Image sensor system using CMOS image sensor and image sensor apparatus using CMOS image sensor
View Patent ↗An image sensor such as the conventional CMOS image sensor, in which automatic controls including so-called automatic iris control and white balance adjustment for adjusting the sensor sensitivity, namely the charge accumulation time in each pixel, according to the brightness of the image sensing ambience are performed, involves the problem that, when the frame rate of the image sensor is slowed to save power consumption, the operation of the automatic control systems will also become slower and the image quality deteriorates. In the invented image sensor system using a CMOS image sensor, while a CMOS image sensor is operated at the full frame rate all the time, a circuit for processing image signals from the CMOS image sensor is operated at a speed close to that of full frame processing only when the power supply is turned on or when the image sensing ambience varies and switched to a lower frame processing speed when automatic controls, including iris control, have become stabilized.
1. An image sensor system comprising a CMOS image sensor and a signal processing LSI for processing image signals from the CMOS image sensor,
wherein said signal processing LSI reduces the frequency of an operational clock within the signal processing LSI when the variation in image signals from said CMOS image sensor is less than a prescribed level.
2. The image sensor system according to claim 1 , wherein said signal processing LSI separates image signals from said CMOS image sensor into color signals and luminance signals, and reduces the frequency of the operational clock within the signal processing LSI when the variation in the separated luminance signals is less than a prescribed level.
3. The image sensor system according to claim 1 , wherein said signal processing LSI separates image signals from said CMOS image sensor into color signals and luminance signals, and reduces the frequency of the operational clock within the signal processing LSI when the variation in either the separated luminance signals or color signals is less than a prescribed level.
4. The image sensor system according to claim 1 , wherein said signal processing LSI separates image signals from said CMOS image sensor into color signals and luminance signals, and reduces the frequency of the operational clock within the signal processing LSI when the variations in the separated luminance signals and color signals are less than respectively prescribed levels.
5. The image sensor system according to claim 1 , wherein said signal processing LSI comprises: a signal separation circuit for separating image signals supplied from said CMOS image sensor into color signals and luminance signals; a luminance correction circuit for correcting the separated luminance signals; a color correction circuit for correcting the separated color signals; a first detection circuit for detecting the quantity of correction in said luminance correction circuit; and a control circuit for controlling the signal processing LSI and said CMOS image sensor, wherein the control circuit reduces the frequency of the operational clock within the signal processing LSI when the variation in image signals is less than a prescribed level according to a detection signal from said first detection circuit.
6. The image sensor system according to claim 5 , wherein said signal processing LSI further comprises a second detection circuit for detecting the quantity of correction in said color correction circuit, and said control circuit reduces the frequency of the operational clock within the signal processing LSI when the variation in the luminance content of image signals is less than a prescribed level or the variation in the color content of image signals is less than a prescribed level based on the detection signal from said first detection circuit and a detection signal from said second detection circuit.
7. The image sensor system according to claim 5 , wherein said control circuit comprises a data processing unit for performing control by executing a programmed command and a memory for storing the program to be executed by the data processing unit, and the control to reduce the frequency of said operational clock is carried out by program processing by said data processing unit.
8. The image sensor system according to claim 5 , further comprising a frequency divider circuit capable of dividing the frequency of a reference clock signal into a plurality of steps, wherein said control circuit reduces the frequency of said operational clock by varying the frequency division ratio of said frequency divider circuit.
9. The image sensor system according to claim 1 ,
wherein said CMOS image sensor is configured to be able to set the maximum charge accumulation time of each pixel to a longer length of time than the length of time required to scan every horizontal scanning line in a full round,
wherein the maximum charge accumulation time of said CMOS image sensor is set, during a prescribed operation, to a shorter length of time than the length of time required to scan every horizontal scanning line in a full round, and
wherein the maximum charge accumulation time of said CMOS image sensor is set, in a state in which said control circuit is performing control to reduce the frequency of said operational clock and said luminance signal or luminance content is less than a prescribed level, to a longer length of time than the length of time required to scan every horizontal scanning line in a full round.
10. The image sensor system according to claim 9 , wherein said maximum charge accumulation time is set by said control circuit by setting into the CMOS image sensor.
11. An image sensor apparatus comprising: a first semiconductor chip in which a CMOS image sensor is formed; and a second semiconductor chip in which an image signal processing circuit for processing image signals outputted from said CMOS image sensor and a control circuit for controlling said CMOS image sensor and image signal processing circuit are formed, both chips being mounted over a single printed circuit board,
wherein the frequency of the operational clock within said image signal processing circuit is reduced when said control circuit determines that the variation in image signals from said CMOS image sensor is less than a prescribed level.
12. The image sensor apparatus using a CMOS image sensor according to claim 11 , wherein said control circuit comprises: a data processing unit for performing control by executing a programmed command; and a memory for storing the program to be executed by the data processing unit, and the control to reduce the frequency of said operational clock is carried out by program processing by said data processing unit.
13. An image sensor apparatus comprising: a first semiconductor chip in which a CMOS image sensor is formed; a second semiconductor chip in which an image signal processing circuit for processing image signals outputted from said CMOS image sensor is formed; and a third semiconductor chip in which a control circuit for controlling said CMOS image sensor and image signal processing circuit are formed, all these chips being mounted over a single printed circuit board,
wherein the frequency of the operational clock within said image signal processing circuit is reduced when said control circuit determines that the variation in image signals from said CMOS image sensor is less than a prescribed level.