Display device for camera

A display device for a display in a camera. Within a view finder thereof in particular are arranged illuminating light emitting elements to illuminate a display member which is provided with a plurality of photography mode display marks. A segment light emitting element displays a computed value of photography information obtained from photography information computing apparatus.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a display device for displaying photography modes 
and photography information within a view finder of a photographic camera 
and more particularly to a display system which includes a display device 
disposed within a view finder and another display device disposed without 
the view finder. The display lights up or is put out depending on to the 
photography mode selected. 
2. Description of the Prior Art 
Conventional display devices of this kind include devices of the type 
having dot light emitting diodes (hereinafter called dot LED's for short) 
and a display film in combination outside of a view finder visual field to 
make a display by illuminating the display film with the dot LED's in a 
manner shown in FIGS. 1, 2 and 3 of the accompanying drawings. Referring 
to FIG. 1, a light from an object to be photographed, which comes through 
a photo-taking lens 1, is reflected by a turning mirror 2 to be imaged on 
a focus plate 3. The object image thus formed on the focus plate 3 is 
reflected by a penta-Dach prism 4 observable is a view finder field image 
as well known. Reference numeral 6 identifies a Fresnel lens for 
converging and reference numeral 7 identifies a light receiving photo 
sensitive element. They are arranged above an eyepiece 5 to confront the 
exit surface of the penta-Dach prism 4 as a light receiving system for 
light measurement. An information display member A is provided with a 
display film 8 and is below the penta-Dach prism 4 with the display film 8 
opposed to a bottom face 4a of the penta-Dach prism 4. FIG. 2 is an 
enlarged exploded view of the above information display member A. The 
display film 8 is provided with, for example, information display marks 
such as photography mode display marks 8a and 8b and aperture value marks 
8c, 8d, 8e, 8f, etc. Dot LED's 11a, 11b, 11c, 11d, 11e, 11f, etc. are 
secured onto a substrate 12 in positions corresponding respectively to the 
information display marks 8a, 8b, 8c, 8d, 8e, 8f, etc. Between the display 
film 8 and the substrate 12 are interposed, one after another, a diffusing 
tape 9 which has each of the information display marks 8a-8f evenly 
illuminated by the light from the corresponding LED's 11a-11f and a light 
shielding plate 10 which prevents the light of each of the LED's 11a-11f 
from leaking to any of the information display marks 8a-8f that differ 
from the corresponding one. FIG. 3 shows a view finder field. In the 
illustrated example, the information display mark 8e of the display film 
8, which indicates an aperture value "16" of the photo-taking lens 1, is 
illuminated by a light emitted from the corresponding LED 11e via the 
combined arrangement of the light shielding plate 10 and the diffusing 
tape 9, in such a manner that the mark 8e alone appears on one side of the 
photo-taking visual field F as display information I. 
The view finder display device of this type necessitates the provision of 
terminals and lead wires around the display part as power supply terminals 
and lead wires are indispensable to the display part. Therefore, the 
substrate 12 of the LED's 11a-11f includes a large unused area therein. 
In view of this problem, the use of a seven-segment LED for a view finder 
display device in a camera has been proposed. FIG. 4 shows, by way of 
example, the essential parts of that type of view finder display device. 
The illustration of FIG. 4 includes a focus plate 21; a condenser lens 22; 
and a penta-Dach prism 23. An information source 24 is in a lower part 
behind the exit surface of the penta-Dach prism 23. A seven-segment LED 
24b is attached to the surface of a substrate 24a. Numerals and letters 
indicative of shutter time values, aperture values and manual and 
automatic operation modes are formed, one after another, by means of the 
seven-segment LED 24b perpendicular to the paper surface of the drawing. 
Furthermore, the part of the substrate 24a other than the seven-segment 
LED 24b is an unused area 24c. The surface of the substrate 24a is covered 
with a plastic cover 24d. An information light introducing small prism 25 
is disposed between the bottom surface (an incident surface) 23a of the 
penta-Dach prism 23 and the condenser lens 22 in front of the information 
source 24. The small prism 25 has an incident surface 25a, a reflection 
surface 25b and an exit surface 25c. A mask plate 26 is on the bottom 
surface 23a of the penta-Dach prism 23 to define a photo-taking visual 
field and an information display picture plane. 
FIG. 5 shows a view finder visual field obtained by the display device of 
FIG. 4. Photography information 27 appears at a lower part on the lower 
outside of the photo-taking field F. The photography information 27 
consists of shutter time information 27a, aperture value information 27b 
and automatic/manual selection information 27c. In this illustration, for 
example, the shutter time information 27a indicates "1000" (1/1000 sec), 
the aperture value information 27b "5.6" and the selection information 27c 
"M" (for manual). 
