JPS5815369A - Signal processing system - Google Patents

Abstract

PURPOSE:To obtain image quality of excellent reproduced image, by storing fixed pattern information such as fixed pattern noise and performing a prescribed operation for a video output signal from an image pickup device. CONSTITUTION:Since a fixed pattern noise component shows a prescribed value beta regardless of the output value for the case, a video element of an image pickup device 6 producing the component is determined in advance, and stored in a storage means 10 and read out for operational processing at an operator 11 for the purpose of elimination of the noise component. Since the luminous amount fluctuation is dependent on environmental temperature and time, the maximum value multiplied with a coeffficient gamma (0<=gamma<=1) is stored in a storage means 9 for the elimination. Since the shading component shows a prescribed ratio to the output value, it can be eliminated the same as the luminous amount fluctuation. Further, a dark current dispersion component can also be eliminated by storing the component in a storage means 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal processing method, and more particularly to a method for removing imperfections that impair the quality of reproduced images, such as puffiness and fluctuations in a video output signal in an imaging device.

Imperfections such as puffiness or fluctuation components of the video output signal in an imaging device such as a one-dimensional twin sensor include the sensitivity puffiness of each pixel inherent in the sensor, so-called fixed pattern noise, variations in dark current, and the optical system. There is fixed pattern information such as light intensity fluctuations or so-called shading due to characteristics.

FIG. 1 shows an example of a video output signal that appears during one cycle T of the imaging device, and the vertical axis indicates the output level.

In this figure, 1 is the sensitivity variation, 2 is the fixed pattern noise, and 8 is the light intensity variation, and the curved characteristic 4 drawn by the dotted line is
However, for example, the amount of light falls off at both ends of a light source such as a fluorescent lamp,
Alternatively, it is shading that occurs due to the angle of view of the lens, etc. Also, what is shown as 5 indicates the dark current variation that occurs for each pixel of the imaging device.

In this figure, the bottom corresponds to the black level, and the top corresponds to the white level.

Among these fixed pattern information, if the sensitivity variation and fixed pattern noise are relatively low, no correction is required, and if the video output signal is simply binarized. There are no particular problems. However, if the video output signal must be multi-valued, such as in the case of halftone fax, this cannot be left as is.

Regarding light intensity fluctuations and shading caused by the optical system, for example, the light intensity can be monitored and used as a reference, or a nullit having a translucent window in the cross-section of a concave lens can be introduced into the optical system and projected onto the form. Although there is a method to correct the amount of light, it is not possible to achieve a complete correction.

In addition, regarding the dark current buffiness that occurs differently for each pixel of the imaging device, a dedicated light-shielded so-called dummy pixel is provided in the imaging device, and the dark current from the dummy pixel is converted from the output current corresponding to the video output signal. Although there is a method of subtracting and correcting, it is difficult to perform accurate correction.

In other words, since the video output signal must be multivalued in intermediate 14FA construction, etc., it is necessary to make sufficiently precise corrections to the output video signal for the fixed pattern information derived from the imaging system, such as the above-mentioned variations and fluctuations. However, conventionally, it has been difficult to perform the above correction due to the complexity of signal processing.

The present invention has been made in view of these drawbacks, and includes storing information on fixed pattern information such as sensitivity variation, light intensity variation, shading, fixed pattern noise, and dark current variation in advance using a storage means. The purpose of the present invention is to submit a Kubutsu signal processing method that obtains good reproduced image quality by performing predetermined calculations on a video output signal from an imaging device, and is explained in detail using the block diagram shown in Fig. 2. do.

FIG. 2 is an embodiment of a block diagram used in the signal processing method according to the present invention.

First, the sensitivity variation component shown as 1 in Figure 1 exhibits a certain variation ±α with respect to the video output IjV 41mA at that time, and the output value taking this into account, that is, the output level p, is A(1±a). Therefore, after setting the object to be imaged as a blank form in advance, the output value B (not shown) for the white background outputted from the imaging device w6 (1±
α) The first storage means 9 (RAMI) shown in FIG.
31 [, A in device 11]
If we perform the calculation (1±α)/B(1±a)=A/B, we get
The above-mentioned variations are removed. However, 7 is an A/D converter that digitizes the analog signal from the imaging device 6.

