JPH03186833A - Stereoscopic photographic printing machine with linear aperture - Google Patents

Abstract

PURPOSE: To obtain a stereoscopic photograph high in sharpness and uniform density by providing a light for projection, a negative carrying machine, a lens for projection and a linear diaphragm equipped with an aperture. CONSTITUTION: This printer uses a large-aperture lens 7 equipped with the linear diaphragms 8a and 8b so that the aperture of the lens for projection in a vertical direction may be small. Namely, the lens 7 is equipped with the upper and the lower linear diaphragms 8a and 8b, and the definition of a picture element printed in a picture band is enhanced by covering the upper part and the bottom part of the lens with the upper and the lower diaphragms 8a and 8b. It is good to linearly form the edge of the aperture of the linear diaphragm but it is preferable to form it to be curved in order to compensate the brightness curves of the lens 7 and lenticulars 3, 4 and 5. By making the height of the aperture at the edges 9L and 9R large, the lowering of the brightness at the edge is compensated. Thus, the high-quality stereoscopic photograph having uniform density and improved sharpness is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Conventional Technology A lenticular screen type stereoscopic photograph is produced by sequentially printing planar images of a target object taken from various viewpoints onto a film using lenticular printing.

・Sequentially pass the V-plane image through a lenticular screen, or 1. - Expose the photographic emulsion coating in the focal plane of the lenticule by projecting at time i1.

“N, ^, Valyus”
Stylistic Visual (SLereoscopy) J (196
6 years of Focal Press magazine (Focal Press)
), pages 199 to 203, disclose that a right image and a left image can be simultaneously printed on film. A single dense image from each image is burned. This method
Multiple planar images are required to create an image dense enough to fill the lenticular space. This large number of dense images is commercially impractical and leaves a large number of unexposed strips under each lenticule, thereby creating an inferior stereoscopic picture. Varrius contributed to three-dimensional art by showing methods and principles for controlling the displacement of foreground and background images.

Dudley's ``Applied Optics &Optics''
l Englneerlng) J (1965 Rudolr Kingslakc
) discloses on pages 114-116 the movement of a lenticular screen and the intermittent exposure of each of the eight images recorded on the film.

Okoshl's ``3D image technology (Thrcc)''
-Dlmcnslonal Imaglng Te
chnique) J (7 of 197 [1st year]
Pages 1-88 disclose the use of several projectors to project images onto the emulsion. Okoshi provides a detailed analysis of the optimal separation of projectors and the theory of printing images onto photographic emulsions.

Furthermore, Okoshi analyzes the spreading of the image on the emulsion and points out that excessive spreading reduces the resulting directional quality of the photograph.

Lo and Nym, dated July 2211, 1975.
No. 3,895.867 to N1i+s),
Techniques are disclosed for recording images on all film areas below the lenticule. This is accomplished by repeatedly turning the projector light on and off and shifting the screen or film intermittently.

A disadvantage of this method of spreading out dense images intermittently is that it takes time to make each incremental change in projection angle. When the negative is rapidly stopped and moved again, large lenses and prints cause the film to create shocks and vibrations during construction. This overlaps dense images,
Reduce the eave sharpness of the resulting stereoscopic image. Additionally, this patent shows a method of continuously spreading a dense image by turning on and off the projector's lights while the projector is in motion.

This creates a continuous overlapping dense image across the entire width of the lenticule. A disadvantage of this scanning technique is that the overlapping images reduce image sharpness and contrast, reducing the quality of the resulting stereoscopic image.

These patents also disclose early techniques for constructing stereoscopic photographs.

Japanese Patent No. 42-5 granted on March 6, 1967
No. 473, Kuchikida Patent No. 49-6 (No. 17), granted on January 9, 1974.

Mouth and Nim, in U.S. Pat. No. 4,120,562, issued Oct. 17, 1978, disclose a method of scanning a projected image to fill a lenticule with the image. The arrangement disclosed in this patent is also configured to vary the projection angle by a predetermined amount during a scanning operation.

Lao, in U.S. Pat. are doing. The projector scans continuously, resulting in large image overlaps that reduce the sharpness of the photo.

The intermittent projections disclosed in the prior art have the disadvantage that a large number of projections must be made to fill the area behind the lenticule with an image, which is not commercially attractive.