The view finder display device of this type is extremely expensive as it 
necessitates the use of the seven-segment LED's 24b for many figures and 
the small prism 25 for light introduction. Compared with the penta prism 
4, 23 generally used in conventional devices, use of a larger penta-prism 
4, 23 is necessary since the lower visual field must be enlarged. 
The present invention is directed to the solution of the above problems of 
conventional display devices. The invention aims to provide a view finder 
display device for a camera in which the display device of the type using 
an optical system as shown in FIG. 1 is modified; and a film display 
member illuminated by the dot LED's 11a-11f is on the same substrate 12 as 
that of a seven-segment LED 24b, so that a device capable of indicating 
many kinds of information 27 can be obtained at reduced size and cost. 
Meanwhile, for driving the LED's 11a-11f, at constant current circuit which 
is shown in FIG. 6 or 7 has been employed. In the circuit shown in FIG. 6, 
a constant voltage of a constant voltage circuit 31 is impressed on the 
non-inversion input terminal of an operational amplifier 32, as well 
known, when voltage is supplied between a power source Vcc and a ground 
GND. Therefore, a negative feedback action brought about by the 
operational amplifier 32 and an NPN transistor 36 causes the potential of 
the inversion input terminal of the operational amplifier 32 to become 
equal to the constant voltage of the constant voltage circuit 31. As a 
result, a constant current flows to a resistor 35. When the current 
amplification rate (hfe) of the NPN transistor 36 is sufficiently high, 
the collector current and the emitter current of the NPN transistor 36 
become equal. This also causes a constant current to flow to an LED 34. 
The LED 34 thus has a constant current flow thereto regardless of the 
voltage between the power source Vcc and the ground GND. Therefore, a 
display within the view finder remains stable. However, the operational 
amplifier 32 includes many transistors and thus has a great number of 
elements included therein, resulting in a complex structural arrangement. 
Furthermore, assuming that four LED's 34 are used for the display, for 
example, in order to equalize the brightness of these LED's 34 by 
individually adjusting currents for them according to their various 
characteristics, a total of four sets of the circuit of FIG. 6 is 
necessary with the exception of the constant voltage circuit 31 (the 
current value is adjusted by means of the resistor 35). The conventional 
circuit arrangement thus results in a great number of elements. Then, an 
attempt to reduce the number of elements has resulted in the circuit shown 
in FIG. 7. In this circuit arrangement, when a voltage is supplied between 
the power source Vcc and the ground GND, a constant voltage of a constant 
voltage circuit 41 is impressed on the base of an NPN transistor 42. The 
emitter of the NPN transistor 42 then produces a voltage which is obtained 
by subtracting a voltage between the base and emitter of the NPN 
transistor 42 from the constant voltage of the constant voltage circuit 
41. A resistor 43, thus, approximately has constant voltages applied to 
the two terminals thereof. As a result, a nearly constant current flows to 
the resistor 43. This constant current also flows to a PNP transistor 44 
which is diode connected. PNP transistors 45 and 46 have their bases 
connected in common with the PNP transistor 44. Therefore, if the 
resistance values of resistors 47 and 48 are zero, the collector currents 
of the PNP transistors 45 and 46 become equal to that of the PNP 
transistor 44. Therefore, it would be possible to adjust the uneven 
characteristics of LED's 49 and 50 by adjusting the value of the resistors 
47 and 48 causing the LED's 49 and 50 to emit a light of even brightness. 
However, the voltages between the collectors and emitters of the PNP 
transistors 45 and 46 vary with the voltage between the power source Vcc 
and the ground GND. Then, the Early effect (base width modulating effect) 
of the transistors causes the collector currents of the PNP transistors 45 
and 46 to change with the power supply voltage (or the voltage between the 
power source Vcc and the ground GND). The camera uses a battery the 
voltage of which decreases with the length of time in service. Therefore, 
variations in the brightness of display LED's present great inconvenience. 
A first object of this invention is to provide a display device which can 
be compactly arranged with a small number of parts for displaying a 
selected photography operation mode and exposure information computed on 
the basis of information on a preset value. 
A second object of this invention is to provide a display device wherein 
shutter time information and aperture value information are computed 
according to the photography operation mode selected; the selected mode 
and the computed information are displayed; and one information display 
can be shifted to another depending on the result of computation. 
A third object of this invention is to provide a display device for display 
photography information for a camera capable of switching from one 
photography operation mode to another, wherein exposure information is 
displayed in a symbolized form when the number of numeral places of 
computed exposure information exceeds the number of places that can be 
displayed. 
A fourth object of this invention is to provide a display device consisting 
of a view finder display device and an external display device which are 
arranged such that the illumination of the view finder display device is 
put out and exposure information is displayed by the external display 
device when an eyepiece shutter is closed. 
These and further objects and features of the invention will become 
apparent from the following detailed description of preferred embodiments 
thereof taken in conjunction with the accompanying drawings. 
