JPS6258494B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an information mark display device, particularly an information mark display device in which a relief type diffraction grating is arranged in the finder light beam of a cine camera, etc., and a reproduced mark from the diffraction grating can be observed along with the finder screen. It is related to.

The present applicant has already filed an application for an information mark display device using a relief type hologram (Japanese Patent Laid-Open No. 18664/1983). However, the hologram in the above application is a normal relief type hologram, and the first-order diffracted light is used as the information mark reproduction light to prevent harmful diffracted light from being mixed into the eyepiece, and the noise light of the finder light beam generated by being diffracted by the hologram is Avoid being observed. For these reasons, it was necessary to increase the spatial frequency of the hologram, that is, to use a relief structure with a fine period. For this reason, there was a drawback in that it was technically difficult to produce the original hologram.

An object of the present invention is to provide an information mark display device that does not adversely affect a light beam having image information such as a finder light beam even when using a relief-type diffraction grating (also referred to as a relief-type diffraction grating structure), and which is easy to manufacture. An object of the present invention is to provide a device that can use a relief type diffraction grating.

The present invention is particularly effective when the information mark is displayed on the side opposite to the light source for reproducing the information mark with respect to the surface on which the diffraction grating is arranged.

The present invention will be explained below using the drawings. FIG. 1 shows a first embodiment in which the information mark display device of the present invention is applied to an 8 mm cine camera. In Figure 1, 1 is a point on the object, 2 is the front group of the photographic lens, 3 is the half mirror, 4 is the rear group of the photographic lens, 5 is the film surface, 6 is the imaging lens, 7 is the mirror, and 8 is the display. Relief type focussing with recorded patterns
A focusing plate having an image hologram, 9 a white light source for illuminating the hologram, 10 and 11 finder relay lenses, 12 a secondary focusing surface, and 13 an eyepiece. Now, the light beam from the point 1 on the object passes through the photographing lens front group 2, the half mirror 3, and the imaging lens 6, and forms an object image on the focusing plate 8. In addition, the relief type focus image hologram on the focus plate illuminated by the white light source 9 also reproduces an information mark near the focus plate, and these object images and information marks overlap and are almost transmitted through the finder relay lens and eyepiece lens. Observed at the same diopter.

An example of a relief type diffraction structure as a focused image hologram is shown in the cross-sectional view of FIG.

A dielectric reflective film 17 having a designed reflectance is deposited on a relief diffraction grating formed on a transparent substrate 15 having a split distance measuring section 16, and a transparent adhesive 18 having the same refractive index as the focusing plate member is used to The structure is such that this relief diffraction structure is embedded. 19 is a transparent member for a cover.

Furthermore, the information pattern is realized by the presence of a reflective film 17 corresponding to the pattern "OK" on the relief diffraction grating 20, as shown in FIG. This can be done by providing a mask having an opening corresponding to "OK" on the relief diffraction grating when depositing the reflective film, and depositing the reflective film through this opening.

As shown in Figure 2, illumination light 21 from the reproduction light source
is reflected and diffracted by the reflective film portion to generate diffracted light 23 to reproduce the information mark. 24 is O-order diffracted light. At this time, if the relief diffraction grating is designed so that the N-order diffracted light (N2) mainly goes to the finder optical system, it is possible to use a diffraction grating with a period N times coarser than when the first-order diffracted light (N2) is used as reproduction light. can be used, which is advantageous in terms of production. especially,
A diffraction grating with N-order prisms is desirable from the viewpoint of light utilization efficiency.

By adopting the structure shown in Fig. 2, as detailed in the specification of Japanese Patent Application No. 54-10190, it is possible to almost eliminate the negative influence of the relief diffraction grating on the finder luminous flux. . In other words, out of the finder luminous flux,
If the mutual refractive index matching of the focusing plate 15 and the transparent adhesive 18 is good, the light transmitted through the relief diffraction grating section without a reflective film will not be affected by the relief structure, and therefore the finder image will be clear. On the other hand, in pattern areas where a reflective film is applied, the amount of light that passes through the hologram and reaches the eye is reduced by an amount corresponding to the reflectance of the reflective film, making the pattern area appear dark and the view of the viewfinder image deteriorate. However, this is not a problem if the reflectance of the reflective film is kept at a low value, for example, about 4%.

By the way, the relief type diffraction grating shown in Figure 2 is for the case where the illumination side and the observation side are the same side, but in terms of spatial conditions and light usage efficiency when actually incorporating it into a camera viewfinder, etc. As shown in FIG. 1, in many cases it is desired to perform transmission type illumination, that is, to perform illumination from the side opposite to the viewing eye. When the relief type diffraction grating having the configuration shown in FIG. 2 is designed to be applied to such a case, it becomes as shown in FIG. 4. In this case, as is clear from FIG.
In order to make the 0 emit approximately in the direction of the optical axis, a relief shape with sharp peaks is required, which is extremely difficult to manufacture.

FIG. 5 shows a cross-sectional view of an embodiment in which such drawbacks have been improved. In the relief-type diffraction grating shown in FIG. 5, a unit cell structure is formed by two slopes 27 and 28 that are inclined with respect to the grating plane arranged almost coincident with the focal plane. A dielectric reflective film having a designed reflectance is deposited on a surface 28 with a large angle, that is, a steep slope, and this relief diffraction structure is embedded with a transparent adhesive 18 having the same refractive index as the focusing plate member. It's structured well.
19 is a transparent member for a cover.

