An indication-within-finder free from ghost light is provided at a minimal cost even in the case of a pentagonal prism or the like. The finder includes an objective system (61) having a positive refracting power, an image-inverting system including a roof prism (62) and a pentagonal prism (63), and an ocular system (64) having a positive refracting power. An object image is formed on an intermediate image plane (65) by the objective system (61) and the roof prism (62). The object image is viewed with the ocular system (64) through the pentagonal prism (63). The position of the intermediate image plane (65) is approximately coincident with the entrance surface of the pentagonal prism (63). A deflecting member (67) projecting in a wedge shape is provided on the entrance surface of the pentagonal prism (63). Light rays (68') passing through the deflecting member (67) are deflected by refracting surfaces (67' and 67"). Therefore, the rays (68') do not reach a viewer's pupil, but blacked-out indications are seen.

BACKGROUND OF THE INVENTION
 The present invention relates to an indication display device of a finder
 optical system used in a camera for photography or an electronic camera.
 A finder for a camera needs indication display within the field of view to
 display an indication of a distance measurement range for autofocusing and
 an indication for parallax correction in photography at the closest
 focusing distance. Conventionally, a real-image finder is provided with an
 indication display member near an intermediate image formation plane.
 Known indication display methods include a method wherein incident light
 is blocked to display an indication, and a method wherein a wedge-shaped
 deflecting member is provided on the surface of an optical element of a
 Porro prism to deflect incident light in a direction in which it does not
 reach a viewer's pupil, as disclosed in Gazette Containing the Japanese
 Patent No. 2629690.
 However, the method wherein incident light is blocked requires extra
 processing, e.g. vapor deposition onto a transparent member. This causes
 an increase in the cost. In the case of the method wherein incident light
 is deflected, if an indication display member is formed as a molded part,
 it is unnecessary to subject each individual parts to extra processing,
 and there is no increase in the cost. However, in the case of a prism in
 which an entrance surface and an exit surface are disposed close to each
 other as in a pentagonal prism, for example, deflected rays may be totally
 reflected by the exit surface to reach the viewer's pupil as light still
 having a strong intensity, thus causing ghost light. Rays deflected by a
 deflecting member for indication deviate from a visual field viewing light
 path but are still directed toward the pupil. In a Porro prism such as
 that shown in FIG. 1, an entrance surface 11 is surrounded with a first
 reflecting surface 12 and three diffusing surfaces 13. Therefore, most of
 deflected rays impinge on the diffusing surfaces 13 to become diffused
 light of weak intensity. Accordingly, only a slight amount of light
 reaches the viewer's pupil and is not recognized as ghost light. In the
 case of a pentagonal prism such as that shown in FIG. 2, light that
 travels along a normal light path enters the prism through an entrance
 surface 21 and is successively reflected by reflecting surfaces 23 and 23'
 to exit from an exit surface 22. However, the exit surface 22 has a mirror
 surface not included in the normal light path in the neighborhood of the
 entrance surface 21. Therefore, as shown in part (a) of FIG. 4, deflected
 rays 40 may be totally reflected by an exit surface 41 (22) and reflected
 by a first reflecting surface 42 and a second reflecting surface 43 to
 reach a viewer's pupil without being diffused. In this case, a bright
 ghost image having a size equivalent to the indication is undesirably
 observed, giving rise to a problem.
 SUMMARY OF THE INVENTION
 In view of the above-described problems with the prior art, an object of
 the present invention is to provide an indication-within-finder made free
 from ghost light at a minimal cost even in the case of a prism having a
 mirror surface not included in the normal light path in the neighborhood
 of an entrance surface thereof as in a pentagonal prism.
 To attain the above-described object, the present invention provides a
 real-image finder including an objective system having a positive power,
 and an image-inverting system including a prism. The real-image finder
 further includes an ocular system having a positive power. A deflecting
 member is placed near an intermediate image plane formed by the objective
 system to deflect incident light rays with respect to a visual field
 viewing light path. A prism is placed closer to the ocular system than the
 intermediate image plane. The prism has a mirror surface not included in a
 normal light path in the neighborhood of an entrance surface thereof.
 Light rays deflected by the deflecting member and totally reflected by the
 mirror surface are blocked or scattered before reaching the ocular system.
 It is desirable that the deflected light rays should satisfy the following
 condition (1):
 20.degree.&lt;.omega. (1)
 where .omega. is an angle formed between the deflected light rays and the
 mirror surface.