SUMMARY OF THE INVENTION 
To attain the first object, in accordance with the invention, the 
photography operation mode display is effected by a mode mark indicative 
of a mode selected in conjunction with an illumination light emitting 
element which illuminates the mode mark. As for the exposure display 
information display, segment light emitting elements make a numerical 
display. The arrangement is such that the photography operation mode and 
the exposure information can be accurately and clearly observable to 
prevent an erroneous photography operation due to erroneous observation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A first embodiment of this invention is shown in FIGS. 8 through 12. FIG. 8 
is an exploded oblique view showing essential parts of the first 
embodiment. The view finder optical system of this example is identical 
with that of the conventional device shown in FIG. 1 and is therefore 
omitted from the illustration of FIG. 8. What is shown in FIG. 8 
corresponds to the information display member A of FIG. 1. 
Referring to FIG. 8, a display film 100 has information display marks 100a, 
100b, 100c and 100d indicative of photography operation modes, etc. 
arranged thereon. Dot LED's 101a, 101b, 101c and 101d are wire bonded to 
the surface of a substrate 102 and respectively oppose the information 
display marks 100a, 100b, 100c and 100d. A shield plate 103 is around the 
dot LED's 101a, 101b, 101c and 101d to ensure that the light of each of 
the LED's 101a, 101b, 101c, and 101d does not leak to any of the 
information display marks 100a, 100b, 100c and 100d other than the 
corresponding mark. A diffusion tape 104 is between the display film 100 
and the shield plate 103 to ensure that the light of the dot LED's 101a, 
101b, 101c and 101d evenly illuminate corresponding display marks 100 a, 
100b, 100c and 100d. An LED 105, which has seven-segments for each of two 
numeral places and one dot monolithically formed therein, is wire bonded 
to the surface of the substrate 102. The above shield plate 103 is 
provided with holes 103a-103e, which are formed in places corresponding to 
the light emitting parts, and also prevents the light of the LED 105 from 
leaking to the above display film 100. For this purpose, the display film 
100 and the diffusion tape 104 avoid the hole 103a. An IC 106 drives the 
LED's 101a-101d and 105 to light up as required. A flat cable 107 is 
provided for connecting the substrate 102 to another circuit of the camera 
(not shown). 
The operation of the embodiment which is arranged as described above 
operates as follows: Referring to FIG. 9 which shows a view finder visual 
field, when a program mode is selected from the selectable photography 
operation modes depending on photographing conditions, for example, the 
LED 101b emits a light to evenly illuminate a corresponding display mark P 
which stands for "program" with the emitted light limited by the shield 
plate 103 and diffused by the diffusion tape 104. The display information 
light, which is thus produced from the display mark 100b, comes from the 
bottom of a penta-Dach prism to be displayed as "P" as display information 
I1 on one side of the photography visual field F via an optical path which 
is similar to that of a photography field light. Furthermore, when an 
aperture value of the photo-taking lens 1 is determined by an electric 
circuit which will be described later herein, is the photographing 
information is determined based on to the photography conditions, for 
example, the seven-segment LED 105 emits a light to make a display "5.6". 
The light from the LED 105 then comes from the bottom surface of the 
penta-Dach prism 4, 23 to also be displayed as "5.6" and as display 
information I2 on the side of the photographing visual field F. 
When a shutter speed priority mode is set by means of an external operation 
member (not shown), the LED 101c lights up to illuminating the display 
mark 101c which is "T". Meanwhile, the brightness of an object to be 
photographed is measured via a light receiving photo-sensitive element. 
Then, an aperture value, which is obtained through computation performed 
by an electric circuit which will be described later, is displayed by the 
seven-segment LED 105. 
An example of an electric circuit required for operating the above display 
device is arranged as described below, referring to the block diagram of 
FIG. 10. 
