JPH0453300B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method for calibrating an input section of a color film verification apparatus for evaluating a color original prior to photographic printing.

(Technical Background of the Invention and Problems Thereof) Conventionally, as such a color film verification device, the one disclosed in Japanese Patent Application Laid-Open No. 57-207238 is known, and this device is capable of checking the color and density appropriately. Color images that are automatically corrected so that they appear are now displayed on a color monitor. Therefore, a monitor who inspects color originals such as negative film only needs to observe the automatically corrected color images and judge only those that are inappropriate in density and color balance, and those that are out of focus and do not need to be printed. , only for matters that are difficult to correct automatically (color area, backlighting, different light sources, etc.), the monitor person only needs to operate the manual operation input section to correct the color and density of the color image, which requires experience and ability. It is now possible to obtain prints of excellent quality even if you are not an excellent monitor or have a highly accurate color film automatic analysis device. The correction information determined by the monitor or the correction information automatically generated is recorded on a recording medium such as a paper tape or magnetic tape, and the color film is loaded into an automatic printer at the time of photo printing. Printing is performed by controlling the printing exposure amount based on the correction information read from the recording medium.

However, such a verification method using a conventional device does not take into account the calibration of the image input section of the device, and therefore has the drawback that the accuracy of verification cannot be maintained against changes in gain or offset.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an efficient and accurate method for calibrating the input section of a color film verification device.

(Summary of the Invention) The present invention relates to a calibration method for a color film verification device, and the color film verification device includes an imaging device for imaging an original color image to be verified, and a video signal from the imaging device in a digital quantity. A conversion table that converts the output digital quantity of this AD converter into a density signal using a logarithmic table, a color correction circuit that performs color correction on the output of this conversion table, and 3 signals from this color correction circuit. It consists of a gradation converting means for independently converting the gradation of the primary color signal, and a color monitor means for converting the output of the gradation converting means into an analog quantity and displaying it,
Offset correction is performed by shifting the conversion table horizontally toward the input shaft, and gain correction is performed by shifting the conversion table vertically toward the output shaft.

(Embodiment of the Invention) FIG. 1 shows a color film verification device which is an object of the present invention, in which a negative film 1 as a color original is irradiated by a light source 3 through a light control section 2 and a mirror box 2A. The entire image is captured by a TV camera 4 serving as an imaging device. TV
The three primary color RGB video signals VS from the camera 4 are input to the AD converter 5 and converted into digital quantities, and then logarithmically converted using a function as shown in FIG. 6 and is converted into a density signal DS. Concentration signal DS obtained by logarithmic conversion in logarithmic conversion circuit 6
are each input to the color correction circuit 7, color correction is performed according to a predetermined arithmetic formula, and negative/positive variables are performed if necessary, and input to the lookup table 8 that performs gradation conversion. It is converted into an analog quantity by a device 9 and displayed on a color monitor 10 such as a CRT.
The image of negative film 1 is displayed.
In addition, a control circuit 2 consisting of a microcomputer, etc.
0 is designed to perform overall control, and this control circuit 20 controls the light amount of the light source 3, the aperture of the light control unit 2, and the magnification for imaging the TV camera 4. In addition to controlling the aperture of the light control unit 2 and the magnification for imaging by the TV camera 4, it also controls the logarithmic conversion circuit 6, color correction circuit 7, and lookup table 8. A keyboard 30 operated by a monitor is connected thereto, and a data output device 40 for recording the test results of the negative film 1 on a magnetic tape, floppy disk, or the like is also connected.

In addition, as shown in FIGS. 3A and 3B, the light control unit 2 has a rectangular opening 21 at the top, and
It consists of a box-shaped frame 23 with a circular optical path hole 22 at the bottom, and a pair of light shielding plates 24 and 25 are placed inside the frame 23 so as to sandwich the optical path hole 22.
are arranged in different levels, and are adapted to move in conjunction with each other in the direction of the arrow shown in the figure by a drive mechanism (not shown). The aperture of the light control unit 2 is adjusted by the amount of movement of the light shielding plates 24 and 25, so that an optical path is generated. Further, in the lookup table 8, different gradation conversion tables are set for each color RGB, and for example, a data table as shown in FIG. 4 is set.