The misalignment of many image elements due to the intermittent projection method reduces the sharpness of the image photograph. However, although the continuous scanning method does not fill the entire area behind each lenticule with the image, it does reduce the clarity of the photograph due to overlapping images.

U.S. Pat. No. 4,852,972 discloses an improvement in stereoscopic imaging that involves using high intensity light beams in exposing image bands near the edges and near the center of the lenticule. Discloses a baking method. This method makes it possible to obtain an image band whose density is essentially equal across the width of the lenticule. The method of this patent can be used to create a single image element in each image band. However, the quality of stereoscopic photographs created by this method is limited by the fact that the two-dimensional image is
! ! This can be corrected by expressing tq in the Ii image. These multiple discrete dense images are produced by lenticular printing with minimal overlap between the lenticular dots of the film.
That is, they are printed edge-to-edge, uninterrupted by discrete, dense, unexposed strips between the images. The method of this patent equalizes the density of the image across the field of view of the lenticule, improving the quality of the photograph.

U.S. Pat. No. 4,101,210 to Kuchi et al. uses multiple projection lenses along multiple rows parallel to a lenticular screen so that there are no gaps between adjacent dense images in the image band. Disclose how to do so. This patent also discloses arranging the negatives in parallel rows in the projection process. This method is favorable because of the use of a large number of projection lenses arranged in rows and the large number of negatives used in this process.

This multi-lens projection system is based on U.S. Patent No. 4.1 of Mou et al.
It is also disclosed in No. 32.488.

This patent also discloses the use of a metal aperture with a number of different apertures to vary the intensity of the light as desired.

In theory, the highest quality stereoscopic photographs can be produced by printing a single element into each image zone. When more than one image element is printed in one image/death area, overlapping tends to occur, resulting in loss of clarity. In order to print a single image element in one image/death area, it is necessary to increase the projection angle and the width of the image element, so it is necessary to use a projection lens with a large diameter. No. In such a situation, neither continuous scanning nor intermittent repetition of images is required to fill each image band.

The main disadvantage of using a large diameter projection lens is that the sharpness of the image 0 is drastically reduced due to the low resolution of a large diameter lens.

Additionally, large diameter lenses dramatically increase the vignetting effect, so that less light is exposed at the edges of the image than near the center of the lenticule. This lowers the overall quality of the stereoscopic photograph.

Due to the lenticular radial erosion effect, less light is exposed to the image zone near the edges of the lenticule than near the center of the lenticule. This causes the image band near the center of the lenticule to be more bright than the image band near the edge of the lenticule. Therefore, when viewing a stereoscopic photograph, the eye sees a stereo pair formed by two image bands of density. Both 1f1. near the center of the lenticule. The Wr region is brighter than the image band near the edge of the lenticule. Because the stereo pairs are not in the same concentration, the eyes must make great efforts to adjust and view the photograph, causing eye strain. The radial eclipse effect is due in part to the fact that the distance from the curvature of the lenticule to the image bands near the edge of the lenticule is greater than the distance to the image band near the center.

SUMMARY OF THE INVENTION A new type of stereophotograph printing machine has been developed for producing stereophotographs with improved image sharpness for the rat-image elements of each image band. This stereographic printing machine has a large diameter lens with a new type of diaphragm that is straight to reduce the vertical aperture of the projection lens. This increases the resolution of the lens, thereby improving image sharpness. The height and shape of the diaphragm aperture can vary depending on the type of negative, lenticular curvature, and projection lens. Typically, the diaphragm aperture varies from one edge of the lens to the other to compensate for the effects of radial eclipse of the lens.

By varying the aperture height of the diaphragm from the center to the edges, the photographic image has a density of 1r throughout the photograph.
The sharpness is improved by 11 points.

In such a situation, a stereo pair of images with the same density and clarity can be seen from any viewing angle. The highest quality stereoscopic photographs produced by this stereographic printing machine are those in which a single image element is an image:
1) A photograph printed on the area from one edge to the other. In such a situation, (2) there is no image overlap and no unexposed strips between images;

However, it must be pointed out that the stereographic printing machine of the invention can also be used to print a number of discrete image elements of the same image into one image zone. The aperture of the lens can be adjusted to compensate for the vignetting effects of the projection lens and lenticular curvature to obtain an image of equal density throughout the photographic body.