The block diagram includes a light measuring circuit 106 which 
photo-electrically converts the brightness of an object received through a 
lens, a prism, etc. by means of a photosensitive element such as a silicon 
photo cell (SPC) or the like. An A/D converter 107 repeatedly converts in 
a predetermined cycle the light measurement output voltage of the light 
measuring circuit 106 into a digital pulse number. A pulse code plate 108 
is provided for film sensitivity information (ISO) and produces a pulse 
code corresponding to a film sensitivity value set at an ISO film 
sensitivity dial (not shown). A pulse code plate 109 for information on 
the maximum F-number of the lens produces a pulse code corresponding to 
the maximum F-number of the lens mounted on the camera. A shutter time 
information pulse code plate 110 produces a pulse code corresponding to a 
shutter time value set at a shutter time setting dial (not shown). A 
photography operation mode setting switch 111 is composed of a two-bit 
switch and permits selection of any of photography operation mode 
including manual (M), programed (P) and shutter priority (T) photographing 
modes or the like. An APEX computing circuit 112 digitally computes and 
produces information necessary for the photography mode set by the 
photography mode setting switch 111 by carrying out the computation on the 
basis of the object brightness information from the A/D converter 107 and 
the information values set at the pulse code plates 108, 109 and 110. A 
decoder 113 decodes the two-bit information of the mode setting switch 111 
and selects one of the four-bit output lines that corresponds to the 
selected photography mode. An LED driving circuit 115 lights up display 
dot LED's 114a, 114b, 114c and 114d by supplying a current to them when 
applicable. The display dot LED's 114a, 114b, 114c and 114d respectively 
correspond to the dot LED's 101a, 101b, 101c and 101d shown in FIG. 8. A 
digital memory circuit 116 temporarily stores the output of the APEX 
computing circuit 112 at every predetermined recurrent period. A program 
control circuit 117 allocates, at the time of the programed photographing 
mode, an exposure information value (Ev value) obtained from the APEX 
computing circuit 112 via the digital memory circuit 116 to a shutter time 
information value (Tv) and an aperture information value (Av) in 
accordance with a prescribed program diagram. The outputs of the program 
control circuit 117 are supplied to an Av register 118 and a Tv register 
119. In the shutter time priority photography mode, the shutter time 
information (Tv) from the shutter time information pulse code plate 110 
and the computed exposure information (Ev) produced from the APEX 
computing circuit 112 are supplied directly to the Av register 118 and the 
Tv register 119. The Av register 118 and the Tv register 119 respectively 
store pulses corresponding to the aperture value and shutter speed 
information received from the program control circuit 117. Furthermore, 
they produce overflow outputs when the aperture value and the shutter time 
value are outside the control range such as when an excessively dark 
object is to be photographed. An OR gate 120 produces a high level output 
when either the Av register 118 or the Tv register 119 produces the 
overflow output. Then, the high level output of the OR gate 120 is 
supplied to the LED driving circuit 115. A coincidence circuit 121 
supplies a signal to an aperture control circuit 123 when the digital 
value of an aperture pulse code plate 122 coincides with the value of the 
Av register 118. The aperture pulse code plate 122 produces a pulse signal 
which corresponds to the aperture value of the lens. The aperture control 
circuit 123 controls an aperture control magnet 124 on the basis of the 
signal received from the coincidence circuit 121 when the computed 
aperture value, which is stored at the Av register 118, coincides with the 
actual aperture value of the lens which is the set value of the aperture 
pulse code plate 122. Furthermore, when the manual photography mode is 
selected via the photography mode setting switch 111, a signal from the 
decoder 113 renders the aperture control circuit 123 inoperative, 
permitting thereby a manual adjusting operation on the aperture. 
A release sequence circuit 129 instructs the aperture pulse code plate 122 
to slide and the aperture control circuit 123 to operate when a release 
switch 130 turns on. In addition, the release sequence circuit 129 
performs a sequential control over the various parts of the camera (not 
shown). The release switch 130 operates in response to the second stroke 
on a release button (not shown). The aperture control magnet 124 is 
controlled by the aperture control circuit 123 and coincides the aperture 
value of the lens with the computed aperture value by preventing the 
aperture pulse code plate 122 from sliding. A clock pulse oscillator 131 
produces reference pulses. A frequency divider 132 frequency divides clock 
pulses produced from the clock pulse oscillator 131 into a predetermined 
frequency. A shutter time expanding circuit 133 expands the digital value 
of the Tv register 119 to a shutter time value on the basis of the output 
of the frequency divider 132. A shutter control circuit 134 controls a 
shutter driving magnet 135 based on the output of the shutter time 
expanding circuit 133. The shutter driving magnet 135 controls a shutter 
(not shown). A decoder 136 converts the digital value (a binary value) of 
the Av register 118 into a decimal value. A LED driving circuit 137 lights 
up a seven-segment LED 138 by supplying a current thereto based on the 
output of the decoder 136. The seven-segment LED 138 corresponds to the 
seven-segment LED 105 of FIG. 8 and displays an aperture value. 
The electric circuit which is arranged as described above operates as 
follows: When the shutter button is depressed a first stroke, the power 
source supplies a current to each part of the circuit arrangement. The 
light measuring circuit 106 then produces a voltage corresponding to the 
brightness of the object to be photographed. This voltage is repeatedly 
A/D converted by the A/D converter 107 of FIG. 8 in a predetermined cycle. 
The voltage is thus converted into a pulse number. In other words, as to 
an APEX value, the number of pulses corresponds to a value Bv-Avo. This 
pulse number is respectively computed by the APEX computing circuit 112 
together with the signals Sv and Avo produced from the film sensitivity 
information pulse code plate 108 and the lens' maximum F-number 
information pulse code plate 109. Through this computing operation, an 
exposure value Ev expressed as (Bv-Avo)+Sv+Avo is obtained. In the 
programed photography mode, this value is used to obtain the values Tv and 
Av according to the prescribed program diagram in a manner further 
described later herein. In a shutter priority photography operation, the 
exposure value Ev thus obtained is further computed with the signal Tv of 
the shutter time information pulse code plate 110 (Ev-Tv=Av). Then a pulse 
signal corresponding to the value Av is produced from the APEX computing 
circuit 112. 