In such a configuration, the negative film 1 is irradiated with a predetermined amount of light by a light source 3 controlled by a control circuit 20, and its image is captured by a TV camera 4 and converted into a digital quantity by an AD converter 5. Thereafter, color correction is performed using the density signal DS converted by the logarithmic conversion circuit 6, gradation conversion is performed by the lookup table 8, and the image is displayed as a positive image on the color monitor 10. In this case, the control circuit 20 controls the light amount of the light source 3 to be constant,
The brightness of the color monitor 10 is adjusted by controlling the aperture of the light control section 2. That is, under the control of the control circuit 20, the light shielding plates 24 and 25 are moved toward the center of their respective optical paths to reduce their apertures, thereby narrowing the optical path and reducing the amount of light irradiated from the light source 3 to the negative film 1. The brightness of the displayed image on the color monitor 10 decreases. Conversely, by moving the light shielding plates 24 and 25 to outside the optical path and increasing the aperture, the optical path becomes larger, and the amount of light irradiated from the light source 3 to the negative film 1 increases, thereby increasing the display on the color monitor 10. The image brightness increases. Therefore, the amount of light transmitted through the negative film 1 depending on the aperture of the light control unit 2 changes at the same ratio for the three primary colors of RGB. The change in color does not affect the other G and B color corrections, and the entire display image can be controlled only by the brightness. The aperture of this light control unit 2 is the same as that of the monitor manga color monitor 10.
Check the brightness of the image displayed on the screen, and if the brightness is insufficient or excessive, use the keyboard 30 to adjust the brightness to the appropriate level. The light adjustment section 2 is then controlled via the control circuit 20, and an image with a corresponding brightness is displayed on the color monitor 10.

Here, in the present invention, calibration for offset drift and gain drift is performed by shifting the conversion table in the horizontal and vertical directions in the logarithmic conversion circuit 6 having the characteristics shown in FIG. The operation of this calibration will be explained below with reference to FIG.