 It is more desirable that the deflected light rays should satisfy the
 following condition (1'):
EQU 20.degree.&lt;.omega.&lt;50.degree. (1')
 It is also desirable that the deflecting member should have a pair of
 refracting surfaces, and the refracting surfaces should satisfy the
 following condition (2):
EQU .omega.'&lt;40.degree. (2)
 where .omega.' is an angle formed between each of the refracting surfaces
 and the mirror surface.
 It is more desirable that the deflecting member should have a pair of
 refracting surfaces, and the refracting surfaces should satisfy the
 following condition (2'):
EQU 10.degree.&lt;.omega.'&lt;40.degree. (2')
 It is also desirable that the deflecting member should have a pair of
 refracting surfaces, and the refracting surfaces should satisfy the
 following condition (3):
EQU 40.degree.&lt;.theta.&lt;100.degree. (3)
 where .theta. is a vertex angle formed between the pair of refracting
 surfaces.
 It is more desirable that the deflecting member should have a pair of
 refracting surfaces, and the refracting surfaces should satisfy the
 following condition (3'):
EQU 50.degree.&lt;.theta.&lt;90.degree. (3')
 In addition, the present invention provides a real-image finder including
 an objective system having a positive power, and an image-inverting system
 including a prism. The real-image finder further includes an ocular system
 having a positive power. A deflecting member is placed near an
 intermediate image plane formed by the objective system to deflect
 incident light rays with respect to a visual field viewing light path. A
 prism is placed closer to the ocular system than the intermediate image
 plane. The prism has a mirror surface not included in a normal light path
 in the neighborhood of an entrance surface thereof. The deflecting member
 has a pair of refracting surfaces. A ridge formed between the pair of
 refracting surfaces is not parallel to the mirror surface.
 In addition, the present invention provides a real-image finder including
 an objective system having a positive power, and an image-inverting system
 including a prism. The real-image finder further includes an ocular system
 having a positive power. A deflecting member is placed near an
 intermediate image plane formed by the objective system to deflect
 incident light rays with respect to a visual field viewing light path. A
 prism is placed closer to the ocular system than the intermediate image
 plane. The prism has a mirror surface not included in a normal light path
 in the neighborhood of an entrance surface thereof. The deflecting member
 has a diffusing surface.
 It is desirable that the deflecting member should be provided on the
 entrance surface of the prism.
 It is desirable that the prism should be a pentagonal prism.
 It is desirable that the prism should be formed by injection molding of a
 plastic material.
 The reasons for adopting the above-described arrangements, together with
 the functions thereof, will be described below.
 If the system is arranged to block or diffuse 80% or more of light rays
 reflected by the mirror surface, which is not included in the normal light
 path, after being deflected by the deflecting member, ghost light gives
 rise to no problem even at a position other than the pupil position
 assumed in design. The ocular system, which extends from the intermediate
 image plane to the finder exit part, can be arranged in a compact form by
 allowing the deflected light rays to impinge at a deep angle on the mirror
 surface, which is not included in the normal light path. Visual field rays
 near the intermediate image plane are approximately telecentric, i.e.
 approximately parallel to the optical axis. Therefore, in the case of a
 finder with a small-sized ocular system, as shown in FIG. 5, if the angle
 .omega. formed between a mirror surface 51 and a light ray 50 deflected by
 a deflecting member 54 is small, the ray 50 is totally reflected by the
 mirror surface 50 and then passes through an ocular system 52 to reach a
 viewer's pupil with a strong intensity without being blocked. Conversely,
 if the angle .omega. formed between a deflected ray 53 and the mirror
 surface 51 is large, it becomes more likely that the ray 53 will not
 satisfy the condition for total reflection at the mirror surface 51. Even
 if the ray 53 is totally reflected, there is a strong probability that the
 reflected ray 53 will be blocked before passing through the ocular system
 52. For the reasons stated above, it is preferable for the deflected light
 rays to satisfy the following condition.
EQU 20.degree.&lt;.omega. (1)
 where .omega. is an angle formed between the deflected light rays and the
 mirror surface.
 If the angle .omega. is not larger than the lower limit of the condition
 (1), the amount of deflection is excessively small, and it becomes more
 likely that ghost light will occur.
 There is also a likelihood that deflected light rays will pass through the
 mirror surface instead of being reflected thereby and exit from the ocular
 lens as stray light. Therefore, it is even more desirable that the
 deflected light rays should satisfy the following condition (1'):
EQU 20.degree.&lt;.omega.&lt;50.degree. (1')
 In a case where the deflecting member is, as shown in FIG. 3, a refracting
 member 31, e.g. a small prism, if the angle formed between each refracting
 surface 32 and a mirror surface 33 is large [see part (a) of FIG. 3], the
 amount of deflection is small. Consequently, a deflected light ray 34
 impinges on the mirror surface 33 at a shallow angle unfavorably.