The manner in which the above computation is accomplished according to the 
photography mode selected is determined by the photography mode setting 
switch 111. The pulse signal which is produced from the APEX computing 
circuit 112 according to the photography conditions and the photography 
mode is temporarily stored at the digital memory circuit 116. In the 
programed photography mode, this stored value is then used to determine 
the values Av and Tv according to a prescribed program diagram based on 
the stored value. The value signals Av and Tv are respectively supplied to 
the Av and Tv registers 118 and 119. Under the shutter priority 
photography mode, a number of pulses corresponding to the signal Tv 
produced from the shutter time information pulse code plate 110 is 
supplied to the Tv register 119 via the program control circuit 117. 
Meanwhile, a number of pulses corresponding to the value Av obtained by 
computing the object brightness, film sensitivity and shutter time is 
supplied to the various elements, one after another, in order, including 
the APEX computing circuit 112, the digital memory circuit 116, the 
program control circuit 117 and the Av register 118. If the values of the 
Av and Tv registers 118 and 119 are outside the control ranges of the 
shutter time and the aperture value, either one or both of the registers 
118 and 119 produce overflow outputs. In that event, the OR gate 120, 
which serves as the detecting means, to produces a high level outputs. 
The dot LED's 114a, 114b, 114c and 114d perform a display operation as 
follows: With one of the photography modes selected by means of the 
photography mode setting switch 111, the decoder 113 produces a signal 
from a selected output line. In response to this signal, the LED driving 
circuit 115 operates, lighting up one of the dot LED's 114a-114c. When the 
programed photography mode is selected, for example, the LED 114b lights 
up. If the selected mode is the manual photography mode, the LED 114a 
lights up. If the shutter time or aperture value is outside the control 
range as mentioned above, the high level signal from the OR gate 120 is 
impressed on the LED driving circuit 115. In that instance, the LED 
driving circuit 115 operates, lighting up the LED 114d giving a warning in 
addition to one of the other LED's 114a, 114b ad 114c. Further details of 
the operation of the LED driving circuit 115 will be described later 
herein. 
The aperture control operation of the embodiment is as follows: When the 
release switch 130 turns on in response to the second depression stroke on 
the above release button, the release sequence circuit 129 instructs the 
aperture control circuit 123 to operate. In response to the instruction, 
power is supplied to the aperture control magnet 124. The aperture of the 
lens instantly shifts from full open toward a position with a smaller 
opening. In association with this aperture shift, the number of pulses of 
the aperture pulse code plate 122 changes. Since the pulse number of the 
aperture pulse code plate 122 corresponds to the aperture value of the 
lens, when the pulse number coincides with that of the Av register 118, 
the coincidence circuit 121 detects this coincidence and sends a signal to 
the aperture control circuit 123, cutting off the power to the aperture 
control magnet 124. With the power to the aperture control magnet 124 thus 
cut off, the lens aperture shift stops and the lens is fixed at that 
aperture value. Furthermore, the controlled aperture value obtained under 
the programed photography mode or the shutter priority photography mdoe 
and the aperture value of the lens to be set under the manual photography 
mode are displayed as follows: The binary code of the Av register 118 is 
converted into a decimal code by the decoder 136. The decimal code thus 
obtained is then displayed via the LED driving circuit 137 at the 
seven-segment LED 138. 
Control over the shutter time is as follows: The shutter time expanding 
circuit 133 expands the pulse number of the Tv register 119 based on the 
frequency divider 132 output obtained by frequency dividing the reference 
clock pulses produced from the clock pulse oscillator 131. The expanded 
signal thus obtained is supplied to the shutter control circuit 134 
thereby driving the shutter driving magnet 135. The shutter driving magnet 
135 in turn controls the shutter (not shown). 
FIG. 11 shows, by way of example, the details of the above LED driving 
circuit 115. Referring to FIG. 11, a constant voltage circuit 140 is 
connected to the power source Vcc to producing a constant voltage. An 
operational amplifier 141 has the constant voltage of the constant voltage 
circuit 140 impressed on the inversion input terminal. A resistor 142 has 
one terminal thereof connected to the power source Vcc and the other to 
the non-inversion input terminal of the operational amplifier 141. 
