JPS61191165A - Picture processing method - Google Patents

Abstract

PURPOSE:To convert a picture to a filtered electric signal easily by exposing the same picture on a solid-state image pickup element plural times and adding the induced distributed electric charge corresponding to the picture in each exposure while shifting the position in the solid-state image pickup element. CONSTITUTION:An input picture 2 is focused on an image sensor 4 of electric charge transfer type by a lens 3. The sensor 4 has picture elements arranged two-dimensionally in X and Y directions. An image sensor driver 42 sweeps out all of the electric charge in the sensor 4 in accordance with the sweep-out command from a controller 43 to start the exposure. Next, the driver 42 drives the sensor 4 by clocks modulated in accordance with weight coefficients ai [i=1-(n) and (n) is the number of picture elements in the range of weighted mean], and the exposure is repeated while transferring an electric charge Xi of every picture element. Finally, stored electric charges are added by the sweep- out command from the controller 43, and filtered outputs Y=SIGMAaiXi [i=1-(n)] are taken out as a time series electric signal, and this signal is outputted through an amplifier 45.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an image processing method for converting an image into a filtered electrical signal.

[Prior art]

Currently, there are demands for image processing in a wide range of fields, and among them, filtering processing that removes the effects of noise and the like from image signals is important as a basic processing. Filtering processing is performed, for example, when an image is divided into pixel columns and read, and the read value of a certain pixel is calculated as a weighted average of the outputs of a plurality of neighboring pixels including that pixel. Conventionally, in such processing, the output signal of the imaging device has been repeatedly multiplied and added using software using a computer or dedicated hardware. Therefore, when the number of pixels is large, the calculation time becomes extremely long, or expensive equipment has to be used to increase the processing speed.

[Summary of the invention]

An object of the present invention is to provide an image processing method that easily converts an image into a filtered electrical signal.

The above-mentioned object of the present invention is to expose the same image to a solid-state image sensor multiple times, and add charges induced by each exposure and distributed corresponding to the image at different positions within the solid-state image sensor, and then add them together. This is achieved by extracting it as an electrical signal.

〔Example〕

The present invention will now be described in detail with reference to the drawings.

FIG. 2 is an enlarged view showing a part of the image, and ■ indicates the image. Filtering processing for image l is performed by the following calculation. Assuming that the range of pixels on which weighted modulation is performed is 3×3 pixels, the filtered output Y of pixel x5 is given by the following equation, for example.

Y=Σa i X i (1) where X
i is the brightness of the pixel, and at is a coefficient representing the weight for each pixel. Similar calculations are performed using the same weights for other pixels to perform filtering of the entire image.

FIG. 1 is a schematic diagram showing an example of the configuration of an image processing apparatus that executes the method of the present invention. Here, a human image 2 such as an original 7 film or photographic paper is imaged by a lens 3 onto a charge transfer type image sensor (solid-state image pickup device) 4F. The image sensor 4 has pixels arranged in two-dimensional x and y directions, and can transfer charges in the x and y directions in response to a clock from the image sensor driver 42, respectively. Further, the image information read by the image sensor 4 is extracted as an electric signal 45, amplified by an amplifier 45, and then sent to an appropriate processing circuit at the next stage.

Charge transfer and information sweeping of the image sensor driver 42 are controlled by a controller 43.

Next, the principle of filtering according to the method of the present invention will be explained using FIG. Here, for the sake of simplicity, explanation will be given in terms of − dimension. In FIG. 3, 5 is an image of an input image formed on the image sensor 4, and 6, 7, 8.9 are light receiving parts of the image sensor 4, respectively. Light receiving section 6, 7, 8.
Let the brightness of image 5 on 9 be X 1 , X2 , X3 ,
Let it be X4. At this time, if the pixel range of the weighted average is 3 pixels, the filtering output Y2 of the image at the position corresponding to X2 is obtained as follows. Here, ai is the weight for each pixel.

In FIG. 3, first, the image 5 is exposed to the charge transfer type image sensor 4 with a light amount proportional to al.

The electric charges accumulated in the light receiving parts 6, 7, 8.9 are respectively at x
,,a,x2,a,X3,a'lX4. Next, the charge is shifted to the right by one pixel, and the same image 5 is given with the amount of light proportional to a2, and the charge is accumulated. Since the charges are added to the initial charges and accumulated, the light receiving parts 7, 8.9
The charges accumulated in are respectively al x, +a, X, , a',
X2+a7. X3°at X3+ a2 X4.

If the charge is further shifted to one pixel component and the image 5 is created with a light intensity proportional to a3, the charge accumulated in the light receiving section 8.9 is as follows.
X2 +a7 x3+ a3 'The charge on the light receiving section 8 is proportional to X4, and the filtering output Y2 shown in equation (2)
It can be seen that Therefore, if this charge is read out, a filtering output corresponding to X can be obtained. On the other hand, the filtering output Y corresponding to x3
3 is, which is determined from the amount of charge accumulated in the light receiving section 9. In this way, three exposures and two charge transfers allow filtering over the entire image.