In Figure 5, which shows a conversion table for one color,
The horizontal axis Vx indicates the output of the TV camera 4, that is, the input of the logarithmic conversion circuit 6, the vertical axis x indicates the amount of light incident on the TV camera 4, and Fo and Vx indicate the output of the logarithmic conversion circuit 6. And the function (Vx=x)
shows a reference function with an offset of "0" and a gain of "1", and the reference conversion table for this reference function is as follows. When the reference function has an offset drift β and a gain drift α, the function is (V=αIx+β), and it is sufficient if a conversion table corresponding to this can be obtained. As shown in the figure, the correction relationship is f ₀ (Vx)=-logVx, and the offset correction is performed by providing a light amount such that x= ₁ . Light level ₁ is a sufficiently dark level, for example, about 1% of the AD conversion saturation level,
The light shielding plates 24 and 25 of the light control unit 2 are adjusted and set to corresponding positions. Then, the 2n-order correction function is f _2o
When (Vx)=a _2o Vx+b _2o , the (2n+1)th order correction function corrects the 2nth order correction function so that f _2o+1 (V ₁ )=−log ₁ at x= ₁ . here,
The 2nth order correction function is f _2o (V ₁ ) = −log (a _2o V ₁ + b _2o ), and the error from the target value is logΔ=f _2o+1 (V ₁ ) − f _2o (V ₁ ) = − log ₁ −(−log(a _2o V ₁ +b _2o )) = log(a _2o V ₁ +b _2o )/ ₁ . Here, assuming that f _2o (Vx) has been gain-corrected for x, f _2o (V ₁ ) = −log ( ₁ + β') logΔ = log ( ₁ + β') / ₁ , and thus Therefore, _the correction function _{is f 2o+ 1 ( Vx ) = f 2o ( Vx−} β′) = −log(s _2o Vx+b _2o −a _2o V ₁ −b _2o + ₁ ) = −log(a _2o Vx+ ₁ −a _2o V ₁ ). Also, the gain correction is x = ₂
Perform this by providing an amount of light such that . Light level ₂ is a sufficiently bright level, for example, the saturation level of AD conversion.
At about 90%, the light shielding plates 24 and 25 of the light control unit 2 are adjusted and set to corresponding positions. And 2n−
The first-order correction function is f _2o-1 (Vx) = −log (a _2o1 Vx+
