CN1069334A - Analog scan convertor based on dmd - Google Patents

Abstract

A scan converter system, which may include: a shift register 32 receiving at least one serial input data stream from an input device 30; a serial-to-parallel converter 34 connected to the shift register 32; A parallel converter 34 is connected to the _DMDs 36 so that when the light source is reflected from the DMD it produces an image of approximately the same intensity as the image received at the input device. Other methods and systems are disclosed herein.

Description

This invention relates generally to analog scan converters, and more particularly to analog scan converters constructed using deformable mirror devices (DMDs).

The background of the invention is described in connection with a system employing an IR (infrared ray) sensor, without limitation in scope. Traditional systems relying on linear IR sensors are being replaced by systems employing multi-line sensors. These multiline sensors increase resolution and the associated signal/noise ratio, and also reduce blur problems. Due to manufacturing complexity, these sensors typically contain only the number of pixels needed to scan the vertical scene dimensions. The movement of this scene data from the vertical sensor is naturally in the form of a vertical raster scan. However, the human eye is accustomed to viewing horizontally raster scanned images. Therefore, these sensors typically require a scan converter in order to reconstruct the IR image in the visible region that humans view. A typical high dynamic range digital scan converter for this task is expensive, bulky and power hungry.

DMDs have several attractive features. The mirror elements are highly reflective over a wide optical bandwidth. Thus, they are capable of light modulation from UV (ultraviolet) to IR. Typical pixel response times are 10-20 ^μs and the pixel can be operated in analog or digital state. The DMD can be used both as an amplitude-controlled modulator and as a phase-controlled modulator by simply changing the mirror structure. DMDs are suitable for low-voltage, high-density addressable circuits fabricated monolithically. Due to the low power consumption of the DMD, high frame rates (typically above 5KHz) can be achieved without harmful thermal effects.

Numerous DMD pixel structures exist, each designed for a specific application. They can be distinguished by deformation modes such as flexure or cantilever; pixel shapes and articulated support structures

This is a scan conversion system. It can comprise: a shift register receiving at least one serial input data stream from an input device; a serial-to-parallel converter connected to the shift register; and _DMDs connected to the serial-to-parallel converter such that, When the light source reflects off the DMD, it produces a brightness pattern that is nearly identical to the image received by the input device. The _DMDs are preferably imaged on a solid state detector, which is a CCD, and the detector processes the images from the _DMDs , where the images are output in a different order than the images input to the detector. _DMDs , on the other hand, can be imaged on the back of the scanning mirror, and the image from the back of the mirror can be optically projected to produce an image nearly identical to the image received by the input device. The _DMDs are preferably twisted beam plate _DMDs . Exemplary input devices are an IR sensor or computer. The shift registers, serial-to-parallel converters and _DMDs are preferably housed on a monolithic integrated circuit.

The scanning system may also comprise: at least one shift register receiving at least one serial input data stream from an input device; at least one serial-to-parallel converter connected to the shift register; at least one comparator, the One input of the comparator is connected to the output of the serial-to-parallel converter, and the other input is connected to a saw-tooth-shaped scanning voltage; and at least one DMD connected to the comparator, so that when the light source is reflected from the DMD, a Almost the same brightness pattern as the image received by the input device. The comparator is preferably a sawtooth comparator, and the shift register, serial-to-parallel converter, comparator and _DMDs are arranged on a monolithic integrated circuit.

The present invention is also a method of forming a scan converter system, generally comprising: receiving at least one data stream of serial input data from an input device; converting the serial data stream to a parallel data stream; and passing the parallel data stream to the DMD _s , whereby when a light source is reflected from the DMD, it produces an intensity pattern that is nearly identical to the image received by the input device.

Attached picture:

Figure 1 is a traditional IR imaging system;

Figure 2 is an electronic part of an improved IR imaging system;

Figure 3 is a view of the twisted beam plate DMD;

Figure 4 is a top view of various twisted beam plate DMD articulation options;

Fig. 5 is the first preferred embodiment of the present invention;

Fig. 6 is the third preferred embodiment of the present invention with pulse width modulation;

Fig. 7 is a block diagram of part of the system in Fig. 6;

Corresponding numerals and symbols in the different drawings refer to corresponding parts unless otherwise indicated.

