JPH0447294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color photographic printing apparatus (hereinafter referred to as a color printer) that creates a print from a color original image by exposure.

[Prior art and problems to be solved by the invention]

Generally, it is known as a rule of thumb that in a normal photographic scene, the average reflectance of each color of blue, green, and red, which is integrated over the entire scene, is approximately constant. Therefore, conventional color printers use an integral neutral method to control the exposure amount of blue, green, and red colors to a constant level based on the amount of transmitted light of the color original image to create prints with well-balanced color and brightness. . If this method is followed, high-quality prints will be created from the majority of color originals, but for shooting scenes that are exceptional to the above rule of thumb, appropriate corrections will be made based on the above fixed exposure amount depending on the scene. ing. However, if the above-mentioned constant exposure amount is not appropriately applied, it becomes very difficult to obtain high-quality prints because the above-mentioned control premise is not established.

Here, the exposure amount for each color is the integral amount of transmitted light of the color original image that contributes to exposure in the blue, green, and red photosensitive layers of photosensitive materials (mainly color paper), and is measured by the color printer. It is customary to control the amount of transmitted light to be constant based on the measured amount of transmitted light of each color of blue, green, and red. (Hereinafter, in this description, unless otherwise specified, the exposure amount refers to the above-mentioned integral amount.) Further, the above-mentioned fixed exposure amount for each color is determined in the process of setting conditions. In general, setting conditions means using a standard original image that represents the average transmission density of an average color original image determined statistically and empirically, and repeating printing trials on the standard original image while varying the exposure amount. This is a process in which a reference exposure amount that provides a predetermined target density is determined, and is carried out for each recording medium (mainly color film) for color originals, depending on the sensitivity of the photosensitive material. This process requires burn trial costs and time depending on skill, which are significant even for experienced operators. In addition, in order to produce high-quality prints, it is necessary to set these conditions well.

Furthermore, maintaining a constant exposure amount during printing is a necessary condition for stably producing high-quality prints, and if this condition is not met, it will be difficult to produce high-quality prints.

However, it is a common phenomenon during printing that the exposure amount is not maintained constant and fluctuates unnecessarily. As mentioned above, the exposure amount is controlled based on the relationship between the amount of transmitted light that contributes to exposure in each color photosensitive layer of the photosensitive material and the amount of transmitted light of each color measured by a color printer, but this relationship does not match. This is common in the blue, green, and red photosensitive layers of photosensitive materials and in the blue, green, and red photosensitive layers of color printers.
This is based on the difference in spectral sensitivity of the light receivers used to measure the amount of transmitted light of each red color. During printing, the light transmitted through the color original image usually changes due to a change in the light quality of the printing light source, a change in the average transmission density of the color original image, or a change in both of these, but due to the discrepancy in the above relationship, the exposure amount changes to the target amount. is not controlled and therefore cannot be maintained constant.

Therefore, in a known example, a filter that absorbs light in the low-sensitivity wavelength range of each color photosensitive layer of a photosensitive material is inserted into the printing optical path between the printing light source and the above-mentioned photoreceptor in order to match the above relationship. However, the intended effect has not yet been achieved because the difference in spectral sensitivity cannot be eliminated.

Conventionally, color printers have a correction means for correcting the measured amounts of transmitted light for each color of blue, green, and red using their functions. The change is approximately normalized to the change in the amount of transmitted light that contributes to exposure in each color photosensitive layer of the photosensitive medium, and as long as this correction means does not cause a change in the light quality of the printing light source, high quality prints will be produced. Ru. However, since the spectral intensity changes in the transmitted light due to changes in the average transmitted density of the color original image and changes in the light quality of the printing light source are different, if a change occurs in the light quality of the printing light source, this change can be corrected by the above-mentioned correction means. It is difficult to standardize the changes in the measured amount of transmitted light as described above, and there is a drawback that unnecessary fluctuations occur in the exposure amount and it is not always possible to produce high-quality prints.