In the above method, the exposure with the amount of light proportional to the weighting coefficient ai is
This is done by controlling the timing of charge transfer according to the weighting coefficient ai. This will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a sectional view of a two-phase drive charge transfer type image sensor. 20 is a two-phase CCD (ChargeCoup
led device), 21, 22, 23
, 24 are light receiving units that also serve as transfer units, 25, 26, 27
28 are transfer gates. The two-phase CCD 20 has two
It is driven by phase clocks φ1 and φ2. The light receiving section 21゜22.23.24 by the clocks φ1 and φ2.
The charges accumulated in the transfer game) 25, 26, 27.2
The light is sequentially transferred to the right via 8 etc. and the light reception is repeated. At this time, the weighting coefficient ai can be realized by controlling the timing of the clocks φ1 and φ2.

FIG. 5 shows a time chart of the clocks φ1 and φ2. Here, 30 is a signal waveform of clock φ1, and 31 is a signal waveform of clock φ2.

Charge transfer occurs when the clock φ1 is V, and images are received during the times indicated as T, , T2, T, etc. in FIG.
Charge accumulation occurs. Between this storage part T, , T2 , "r
3, --- each weighting coefficient alra2 + a3
If the setting is made so that it is proportional to +---1, the amount of charge accumulated in the light receiving parts 21, 22, 23, 24 during that time will be a
Proportional to i.

From the above explanation, the process of the embodiment of the present invention can be summarized as follows:
First, in accordance with a sweep command from the controller 43, the image sensor driver 42 sweeps out all the charges in the image sensor and starts exposure. Next, the image sensor is driven with a clock modulated according to the weighting coefficient as shown in FIG. 5, and exposure is repeated while transferring charges pixel by pixel. Finally, the accumulated charge is extracted as a time-series electric signal by a sweep command from the controller 43, and outputted via the amplifier 45.

FIG. 6 is a schematic diagram showing the principle of two-dimensional filtering. 11, 12, 13, 14° 15.16, 1.7
, 18 and 19 are the light receiving parts of the charge transfer image sensor, and the brightness of each part of the corresponding image is expressed as x, , x2
, x3. x4゜Xs ,X6 ,X7 ,Xs ,X
9. Charge transfer is performed in the order of the arrows, and the amount of light of the image exposed to the image sensor is determined by the weighting coefficient a I +
a2 + a3 +a6 +aS + aa +
A charge proportional to 7 + aa + a9 is accumulated, and a weighted average processing result within the 3×3 pixel corresponding to X is obtained.

FIG. 7 is a diagram showing the results of filtering processing according to the method of the present invention, in which (a) is an image before processing, and (b) is an image after processing. Here, the horizontal axis shows the position, and the vertical axis shows the light intensity at that position. As described above, according to the present invention, an original image with a lot of noise as shown in 40 can be made into a processed image with noise removed as shown in 41. In the present invention, the number of pixels and weighting coefficients for weighted averaging are determined depending on the degree of filtering desired, but in the simplest case, the pixel range is set to 3 x 3 pixels as shown in Figure 6, and nine weighting coefficients are set. All should be set to 1. In order to obtain better filter characteristics, there are various methods such as expanding the pixel range to 5×5 pixels, etc., and determining the weighting coefficient according to a Gaussian function.

The present invention is not limited to the above-described embodiments, and can be applied in various ways. For example, in the embodiment, the exposure amount was adjusted by changing the transfer timing, but it can also be done by providing a shutter between the input image and the image sensor and changing the opening time of this shutter according to the weighting coefficient. In addition, by changing the brightness of the illumination light source of the input image, or inserting a variable transmittance filter used in a spatial light modulator between the input image and the image sensor, the amount of light reaching the image sensor can be modulated according to the weighting coefficient. You may do so. In these cases, charge transfer can occur at equal time intervals.

〔Effect of the invention〕

As explained above, according to the image processing method of the present invention,
Since arithmetic processing is performed on the image sensor, there is no need for a computer or special hardware to process the output electrical signals, making the device configuration simple and inexpensive. Furthermore, since processing is performed in parallel on all pixels, the processing time remains the same even if the number of pixels increases, and even a large amount of image information can be processed at high speed.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the configuration of an image processing device that executes the method of the present invention, FIG. 2 is a plan view showing a part of an image, and FIG. 3 is a diagram of an image sensor illustrating the principle of filtering according to the present invention. 4 is a schematic sectional view showing a configuration example of an image sensor used in the present invention, FIG. 5 is a diagram showing a signal waveform of a clock that drives the image sensor in FIG. 4, and FIG. 6 is a two-dimensional diagram. FIGS. 7A and 7B are plan views of an image sensor showing the principle of filtering. FIGS. 7A and 7B are diagrams showing images before and after filtering processing, respectively. 2-111 power image, 3-111 lens, 4----image sensor, 42----image sensor driver, 43----controller, 44--1 electric signal, 45-- --Amplifier.

Claims (1)

[Claims] (1) In an image processing method for converting an image into an electrical signal, the image is exposed to a solid-state image sensor multiple times, and charges induced by each exposure and distributed corresponding to the image are transferred to positions within the solid-state image sensor. An image processing method characterized by shifting and adding together the signals and then extracting them as electrical signals.