b _2o-1 ), the 2n-order correction function corrects the 2n-1st-order correction function so that f _2o (V ₂ )=−log ₂ at x= ₂ . Here, the 2n-first order correction function is f _2o-1 (V ₂ ) = -log (a _2o-1 V + b _2o-1 ), and the error from the target value is logΔ = f _2o (V ₂ ) - f _2o-1 (V ₂ ) = −log ₂ − {(−log (a _2o-1 V ₂ + b _2o-1 )} = log (a _2o-1 V ₂ + b _2o-1 )/ ₂ , so correction The function is f _2o (Vx) = f _2o-1 (Vx) + logΔ = −log (a _2o-1 Vx + b _2o-1 ) + log (a _2o-1 V ₂ +
b _2o-1 ) / ₂ = −log{ ₂ (a _2o-1 Vx + b _2o-1 ) / (a _2o-1 Vx
+b _2o-1 )/(a _2o-1 V ₂ +b _2o-1 )}. Next, the n-th correction function is f _o (V _x ) = −log (a _o
Vx + b _o ), then a _2o = ₂ a _2o-1 / (a _2o-1 V ₂ + b _2o-1 ) a _2o+1 = a _2o , so a _2o = ₂ a _2(o-1) / (a _2(o-1) V ₂ +b _2o-1 ), and further b _2o+1 = ₁ −a _2o V ₁ b _2o-1 = ₁ −a _2(o-1) V ₁ b _2o = b _{2o-1 2} / (a _2o-1 V ₂ +b _2o-1 ) =b _{2o-1 2} / (a _2(o-1) V ₂ +b _2o-1 a _2o = ₂ a _2(o-1) / {a _{2 (o-1)} V ₂ + ₁ −a _2(o-1) V ₁ } = ₂ a _2(o-1) / {(V ₂ −V ₁ ) a _2(o-1) + ₁ } = ₂ a _2(o-1) / {V ₀ a _2(o-1) + ₁ } Here, V ₀ = V ₂ −V ₁ b _2o = b _{2o-1 2} / (a _2(o-1) V ₂ +b _2o-1 = ₂ { ₁ −a _2(o-1) V ₁ } / {a _2(o-1) V ₂ + ₁ −
a _2(o-1) V ₁ } = { _{1 2} −V _{1 2} a _2(o-1) } / {V ₀ a _2(o-1) +
₁ }, and the coefficients a _n and b _n can be expressed by the relational expressions a _n-1 and b _n-1 , respectively. Then, finding a general solution for the coefficients a _n and b _n , a _2o = I ₂ a _2(o-1) /V ₀ a _2(N-1) + ₁ ) = ₂ I ₂ a _2(o-2) /V ₀ a _2(o-2) +I ₁ /V ₀ 1 ₂ a _2(o-2) /V ₀ a _2(o
-2) +I ₁ = ₂ ² a _2(o-1) /V _{0 2} a _2(o-1) + ₁ (V ₀ a _2(o-1) + ₁ ) = ₂ ² a _{2(o-2 )} /V _{0 1} ( ₁ + ₂ )a _2(o-1) + ₁ ² = ₂ ² I ₂ a _2(o-3) /V ₀ a _2(o-3) +I ₁ /V ₀ ( ₁ + _{2 ) I2a2
(o-3)} /V ₀ a _2(o-3) +I ₁ + ₂ = ₂ ³ a _2(o-3) /V ₀ ( ₁ + ₃ ) ₂ a _2(o-3) + ₁ ² (V ₀ a
_2(o-3) + ₁ ) = ₂ ³ a _2(o-3) /V ₀ ( ₁ ³ + _{1 2} + ₂ ² ) a _2(o-3) +
₁₃ = ₂ ³ I ₂ a _2(o-4) /V ₀ a _2(o-4) +I ₁ /V ₀ ( ₁ ² + _{1 2} +
₂ ² ) I ₂ a _2(o-4) /V ₀ a _2(o-4) +I ₁ +I ₁ = ₂ ⁴ a _2(o-4) /V ₀ ( ₁ ² + _{1 2} + ₂ ² ) ₂ a _2(o-4)
+ ₁ ³ (V ₀ a _2(o-4) + ₁ = ₂ ⁴ a _2(o-4) /V ₀ ( ₁ ² + ₁ ² ₂ + _{1 2} ² + ₂ ³ ) a
_2(o-4) + ₁ ⁴ a _2o = ₂ ⁿ a ₀ /V ₀ ( ₁ ^n-1 + ₁ ^n-2・₂ …+ _{1 2} ^n-2
+ ₂ ^n-1 ) a ₀ + ₁ ⁿ a _2o+1 = a _2o , and further the following conditions Vx = αx + β a ₀ , b ₀ = 0 ₁ = p ₀ 0 < p < q ₂ q = ₀ 0 < q <1, V ₀ =V ₂ −V ₁ =αq ₀ +β−α(q−p) ₀ a _2o = _{2 na 0} /V ₀ ( ₁ ^{n -1} + _1o-2・…+ _{1 2} ^n-2 +
₂ ^n-1 ) a ₀ + ₁ ⁿ = q ^{n n} /V ₀ (p ^n-1 ₀ ^n-1 +p ^n-2 q ₀ ^n-1 +...+p ^n-2・
₀ ^n-1 +q ^n-1・₀ ^n-1 )+P ⁿ ₀ ⁿ =q ⁿ ₀ ⁿ ／V _{0 0} ^n-1 (p ^n-1 +P ^n-2 q+...+pq ^n-2・q ^n-1
) +P ⁿ ₀ ⁿ =q ⁿ ₀ ⁿ /α(q-p) ₀ ⁿ (p ^n-1 +p ^n-2 q+...+pq ^n-
2・q ^n-1 )＋P ⁿ ₀ ⁿ =q ⁿ ／α(q−p)(p ^n-1 +p ^n-2 q＋…＋pq ^n-2・q ^n-1
)P ⁿ =q ⁿ /{α(p ^n-1 +p ^n-2 +…+pq ^n-1 +q ⁿ −p ⁿ −p ^n-1 q
−…−p ⁿ q ^n-2 −pq ^n-1 ) + P ⁿ } = q ⁿ / {αp ⁿ + (1-α) p ⁿ } = p ⁿ / (αP ⁿ + (1-α
)q ⁿ }, and under the same conditions for the coefficient b _2o , b _2o = _{1 2} −V _{1 2} a _2(o-1) /V ₀ a _2(o-1) + ₁ = _{1 2} −V _{1 2} I ₂ ^n-1 a ₀ /V ₀ (I ₁ ^n-2 +I ₁ ^n-3・I ₂ +...I ₁
・I ₂ ^n-3 /V ₀ I ₂ ^n-1 a ₀ /V ₀ (I ₁ ^n-2 +I ₁ ^n-3・I ₂ +…I ₁・I ₂
^n-3 + I ₂ ^n-3 ) = (V ₀ ( ₁ ^n-2 + ₁ ^n-3・₂ +...+ _{1 2} ^n-3 + ₂ ^n-3
) a ₀ + ₁ ^n-1 ) _{1 2} −V _{1 2} ⁿ a ₀ /V _{0 2} ^n-1 a ₀ + ₁ (V
₀ ( ₁ ^n-2 + ₁ ^n-3・₂ +…+ _{1 2} ^n-3 + ₂ ^n-2 ) a ₀
+ ₁ ^n-1 = V ₀ a ₀ ( ₁ ^n-1 ₂ + ₁ ^n-2 ₂ ² +...+ ₁ ² ₂ ^n-2 + _1
2 ^n-1 ) + ₁ ⁿ ₂ −V _{1 2} ⁿ a ₀ /V ₀ a ₀ ( ₁ ^{n-1 n-2} ₂
+…+ ₁ ² ₂ ^n-3 + _{1 2} ^n-2 + ₂ ^n-1 ) + ₁ ⁿ b _2o = V ₀ a ₀ ( ₁ ^n-1 ₂ + ₁ ^n-2 ₂ ² +…+ ₁ ² ₂ ^n-2 +
₂ ^n-1 ) + ₁ ⁿ ₂ −V _{1 2} ⁿ a ₀ /V ₀ a ₀ ( ₁ ^n-1 + ₁ ^n-2
₂ +…+ _{1 2} ^n-2 + ₂ ^n-1 ) + _1o =
α(p-q) ₀ (p ^n-1 q ₀ ⁿ +P ^n-2 q ² ₀ ⁿ +...p ₂ q ^n-2
₀ ⁿ +pq ^n-1 ₀ ⁿ ) +p ⁿ q ₀ ⁿ⁺¹ −(αp ₀ +β)q ⁿ ₀
ⁿ / α (p-q) ₀ (p ^n-1 ₀ ^n-1 +P ^n-2 q ₀ ^n-1 +...+
pq ^n-2 ₀ ^n-1 +q ^n-1 ₁ ^n-1 )p ⁿ ₀ ⁿ =α ⁿ⁺¹ⁿ⁺¹ (p ^n-1 q ^n-2 q ³ +...p ² q ^n-1 +pq ⁿ − p ⁿ q−p ^n-
1 q ² −…−p ³ q ^n-2 −p ² q ^n-1 )＋P ⁿ q ₀ ⁿ⁺¹ −βp ⁿ ₀ ⁿ /
α ₀ ⁿ (p ^n-1 q+P ^n-2 q ² +...pq ^n-1 +q ⁿ −p ⁿ −p ^n-1 q−
…−p ² q ^n-2 −pq ^n-1 )＋p ⁿ ₀ ⁿ = α ₀ ⁿ⁺¹ (pq ⁿ −p ⁿ q)＋ ₀ ⁿ⁺¹ p ⁿ q−αpq ⁿ ₁₀ ⁿ⁺¹
−βp ⁿ ₀ ⁿ ／α ₀ ⁿ (q ⁿ −p ⁿ )＋p ⁿ ₀ ⁿ = ₀ (αpq ⁿ −αp ⁿ q＋p ⁿ q−αpq ⁿ )−βq ⁿ ／αq ⁿ (
1-α)p ⁿ = ₀ (1-α)p ⁿ q-βq _o /αq ⁿ + (1-α) p ⁿ holds true.