Reference numerals 143, 144, 145 and 146 also identify resistors. Each of 
these resistors 143, 144, 145 and 146 has one terminal thereof connected 
to the output terminal of the operational amplifier 141. The other 
terminals of the resistors 143, 144, 145 and 146 are respectively 
connected to the bases of NPN transistors 147, 148, 149 and 150. The 
collectors of these NPN transistors 147, 148, 149, and 150 are all 
connected to the other terminal of the resistor 142. Meanwhile, the 
emitters of these NPN transistors 147, 148, 149 and 150 are connected to 
the anode terminals of the dot LED's 114a, 114b, 114c and 114d. Other NPN 
transistor 152, 153, 154 and 155 have their emitters connected to the 
ground GND and their collectors respectively connected to the bases of the 
NPN transistors 147, 148, 149 and 150. The bases of the NPN transistors 
152, 153 and 154 are connected to the decoder 113. A NAND gate 156 has its 
input terminals connected to the OR gate 120 and an inverter 157 and its 
output terminal is connected to the base of the NPN transistor 155. The 
inverter 157 inverts the output of a pulse oscillator 158 which produces 
pulses in a predetermined cycle. 
The LED driving circuit 115 which is arranged as described above, operates 
in the following manner: When a power supply switch (not shown) is 
depressed, a DC voltage is impressed between the power source Vcc and the 
ground GND. The constant voltage circuit 140 then produces a constant 
voltage, which is impressed on the inversion input terminal of the 
operational amplifier 141. The operational amplifier 141 has negative 
feedback applied thereto in such a way as to coincide the voltage of the 
non-inversion input terminal with that of the inversion input terminal. 
Then, the terminal of the resistor 142, which is not connected to the 
power source Vcc, has the same voltage as that of the output of the 
constant voltage circuit 140. In other words, a constant voltage, which is 
the difference between the voltage of the power source Vcc and the output 
voltage of the constant voltage circuit 140, is impressed on the two 
terminals of the resistor 142. As a result, a constant given current flows 
to the resistor 142. 
Assuming that the NPN transistor 152 is non-conductive with its base 
potential at a zero level while the NPN transistors 153, 154 and 155 are 
all conductive with their base potential at a high level, the NPN 
transistors 148, 149 and 150 become non-conductive with no base currents 
supplied from their resistors 144, 145 and 146 as their base potentials 
are at a low level. Each of these NPN transistors 148, 149 and 150 has no 
current flow between the collector and emitter. The NPN transistor 147 
solely becomes conductive. A constant current, which flows to the resistor 
142, thus flows between the collector and the emitter of the NPN 
transistor 147. Accordingly, a constant current also flows to the LED 
114a, which is connected to the emitter of the NPN transistor 147, 
lighting up the LED 114a. Likewise, a constant current flows to the LED 
114b to light it up if the base potentials of the NPN transistors 152, 154 
and 155 are at a high level and if the base potential of the NPN 
transistor 153 alone is at a low level. The operational amplifier thus 
causes a constant current to flow only to one of the plurality of LED's 
114a, 114b, 114c. 
The lighting up conditions of these LED's 114a, 114b, 114c are as follows: 
The level of only one of the outputs of the decoder 113 becomes low 
depending on the selected photography mode. The change to the low level 
only takes place when the output level of the pulse oscillator 158 becomes 
high. In other words, one of the LED's 114a, 114b and 114c intermittently 
lights up according to the time it takes for the pulse oscillator 158 
output level to become high. Furthermore, as mentioned in the description 
of the operation of the electric circuit shown in FIG. 10, when either the 
shutter time or the aperture value is outside of the control range, i.e. 
in the event of a warning, the output level of the OR gate 120 becomes 
high. In that event, however, the output level of the NAND gate 156 
becomes low only when the output level of the pulse oscillator 158 is low, 
causing a constant current to flow to the LED 114d. Accordingly, the LED 
114d does not light up even at the warning time if any one of the LED's 
114a, 114b and 114c is lit. The LED 114d lights up in the event of a 
warning only when none of the LED's 114a and 114c are lit. If the 
recurrent output cycle of the pulse oscillator 158 is sufficiently short, 
the LED 114d and one of the LED's 114a, 114b and 114c appear to be 
simultaneously lit up because of the eye after image effect. 
FIG. 12 is a circuit diagram showing the details of another example of the 
LED driving circuit 115. In this situation, a constant voltage circuit 160 
is connected between the power source Vcc and the ground GND and produces 
a constant voltage. A resistor 161 has its one terminal grounded. An NPN 
transistor 162 has the constant voltage of the constant voltage circuit 
160 impressed on its base and has the other terminal of the resistor 161, 
which is not grounded, connected to its emitter. A PNP transistor 163 has 
its base and collector interconnected and is also connected to the 
collector of the above NPN transistor 162. A PNP transistor 164 has its 
emitter connected to the power source Vcc and its collector is connected 
to the emitter of the above PNP transistor 163. Each of the other PNP 
transistors 165, 166, 167 and 168 has its base is and collector 
interconnected and its base is connected in common with the PNP base of 
the transistor 164. Each variable resistor 169, 170, 171 and 172 has one 
terminal thereof connected to the emitter of one of the corresponding PNP 
transistors 165, 166, 167 and 168 while the other terminal thereof is 
connected to the power source Vcc. PNP transistors 173, 174, 175 and 176 
have their bases connected in common with the base of the PNP transistor 
163 and their emitters are respectively connected to the collectors of the 
PNP transistors 165, 166, 167 and 168 while their collectors are 
respectively connected to the anodes of the LED's 114a, 114b, 114c and 
114d. NPN transistors 177, 178, 179 and 180 have their emitters grounded 
and their collectors connected respectively to the collectors of the PNP 
transistors 173, 174, 175 and 176. The bases of the NPN transistors 177, 
178 and 179 are connected to the decoder 113. However, the base of the NPN 
transistor 180 is connected to the output terminal of an inverter 181. The 
input terminal of the inverter 181 is connected to the output terminal of 
the OR gate 120. 