In a conventional IR system (see FIG. 1 ), an input image 10 is focused with a suitable optical system 24 onto the plane of the IR detector 12 in a linear discrete pixel structure. Obviously, only one line of the image 10 can be detected at a given moment. Thus, one element of the imaging system is a mirror 14 rotating about its central axis, with the result that a fixed rotation of the mirror 14 enables any desired line of the image 10 to be focused on the detector 12 .

Signals from each discrete sensor element in detector 12 are connected to discrete light emitting elements (typically LEDs) of array 16 . The visible light emission of the line 16 is reflected off the rear surface 18 of the scanning mirror 14, and the rear mirror surface is viewed by an observer 20 through a suitable optical system 22 as the mirror 14 scans that scene 10 past the IR detector 12. 18, a rendition of the input IR scene 10 will be seen. Each individual connection path typically includes amplifiers with compensation and linear adjustment to compensate for pixel-to-pixel sensitivity and emissivity variations of both detectors and emitters.

Improved IR sensors typically consist of rows of pixel elements rather than a single row. Attaching many pixel elements to each detector creates a large number of output connections. Such interconnections are often the source of yield loss and failure in field use. Therefore, these improved sensors often forego parallel pixel output and instead use serial shift registers to output each row of pixels. Connecting these serial outputs to arrays _{of LEDs} (Light Emitting Diodes) requires complex structures such as a monolithic LED substrate including a serial-to-parallel converter or configuring multiple LEDs on an upper substrate with a single serial-to-parallel converter chip. Complex hybrid substrates for single-line LED arrays. The cost effectiveness of this type of LED array is beyond the current state of the art, so a different type of display is required. A typical solution is shown in Figure 2 which digitizes and stores multiple parallel or serial outputs 72 of a multi-line IR sensor 74 in a digital video memory 70. Video memory 70 is then read out in serial to drive a CRT display 76 or in parallel to drive a mixed array of linear LED elements 78 .

A twisted beam plate DMD can be used in the embodiments to be described below. Twisted beam plate DMD pixels typically consist of a raw reflective beam plate 50 suspended on an air gap/spacer 52 as shown in Figures 3 and 4 and connected to a rigid support or on the support layer 54 . When the addressing electrodes 58 located under the beam plate 50 are energized, the torsion hinges 56 are twisted and the beam plate 50 rotates about the axis of the two hinges 56 until it stops on the "landing" electrical plate 60 below. Such a structure is typically fabricated on, for example, a silicon wafer 62 . Figure 4 shows several hinge options that can be used in twisted beam plate DMDs.

The solution to the display problem for the improved IR system appears in the first preferred embodiment shown in FIG. The DMD chip 28 is manufactured in such a way that its structure is essentially the inverse of that of the IR sensor device 30 . Numerous analog serial shift registers 32 can be fabricated on chip 28, or can be placed outside the DMD chip if desired. Their number and length match the number and length of the output shift registers on the IR sensor device 30 . Each of these shift registers 32 preferably feeds out the same number of DMD pixels 36 through a serial-to-parallel converter 34 as feeds into a corresponding shift register on the IR device 30 . The individual DMD pixels 36 may (except perhaps for a full scale factor) be arranged as the input IR device 30 pixels are arranged. Thus, a visible light source (or other wavelength) reflected from the DMD will produce a brightness pattern that is nearly identical to an image incident on sensor 30 in the IR spectrum.

In a second preferred embodiment, the reproduced image can be projected and viewed reflectively from behind a scanning mirror (mirror) 14 as shown in FIG. 1 . Conventional IR systems operate reproducibly without expensive digital scan converters or complex LED assemblies.

