JPH0962172A - Duplication method of hologram array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to duplicate the recording regions of the respective element holograms of a hologram array by magnification and reduction at an arbitrary magnification including unmagnification with respect to the recording regions of an original plate. SOLUTION: A photosensitive material is arranged apart a first distance from a hologram array original plate and is irradiated with the reconstructing illumination light thereof from the original plate side. The diffracted light therefrom and the rectilinearly transmitted light are interfered in the photosensitive material to duplicate an intermediate hologram array H1. The resulted intermediate hologram array H1 is then used as the original plate and a hologram photosensitive material 8 is then arranged apart a second distance Δ from an intermediate hologram array H2 on the original plate side at time of this duplication and is irradiated with the reconstructing illumination light 9' in the direction advancing in the direction opposite to the rectilinearly transmitted light at the time of the reproduction from the intermediate hologram array H1 side. The diffracted light 10' therefrom and the rectilinearly transmitted light 11' are interfered in the photosensitive material 8 to obtain the duplicated hologram array of the original plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram array duplication method, and more particularly to a hologram array duplication method capable of enlarging or reducing a recording area of each element hologram of a hologram array such as a hologram color filter at an arbitrary magnification. Regarding

[0002]

Holographic arrays can be used, for example, instead of microlens arrays. As one of such hologram arrays, the applicant of the present invention has proposed a Japanese Patent Application No.
No. 12170, etc., proposed a hologram color filter for liquid crystal display devices. The structure is composed of an eccentric Fresnel zone plate-shaped micro hologram array. The hologram color filter will be briefly described below.

A liquid crystal display device using this hologram color filter will be described with reference to the sectional view of FIG. In the figure, a hologram array 5 constituting this hologram color filter is arranged at a distance from the backlight 3 incident side of a liquid crystal display element 6 which is regularly divided into liquid crystal cells 6 '(pixels). On the back of the liquid crystal display element 6,
A black matrix 4 provided between the liquid crystal cells 6'is arranged. In addition to the above, polarizing plates (not shown) are arranged on both sides of the liquid crystal display element 6. It should be noted that an absorption type color filter that transmits light of colors corresponding to R, G, and B color separation pixels is arranged between the black matrix 4 as in the conventional color liquid crystal display device. Is also good.

The hologram array 5 has a repetition period of R, G, and B color separation pixels, that is, a set of three liquid crystal cells 6 ′ adjacent to each other in the direction of the liquid crystal display element 6 in the plane of the paper. The micro holograms 5 'are arranged in an array at the same pitch as the repetition pitch. The micro holograms 5' are aligned with each set of three liquid crystal cells 6 'adjacent to each other in the direction of the plane of the liquid crystal display element 6, and each hologram 5' Each of the micro holograms 5 ′ corresponds to the light of the green component in the backlight 3 that enters at an angle θ with respect to the normal to the hologram array 5 and corresponds to the micro hologram 5 ′. It is formed in a Fresnel zone plate shape so that light is condensed on the liquid crystal cell G at the center of the three color separation pixels R, G, and B. The micro hologram 5 ′ has a relief type, which has no or little wavelength dependence of the diffraction efficiency.
It consists of transmission holograms such as phase type and amplitude type. Here, the fact that there is no or little wavelength dependence of the diffraction efficiency is not a type that diffracts only a specific wavelength and does not diffract other wavelengths like a Lippman hologram,
Means that one diffraction grating diffracts any wavelength,
The diffraction grating having a small wavelength dependence of the diffraction efficiency diffracts at different diffraction angles according to the wavelength.

[0005] With such a configuration, when the white backlight 3 that enters at an angle θ with respect to the normal line from the surface of the hologram array 5 opposite to the liquid crystal display element 6 is incident, the wavelength is reduced. Accordingly, the diffraction angle of the minute hologram 5 'is different, and the light condensing position for each wavelength is dispersed in a direction parallel to the hologram array 5 surface. Among them, the red wavelength component is located at the position of the liquid crystal cell R displaying red, the green component is located at the position of the liquid crystal cell G displaying green, and the blue component is located at the position of the liquid crystal cell B displaying blue. By arranging the hologram array 5 so as to diffract and collect light, each color component passes through each liquid crystal cell 6 ′ with almost no attenuation in the black matrix 4 and the liquid crystal cell 6 ′ at the corresponding position. Color display can be performed according to the state.