When using this stereophotographic printing machine, it is preferable to perform each exposure when the printing machine is in the static position to avoid vibrations. In order to obtain high quality images with maximum sharpness, exposure times should be kept as short as possible.

Because the distance traveled by the projection lens between each exposure is equal to the width of the projection lens aperture, it is possible to create a single image band without creating any overlap or leaving strips of vermilion exposure between image bands. A 1it-image element is obtained which is printed edge to edge. This stereophotographic printing machine may be an 11-lens printing machine or a multi-lens printing machine. /4 When using a Luns printing machine, the difference between exposures can be made by moving the magnifying lens and negative while the printing material is stationary, or by moving the magnifying lens and printing material while the negative is stationary. It is better to change the projection angle. Furthermore, the negative and printing material may be moved while the magnifying lens remains stationary.

A fourth system that can be used is one in which only the printing material is moved while the negative and magnifying lenses remain stationary.

In the case of a multi-lens projector, all of these components remain stationary: the negative, the magnifying lens, and the printing material. The diaphragm aperture of a multi-lens projector is typically small.

A new 4 construction method is used to create stereoscopic photographs consisting of image bands of approximately equal density across the lenticular field of view. This is achieved by varying the height and shape of the aperture between the edges and the center of the aperture to compensate for projection lens and lenticular vignetting effects according to the principles described above.

When printing only one plane image in each image area according to this method, there is a possibility that the printing (-J digit image will be distorted) due to vibrations and misalignment of the printing machine, or the start and stop of lens movement. is greatly reduced because the magnifying lens and printhead remain stationary during the exposure.In such a situation, only one exposure is made for each qZ plane image, and the tjj sequence of exposures (2) Since the +1 interval is short, all movement stops, and the continuous scanning technique improves image quality over the intermittent method.

01 - The width of the image band of the element is the length of the aperture of the magnifying lens, the distance between the magnifying lens and the lenticular printing material,
and is a function of lenticular thickness.

DETAILED DESCRIPTION FIG. 1 is a schematic representation of a stereoscopic photograph in which a single image element is printed in each image zone. When a printing machine with a small diameter projection lens is used to print a single image element into an image zone, the result shown in FIG. 1 is obtained.

The lenticular printing material 1 consists of a photographic emulsion layer 2, a plurality of lenticules 3.4 and 5. Each lenticule has a curvature 6 through which an image is projected onto the photographic emulsion layer 2 by a projector (not shown). Each lenticule has three image bands B', B', and B
″′ is white.

Then, images are projected onto these image bands. The projector is
It has a projection lens with a small round or square aperture. Only the printed image elements I', I' and B'' fill part of the image bands B r , B # and B''.

FIG. 2 is a schematic diagram showing the width of the image element relative to the horizontal width of the aperture of the magnifying lens of the printing machine.

When the opening of the magnifying lens 7 has a horizontal width A1, an image I' having a width AI' is printed as shown in FIG.

If the projection lens 7 has a width of A2 and an aperture of 14, an image element of width A2' is printed to fill the image band B'' as shown in FIG. It is common practice to place the aperture around the edge of the lens to prevent images from projecting through the lens.
: Therefore, it is necessary to make sure that the horizontal aperture widths A1 and A2 are not actually the full width of the lens in the horizontal direction. FIG. 2 shows the direct relationship between the horizontal aperture width of the lens and the width of the image element. There are factors such as the distance from the lens to the material and the thickness of the lenticule that affect the exact width of the image that is printed.

FIG. 3 is a schematic diagram showing the eye looking at the stereo pair of lenticules. Figure 'd' shows each of the two image bands B', B',
and B″′ respectively 1li- image elements I′, I′, and B″′ are illustrated. As shown in FIG.
This can be done by using a printing machine equipped with an A2 large diameter projection lens. In such an environment, the 1st eye and the right eye see the stereo pairs 1/, and 1'.

The problem with using a lens with a large aperture (horizontal width A2) as shown in Figure 2 is that the sharpness of the photographic image is drastically reduced due to the low resolution of the large aperture. It is. Historically, large-diameter lenses drastically increase the radial eclipse effect, which quickly lowers the brightness from the center of the image toward the edges, reducing the overall Reduce quality.