Next, since the defined pattern noise component 2 in FIG. 1 shows a constant value β regardless of the output value at that time, it is determined in advance from which E element in the imaging device 6 this is generated, and for example, In the manual μ, the eighth storage means IQ (ROM
), read it out, and use the calculator 1.
1 and the output value for the original signal or white background.
It can be removed by subtracting -β or B-β.

Furthermore, since the light amount fluctuation component 8 varies with environmental temperature and time, the maximum 1i Brua is multiplied by a coefficient γ (0≦γ≦1), Bas B m1.
It can be expressed as kX f. By the way, if the output mA is the brightness of the light incident on the imaging device 6 as d (0≦d≦1), the video output signal A at that time can be expressed as A=Bd. After keeping it as a form, the output B for the white nuclear background is stored in the first storage means 9 (RAMI), and when it is read out and the arithmetic unit 11 performs the calculation A/B, A/B m Bd/B. =B
A division of max, γ, d/'BruaxrMd is performed, and the above-mentioned light amount fluctuation component can be removed.

Furthermore, since the shading component 4 exhibits a constant ratio S (however, 0≦8≦1) with respect to the output value at that time, the above-mentioned division of the light it & dynamic component minus A・8/B・S−mu/B Can be removed.

Finally, the dark current variation component 5 varies with temperature, but the output corresponding to the dark current for a black background, that is, a state in which the light source is turned off, is calculated in advance by the second (R
AM2) can be stored in the recording means 8, read out, and removed by having the arithmetic unit 11 perform subtraction AD or BD.

In the end, the dark current component is stored in the second storage means 8, the fixed pattern noise component is stored in the eighth storage means 10, and the components of sensitivity variations, shading, and light intensity fluctuations are stored in the first storage means 9. It will be read after being stored, but to summarize the above calculations, A-β-D □ ・・・・・・・・・・・・・・・・・・ (1) B
As a result of the above calculation, the precisely corrected video output signal is output to the output terminal 1.
2nd place will be taken out.

Since the fixed pattern noise is stored in advance in the eighth storage means, the time required for correction is, for example, 1m5ec, which is required for sensitivity puffiness, color shift, and light amount fluctuation to be stored in the first storage means 9. , it takes, for example, 1m5ec for the dark current to be stored in the second storage means.
It is possible to process a signal of, for example, 1024 bits with a total of, for example, 1 ms θC calculation time in the arithmetic unit, that is, with only B mice.

According to the above-described signal processing method according to the present invention, a video output signal can be precisely corrected in a short time, so that great practical effects can be expected.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a video output signal appearing during one cycle T of an imaging device, and FIG. 2 is a diagram showing an example of a Zorock diagram used in the signal processing method according to the present invention. 1: Sensitivity/...; Fluctuation, 2: Fixed pattern noise, 8: Light amount fluctuation, 4: Shading, 5: Dark current variation, 6
: imaging device, 7: A/D converter, 8: second storage means,
9: first storage means, 10: 80th storage means, ll: arithmetic unit. Figure 1

Claims (2)

[Claims] (1) When removing fixed pattern information unique to the imaging system included in the video signal output from the imaging device, fixed pattern information in which pattern information unique to the imaging system is stored in advance is removed from the video signal from the imaging device. 1. A signal processing method comprising: a computing unit for removing fixed pattern information from the video signal; and fixed pattern information and the video signal are introduced into the computing unit to remove the fixed pattern information from the video signal. (2) The storage means includes a first storage means for storing an output value for a white background, an eighth storage means for storing an output value for a black background, and a second storage means for storing a constant value regardless of the output value. In the arithmetic unit, a first subtraction is performed between the video signal from the imaging device and the values stored in the second and eighth storage means, and the values stored in the first storage means are subtracted. A patent characterized in that a second subtraction is performed between the value and the values stored in the second and eighth storage means, and the first subtraction result is divided by the second subtraction result. A signal processing method according to claim (1).