As described above, by using the hologram array 5 as a color filter, each wavelength component of the conventional color filter backlight can be made incident to each liquid crystal cell 6'without being absorbed, and its utilization efficiency is improved. Can be significantly improved.

The production of such a color filter composed of a hologram array is performed, for example, by a duplication method using two-beam interference of multipoint convergent light and zero-order transmitted light emitted from a minute hologram lens array composed of a computer hologram (Japanese Patent Application No. Hei 10-26139). 5
-14572). The duplication method will be briefly described with reference to the cross-sectional view of FIG. 6. The hologram interference fringes of the minute hologram 5 ′ are calculated by a computer, and the interference fringes are projected onto a glass substrate coated with an electron beam resist by an electron beam. Draw and develop the relief type computer generated hologram (CGH: Computer Gen)
An array 7 of erased Hologram) 5 ″ is produced. Next, as shown in FIG. 6, the hologram sensitive material 8 is formed on the relief surface of the CGH array 7 thus produced.
CG
Laser light 9 is made incident from the H array 7 side at an angle θ corresponding to the backlight 3 in FIG. 5, and each CGH of the CGH array 7 is made incident.
The convergent diffracted light 10 and the linearly transmitted light 11 generated by 5 ″ are interfered in the hologram photosensitive material 8 to duplicate the CGH array 7. This duplicated hologram is used as the hologram array 5 in FIG. The hologram array 5 can also be manufactured by further duplicating a duplicate hologram as an original plate.

[0008]

SUMMARY OF THE INVENTION However, CGH
The hologram array 5 obtained by duplicating the array 7 as a master by the method as shown in FIG. 6 has each minute hologram 5 ′ even if each CGH 5 ″ forming the CGH array 7 has interference fringes drawn on the entire surface thereof. The interference fringes are not recorded on the entire surface of the hologram photosensitive material 8 because the photosensitive layer 13 is usually coated on the glass substrate 12 and the cover film 14 is laminated thereon as shown in FIG. Therefore, even if the CGH array 7 and the hologram photosensitive material 8 are brought into close contact with each other, a gap (about 50 μm) due to the cover film 14 is formed between the relief surface of the CGH array 7 and the photosensitive layer 13 and converges in the photosensitive layer 13. This is because the region N where the diffracted light 10 does not enter is generated.

As described above, in the copying method as shown in FIG. 6, the area in which interference fringes are recorded becomes smaller as the copying is repeated. Further, the focal length of the minute hologram 5'is also shortened. Further, the degree of modulation of the recorded interference fringes also becomes small. The distance (pitch) between the centers of the minute holograms 5'is not changed by such a duplication method.

When the interference fringe recording area of each minute hologram 5'is made smaller than the entire surface by duplication in this way, when the backlight 3 is irradiated, the incident light is diffracted to generate a region N in which wavelength dispersion is not possible, resulting in spectral efficiency. Is decreasing,
Unnecessary zero-order light increases.

The present invention has been made in view of the above problems of the prior art, and its object is to make the recording area of each element hologram of a hologram array such as a hologram color filter relative to the recording area of the original plate. (EN) A hologram array duplication method capable of enlarging / reducing and duplicating at any magnification including double.

[0012]

A hologram array duplication method of the present invention that achieves the above object is a method of duplicating a hologram array from a hologram array original plate by optical duplication. Then, the hologram sensitive material is arranged, the reproduction illumination light is irradiated from the hologram array original plate side, and the diffracted light and the straight transmitted light are interfered in the hologram sensitive material to duplicate the intermediate hologram array, and then, The obtained intermediate hologram array is used as an original plate, and a hologram photosensitive material is arranged on the hologram array original plate side at the time of duplication at a second distance from the intermediate hologram array. Reconstruction illumination light is emitted in the opposite direction, and the diffracted light from that direction and the straight transmitted light are recorded in the hologram sensitive material. A method characterized by obtaining a duplicate hologram array of the hologram array master by interference.

In this case, by making the first distance and the second distance substantially equal to each other, the same hologram array as the hologram array original plate can be obtained.

As the hologram array original plate, for example, a computer generated hologram array can be used.