The problem with using a lens of small diameter (horizontal diagonal 2) as shown in FIG. The entire image band B' shown in
, B', and B''. A viewer viewing these unexposed areas of the photographic emulsion layer 2 views these unexposed areas from various viewing angles. View image elements only at a particular line of sight.

To take advantage of the greater sharpness of photographic images obtained with small diameter lenses, continuous scanning techniques have traditionally been used to fill the entire image band, as shown in FIG.

FIG. 5 is a schematic diagram of an overlapping and intermingled double image profile constructed in a prior art scanning method. Image I shows that the magnifier beam remains across the entire scanning lower stop;
overlap. This overlap of images impairs clarity.

°U.S. Pat. No. 4,852,972 discloses a method of printing images in side-by-side relation to the image zone without overlapping the images. FIG. 4 schematically illustrates the arrangement of discrete image elements created by this patent. Image I in Figure 4 was created using a technique that continuously eclipses the projection angle, but the light rays appear short and intense intermittently. For example, the same images 1a, Ib in image band B'.

Ic is in a horizontal relationship. These images do not overlap and there is no unexposed space between them.

The technique disclosed in US Pat. No. 4,852,972 produces high quality stylistic photographs. However, high quality photographs can be obtained if 1 1/2-image elements are printed to fill the image band and clarity is obtained with a small aperture lens.

Figure 6 shows a comparison of the brightness curves of a large diameter lens and a small diameter lens. This figure shows a large-diameter lens (f/1
) shows that the brightness of the image decreases rapidly from the center to the edge compared to the small diameter lens (f/10). Such a rapid reduction in brightness of a large aperture lens drastically increases the vignetting effect, which reduces the overall quality of the stereoscopic image. These curves are based on the percentage of maximum brightness of the lens for a particular f-number. It is desirable to use a large aperture lens to print a single image element into an image zone if a method can be found that compensates for the extreme vignetting effects of a large aperture lens.

FIG. 7 is a graph showing a radial erosion curve of the brightness of the lenticule of the material for three-dimensional printing. This figure shows that if the light source is constant, the brightness decreases. The brightness ranges from approximately 95% to 65% over the lenticular field of view.
%It can be seen that it is.

0 Linear aperture The lack of clarity when using a large aperture magnifying lens to print a single image element into the image zone is solved by providing a linear aperture for the magnifying lens. .

FIG. 8 is a schematic diagram of a magnifying lens with a linear aperture. The magnifying lens 7 has an upper linear diaphragm 8a and a lower linear diaphragm 8b. The upper aperture 8a and the lower aperture 8b reduce the vertical height h of the lens aperture.

Covering the top and bottom of the lens with an aperture enhances the clarity of the image dye printed in the image zone.

In fact, it has been found that much of the low resolution of large aperture lenses is created by the top and bottom of the lens when printing stereoscopic photographs. By using linear fringes on a large-diameter lens, medium-
image elements can be printed.

The edges of the straight diaphragm aperture may be straight, but are preferably curved to compensate for lens and lenticular brightness curves. FIG. 8 illustrates a curved aperture in which the separation between the upper and lower apertures is narrower in the middle than on the sides. lens is in position 1
0B, the image band B' is filled with a high clarity qt- image 1'.

When the lens is in any of the positions 10A, 10B, or 10C, the centers of projection 11A, IIB, and 11C pass through the center of the lens, which has a greater brightness than at the edges. have a sense of By increasing the height of the aperture at the edges QL and 9R, the decrease in brightness at the edges is compensated for.

FIG. 10 is a schematic diagram showing the brightness curve of a magnifying lens corrected by an appropriately shaped linear aperture. In this case, to compensate for the lens brightness curve so that the brightness is the same across the field of the lens, the vertical width of the aperture opening at the edge of the lens is proportionally larger with respect to the center. It is.

The 7th garden shows the brightness curve of the lenticule used for printing. The shape of the linear aperture can also be adjusted to compensate for this difference.

It is understandable that the brightness decreases at the edges of the lenticule.

By using a linear diaphragm, the brightness curve of the magnifying lens and lenticule can be compensated for.

FIG. 11 is a graph showing the density of the image .:1'I region over the field of view of the lenticule exposed by using the aperture shown in FIG. 9 with appropriate height and shape. By using a linear aperture with an aperture of proper shape and size, equal brightness across all image bands can be achieved.