Furthermore, the information pattern in this embodiment is similar to that shown in FIG. This is achieved by depositing a film. This can be done by providing a mask having an opening corresponding to "OK" on the relief diffraction grating when depositing the reflective film, and depositing the reflective film toward one side of the chevron through this opening.

Illumination light 21 from the reproduction light source as shown in FIG.
is reflected and diffracted by the reflective film portion 22 to generate diffracted light 23 to reproduce the information mark. 24 is O-order diffracted light. A more detailed diagram of the diffraction situation is shown in FIG.

In FIG. 7, illumination light 21 is transmitted through a gentle slope 27 having a small angle of inclination with respect to the lattice plane, and then reflected by a steep slope 28 having a large angle of inclination and provided with a reflective film.
These reflected lights cause diffraction, and the N-order diffracted light 24 is emitted toward the viewing eye. In this embodiment, the condition for the pitch P of the relief diffraction grating is Psinθ=Nλ (1). However, λ is the material 15 that constitutes the diffraction grating.
It is the wavelength of light within. Here, θ is the incident angle of the illumination light as shown in FIG. At the same time, the geometrically optically reflected light of the illumination light on the surface of the relief diffraction grating on which the reflective film is vapor-deposited is directed mainly toward the finder optical system, thereby increasing the light amount utilization rate, thereby enabling a bright display. The condition for this is =θ/2...(2). However, as shown in FIG. 7, is the angle that the surface 28 on which the reflective film is deposited forms with the perpendicular to the diffraction grating surface. The height h of the peaks of the diffraction grating and the reflectance on the surface of the deposited film can be roughly determined in the following way (more precisely, the diffraction pattern by one diffraction element and the synchronous structure are used to diffract the material in a specific direction). The direction and intensity of light emitted can be calculated from the product with the comb-shaped δ function, which indicates that light is emitted, and that characteristic should be used to determine the reflectance). The proportion of the amount of light required to display the information mark in the incident luminous flux, that is, the effective reflectance is Reff, and the angle of incidence of the illumination light is θ (the angle of incidence on the reflective surface is π/2 + 4 - θ). If the reflectance is R〓, then Reff=Rθ・ω/Pcosθ...(3) However, ω is the width of the portion of the incident light beam that reaches the reflecting surface as shown in Fig. 7, and ω=hsinθ/cos... ...(4)

From (3) and (4), Rθ・h＝Reff・Pcoscotθ ...(5). As an example Then, from equations (1) to (5), Rθ·h=0.81 (μ) ...(8) The reflectance of the vapor-deposited reflective surface and the height of the peaks of the diffraction grating may be determined so as to satisfy (8). The above is a case where all the diffracted light is included in the N = 12th (order) diffracted light using the conditions of a blazed diffraction grating, but in reality there is some inflow into other orders as well, so regarding Reff. It is also necessary to take this into consideration when designing.

Still other examples are shown below.

The relief-type diffraction gratings shown in the examples so far had a reflective film deposited on only one side of the chevron, but in order to make this deposition easier, both sides of the chevron were vapor-deposited on all sides. Good too. In this case, the amount of light naturally decreases, but there is no problem as long as the reflectance of the reflective film is kept low.

Further, another embodiment of the vapor deposition method of the reflective film on the information pattern is shown in FIG.

FIG. 8 is a diagram corresponding to FIG. 3. Here, the relief diffraction grating exists only in a portion 25 corresponding to the pattern information to be reproduced, and the entire surface of the base 26 is coated with a reflective film. In this embodiment as well, the information pattern is reproduced by the reproduction light source from the relief diffraction grating portion in the same manner as in FIG. 4.

However, the effect on transmitted light is slightly different from the previous embodiment. That is, the reflective film coating is 26
Since this is done over the entire surface of the screen, the entire screen will be dark, but the information pattern will not be the only part that looks dark.

As mentioned earlier, the relief diffraction grating for the information mark display device of the present invention described above uses N-order diffraction light when reproducing the information mark, as is clear from the above equation (1). Therefore, the pitch can be increased, and if equation (2) is satisfied, there is some degree of arbitrariness in the slope of the other planes that make up the mountain shape of the relief diffraction grating and the depth of the diffraction grating, making it easy to fabricate the diffraction grating. Above, it is very advantageous.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment in which the present invention is applied to an 8 mm cine camera, FIG. 2 is a sectional view showing an example of a display device using a relief type diffraction grating, FIG. 3 is a plan view thereof, and FIG. The figure shows an embodiment in which the diffraction grating shown in Fig. 2 is used in a transmission type, Fig. 5 is a cross-sectional view of a relief type diffraction grating used in another embodiment of the present invention, and Fig. 6 is a diagram showing an embodiment in which the diffraction grating shown in Fig. 5 is used. Figure 7 shows information mark reproduction on the relief-type diffraction grating shown in Figure 6.
Enlarged view showing the diffraction state during reproduction shown in Figure 8.
The figure is a plan view of a focusing plate equipped with a relief type diffraction grating. In the figure, 8... focus plate, 9... white light source for illumination, 16... split distance measuring section, 17... reflective film, 18... transparent adhesive material, 19... transparent member.

Claims (1)

[Claims] 1. In an information mark display device that displays an information mark by forming a diffraction grating on a transparent substrate and illuminating the diffraction grating, the diffraction grating is a relief type diffraction grating, and the unit of the diffraction grating is The structure includes a first surface and a second surface that are angled to each other, and the light illuminating the grating is transmitted through the first surface and then reflected by the second surface, and the light illuminating the diffraction grating is reflected by the second surface. An information mark display device characterized in that an information mark is displayed using generated reflected and diffracted light.