Further, as the duplicate hologram array,
For example, each element hologram can be applied to a hologram color filter having a function of wavelength-dispersing white light incident at an angle with respect to the normal line of the recording surface in the direction along the recording surface and separating the light.

In order to separate at least one of the first distance and the second distance described above, it is desirable to interpose a spacer between the hologram array original plate or the intermediate hologram array and the hologram photosensitive material. .

As the spacer, a frame-shaped member having a predetermined thickness or beads having a predetermined diameter can be used. Transparent beads are used as the beads, and the transparent beads are used to separate the second distance, and a transparent liquid having a refractive index substantially the same as that of the transparent beads is interposed between the intermediate hologram array and the hologram photosensitive material. You can choose to let them do it.

Further, one of the hologram array original plate, the intermediate hologram array, or the hologram sensitive material is placed on a substrate, and the other is placed on a plurality of pins which are erected on the substrate so as to be adjustable in height. By arranging, at least one of the first distance and the second distance can be separated.

In the present invention, the hologram light-sensitive material is arranged at a first distance from the hologram array original plate, the reproduction illumination light is irradiated from the hologram array original plate side, and the diffracted light and the straight transmitted light are emitted. The intermediate hologram array is duplicated by causing interference in the hologram sensitive material, and then the obtained intermediate hologram array is used as an original plate, and the hologram sensitive material is separated from the intermediate hologram array by a second distance on the hologram array original plate side at the time of duplication. By irradiating reproduction illumination light from the intermediate hologram array side in the direction that goes in the direction opposite to the straight transmitted light at the time of duplication, and let the diffracted light from that and the straight transmitted light interfere in the hologram photosensitive material. Duplicate hologram array original plate Since we get a hologram array, we duplicate the same hologram as the original plate because of the relationship between the first distance and the second distance. , Or to prevent the occurrence of a region where no diffractive without recording a hologram interference pattern, or can scale the hologram interference fringes recorded area of the original.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The basic principle of the present invention is to reproduce a hologram array original plate 7 in an arrangement as shown in FIG.
In order to prevent the recording area of each element hologram from becoming inevitably small and the area N in which hologram interference fringes cannot be recorded from occurring, the intermediate hologram array H1 obtained in the first replication is used as the original plate and the copy is performed again. As reproduction illumination light to be incident on the intermediate hologram array H1 at that time,
Using the laser light traveling in the direction opposite to the reference light 11 at the time of duplication, the light diffracted from each element hologram of the intermediate hologram array H1 is made into divergent light, and the final hologram array H2 obtained by the second duplication is obtained. The recording area of each element hologram is expanded this time so that hologram interference fringes can be recorded in an area having the same size or an arbitrary size as the hologram array original plate 7.

This principle will be described with reference to FIGS. 1 and 2 are views for explaining an embodiment in which a hologram array 5 constituting a hologram color filter is duplicated from a CGH array original plate 7 in two steps, and FIG. 1 shows the first duplication. It shows the arrangement to be performed. As in the case of FIG. 6, the original plate of the hologram array 5 constituting the hologram color filter is formed as the CGH array 7, and the distance from the relief surface of the CGH array original plate 7 to the photosensitive layer 13 is set to d and the hologram photosensitive material is formed. 8 for CG
It is placed close to the original H-array 7. A laser beam 9 is made incident from the CGH array original plate 7 side at an angle θ corresponding to the backlight 3 of FIG. 5, and the convergent diffracted light 10 and the straight transmitted light 11 generated by each CGH 5 ″ of the CGH array original plate 7 are made into the hologram photosensitive material 8. Interference in the intermediate hologram array H1
Duplicate In this case, even if the diameter of the recording area of each element hologram 5 ″ of the CGH array original plate 7 is D, the light diffracted from it is the convergent light 10, so that the photosensitive layer separated by d from the diffraction surface of the original plate 7 In Fig. 13, the diameter of the recording area of the hologram interference fringes is D'which is smaller than D. The size of the element hologram itself forming the array (the distance between the centers of adjacent element holograms) is CGH array original plate 7. The same applies to the intermediate hologram array H1 and there is no change.

