Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
2000-05-19
2003-02-04
Kim, Robert H. (Department: 2882)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C257S292000
Reexamination Certificate
active
06515271
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to CMOS image sensor units with serial data transmitting function and, more particularly, to CMOS image sensor units with serial data transmitting function, which are simple in construction while being reduced in size and cost, and pick-up units and image data transmitting and receiving systems using the same.
With recent manufacture yield improvement and cost reduction of image pick-up elements, various image pick-up devices utilizing semiconductor image pick-up elements, such as those in which an image pick-up element is set in a predetermined position in various apparatuses or buildings to pick up an image, convert the picked-up image into an electric signal and display the signal thus obtained in a display, have become actually used.
As the image pick-up element adopted for the above purpose, CCD has heretofore been usually used, which can be manufactured with high yield and at relatively low cost and have relatively stable characteristics with low fluctuation between individual elements. However, CCD requires three kinds of driving circuits, causing a relatively large power consumption. For this reason, image pick-up devices using CMOS element as the image pick-up element have recently been attracting attention.
Compared to CCD, however, the characteristics of CMOS have heretofore been fluctuated greatly with individual elements, resulting in appearance of fixed pattern noise in image data obtained by using a number of CMOS elements. For this reason, the CMOS has element not yet been widely used as the image pick-up element. In the mean time, with recent improvement in the CMOS manufacturing techniques, characteristics fluctuations with individual elements have become reduced, and the generation of fixed pattern noise in image data has become suppressed. Thus, the low power consumption merit of CMOS over CCD has started attracting attention.
An image signal which is obtained as electric signal by conversion in such an image pick-up element is transmitted to personal computer or like image processing unit. The image signal obtained as electric signal by conversion in the image pick-up element, is often converted to a digital signal and transmitted as parallel signal via a plurality of cables. The prior art sensor unit as described, however, has the following problems.
(1) System Interface
A digital signal obtained by a two-dimensional sensor, is usually required to be transmitted by multiple-bit high-rate transmission. For example, with a so-called CIF size image constituted by 320×240 pixels, in a case of assigning 8 bits per pixel, signals of total of 11 bits of pixel clocked at 6.75 MHz, vertical and horizontal synchronizing signals and 8 bits of pixel data. Moreover, in color image transmission 8 bits are often considered necessary for each of the R, G and B colors. This means that it is necessary to transmit 27 signals. If it is intended to transmit these signals at a high rate, it gives rise to problems in each data signal skew for the clock. In other words, it is difficult to normalize the impedance, the load capacitance, etc. of all the 27 signal line cables, inevitably resulting in fluctuations, phase deviations of data signal with respect to the clock signal, defective digital signal transmission and consequent image quality deterioration. Therefore, a plurality of signals are necessary as the above two-dimensional image signal. The prior art sensor unit is thus not suited for systems aiming at reducing size and power consumption.
(2) Current Consumption
In a two-dimensional sensor with the digital output as described above, a sudden change in its output may result in noise generation. In view of the interface with external circuitry, usually an output capacity of at least about 2 mA is set for output buffer current. Simultaneous changes in 24 bit data cause a current change of 48 mA caused to momentarily flow into the output buffer. This current exceeds the consumed current in the two-dimensional sensor itself. Therefore, systems aiming at reducing size and power consumption pose problems in consumed current into the output buffer.
(3) Noise Generation
A great current caused to flow to the output buffer affects the sensor unit of the chip. In the chip, the sensor unit, inclusive of photo-diodes and amplifiers, operate analog-wise, and current changes other than the signal are preferably as less as possible. Such great current changes as in the output buffer greatly affect the sensor unit. Since such changes are synchronized to the clock, they are also synchronized to the sensor operation and affect as image noise.
(4) Distance of Data Transmission
In an output buffer which is usually employed, the load capacity is about 50 pF, and the current capacity is about 4 mA. If it is intended to use such an output buffer for data transmission at a high rate, it is inevitable to set a high matching impedance, resulting in shortening the transmission distance. For example, assuming the current capacity to be 4 mA, the least matching resistance is 1.25 k&OHgr; at power supply voltage of 5 V. Where the video signal is transmitted as analog signal, usually the matching is done with 50&OHgr;, and in SCSI interface (for high-rate digital transmission) it is executed with 330/220&OHgr;. Thus, even in the matching impedance alone, for instance, the difference is about 10 times, and with transmission distance increase the signal attenuation is increased by 10 times. This is equivalent to a signal change increase to 10 times. That is, sufficient transmission can not be obtained unless the transmission distance or like influencing factor is reduced to one-tenth. Since common GND to all these digital data is adopted, a change in GND has adverse effects on all the digital signals. This is a significant cause of error occurrence in multiple-bit digital transmission, and adversely affects the image quality as noise (i.e., signal irrelevant to the sense signal) in the sensor unit.
It is summarized that the problems in the above prior art sensor unit are as follows. Since the sensor unit output is parallel data, signal lines (or cables) are required in number corresponding to the number of the parallel channels, thus leading to complication of the construction and size and cost increase thereof.
Besides, the increase of the number of cables gives rise to total current increase and hence consumed current increase.
Furthermore, the plurality of cables slightly vary in length, and characteristics fluctuations result in signal skew generation, giving rise to image quality deterioration problems.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above problems in the prior art by the provision of a CMOS sensor unit with serial data transmission function, which reduces consumed power, has simplified construction, is small in size, is subject to less effects of noise and less image quality deterioration and permits long distance data transmission, as well as an image pick-up unit and an image data transmitting and receiving system using the same.
According to a first aspect of the present invention, there is provided a CMOS image sensor unit with serial data transmitting function comprising: a CMOS sensor unit as a two-dimensional sensor constituted by a plurality of CMOS elements arranged in a regular array in the row and column directions; a clock unit for obtaining a clock signal at a predetermined oscillation frequency; a PLL circuit unit receiving the clock signal from the clock unit; and a parallel-to-serial converter unit for converting parallel data read out from the CMOS sensor unit to serial data in synchronism to the clock signal from the PLL circuit; these units being mounted on a single image sensor unit.
According to a second aspect of the present invention, there is provided a CMOS image sensor unit with serial data transmitting function comprising: a CMOS sensor unit as a two-dimensional sensor constituted by a plurality of CMOS elements arranged in a regular array in the row and column dir
Kim Robert H.
Olympus Optical Co,. Ltd.
Pokotylo John C.
Song Hoon K.
Straub & Pokotylo
LandOfFree
CMOS image sensor unit with serial transmitting function does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with CMOS image sensor unit with serial transmitting function, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and CMOS image sensor unit with serial transmitting function will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3151720