 Accordingly, it becomes more likely that ghost light will occur as shown
 in part (a) of FIG. 4. Conversely, if the angle formed between each
 refracting surface 32 of the refracting member 31 and the mirror surface
 33 is small [see part (b) of FIG. 3], the amount of deflection is large,
 and the deflected light ray 34 impinges on the mirror surface 33 at a deep
 angle. Accordingly, the possibility of ghost light occurring reduces as
 shown in part (b) of FIG. 4. For the reasons stated above, it is
 preferable that the refracting member serving as a deflecting member
 should satisfy the following condition (2):
EQU .omega.'&lt;40.degree. (2)
 where .omega.' is an angle formed between each refracting surface and the
 mirror surface.
 If the angle .omega.' is not smaller than the upper limit of the condition
 (2), the amount of deflection is excessively small, and it becomes more
 likely that ghost light will occur.
 There is also a likelihood that deflected light rays will pass through the
 mirror surface instead of being reflected thereby and exit from the ocular
 lens as stray light. Therefore, it is even more desirable that the
 refracting member serving as a deflecting member should satisfy the
 following condition (2'):
EQU 10.degree.&lt;.omega.'&lt;40.degree. (2')
 In addition, it is preferable that the refracting member serving as a
 deflecting member should satisfy the following condition (3):
EQU 40.degree.&lt;.theta.&lt;100.degree. (3)
 where .theta. is a vertex angle formed between the pair of refracting
 surfaces.
 If the angle .theta. is not larger than the lower limit of the condition
 (3), as shown in part (c) of FIG. 3, incident light 34 deflected by one
 refracting surface 32' of a pair of refracting surfaces 32' and 32" may be
 totally reflected by the other refracting surface 32" and thus deflected
 again, remaining as a light ray 44 of shallow angle as shown in part (c)
 of FIG. 4. If the angle .theta. is not smaller than the upper limit of the
 condition (3), there may be light rays that undesirably enter the ocular
 system directly without being satisfactorily refracted by the refracting
 member 31. Consequently, displayed indications cannot be completely
 blackened. Thus, it becomes impossible to perform the intended indication
 display.
 In a case where the prism is formed by injection molding of a plastic
 material, it is preferable that the refracting member serving as a
 deflecting member should satisfy the following condition (3'):
EQU 50.degree.&lt;.theta.&lt;90.degree. (3')
 If the angle .theta. is not larger than the lower limit of the condition
 (3'), the refracting member 31 becomes excessively thin. Consequently, it
 becomes difficult to charge the plastic material, and moldability
 degrades. If the angle .theta. is not smaller than the upper limit of the
 condition (3'), there may be light rays that enter the ocular system
 without being satisfactorily refracted by the refracting member 31.
 Even in the case of a prism having a mirror surface not included in the
 normal light path in the neighborhood of an entrance surface thereof, if a
 ridge formed between a pair of refracting surfaces that constitute a
 refracting member serving as a deflecting member is not parallel to the
 mirror surface, no light rays are deflected toward the mirror surface.
 Therefore no ghost light occurs.
 Furthermore, if deflected light rays are diffused by the deflecting member
 itself, even if light rays reach the viewer's pupil, the light intensity
 is weak, and ghost light is inconspicuous. In a case where the refracting
 surfaces are mirror surfaces, even if the deflecting member is arranged as
 stated above, it is still likely that stray light due to light, exclusive
 of visual field light, e.g. light internally reflected by the objective
 lens frame, will reach the viewer's pupil as ghost light. However, if the
 refracting surfaces are formed in the shape of diffusing surfaces, it is
 possible to reduce the quantity of stray light undesirably reaching the
 viewer's pupil.
 Still other objects and advantages of the invention will in part be obvious
 and will in part be apparent from the specification.
 The invention accordingly comprises the features of construction,
 combinations of elements, and arrangement of parts which will be
 exemplified in the construction hereinafter set forth, and the scope of
 the invention will be indicated in the claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Embodiments of the real-image finder according to the present invention
 will be described below.
 As shown in part (a) of FIG. 6, a real-image finder according to a first
 embodiment of the present invention includes, in order from an object side
 thereof, an objective system 61 having a positive refracting power, an
 image-inverting system including a roof prism 62 and a pentagonal prism
 63, and an ocular system 64 having a positive refracting power. The ocular
 system 64 includes an ocular lens 64' and an ocular window 64". An object
 image is formed on an intermediate image plane 65 by the objective system
 61 and the roof prism 62. The object image is viewed with the ocular
 system 64 through the pentagonal prism 63. The pentagonal prism 63 has an
 entrance surface that is convex toward the object side. The position of
 the intermediate image plane 65 is approximately coincident with the
 entrance surface of the pentagonal prism 63. As shown in part (b) of FIG.
