 and plotted on the right side of Figure 2 Int_period=0.5, (for Eg 0.15 ms @ 2m GSD)

3 is a system block diagram of the embodiment of FIG. 2. After the clock rate is increased to 2 times of the conventional one, for example, the original 0.3 milli sec count is changed to 0.15 milli sec once, and the CCD takes only half of the image. At the time, the first half of the time signal is collected into the buffer, and the second half of the signal is ignored and discarded. Therefore, the sampled signal is still the same resolution as the CCD IFOV. The TDI CCD/CMOS sensing component transmits the image signal during the sampling time. If the CCD transmits the analog signal to the Analog Front End (AFE), the AFE converts it into a digital signal. If it is a CMOS, the digital signal is directly transmitted. Signal. The sensing component collects multiple stages of signals, first storing Saved to the scratchpad, and finally added to a linear signal output, because the clock rate is adjusted to twice the original, the signal taken in the first half of the sampling time (the grayscale value of two meters) is stored in the buffer Buffer A. The signal taken in the second half of the sampling time is stored in the buffer Buffer 0. Only the data in the buffer Buffer A is transmitted to the AFE for subsequent processing, and the data in the buffer Buffer 0 is discarded. The output signal processed by the AFE is then passed down to the compression processor for processing, and the data is formatted according to a certain format and compressed to be processed and transmitted below.

Although the foregoing method can reduce the blurring effect and improve the MTF, but the relative loss of SNR, in order to compensate for the loss of SNR, the present invention also increases the Time Delay Integration (TDI) stage, and TDI is a different stage (CCD Line). In order to collect the charge, when the image moves from a CCD line to the next line, the integrated charge is passed down until the last stage's charge is collected into the register and then output, thereby increasing the signal-to-noise ratio. The signal-to-noise ratio is proportional to the rms square of the stage N. The steps of the TDI stage are included in the CCD/CMOS sensing component. Since TDI has been designed as a stage number in recent years, the design is more than one stage (such as 128). The direction, Table 2, is an example in which PAN, B1, B2 refer to spectra of different wavelength bands, which are known to those skilled in the art of the present invention. Figure 4 shows the TDI scan with four stages of sensors. The four scan lines of the sensor sweep to the same target line at different times. After the clock is controlled, the signals of the same target are collected and integrated. .

TDI Sensor Steps

720 km, f=3600 mm, d=450 mm pan=2m, ms=4 m, full intg.time

Table 2

While the present invention has been described in its preferred embodiments, the present invention is not intended to limit the invention, and various modifications, changes and modifications may be made without departing from the spirit and scope of the invention. The protection of the invention is defined in the scope of the patent application.

1 is a schematic diagram of sampling of a conventional push-broom telemetry satellite; FIG. 2 is a schematic diagram of an embodiment of an image capturing method according to the present invention; FIG. 3 is a system block diagram of the embodiment of FIG. 2; and FIG. Schematic diagram.

Claims (2)

An image capturing method of a push-broom type telemetry instrument, the telemetry instrument having a sensing element connected to a clock generator, the image capturing method comprising the following steps: (A) multiplying the clock of the clock generator Speed to shorten the sampling time of the sensing element; (B) sensing the sensing element to generate the previous half image capturing signal in the first buffer; (C) discarding the sensing element Taking the image signal; and (D) processing the data in the first buffer to generate an image. The image capturing method of claim 1, wherein the step (C) comprises storing the second half image capturing signal in the second buffer.