Next, as shown in FIG. 2 showing an arrangement for performing the second duplication, the intermediate hologram array H1 obtained by duplication in FIG. 1 is used as an original plate and the duplication is performed again. In this case, the hologram photosensitive material 8 is arranged on the original plate 7 side when the intermediate hologram array H1 is duplicated, and the laser beam 9'for reproduction illumination is on the side opposite to the hologram photosensitive material 8 and the intermediate hologram array H1. Is transmitted in the direction opposite to that of the transmitted light 11 in the case of replicating. Then, the distance from the diffraction surface of the intermediate hologram array H1 to the photosensitive layer 13 of the hologram photosensitive material 8 is set to Δ. When the laser light 9'for reproduction illumination is incident on the intermediate hologram array H1 in such an arrangement, the light diffracted from each element hologram of the intermediate hologram array H1 travels in the opposite direction of the convergent diffracted light 10 of FIG. It becomes divergent light 10 '. The multi-point divergent light 10 'and the straight traveling light 11' interfere with each other in the hologram photosensitive material 8 to duplicate the final hologram array H2. This time, even if the diameter of the recording area of each element hologram of the intermediate hologram array H1 is smaller than the dimension of the element hologram itself, D ', the light diffracted from the element hologram is divergent light 10'. Photosensitive layer 13 separated from the diffractive surface by Δ
In this case, the diameter of the recording area of the hologram interference fringes is D ″ which is larger than D ′. In this case also, the dimensions of the element holograms themselves forming the array are the same as those of the CGH array original plate 7 and the intermediate hologram array H1. Absent.

In the above, from the diffractive surface of the hologram original plate 7 at the time of the first replication, the photosensitive layer 1 of the hologram photosensitive material 8 is formed.
3 and the distance Δ from the diffraction surface of the intermediate hologram H1 to the photosensitive layer 13 of the hologram photosensitive material 8 at the time of the second duplication are equal, the hologram interference fringe recording area of the final hologram array H2 is The diameter D ″ is the same as the diameter D of the hologram interference fringe recording area of the CGH array original plate 7,
The CGH array original version 7 has been completely reproduced. Also, the focal lengths of the element holograms are the same. On the other hand, when Δ is larger than d, D ″> D, the hologram interference fringe recording area is enlarged, the focal length of the element hologram is large, and when Δ is smaller than d, D ″ <D,
The hologram interference fringe recording area is reduced, and the focal length of the element hologram is reduced. In any case, the dimension of the element hologram itself (distance between centers of adjacent element holograms: pitch) does not change.

Therefore, the duplication method of the present invention uses Δ≈d
In the case of, the same hologram as the original plate is duplicated to prevent the generation of the non-diffracted region N. In the case of Δ> d, the hologram interference fringe recording region of the original plate is enlarged (for example, the entire area of the element hologram). (If the hologram interference fringes are recorded in the entire area of the element hologram by duplication instead of drawing in a smaller area), and if Δ <d, draw the interference fringe spacing wider than it actually is and reduce it by duplication. Available to do In particular, in order to prevent the generation of the region N (FIG. 6) in which the incident light is diffracted and the wavelength cannot be dispersed, when manufacturing the hologram color filter as described with reference to FIG. The method of duplication is suitable. The duplication method of the present invention can also be used to increase or decrease the focal length. Incidentally, not only the hologram array but also any hologram, by applying the duplication method of the present invention, reproduction of the hologram interference fringe recording area,
The scaling can be performed.

By the way, in order to control the distance d in the first duplication and the distance Δ in the second duplication, the intermediate hologram H1 between the hologram master 7 and the hologram photosensitive material 8 is controlled.
The gap between the hologram photosensitive material 8 and the hologram photosensitive material 8 can be controlled by adjusting the thickness of the spacer inserted between them. FIGS. 3A and 3B show an example in which a spacer is interposed. 3A is a plan view of the spacer 21, and FIG. 3B is a spacer 2 in the gap between the hologram master 7 or the intermediate hologram H1 and the hologram photosensitive material 8.
It is a figure which shows the state which intervened 1. Spacer 21
Is the thickness δ and is the hologram master 7 or the intermediate hologram H.
1 or hologram sensitive material 8 which has a frame-like shape that fits the smaller outer shape, and a plurality of spacers 21 having different thicknesses δ are prepared in advance to obtain the desired d or Δ.
Multiple spacers 2 prepared in advance to obtain
The one having an appropriate thickness δ is selected from 1 and used.