From the above, the 2nth order correction function is f _2o (Vx) = −log (a _2o V _x + b _2o ) = −iog {q ⁿ /αq ⁿ + (1 − α) p ⁿ Vx + Io (1 − α) p ⁿ
q-βq ⁿ /αq ⁿ + (1-α) p ⁿ }, and if n is sufficiently large, p ⁿ =0
Therefore, 1imf _2o (Vx) = -log (1/αVx - β/α) = -log (1/α (αx + β) - β/α) = -logx, and the input gain drift α and focus drift β can be corrected.

In Figure 5, the above calculation formula first calculates the amount of light ₁
After shifting the offset drift component β' to the right to obtain f ₁ (Vx), obtain f ₂ (Vx) by shifting the offset drift component β' upward by the gain drift log Δ2 relative to the light amount ₂ . In this way, in one calibration, for example, an error logΔ occurs for a light amount _{of 1} , so if the above shift operation is repeated several times in the opposite direction, the value converges to a value that compensates for the drift.

Furthermore, in this invention, the conversion table itself is created using n bits, for example, and the calculation of gain drift α and offset drift β is performed using, for example, (n+2).
This is done in bits and loaded into the conversion table. In this way, calculations can be performed quickly and shift data can be obtained with high precision.

From the above, when f ₀ = -log (Vx) Vx = αx + β ₁ = p _{0 2} = q ₀ , the offset correction (x = ₁ ) is the error logΔ = -log ₁ - (-logV ₁ ) = log V ₁ /
₁ Consider Vx = x + β' V ₁ = I ₁ + β' log (V ₁ / ₁ ) = log ( ₁ + β') / ₁ β' = V ₁ - ₁ = α ₁ + β- ₁ = (α-1) ₁
+β f ₁ (Vx) = f ₀ (Vx-β') = -log (Vx-V ₁ + ₁ ) = -log (αx+β-α ₁ -β+ ₁ ) = -log (αx+ ₁ - α ₁ ) , the gain correction (x = ₂ ) is the error logΔ = -log ₂ -f ₁ (V ₂ ) = -log ₂ -log (V ₂ -V ₁ + ₁ ) = log (V ₂ -V ₁ + ₁ )/ ₂ = log (α ₂ + β − α ₁ − β + ₁ ) / ₂ = log (α ₂ − α ₁ + ₁ ) / ₂ f ₂ (Vx) = f ₁ (Vx) + logΔ = −log (αx + ₁ − α ₁ ) +log( _α2 − _α1 + ₁ )/ ₂ =−log(αx+ ₁ − _α1 ) ₂ /( _α2 − _α1 + ₁ ).

(Effects of the Invention) As described above, according to the calibration method of the input section of the color film verification device of the present invention,
This can be easily and reliably realized by simply shifting the data in the conversion table in parallel or up and down for gain drift and offset drift.

[Brief explanation of the drawing]

Fig. 1 is a block configuration diagram showing an example of a color film verification device, Fig. 2 is a diagram showing an example of output characteristics of logarithmic conversion, Fig. 3A is a plan view showing an example of a light control section, and Fig. 3B is a diagram showing an example of output characteristics of logarithmic conversion. A cross-sectional side view thereof, FIG. 4 is a diagram showing an example of characteristics of a gradation conversion table, and FIG. 5 is a diagram for explaining the method of the present invention. 1...Negative film, 2...Dimmer, 3...Light source, 4...TV camera, 5...AD converter, 6...
... Logarithmic conversion circuit, 7 ... Color correction circuit, 8 ... Lookup table, 9 ... AD converter, 10 ...
Color monitor, 20...control circuit, 30...keyboard, 40...data output device.

Claims (1)

[Claims] 1. An imaging device that captures an image of a color original image to be verified illuminated by a light source, an AD converter that converts a video signal from this imaging device into a digital quantity, and
A conversion table that converts the output digital quantity of the AD converter into a density signal using a logarithmic table, a color correction circuit that color-corrects the output of this conversion table, and gradation conversion of the three primary color signals from this color correction circuit independently. In a method for calibrating an input section of a color film verification device comprising a tone converting means and a color monitor means for converting the output of the tone converting means into an analog quantity and displaying it, the conversion table is set on the input shaft side. Offset correction is performed by shifting the conversion table in the horizontal direction, gain correction is performed by shifting the conversion table vertically toward the output axis side, and the brightness of the light source is set to a reference level to perform the offset correction. A method for calibrating an input section of a color film verification device, characterized in that offset correction is performed. 2. The input calibration method for a color film verification apparatus according to claim 1, wherein the reference level is set by moving in and out a light control member that adjusts the brightness of the light source. 3. The conversion table is created using n bits, and the offset correction and gain correction calculations are performed using bits larger than n, and when data is loaded into the conversion table, n bits are used. Calibration method for the input section of the color film verification device described in Section 1. 4 An imaging device that images the original color image to be verified illuminated by a light source, an AD converter that converts the video signal from this imaging device into a digital quantity, and
A conversion table that converts the output digital quantity of the AD converter into a density signal using a logarithmic table, a color correction circuit that color-corrects the output of this conversion table, and gradation conversion of the three primary color signals from this color correction circuit independently. In a method for calibrating an input section of a color film verification device comprising a tone converting means and a color monitor means for converting the output of the tone converting means into an analog quantity and displaying it, the conversion table is set on the input shaft side. Offset correction is performed by shifting the conversion table in the horizontal direction, gain correction is performed by shifting the conversion table vertically toward the output axis side, and the brightness of the light source is set to a reference level to perform the offset correction. A method for calibrating an input section of a color film verification device, characterized in that gain correction is performed. 5. A method for calibrating an input section of a color film verification apparatus according to claim 4, wherein the reference level is set by moving in and out a light control member that adjusts the brightness of the light source.