With the LED driving circuit 115 arranged as described above, it operates 
in the following manner: When a power supply switch (not shown) turns on, 
a DC voltage is impressed between the power source Vcc and the ground GND. 
The constant voltage circuit 160 produces a constant voltage. The constant 
voltage is impressed on the base of the NPN transistor 162. Assuming that 
a voltage between the base and the emitter of the NPN transistor 162 is 
nearly constant, a constant voltage is impressed on the two terminals of 
the resistor 161. A constant current then flows to the resistor 161 and a 
constant current thus flows between the collector and the emitter of the 
NPN transistor 162. This constant current also flows to the PNP 
transistors 163 and 164. Then, the voltage between the base and the 
emitter of each of the PNP transistors 163 and 164 corresponds to the 
constant current flowing to the collector of the NPN transistor 162. Since 
the bases of the PNP transistors 164, 165, 166, 167 and 168 are connected 
in common, each has the same voltage between the power source Vcc and the 
base. Furthermore, since the PNP transistors 165, 166, 167 and 168 have 
the variable resistors 169, 170, 171 and 172 connected to their emitters, 
a constant current flows between the collector and the emitter of each of 
these PNP transistors 165, 166, 167 and 168 based on the resistance value 
of the corresponding variable resistor. For example, assuming that the 
collector currents of the PNP transistors 164 and 165 are I1 and I2 and 
the resistance value of the variable resistor 169 is R, the following 
relation is obtained: 
##EQU1## 
Therefore, the value of I2 obtainable from 
##EQU2## 
is determined by I and R. I1=I2 if R=0. 
The collector currents of the transistors 165, 166, 167 and 168 are 
respectively supplied via the transistors 173, 174, 175 and 176 to the 
LED's 114a, 114b, 114c and 114d if the transistors 177, 178, 179 and 180 
are non-conductive. 
Having selected the photography mode, when the output line of the decoder 
113 is operating with the bases of the transistors 178 and 179 at a high 
level and those of the transistorr 177 solely at a low level, a constant 
current from the transistor 173 flows to the LED 114a lighting it up. 
Meanwhile, the constant currents from the transistors 174 and 175 flow to 
the transistors 178 and 179 and do not light up the LED's 114b and 114c. 
In the event of a warning, the OR gate 120 output level becomes high in the 
same manner as in the embodiment shown in FIG. 11. Accordingly, the 
inverter 181 output level becomes low to rendering the transistor 180 
non-conductive. Then, a constant current produced from the transistor 168, 
based on the resistance value of the variable resistor 172, flows via the 
transistor 176 to the LED 114d lighting it up. 
The reason for arranging the current, which is the same as the collector 
current of the transistor 164 to be supplied to the LED's 114a, 114b, 
114c, and 114d by using the variable resistors 169, 170, 171 and 172, lies 
in that: Unevenness in the characteristics of the LED's 114a, 114b, 114c, 
and 114d results in various quantities of light emitted from these LED's 
114a, 114b, 114c, and 114d even when they receive the same current. 
Therefore, such variations of the LED's 114a, 114b, 114c, and 114d are 
thus absorbed by variations of the current. 
Variations in the currents flowing to the LED's 114a, 114b, 114c, and 114d 
in relation to variations in the voltage between the power source Vcc and 
the ground GND are as follows: The constant current which is determined by 
the constant voltage circuit 160, the resistor 161 and the transistor 162 
flows via the transistor 163 to the transistor 164. The voltage between 
the base and emitter of the transistor 164 corresponding to this constant 
current is changed by a voltage between the collector and the emitter due 
to the Early effect (or a base width modulation effect). Meanwhile, 
however, the collector voltage of the transistor 164 is kept nearly 
constant by the emitter of the transistor 163 (the emitter voltage of the 
transistor 163 is determined by the base voltage and the base voltage 
which is the same as those of the transistors 173, 174, 175 and 176 and is 
determined by the collector voltage, i.e. the base voltage of the 
transistor 164). Therefore, the voltage between the base and the emitter 
of the transistor 164 becomes almost unvarying for the above constant 
current quantity and is not relative to the power source voltage. 