By lenticularly arranging the image bands to be of equal density, a person viewing the stereoscopic photograph from any angle sees a stereo pair formed by the image bands of equal density. Matching the concentration of stereo pairs makes it easier to see these pairs in the mouth. If the density of the three-dimensional A diaphragm may also be formed. These plates are
They can be moved away from each other or towards each other depending on the change of heart.

These plates may be attached to the printing machine by any suitable means so that they can be easily immovable.

As mentioned above, the width of the image printed on the lenticular is
It depends in part on the width of the aperture of the diaphragm in the horizontal h° direction. 1st
FIG. 2 illustrates a diaphragm that controls the horizontal width of the aperture of the lens 7. This aperture is the right plate 16 and the left plate 15.
These plates have a horizontal width of the opening of 9
Control is performed as shown by L and 9R. These plates 15 and 16 are the first to adjust the horizontal width of the aperture.
It can be mounted on any of the plates shown in Figure 2, Figure 13, and Figure 14.

The linear aperture of the present invention can be used in combination with a linear shutter. In this case, the 4 tmi-shaped aperture preferably has an aperture with the same vertical height h across the lens when printing at each position shown in FIG. FIG. 4 illustrates a linear moving shutter in combination with a linear diaphragm. This printing machine includes a lamp housing section 34 equipped with a lamp 30, and a servo motor 1.
8.19.
, and 20 in the proper position for projection. This printing machine has a lens 7. The printer has a shutter housing (not shown) that accommodates a linear moving shutter blade 41 with an aperture 42. The shutter blade 41 is moved from the closed position to the open position and closed again by a servo motor or stepper motor 43 controlled by a microprocessor or computer 44. Shutter blade 41 is a t1'' reciprocating blade that opens and closes as it moves in the direction of arrow 46, h', and opens and closes again as it moves in the direction of arrow 45 for the next exposure. The printer has a linear aperture IOA or 10B attached to the disk 512 as described above. The aperture shown in FIG. 13 has a uniform vertical height h over its width. The linear diaphragm 10B (not made by the military) has a small opening as shown in FIG. computer 4
Motor 47, controlled by 4, moves easel 48 to position photo+4 material 2 in a suitable IE position for printing the entire image zone.

A linear aperture can be used in combination with a variable density ψ optical filter. This filter transmits more light near the edges of the filter than in the central blade to compensate for the lens brightness curve shown in FIG. Although this filter can be used with a linear diaphragm of the bald type, it is preferably used with a diaphragm having an aperture of uniform vertical height as shown in FIG. In this way, an image area of equal density can be obtained over the field of view of the lens, as obtained in FIG. These image bands are the ancestors of lenticular! FJ'
Is q equal? It has a degree.

6. As shown in FIG. 14, the computer or microprocessor 44 is programmed to equalize the brightness values between exposures of each image element in each image band. position 1
When performing printing at nA, the shutter blade 41
opens at high speed and gradually reduces acceleration across the negative.

As shown in FIG. 13, when printing one negative, the shutter blade 41 opens at position 10B, accelerates toward the center of one negative, and accelerates toward the other edge of the negative. Gradually reduce acceleration.

The shutter blade 41 is baked at position 10 as shown in FIG.
At C, the acceleration is slowly increased toward the center of the negative 20, and the acceleration is gradually increased toward the other edge of the negative. The vertical axis in FIG. 13 represents the shutter speed and the horizontal axis represents the various positions in which the lens was placed during printing.

Lenticular vignetting effects should also be taken into account in programming the microprocessor or computer 44 to obtain both images of ray density across the photograph. The cumulative effect of these factors determines the speed of the shutter blade 41 at each position as it prints each image element in each 7 inch area of each image.

In general, the length of exposure of a negative is directly correlated to the brightness curve of the magnifying lens and lenticule and the position of the negative with respect to this brightness curve in the printer. Generally, the larger the projection angle, the greater the duration of exposure required.

When printing a negative, the shutter speed is substitute speed near the edge of the field of view of the magnifying lens, and high speed near the center of the field of view of the widening lens.

When we introduce a linear aperture and a linear shutter,
There is less variation in density across the field of view of the lenticule.

The aperture of the diaphragm and the linear shutter compensate for the vignetting effects of the projection lens and lenticules.