FIG. 4A shows the hologram master 7 (or
This is an example in which the height-adjustable pins 23 are used to control the thickness of the gap between the intermediate hologram H1) and the hologram photosensitive material 8, and the height-adjustable screws are provided at the four corners of the substrate 22. The pins 23 are set up, and the hologram sensitive material 8 is placed on the substrate 22 between them, while the hologram master 7 (or the intermediate hologram H1) is placed on the tips of the four pins 23, and both of them are placed. A gap of desired thickness is obtained between them. In addition, the hologram sensitive material 8 and the hologram original plate 7
(Or, the positional relationship of the intermediate hologram H1) may be reversed.

FIG. 4B shows the hologram master 7 (or
A plurality of types of beads 24 having different diameters are used as spacers arranged between the intermediate hologram H1) and the hologram photosensitive material 8.
Is prepared in advance, and in order to obtain the desired d or Δ, one having an appropriate diameter is selected from the plurality of kinds of beads 24 prepared in advance, and the peripheral portion between them is selected. By sandwiching between the two, a gap having a desired thickness is obtained.

Further, FIG. 4C shows an intermediate hologram H1.
When a final hologram array H2 is reproduced from the above, a method suitable for controlling the gap between the intermediate hologram H1 and the hologram photosensitive material 8 when a transparent liquid 25 such as an index matching liquid (refractive index matching liquid) is interposed. Yes,
A plurality of types of transparent beads 26 having different diameters having a refractive index substantially equal to that of the transparent liquid 25 are prepared in advance, and the plurality of types of transparent beads 26 prepared in advance are used to obtain the desired d or Δ. By selecting one having an appropriate diameter from among the above and randomly sandwiching the two, a gap having a desired thickness is obtained.

In addition to the method of interposing a spacer as described above, the gap between them is measured by a laser focus displacement meter (gap measuring machine), a contact type displacement sensor,
The replication may be performed while controlling to a desired thickness while measuring with a sensor such as a non-contact displacement sensor or an air sensor. Further, the gap between them can be controlled by adjusting the pressure and amount thereof using an index matching liquid (refractive index matching liquid) filled therebetween.

Further, the gap between them may be duplicated while a positioning mark is previously attached to the hologram master 7 or the hologram sensitive material 8 and controlled by using a focal length measuring device such as a microscope or a CCD camera. it can. Further, it is also possible to record a hologram having a focal point at an arbitrary distance on the hologram original plate 7 or the hologram sensitive material 8 and use the generated image of the hologram itself to control and reproduce the gap between them.

Further, the hologram master plate 7 to be duplicated has CGH5 ″ attached on multiple sides, but the hologram original plate 7 is not limited to this and may be an optically recorded hologram array. Although the hologram color filter is assumed as the hologram array, it is needless to say that the duplication method of the present invention can be applied to duplication of hologram arrays, hologram lens arrays, and the like for other purposes.

Although the hologram array duplication method of the present invention has been described above based on the embodiments, the present invention is not limited to these embodiments and various modifications can be made. Note that FIG.
When replicating the original 7 by one-time replication method such as
In order to prevent the region N in which the wavelength of light cannot be dispersed by diffracting the incident light on the duplicated hologram array, the CGH array 7 is formed by overlapping and drawing the adjacent CGH 5 ″ with a slight overlap. This is also possible by making 7. By doing so, by making the photosensitive layer 13 so that the convergent diffracted lights 10 diffracted from each CGH 5 ″ are separated from each other in FIG. It is also clear from the fact that the region N where the convergent diffracted light 10 does not enter is not formed in the photosensitive layer 13.