Changes in the light quality of the printing light source mainly occur in the following cases. First, there is a change in the characteristics of the light source lamp used as the light source for printing. That is, it is difficult for the light source lamp to maintain constant light quality during long-term use. Furthermore, when replacing the lamp due to its durable life, the light quality usually differs before and after the replacement. Further, when the light is dimmed by the lighting voltage of the light source lamp, a similar change in light quality is brought about. Second, the light may be modulated by a dimming filter, resulting in a change in light quality. In particular, in color printers that control the exposure amount of blue, green, and red colors using cut filters and shutters, the cut filter for an average color original image is adjusted according to the reference exposure amount determined by condition settings. In many cases, the light is dimmed so that the shutter operating time is approximately the same. This improves printing production efficiency by making the operating time almost the same as above, and
This is because, in some color printers, the effect of color correction is determined by improper absorption of each color other than the main absorption color of the cut filter.

In this way, changes in the light quality of the printing light source occur not only when the light is adjusted artificially, but also due to accidental changes in daily life. In order to eliminate the influence, there is no choice but to spend new trial costs and time and set conditions. Furthermore, unless the above-mentioned influence is eliminated, it is not necessarily possible to produce high-quality prints.

In view of the above-mentioned problems, the present invention has been developed to provide stable, high-quality light at all times even if the transmitted light of a color original image changes due to a change in the light quality of the printing light source, a change in the average transmitted density of the color original image, or a change in both. The purpose was to provide a color printer for making prints.

[Means to solve the problem]

The above purpose is to provide a first measuring means for measuring the amount of transmitted light of each color of blue, green, and red of a color original;
a second measuring means for measuring the amount of light of each color of green and red;
Calculating a change in the amount of transmitted light of the original image from the amount of transmitted light of the standard original image and the amount of transmitted light of the printed color original image when determining the reference exposure amount measured by the first measuring means,
A change in the light source light amount is calculated from the light amount of the light source when determining the reference exposure amount measured by the second measuring means and the light amount of the light source when printing the printing color original image, and the change in the light amount transmitted through the original image and the light source It is characterized by having a calculation means for calculating an exposure condition based on a change in the amount of light, and an exposure control means for controlling the exposure amount of each color of blue, green, and red by driving a filter and shutter according to the exposure condition. This is accomplished using a color photographic printer.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram of an embodiment of a color printer according to the present invention.

The light emitted from the light source lamp 100 passes through a light control section formed by light control filters 101 to 103, is mixed and diffused in a mixing chamber 104, and is sent to a light receiver 105 for measuring the amount of light from the light source, which is a second measuring means. hand,
The amount of light is measured for each color of blue, green, and red.
The mixed and diffused light illuminates the original color image on the color film 107 held by the film mask 106, and the image is projected onto the color paper 116 by the lens 108. Further, the amount of transmitted light of the color original image is measured for each color of blue, green, and red by a light receiver 109 for measuring the amount of transmitted light, which is a first measuring means. The exposure amount on the color paper 116 is determined by the shutter 110 and cut filter 11.
1 to 113 are driven and controlled.

FIG. 2 shows the color combination shown in FIG. 1 according to the present invention.
FIG. 2 is a block diagram of an exposure control circuit in a printer.

Operation input signals whose main contents are an exposure correction signal and an exposure command signal inputted from the operation section 218 during printing are sent to the central control section and the numerical processing section 200 via the operation section interface 219. The central control section and numerical processing section 200 receives the exposure command signal and sends a sampling control signal to the analog signal switch 213 and A/D converter 214 via the A/D interface 215. In addition, the light receivers 201 to 203 for measuring the amount of light from the light source (Fig.
5) and light receivers 204 to 206 for measuring the amount of transmitted light
The measurement signals based on the printing light source light amount and transmitted light amount of each color of blue, green, and red measured in (109 in FIG. 1) are logarithmically converted by logarithmic amplifiers 207 to 212. This logarithmically transformed signal S is expressed as S=-log _a i/io (1). Here, i is the photoreceiver output, io is the photoreceiver reference output, and a is a constant determined by the logarithmic amplifier. The output signal of each logarithmic amplifier is appropriately selected by the analog signal switch 213 according to the above-mentioned sampling control signal, converted into a digital signal S' by the A/D converter 214, and then sent via the A/D interface 215. Central control section and numerical processing section 2
Sent to 00.

The central control section and numerical processing section 200 perform the following processing based on the sent signals.

First, based on the exposure correction signal, a column [C] of exposure correction amounts having blue, green, and red as elements is determined. [C]
is a 3×1 matrix, and the exposure correction signal is generally not input. In this case, the element C of [C]
(i) For all, C(i)=0 (2).