By programming all the scattering into a computer or microprocessor, the shutter blade can be opened and closed in different directions at variable speeds, so that the brightness values of each image in all image bands are approximately Be in between. The microprocessor or computer also moves the disk 12 with the various apertures into the proper position, if desired.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a printed stereoscopic photograph in which a single image element is printed in each image zone; FIG. FIG. 3 is a schematic diagram showing the eye looking at the stereo pairs within the lenticule; FIG. FIG. 5 is a schematic diagram showing an arrangement of discrete image elements arranged in a row, and FIG. Figure 6 is a graph showing a comparison of the brightness curves of a large-diameter lens and a small-diameter lens, and two graphs, Figure 7, are graphs showing the vignetting curve of the brightness of the lenticular material. 8 is a schematic diagram of a magnifying lens with a linear diaphragm having an aperture whose vertical height at the edge of the lens is greater than the height at the center of the lens, and FIG. 10 is a schematic diagram of a magnifying lens with a linear diaphragm having an aperture whose vertical height at the edge of the lens is greater than the height at the center of the lens; FIG. FIG. 11 is a schematic diagram showing the brightness curve of a large lens captured by a linear diaphragm with an aperture, and FIG. 12 is a graph showing the density of the image band over the field of view of an exposed lenticule; FIG. 12 is a schematic diagram of the aperture used to control the horizontal length of the aperture; and FIG. 14 is a graph showing the variation of linear shutter speed over the origin of a magnifying lens having an aperture of 0.0 FIG. 1 is a schematic diagram of a printing machine. DESCRIPTION OF SYMBOLS 1... Lenticular printing H material, 2... Photographic emulsion layer 3.4.5... Lenticular, 6... Curved part, 7
...projection lens.

Claims (1)

[Claims] 1. A projection light, a negative conveyor, a projection lens, and a linear diaphragm with an aperture, and a plurality of half-plane images of a target object taken from various viewpoints on a lenticular printing material. A stereoscopic photo printing machine for printing on. 2. The stereophotographic printing machine according to claim 1, further comprising means for changing the height of the aperture. 3. The means for varying the height of the aperture of the diaphragm has adjustable upper and lower plates, with an aperture formed between them, the shape of the aperture depending on the shape of these two plates. 3. A stereophotographic printing machine as claimed in claim 2, which can be varied by adjusting the relative positions. 4. The means for varying the height of the apertures is obtained by arranging a plurality of apertures of different shapes in a rotatable disk so that a desired aperture can be placed in a predetermined position. 2. The stereophotographic printing machine according to item 2. 5. The stereophotographic printing machine according to claim 1, wherein the linear aperture has an aperture whose vertical height at the edge of the projection lens is larger than that at the center. 6. The stereophotographic printing machine of claim 1 having apertures having substantially the same vertical height across the apertures. 7. A stereophotographic printer according to claim 1, further comprising means for varying the horizontal width of the aperture of the aperture. 8. The stereographic printing machine of claim 7, wherein the linear diaphragm aperture has substantially the same vertical width across the aperture. 9. A linearly moving reciprocating blade shutter is provided which is opened and closed by the moving means and whose shutter speed is controlled by the computer during printing to vary the duration of exposure of the various portions of the lenticular printing material as desired. 2. The stereophotographic printing machine according to claim 1, wherein the stereophotographic printing machine is controlled to vary. 10. The computer is programmed to operate the moving means to change the size of the aperture of the aperture, and the computer is programmed to operate the moving means to change the size of the aperture of the aperture, and the computer is programmed to operate the moving means to move the easel carrying the lenticular printing material during printing of the various images. 10. A stereographic printing machine as claimed in claim 9, also connected to means. 11. The stereophotographic printing machine of claim 6, further comprising a variable neutral density filter for varying the transmission of light rays through the lens from the center to the edges of the lens. 12. In order to vary the brightness values between different points of the lenticular printing material, a printing machine is equipped with an aperture whose vertical height at the edge of the lens is larger than that at the center. A method of printing multiple planar images of a target object taken from various viewpoints onto a lenticular printing material. 13. The printing machine has a linearly moving reciprocating blade shutter controlled by a computer to vary the shutter speed during printing to vary the exposure time on different parts of the lenticular printing material as desired. 13. The method of claim 12, comprising: