JP2959823B2 - Image processing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus capable of thinning out and outputting output data of a solid-state imaging device having a predetermined resolution.

[Prior Art] Conventionally, an image input device using a solid-state imaging device differs depending on the color filter arrangement on the solid-state imaging device, but it is from a half of the horizontal pixel driving frequency f (mosaic) to a half of a horizontal pixel driving frequency f (mosaic) to 1 / 3f (pure color vertical). An optical low-pass filter for limiting the band of the spatial frequency of the stripe is provided on the entire surface of the image sensor so that aliasing due to spatial sampling is not mixed into the image signal from the image sensor.

[Problems to be Solved by the Invention] However, in the above conventional example, the horizontal pixels are 500 × M
In an area sensor with 500 × n vertical pixels, a spatial frequency band of 1 / 3f (MHz) is limited from 1 / 2f (MHz), which is half the driving frequency f (MHz) of horizontal pixels (all columns). So, for example, 500 x M area sensors, 5 vertical
When thinning out the signals of 500 × M / M horizontal and 500 × n / n vertical (where M and n are integers of 3 to 4 or more) out of the signals of all 00 × n pixels, In the baseband signal, the aliasing component is included.

Therefore, in applications such as video cameras, when thinning out to 500 horizontal × 500 vertical and outputting them to a general monitor or EVF (Electric View Finder) for composition and focus adjustment, folding back appears and there are many moiré screens There was a problem of becoming.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems and to provide an image processing apparatus capable of outputting a high-quality image even when the output of an image sensor is thinned out.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, a solid-state imaging device, an image display means capable of displaying an image by thinning output data of the solid-state imaging device at least in a horizontal direction, and An optical low-pass filter provided at a position in front of the solid-state imaging device in the imaging optical system for the solid-state imaging device and capable of changing an optical transmission characteristic with respect to a spatial frequency; and an all-pixel output mode for outputting all pixels of the solid-state imaging device Switching means for switching between a thinned image display mode for displaying an image of the output thinned in the horizontal direction, and an optical transmission characteristic of the optical low-pass filter according to the operation of the switching means. The Nyquist frequency or higher of the decimated signal is limited, and in the all-pixel output mode, the signal is not decimated in the horizontal direction. And control means for switching so as to limit the Nyquist frequency or higher of the low signal, thereby reducing moire in the thinned image display mode.

Embodiment FIG. 1 shows a configuration of an image processing apparatus employing the present invention.

In FIG. 1, reference numeral 1 denotes a lens, reference numeral 2 denotes a shutter for adjusting an exposure amount, and reference numeral 3 denotes a solid-state image sensor (area sensor).
Where 500 × M and 500 × n in the horizontal and vertical directions, respectively.
Pixels. Here, M and n are integers of 3 to 4 or more. The optical low-pass filter 16 provided between the shutter 2 and the solid-state imaging device 3 will be described later.

The output signals of the solid-state imaging device 3 are A / D converters 4, 5, 6
, And is stored in the buffer memory 7 as a multilevel digital signal.

The memory 8 performs predetermined image forming processing and compression based on the data in the memory 7, and the image data formed in the memory 8 is output via the buffer memory 9.

The solid-state imaging device 3 is controlled by the main control unit 11 by a driver circuit 10.
The drive is controlled via the. The main control unit 11 controls the entire image pickup apparatus, and includes a microprocessor and the like.

In the present embodiment, the digitized output image data of the solid-state imaging device 3 stored in the buffer memory 7 is horizontally and
Vertically to 500 M / M, 500 n / n pixels, that is, 500 × 500
The output is thinned out for each pixel (degree). Reference numeral 12 denotes a buffer memory for storing the thinned image. The thinning-out control is performed by controlling the data reading of the solid-state imaging device 3 by the main control unit 11.

For example, in an application such as a video camera, the thinned data stored in the buffer memory 12 is converted into an analog signal by the D / A converter 13 as shown in FIG. I do.

The optical low-pass filter 16 is an optical low-pass filter that limits the spatial frequency of the solid-state imaging device 3. The characteristics of the optical low-pass filter 16 can be switched by a switch 17 between a case where the area sensor is driven by all pixels and a case where the area sensor is driven at 500 M / M and 500 n / n.

That is, as shown in FIG. 2, the solid-state imaging device 3 having horizontal pixels of 500 × M and vertical pixels of 500 × n drives all the pixels fully to output an image signal, and the horizontal pixel is 500 M / M.
In the mode in which the number of vertical pixels is increased to 500 × n / n and a pixel signal is output, the characteristics of the optical low-pass filter 16 that limits the spatial frequency are switched to characteristics suitable for each mode.

The change of the spatial frequency characteristic of the optical low-pass filter 16 is as follows.
This can be achieved by replacing a plurality of filter elements in front of the solid-state imaging device 3.

In addition, the thinning mode is not limited to one type, and the above M,
You may comprise so that several values of n may be selected. In such a case, a plurality of low-pass filters are switched so as to use the optical low-pass filter 16 suitable for each thinning mode (it is also possible to use the low-pass filters at the same time if necessary). Will be described.

Normally, when the switch 17 is ON, the lens optical system 1,
The subject image passes through 2 and 16 and is formed on the solid-state imaging device 3. The driving pulse from the main control unit 11 passes through the driver circuit 10,
The signals are supplied to the solid-state imaging device 3, and signals for all pixels are output from the solid-state imaging device 3.

Output signals of the solid-state imaging device 3 are converted into digital signals by A / D converters 4 to 6 and stored in a buffer memory 7.

The digital image signal stored in the buffer memory 7 is sent to the memory 8, where the digital image signal is subjected to predetermined image formation and compression (such as compression), and output from the buffer 9.

The optical low-pass characteristic in the normal mode is the characteristic indicated by the symbol a in FIG.
Assuming that the driving frequency of all the rows is 500 × M) is f (MHz), the characteristic is to pass up to the Nyquist frequency 1 / 2f.

Next, when the switch 17 is OFF, the image is thinned out. At this time, by controlling the data reading from the solid-state imaging device 3 by the control signal of the main control unit 11 and the driver circuit 10, the signals interposed between 500 × M / M and 500n / n in both horizontal and vertical directions Is output from the area sensor, sent to the A / D converters 4 to 6, and stored in the buffer memory 7.

The decimated digital signal is sent to a D / A converter 13, converted into an analog signal, and input to a process circuit 14 for performing predetermined video processing.

Video processing (converted to TV rate) by processing circuit 14
And sent to EVF15. The user adjusts the angle of view, composition, and focus using the image projected on the EVF 15.

At this time, the optical low-pass filter 16 is denoted by the symbol b in FIG.
The characteristic is switched to the characteristic indicated by. This is converted into an optical low-pass filter 16 having a characteristic of passing up to 1/2 fz, where fz (Mz) is the driving frequency of the thinned horizontal pixel number.

The switch 17, for example, in the EVF 15, sets the area sensor to the thinning mode in order to use it for composition and focus adjustment, and after completion of adjustment such as composition and focus, switches to the area sensor all-pixel output mode and outputs a signal. It can be used for various applications.

As described above, by converting the optical filter of the lens optical system into a filter having the respective characteristics according to the all pixel output mode and the thinning output mode of the area sensor, the aliasing noise mixed in the image signal particularly in the thinning mode. (Moiré) can be prevented, and clear and high-quality images without moiré can be obtained when projecting images on an EVF or general monitor. For example, in applications such as video cameras, the composition and focus adjustment with the EVF are accurate. Will be able to

[Effects of the Invention] As is apparent from the above description, according to the present invention, a solid-state imaging device, and image display means capable of thinning output data of the solid-state imaging device at least in a horizontal direction and displaying an image,
An optical low-pass filter provided at a position in front of the solid-state imaging device in the imaging optical system for the solid-state imaging device and capable of changing an optical transmission characteristic with respect to a spatial frequency; and an all-pixel output for outputting all pixels of the solid-state imaging device Switching means for switching between a mode and a thinned-out image display mode for displaying an image of the output thinned out in the horizontal direction, and according to the operation of the switching means, the optical transmission characteristic of the optical low-pass filter is set to be horizontal in the thinned-out image display mode. To limit the signal decimated in the direction above the Nyquist frequency,
Control means for switching so as to limit the Nyquist frequency or higher of a signal that is not thinned out in the horizontal direction in the all-pixel output mode, by adopting a configuration for reducing moiré in the thinned-out image display mode. In the thinned image display mode in which the output of the image is thinned out in the horizontal direction, moiré caused by aliasing noise mixed in the image signal can be prevented, and clear and high-quality images without moiré when projected on an EVF or general monitor And an excellent effect that a high quality image can be output even in the thinned image display mode.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of a solid-state imaging device, and FIG. 3 is an explanatory diagram showing spatial frequency characteristics of an optical filter used in the embodiment of the present invention. 1 ... Lens 2 ... Shutter 4,5,6 ... A / D converter 7,9,12 ... Memory buffer 8 ... Memory 10 ... Area sensor driver circuit 11 ... Main control unit 13 ... D / A converter 14 Image processing circuit 15 EVF 16 Optical low-pass filter

Claims (1)

(57) [Claims] 1. A solid-state imaging device, image display means capable of displaying an image by thinning output data of the solid-state imaging device at least in a horizontal direction, and a front of the solid-state imaging device in an imaging optical system for the solid-state imaging device An optical low-pass filter provided at a position and capable of changing an optical transmission characteristic with respect to a spatial frequency; an all-pixel output mode for outputting all pixels of the solid-state imaging device; and a thinned image display for displaying an image of the output thinned in the horizontal direction. Switching means for switching between modes, according to the operation of the switching means, limiting the optical transmission characteristics of the optical low-pass filter to the Nyquist frequency of a signal thinned in the horizontal direction in the thinned image display mode, In the all-pixel output mode, switching is performed to limit the Nyquist frequency of signals that are not thinned out in the horizontal direction. An image processing apparatus characterized in that, by providing control means, moire in a thinned image display mode is reduced.