Furthermore, regarding the signal S', we will now write a sequence of signals S' based on the light intensity of the printing light source for each color of blue, green, and red obtained through sampling as described above, and the amount of light transmitted through the printing color original image under this printing light source. [L],
Let it be [X]. In addition, the columns of signals S' based on the light intensity of the printing light source and the light intensity of the standard original image transmitted under this printing light source at the time of setting the conditions are shown as [LO] and [XO], respectively.
shall be. From these, regarding the signal S', the output [ΔL] related to the light quality change of the printing light source and the output [ΔX] related to the change in the transmitted light of the printing color original image are respectively: [ΔL] = [L] - [LO] (3) [ΔX ]=[X]−[XO] (4)

In order to maintain the exposure amount against changes in transmitted light due to changes in the light quality of the printing light source and changes in the average transmitted density of the color original, the logarithm of the amount of light that contributes to exposure in the blue, green, and red photosensitive layers of the photosensitive material must be [ΔX] needs to be corrected to the exposure factor, which is the amount of change.
Further, the logarithmic change in the amount of light measured by a color printer can be normalized within a practical range to the above-mentioned exposure factor using a linear processing system. On the other hand, since the spectral intensity changes in the transmitted light based on changes in the light quality of the printing light source and changes in the average transmitted density of the color original image are different, it is reasonable to normalize the corresponding light amount measurements using different linear processing systems. It is. From [ΔL] and [ΔX], the output [ΔD] related to the average transmission density change of the color original image is expressed as [ΔD]=[ΔX]−[ΔL] (5).

Next, by normalizing [ΔL] and [ΔD], we obtain [ΔL′] = [NL] × [ΔL] (6) [ΔD′] = [ND] × [ΔD] (7). Here, [NL] and [ND] are 3 x 3 normalization coefficient matrices that normalize the output based on the light quality change of the printing light source and the average transmission density change of the color original image, respectively, and in general, [NL] ≠[ND] (8). Also, [ND] is usually a diagonal matrix with O as the off-diagonal elements.

Here, if the above exposure factor is [ΔX′], then [ΔX′] is the difference between the output due to the change in light quality of the standardized printing light source [ΔL′] and the output due to the change in average transmission density of the color original image [ΔD′]. given by the sum.
That is, [ΔX′] = [ΔL′] + [ΔD′] (9), and therefore, [ΔX′] = [ND]×[ΔX]−([ND]−[NL])×
[ΔL] (10). The above is the central control unit and the numerical processing unit 200.
Then, according to equations (3) and (4), the outputs [ΔL] and [ΔX] due to the printing light source light and the printing color original image transmitted light are obtained, and (10)
According to the formula, the output due to the printing light source light [ΔL] is compared to the output due to the transmitted light of the printing color original image [ΔX]
Correct it based on and obtain [ΔX′].

Further, in the central control section and numerical processing section, operating times of the cut filter and shutter are determined in accordance with [C] and [ΔX'] in order to control the exposure amount.

First, in the blue, green, and red photosensitive layers of a photosensitive material, assuming an ideal cut filter that absorbs all the photosensitive color light in the main absorption photosensitive layer and transmits all the photosensitive color light in the other color photosensitive layers, For the element T(i) of the sequence [T] of the operating time of the cut filter that absorbs each color light, green and red, the maximum value is taken as the operating time of the shutter, log a T(i)/TO(i)= ΔX′(i)+C(i) (11) holds true. Here, a is a constant determined by the logarithmic amplifier, and TO(i) is a constant for the standard original image obtained by setting the conditions, and the operating time of the above ideal cut filter whose maximum value is the operating time of the shutter. Indicate each element of the column [TO], ΔX′(i), C(i)
represent the elements of [ΔX'] and [C], respectively.

From equation (11), T(i)=TO(i)×a〓 ^X ′(i) ^+C (i) (12) From this, [T] is obtained.

Next, the ideal cut filter operating time sequence [T] is converted into an actually used cut filter operating time sequence [T']. [T'] is given by equation (13) with the maximum value of the element being the shutter operating time.

[T'] = [F] x [T] (13) Here, [F] is calculated from the function of the spectral transmittance of each cut filter and the spectral sensitivity of the blue, green, and red photosensitive layers of the photosensitive material. This is a ×3 cut filter transmittance correction matrix, and is appropriately selected from six types of matrices depending on the order in which the cut filters operate.