In such reflected images, brightness (light intensity) can be encoded in several ways. One method is analog modulation. If the outputs of the DMD's analog shift register/serial-to-parallel converters 32, 34 are connected directly to the addressing electrodes below the pixels 36, then the deflection of each pixel 36 will be proportional to the analog signal and thus to the incoming IR light strength. This DMD tilt is typically used with dark field optics to obtain analog light modulation.

In a dark field system, the DMD may be aligned so that the reflected light from a fully deflected DMD pixel falls entirely within the aperture of the display optics. The optical system can be designed with a defined aperture so that the light from the undeflected The reflected light of the pixel falls completely outside of this aperture. Clearly, the intermediate position reflects an intermediate amount of light into the light aperture, thus producing an intermediate brightness level of light in the plane of the projected image.

Another method of light intensity encoding is pulse width modulation. The accuracy of image reproduction from analog modulation depends on many factors including: the linearity and uniformity of the DMD pixel tilt angle and the correct degree of apodization of the projection optics. Using dark field optics as described above, again using pulse width modulation, can obviate the above problems.

In a third preferred embodiment, as shown in FIG. 6, instead of directly driving the DMD pixel 36 from the output of the shift register/serial-to-parallel converters 32, 34, each shift register/serial - A sawtooth (slope) comparator amplifier 38 (or any comparator type circuit providing the same function) is placed between the outputs of the parallel converters 32, 34 and the corresponding DMD 36 addressing electrodes.

As shown in Figure 7, three things happen at the end of each serial-to-parallel conversion: The analog outputs of the shift register/serial-to-parallel converters 32, 34 are sent to one of the comparators at each DMD pixel location On input 40, the pixel drive amplifier 42 at the position of each pixel 36 can be turned on to drive each pixel 36 to its full tilt position, and the common voltage on all other comparator inputs 44 starts from the lowest The detectable shift register signal level is ramped to the highest detectable shift register signal level.

The rate of this ramp is such that it reaches its maximum voltage at the end of the row (scan) time. The output of the comparator 38 is connected to the input of the pixel driver amplifier 42 so that when each comparator 38 triggers the start, the output of the associated DMD pixel driver amplifier 42 falls to zero and the associated DMD pixel 36 returns to its non-tilted state. Thus, the amount of time it takes a given pixel to ramp during a single line time (and thus provide the amount of light it provides to the displayed image during a line (scan)) is proportional to the 32, 34 to deliver the voltage to that pixel 36.

Either of these modulation schemes can be used to mimic the operation of a digital scan converter in those examples, but requires a separate display (ie it does not rely on the scan provided by the rear of the input scan mirror). As an example of this scan converter function, a DMD can image onto the top row of an area array CCD (or other solid state) detector. At the end of each line time, the charge generated in the CCD can be moved into the next line in a pinched fashion. This is done sequentially over the entire video frame time until the entire input image is stored in the CCD. At this point, the CCD can be read directly to the video portion of a CRT or other display system. DMDs can be imaged to CCDs in many different ways. Multiple _DMDs and _CCDs can be combined, and their outputs controlled electrically, to perform complex optical processing tasks.

Conversely, a linear DMD modulator can be used to generate a display from an image stored in a digital frame memory such as a CCD. A serial analog data stream, which can be obtained directly from the CCD via a digital-to-analog converter or directly from the frame memory, is fed into the previously described analog shift register from the IR detector. However, the scan mirrors can be driven in the same way that a typical IR system scan mirror is driven, and the image projected item by item from the DMD can be seen from the reflection on the mirror surface.

Where digital data is readily available or digital manipulation is preferred, the DMD is easily applied in a digital state. This digital state requires crafting a unique DMD that is structurally identical to those above. For a digital data stream with a resolution of N bits, it is necessary to fabricate a linear DMD with N input shift registers. Each shift register represents a different bit of digital resolution, from most significant bit to least significant bit. Each shift register will directly address its own row of DMD pixels, which are activated at the beginning of each row (scan) time. By row (scanning) time, the most significant bit row will be shifted by half, the next most significant bit by a quarter, the third most significant bit by an eighth, and so on. In this manner, each pixel in each row of the image is illuminated by N pixels, and each pixel will provide illumination with a time weight proportional to its binary sum. A binary light amplitude value of N bits in total is then provided.