[0033]

As is apparent from the above description, according to the hologram array duplicating method of the present invention, the hologram sensitive material is arranged at the first distance from the hologram array original plate and reproduced from the hologram array original plate side. The intermediate hologram array is duplicated by illuminating it with illumination light and causing the diffracted light and the linearly transmitted light to interfere with each other in the hologram photosensitive material.Then, the obtained intermediate hologram array is used as an original plate, and the hologram array at the time of duplication is used. A hologram photosensitive material is arranged on the original side at a second distance from the intermediate hologram array, and reproduction illumination light is emitted from the intermediate hologram array side in a direction proceeding in a direction opposite to the straight transmitted light at the time of duplication, Since a duplicate hologram array of the hologram array original plate is obtained by causing the diffracted light and the straight transmitted light to interfere in the hologram photosensitive material, According to the relationship between the distance and the second distance, the same hologram as the original plate is duplicated to prevent the generation of a region where hologram interference fringes are not recorded and are not diffracted, or the hologram interference fringe recording region of the original plate is enlarged or reduced. be able to. The hologram array duplication method of the present invention is particularly suitable for preventing the generation of a region in which wavelengths cannot be dispersed by diffracting incident light when manufacturing a hologram color filter.

[Brief description of drawings]

FIG. 1 is a diagram showing an arrangement for performing a first duplication of an embodiment of a hologram array duplication method of the present invention.

FIG. 2 is a diagram showing an arrangement for performing a second replication of an embodiment of the hologram array replication method of the present invention.

FIG. 3 is a plan view of a spacer to be interposed and a state of being interposed.

FIG. 4 is a diagram showing another example of a spacer.

FIG. 5 is a cross-sectional view of a liquid crystal display device using a hologram color filter.

FIG. 6 is a cross-sectional view for explaining a conventional duplication method.

[Explanation of symbols]

 5 ″ ... CGH 7 ... CGH array original plate 8 ... Holographic material 9 ... Laser light 9 '... Laser light 10 ... Converging diffracted light 10' ... Divergence diffracted light 11 ... Straight transmitted light 13 ... Photosensitive layer 21 ... Frame spacer 22 ... Substrate 23 ... Height-adjustable pins 24 ... Beads 25 ... Transparent liquid 26 ... Transparent beads H1 ... Intermediate hologram array H2 ... Final hologram array

Claims (9)

[Claims] 1. A method of duplicating a hologram array by optical duplication from a hologram array original plate, wherein a hologram photosensitive material is arranged at a first distance from the hologram array original plate, and the reproduction illumination light is emitted from the hologram array original plate side. The intermediate hologram array is duplicated by irradiating the hologram with the diffracted light and the linearly transmitted light from the hologram photosensitive material.Then, the obtained intermediate hologram array is used as the original plate, and the hologram array original plate side at the time of copying is reproduced. A hologram photosensitive material is arranged at a second distance from the intermediate hologram array, and reproduction illumination light is emitted from the side of the intermediate hologram array in a direction opposite to the straight transmitted light at the time of duplication, and diffracted light from that is emitted. By interfering with the straight transmitted light in the hologram photosensitive material, a duplicate hologram array of the hologram array original plate is obtained. A method for replicating a hologram array, which is characterized in that 2. The method of duplicating a hologram array according to claim 1, wherein the first distance and the second distance are made substantially equal to each other. 3. The hologram array replicating method according to claim 1, wherein the hologram array original plate is a computer generated hologram array. 4. The hologram color having a function of wavelength-dispersing white light incident on each of the element holograms at an angle with respect to a normal line of the recording surface in a direction along the recording surface to disperse the duplicate hologram array. The hologram array duplication method according to claim 1, wherein the hologram array duplication method is a filter. 5. A spacer is interposed between the hologram array master plate or the intermediate hologram array and the hologram photosensitive material in order to separate at least one of the first distance and the second distance. The hologram array duplication method according to any one of claims 1 to 4. 6. The method of replicating a hologram array according to claim 5, wherein the spacer is formed of a frame having a predetermined thickness. 7. The method of replicating a hologram array according to claim 5, wherein the spacer is made of beads having a predetermined diameter. 8. The beads are made of transparent beads, and the distance separated by the transparent beads is the second distance, and the transparent beads are refracted between the intermediate hologram array and the hologram photosensitive material. 8. The method of replicating a hologram array according to claim 7, wherein a transparent liquid having a refractive index substantially the same as the refractive index is interposed. 9. One of the hologram array original plate or the intermediate hologram array or the hologram sensitive material is placed on a substrate, and the other is placed on a plurality of pins which are erected on the substrate so as to be adjustable in height. At least one distance of the said 1st distance or a 2nd distance is spaced apart by mounting the said, The any one of Claim 1 to 4 characterized by the above-mentioned.
A method for duplicating a hologram array according to the item.