Based on the sequence [T'] of cut filter operating times whose maximum value is the shutter operating time determined as described above, the central control unit and numerical processing unit 200 sequentially transmit information via the drive unit interface 216. Shutter and filter drive member 217 (first
114) to control exposure.

Note that the light receiver 10 used for measuring the amount of light from the printing light source
5 and the spectral sensitivity of the light receiver 109 used for measuring the amount of transmitted light do not necessarily have to match. That is, since the spectral intensity changes in the transmitted light are different based on changes in the light quality of the printing light source and changes in the average transmitted density of the color original image, the above-mentioned light reception Adjusting the spectral sensitivity of the device using a filter or the like is effective in improving the accuracy of exposure control according to the present invention.

In addition, in the above embodiment, an example was described in which [ΔX] is modified based on [ΔL], but other factors forming the control equation such as [TO] and [C] are modified. It is possible to achieve the same effect by doing things differently. However, this results in the same modification as [ΔX] and is therefore in accordance with the present invention.

Above, we have described an example of simultaneously measuring the amount of light from the printing light source and the amount of light transmitted through the original color image under the light source, but it is extremely rare for the light quality of the printing light source to change during normal continuous printing. . Therefore, the intended effect can be achieved by measuring the amount of light from the printing light source using a transmitted light amount measuring means in the absence of a transparent sample such as a color film in the printing optical path prior to printing.

That is, if a signal indicating that there is no transparent sample such as color film in the printing optical path is input, the above [X] obtained at this time can be used as the above [L] or [LO]. It is.

Also, insert a reference transparent sample for measuring the light amount of the printing light source into the printing optical path, give a light source light amount measurement command, and use the above [X] obtained at this time as the above [L] or [LO]. It is also possible to
A standard original image may be used as the reference transparency sample.

〔Effect of the invention〕

The color printer according to the present invention described above controls the exposure during printing based on changes in the light quality of the printing light source and changes in the amount of light transmitted through the original image. Even if there is a change in the transmitted light of the color original image due to a change in the average transmitted density or a change in both, the influence of unnecessary fluctuations in the exposure amount can be eliminated, making it possible to consistently create high-quality prints. It has the effect of being able to do it. Furthermore, the present invention has the advantage that even if the light quality of the light source changes during printing compared to when the reference exposure conditions were set, there is no need to conduct trial tests again and spend time.

[Brief explanation of the drawing]

FIG. 1 shows one of the color printers according to the present invention.
A schematic configuration diagram of an example is shown. FIG. 2 shows a block diagram of an exposure control circuit in a color printer according to the invention. 100...Light source lamp, 101-103...Dimmer filter (Y, M, C), 104...Mixing chamber,
105...Receiver for measuring the amount of light from the light source, 106...Mask for film, 107...Color film,
108... Lens, 109... Light receiver for measuring amount of transmitted light, 110... Shutter, 111-113...
Cut filter (Y, M, C), 114... Shutter and cut filter drive section, 115...
Paper mask, 116...Color paper, 200...Central control unit and numerical processing unit, 20
1-203...Receiver for light source light intensity measurement, 204-
206...Receiver for measuring amount of transmitted light, 207-21
2...Logarithmic amplifier, 213...Analog signal switch, 214...A/D converter, 215...A/
D interface, 216... drive unit interface, 217... shutter and filter drive unit, 218... operation unit, 219... operation unit interface.

Claims (1)

[Scope of Claims] 1. A first measuring means for measuring the amount of transmitted light of each color of blue, green, and red of a color original; a second measuring means for measuring the amount of light of each color of blue, green, and red of a light source; When determining the reference exposure amount measured by the first measuring means, a change in the amount of transmitted light of the original image is calculated from the amount of transmitted light of the standard original image and the amount of transmitted light of the printed color original image, and the reference exposure amount measured by the second measuring means is calculated. Calculating means for calculating a change in light source light amount from the light amount of the light source when determining the color image and the light amount of the light source when printing the printing color original image, and calculating an exposure condition based on the change in the light amount transmitted through the original image and the change in the light source light amount. A color photographic printing apparatus comprising: an exposure control means for controlling the exposure amount of each color of blue, green, and red by driving a filter and a shutter according to the exposure conditions. 2. The color photographic printing apparatus according to claim 1, wherein the first measuring means also serves as the second measuring means.