 6, which is a sectional view, a deflecting member 67 projecting in a wedge
 shape is provided on the entrance surface of the pentagonal prism 63 to
 display an indication for parallax correction and an indication of an AF
 distance measurement range. The deflecting member 67 has a linear
 configuration extending in a direction normal to the plane of the figure.
 Light rays 68 that do not pass through the deflecting member 67 reach a
 viewer's pupil as visual field viewing light. Light rays 68' that pass
 through the deflecting member 67 are deflected by refracting surfaces 67'
 and 67" and therefore do not reach the viewer's pupil. Accordingly, the
 viewer sees blacked-out indications as shown in part (c) of FIG. 6.
 Reference numeral 69 denotes a parallax correction indication. Reference
 numeral 69' denotes an indication of an AF distance measurement range. In
 this case, there is a possibility that the rays 68' may impinge directly
 on an exit surface 63' and be totally reflected thereby to reach the
 viewer's pupil as ghost light. In this embodiment, however, the angle
 .omega.' between the refracting surface 67' of the deflecting member 67
 and the exit surface 63' is set to satisfy the above-described condition
 (2). Therefore, the totally reflected rays are blocked in the vicinity of
 the ocular lens 64' and do not reach the viewer's pupil. Accordingly,
 ghost light is unlikely to occur.
 A real-image finder according to a second embodiment of the present
 invention is similar to the first embodiment in the arrangement of a part
 thereof that extends from the objective system to the ocular system. The
 second embodiment differs from the first embodiment in that a pentagonal
 prism is arranged as shown in parts (a) and (b) of FIG. 7. More
 specifically, a pentagonal prism 73 in this embodiment has deflecting
 members 77 provided on an entrance surface 71. Each deflecting member 77
 projects in a wedge shape. Each deflecting member 77 has a pair of
 refracting surfaces 77' and 77". A ridge formed between the refracting
 surfaces 77' and 77" is not parallel to an exit surface 72. That is, the
 refracting surfaces 77' and 77" are in a skew relation to the exit surface
 72. Therefore, no rays are deflected toward the exit surface 72, and hence
 no ghost light occurs. With the real-image finder according to this
 embodiment, indications are seen as shown in part (c) of FIG. 7.
 A real-image finder according to a third embodiment of the present
 invention is similar to the first embodiment in the arrangement of a part
 thereof that extends from the objective system to the ocular system. The
 third embodiment differs from the first embodiment in that a deflecting
 member is arranged as shown in FIG. 8. More specifically, a deflecting
 member 87 in this embodiment has refracting surfaces formed from diffusing
 surfaces 81. The deflecting member 87 has a linear configuration extending
 in a direction normal to the plane of the figure. Consequently, deflected
 light rays 88 are diffused by the diffusing surfaces 81. Therefore, even
 if the rays 88 reach the viewer's pupil, the light intensity is weak, and
 ghost light is inconspicuous. In this case, if the prism is a molded part,
 it is only necessary for the surface of a molding die to have diffusing
 surfaces. Accordingly, no extra processing is required, and there is no
 increase in the cost.
 A real-image finder according to a fourth embodiment of the present
 invention is similar to the first embodiment in the arrangement of a part
 thereof that extends from the objective system to the ocular system. The
 fourth embodiment differs from the first embodiment in that a deflecting
 member is arranged as shown in FIG. 9. More specifically, a deflecting
 member 97 in this embodiment has refracting surfaces formed from curved
 surfaces 91. The deflecting member 97 has a linear configuration extending
 in a direction normal to the plane of the figure. Consequently, deflected
 light rays 98 become diffused light. Therefore, advantageous effects
 similar to those in the third embodiment are obtained.
 A real-image finder according to a fifth embodiment of the present
 invention is similar to the first embodiment in the arrangement of the
 portion that extends from the objective system to the ocular system. The
 fifth embodiment differs from the first embodiment in that deflecting
 members are arranged as shown in FIG. 10. More specifically, deflecting
 members 107 in this embodiment have refracting surfaces each formed from a
 conical surface. Consequently, deflected light rays become diffused light.
 Therefore, advantageous effects similar to those in the third embodiment
 are obtained.
 As will be clear from the foregoing description, it is possible according
 to the present invention to provide an indication-within-finder made free
 from ghost light at a minimal cost even in the case of a prism having a
 mirror surface not included in the normal light path in the neighborhood
 of an entrance surface thereof as in a pentagonal prism.