JPH04358417A - Digital data processing circuit - Google Patents

Abstract

PURPOSE:To use an A/D converter of 8 bits, for example, and to process the data with resolution higher than the level decided by these 8 bits. CONSTITUTION:The input analog data are converted into the digital data by a 1st A/D converter 11 and then supplied to a D/A converter 23 and converted into the analog data. The difference of the converted analog data and the input analog date is amplified by (n) times. This amplified output is converted into the digital data by a 2nd A/D converter 12. Then this digital data outputted from the converter 12 are added to the digital date outputted from the converter 11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital data processing circuit suitable for application to, for example, a control system of an autofocus system of a video camera.

0002

[Prior Art] Conventionally, an analog/digital converter built into a microcomputer formed on one chip is
8-bit analog/digital converters that process 8-bit digital data are mainstream. Therefore, the resolution for converting input analog signals into digital data has been limited to that corresponding to 8-bit data.

[0003] In order to increase the resolution of the converted data and to be able to process data of 8 bits or more, it is generally necessary to convert analog/digital data for the corresponding number of bits (for example 12 bits). It was necessary to connect the converter to the microcomputer as a separate component.

For example, when autofocus control of a video camera is performed digitally, in order to perform this focus control with high precision, it is necessary to process data with 8 bits or more, and a separate analog/digital converter is required. It was made up of parts.

[0005]

However, if a one-chip microcomputer is configured to have an analog/digital converter connected as a separate component, the circuit configuration becomes complicated, increasing manufacturing costs, and the circuit There are disadvantages in that the mounting area of components and power consumption become large, and furthermore, data exchange between the microcomputer side and the analog/digital converter side becomes complicated.

An object of the present invention is to provide a digital data processing circuit that uses an 8-bit analog/digital converter built into a microcomputer and can process data with a resolution higher than that determined by the number of bits. It's about doing.

[0007]

[Means for Solving the Problems] The present invention, as shown in FIG.
The digital converter 11 converts it into digital data, supplies the converted digital data to the digital/analog converter 23 to convert it into analog data, and calculates the difference between the converted analog data and the input analog data by n This amplified output is converted into digital data by the second analog/digital converter 12, and the digital data output from the second analog/digital converter 12 is converted into digital data by the first analog/digital converter. This is added to the digital data output by the device 11.

[0008]

[Operation] By doing this, the output data of the second analog/digital converter will indicate the state within one bit of the digital data converted by the first analog/digital converter, and this By adding the output data of the second analog/digital converter to the output data of the first analog/digital converter, the resolution of the digital data is substantially increased.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram of a video camera to which the digital data processing circuit of this example is applied. In the figure, 1, 2, and 3 indicate the imaging lenses of this video camera, 1 is a front lens, 2 is a zoom lens, 3 indicates a focus lens. This imaging lens is of an inner focus type in which the front lens 1 is fixed. By moving the zoom lens 2 with a zoom lens motor 32 (described later), the imaging angle of view (focal length) can be adjusted, and by moving the focus lens 3 with a focus lens motor 34 (described later), the focus can be adjusted. Can be done. Then, the image light that has passed through the imaging lenses 1, 2, and 3 is imaged on a CCD imager 4 as an imaging means, and the CCD imager 4 accumulates charges corresponding to the image light for each pixel.

The charges accumulated in the CCD imager 4 are then read out line-by-line by an output circuit 5 to form an imaging signal, and this imaging signal is supplied to a video processing circuit 7 via an automatic gain control circuit (AGC circuit) 6. The video processing circuit 7 converts the image signal into a video signal in a predetermined format such as the NTSC system, and outputs the converted video signal to an output terminal 8.
get to.

Further, in this example, the image pickup signal output from the AGC circuit 6 is supplied to a focus signal processing circuit 9, and the signal processing circuit 9 detects focus control information from the image pickup signal. The detected focus control information is then sent to the system controller 10 of this video camera.
supply to. The system controller 10 is composed of a one-chip microcomputer, and controls the operation of each circuit of the video camera. It supplies control data for the zoom lens position to the zoom lens drive circuit 31, and also supplies control data for the zoom lens position to the focus lens drive circuit 33. The control data for the focus lens position is supplied to the Then, the zoom lens drive circuit 31 creates a drive signal for the zoom lens motor 32 based on the supplied control data, and generates a drive signal for the zoom lens motor 32.
to the corresponding focal length position. Further, the focus lens drive circuit 33 creates a drive signal for the focus lens motor 34 based on the supplied control data, and moves the focus lens 3 to a corresponding focus position.