A simpler implementation of this binary illuminance weighting can be provided by spatial weighting as opposed to temporal weighting. As mentioned above, an N-bit binary data stream drives N input shift registers. In this scheme, however, spatial weighting is done for each pixel along the shift register. For example, in a 7-bit resolution system, the most significant bit shift register will drive 64 pixels in each DMD cell. The second most significant bit drives 32 pixels. Then there are 16 drivers, and so on. This method does not require temporal resolution of sub-line (scan) time, since a given percentage of illuminance weighting is provided by the percentage utilization of reflective area, not by the percentage utilization of available time. . These two methods of binary illuminance weighting (temporal and spatial) can be combined. Since this method of combining increases the dynamic range, it results in higher resolution pixels.

The DMD can be used in many different embodiments to provide a display device. The DMD can be configured with an appropriate optical system to provide scan converter functionality with small size, light weight, low cost and low power consumption. The composite DMD system can display any stored digital image or analog data stream for viewing regardless of the light source.

Several preferred embodiments have been described in detail above, and the scope of the present invention also includes various embodiments other than those described above within the scope of the claims. For example. Although the input device is described as an IR sensor, the input can also come from various sources such as a TV signal or a computer. Darkfield optics are also discussed in relation to the use of this system, however, schlieren optics or other suitable optical systems may also be used. Likewise, the DMD can be used to directly display and image or apply the image to another detector that may be used in front of the display. The word "comprising" should be interpreted loosely when considering the scope of the present invention.

While the invention has been described with reference to the illustrated embodiments, this description is not to be considered in a limiting sense. Various modifications and combinations of the illustrated embodiments, as well as other embodiments of the invention, will be apparent to those skilled in the art upon reference to the description. The appended claims therefore cover any such modifications or embodiments.

Claims (14)

1. A scan converter system, characterized in that it comprises: a. a shift register receiving at least one serial input data stream from an input device; b. a serial-to-parallel converter coupled to said shift register; and c. _DMDs connected to said serial-to-parallel converter, whereby when a light source is reflected from said DMD, it produces an intensity pattern nearly identical to the image received at said input device. 2. The system of claim 1, wherein said detector controls the images from said _DMDs such that said images are drawn from the detector in a different order than the images input to said detector. output. 3. A scan converter system, characterized in that it comprises: a. at least one shift register receiving at least one data stream of serial input data from an input device; b. at least one serial-to-parallel converter connected to said shift register; c. at least one comparator, one input of which is connected to the output of said serial-to-parallel converter and the other input of which is connected to a sawtooth sweep voltage; and d. At least one DMD connected to said comparator, whereby when a light source is reflected from said DMD, it produces an intensity pattern nearly identical to the image received at said input device. 4. The system of claim 3 wherein said comparator is a sawtooth comparator. 5. A system as claimed in claim 1 or 3, characterized in that said DMD is imaged onto a solid state detector. 6. The system of claim 5 wherein said detector is a CCD. 7. The system of claim 5, wherein said detector controls images from said DMD whereby said images are transferred from said detector in an order different from that of images input to said detector. output. 8. The system of claim 1 or 3, wherein said DMD is a twisted beam plate DMD. 9. The system of claim 3 wherein said DMD images onto the back of a scanning mirror. 10. The system of claim 9, wherein the image from the back of the scanning mirror is optically projected to produce an image substantially identical to the image received at the input device. 11. The system of claim 1 or 3, wherein said input means is an IR sensor. 12. The system of claim 1 or 3, wherein said input device is a computer. 13. The system of claim 1 or 3, wherein said shift register, said serial-to-parallel converter, said comparator, and said DMD are disposed on a monolithic integrated circuit. 14. A method of producing a scan converter system, characterized in that it comprises: a. receiving at least one data stream of input data from an input device; b. transforming said serial data stream into parallel data; and c. Sending the parallel data to the _DMDs , whereby when the light source is reflected from the DMD, an image nearly identical to the image received at the input device is produced.

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