In this case, a potentiometer 21 is attached to the imaging lens in order to detect position information of the zoom lens 2, and the output potential of the potentiometer 21 changes depending on the position (focal length) of the zoom lens 2. The output of the potentiometer 21 is then supplied to the first analog/digital converter 11 in the system controller 10 and also to the non-inverting input terminal of the differential amplifier 22. In this case, the first analog/digital converter 11 is a circuit that converts an input analog signal into 8-bit digital data. Further, the differential amplifier 22 has 16
This is to perform double differential amplification. The output of this differential amplifier 22 is then supplied to the second analog/digital converter 12 within the system controller 10. This second analog/digital converter 12 is also a circuit that converts an input analog signal into 8-bit digital data.

[0014] Then, the 8-bit digital data converted and outputted by the first analog/digital converter 11 is
It is supplied to the digital/analog converter 23 as the output of the system controller 10. This digital/analog converter 23 is a circuit that converts the supplied 8-bit data into analog data, and the analog data obtained by the conversion is
It is supplied to the inverting side input terminal of the differential amplifier 22.

Furthermore, within the system controller 10,
Processing is performed to obtain an added value X by adding the digital data converted and output by the second analog/digital converter 12 to the digital data converted and output by the first analog/digital converter 11. At this time, addition processing is performed using the following equation.

[0016]

[Math 1] X=(AD1×16)+AD2

Here, AD1 is the output data of the first analog/digital converter 11, and AD2 is the output data of the second analog/digital converter 12.

[0018] By performing the arithmetic processing according to the formula [Equation 1], the added value X becomes 12-bit data. That is, in response to the difference amplifier 22 performing 16 times differential amplification, the output data AD1 of the first analog/digital converter 11 is multiplied by 16 times and added.
1 is shifted by 4 bits, and by adding the 8-bit data shifted by 4 bits and the 8-bit data, 12-bit data is obtained.

Then, the system controller 10 uses the above-mentioned addition value X as position data of the zoom lens 2.
Performs processing for focus control. That is, if the imaging lens is configured as a zoom lens whose focal length changes, the movement of the zoom lens 2 (movement of the focal length)
As a result, the in-focus range changes, so when performing autofocus control by controlling the position of the focus lens 3, it is necessary to constantly judge the current position of the zoom lens 2. Therefore, the accurate position of the focus lens 3 is calculated by referring to the position data of the zoom lens 2 based on the added value
3 as control data for the focus lens position.

[0020] The video camera of this example, configured in this manner, can perform autofocus control well. That is, since the position data of the zoom lens 2 necessary for autofocus control is obtained as 12-bit data based on the above-mentioned addition value X, position data with high resolution suitable for autofocus control can be obtained. Therefore, the system controller 10 can accurately determine the position of the zoom lens 2 based on high-resolution position data, accurately determine the in-focus range, and perform accurate autofocus control.

In this case, in this example, analog/digital converters 11 and 12 built into the system controller 10, which is composed of a one-chip microcomputer,
Although it has a normal configuration that processes data in 8 bits, the output of the potentiometer 21 is obtained as 12 bit data. Therefore, there is no need to attach a 12-bit analog/digital converter as a separate part to the system controller 10, and the configuration of a control system that can perform highly accurate autofocus control is simplified, reducing manufacturing costs. The size of the circuit components is reduced, the mounting area is reduced, and the video camera can be made smaller.

In the above embodiment, the differential amplifier 22 performs differential amplification of 16 times, but other amplification degrees may be used. In this case, the number of bits of the obtained digital data changes depending on the amplification degree of the differential amplifier 22, and the amplification degree may be set to correspond to the required resolution. It may be configured to change. Further, although the analog/digital converters 11 and 12 in the system controller 10 are provided as separate circuits, a set of analog/digital converters may be used in a time-sharing manner for processing.

Further, in the above embodiment, the circuit is used to obtain lens position data for autofocus control of a video camera, but it can also be applied to converting various other analog data into digital data with high resolution. .

[0024]

According to the present invention, digital data with a resolution exceeding that of the built-in analog/digital converter can be obtained, and high-resolution digital data can be obtained with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

1 Front lens 2 Zoom lens 3 Focus lens 10 System controller 11 First analog/digital converter 12 Second
analog/digital converter 21 potentiometer 22 differential amplifier 23 digital/analog converter

Claims (1)

[Claims] Claim 1: Converting input analog data into digital data in a first analog/digital converter, supplying the converted digital data to a digital/analog converter to convert it into analog data, and converting the converted digital data into analog data. The difference between the input analog data and the input analog data is amplified by n times, this amplified output is converted to digital data by a second analog/digital converter, and this second analog/digital converter outputs A digital data processing circuit configured to add digital data output from the first analog/digital converter to digital data output from the first analog/digital converter.