Therefore, the transistors 165, 166, 167 and 168, which are diode 
connected, also have constant currents flowing thereto regardless of the 
power source voltage. The currents from the transistors 165, 166, 167 and 
168 are supplied via the transistors 173, 174, 175 and 176 to the LED's 
114a, 114b, 114c and 114d as constant currents regardless of the power 
source voltage if their DC current amplification rate is sufficiently 
high. 
In accordance with the invention as has been described in the foregoing, a 
compact display device can be prepared at a low cost with the display film 
8, which is to be illuminated by dot LED's 11a-11f, on the same substrate 
12 as the seven-segment LED 24b and with many kinds of information 
displayed within a view finder by selectively using these LED's 11a-11f 
according to applicable photography information. 
FIGS. 13 to 23 show a further embodiment of the invention. The feature of 
the embodiment is as follows: In an automatic exposure control camera 
having an external display arrangement for displaying an exposure 
information setting value, etc. and a view finder display arrangement for 
displaying a computed exposure value, etc., there is provided a display 
arrangement which cancels the exposure information setting value of the 
external display device. It also allows the computed exposure value to be 
displayed in a photography operation mode in which an actual stopped down 
aperture has priority. Another display arrangement extinguishes the view 
finder display and also cancels the exposure information setting value of 
the external display device when the eyepiece shutter of the camera is 
closed. 
FIG. 13 is an oblique view showing the appearance of a single-lens reflex 
camera excluding a lens barrel thereof. Referring to FIG. 13, a film 
winding lever 201 and a film rewinding knob 202 are disposed on the upper 
opposite ends of the camera body. On the upper surface of the camera body 
on the side of the above film winding lever 201 are provided a shutter 
release button 203, operation buttons 204 and 204' and a display window 
205, while a safety button 206 is also provided on the upper surface of 
the camera body on the side of the rewinding knob 202. Reference numeral 
207 identifies a knob for shifting an exposure information setting value. 
With a preparation button 208 pushed, which is provided as a safety 
device, the setting value can be shifted from one value to another by 
operating the shift knob 207. The above operation button 204 is provided 
for selection of a photography mode. When this operation button 204 is 
depressed while also depressing the safety button 206, the marks for 
various photography modes appear and change, from one to another, with a 
time lapse. These marks of photography modes an observable through the 
display window 205. An other operation button 204' is for setting the film 
sensitivity value. When the operation button 204' is depressed while 
pushing the safety button 206, marks for various film sensitivity values 
change, from one to another, as the time elapses. This is also observable 
through the display window 205. The above shift knob 207 is provided for 
setting exposure information which has priority over others. With the 
preparation button 208 pushed, when the shift knob 207 slides, marks for 
the setting value of the exposure information change, from one to another, 
with time and this change is also observable through the display window 
205. In the shutter priority mode or the manual photography mode, the 
shutter speed or time can be set in this manner. In the aperture priority 
mode, a desired aperture value can be set. However, setting cannot be 
accomplished by means of this knob 207 in the event of the programed 
photography mode and the actual stopped down aperture priority mode. 
Furthermore, a reference numeral 209 identifies a stopping down button. 
FIG. 14 shows a pattern displayed within the display window 205. The 
pattern is formed by means of an electro-optical element such as a liquid 
crystal. The drawing shows it totally lit up. Actually, however, the 
display varies with the selected photography mode and the condition of the 
camera. In other words, the photography modes to be displayed include the 
shutter priority mode which is denoted by "Tv", the aperture priority mode 
which is denoted by "Av", the manual photography mode which is denoted by 
"M" and the stopped-down actual aperture priority mode "SD". The shutter 
time under the shutter priority mode and the aperture value under the 
aperture priority mode are denoted by the numeral portion "18.80" of the 
display pattern. Furthermore, when the film sensitivity value is set, the 
film sensitivity value is also displayed at the above numeral portion with 
a mark "ISO" or "ASA". 
Meanwhile, the computed exposure value is as will displayed within the view 
finder in a manner as will described later. 
FIG. 15 is a schematic illustration of the optical system of the camera 
based on the embodiment of the invention. FIG. 16 is an enlarged exploded 
view showing the details of the information display member 218 shown in 
FIG. 15. 
The arrangement of FIGS. 15 and 16 is identical to those shown in FIGS. 1 
and 8 and thus requires no further description. 
The display operation for display within the view finder of the embodiment, 
which is arranged as described above, is as follows: Among the selectable 
photography operation modes, when the shutter priority mode is selected, 
for example, an LED 222b lights up. The light of the LED 222b is limited 
by a shield plate 224 and is diffused by a diffusion tape 225. The 
diffused light evenly illuminates a corresponding display mark 221b of a 
display film 221 which is "T" in this instance. The display information 
light from the display mark 221b enters a penta-Dach prism 214 from its 
bottom 214a and is displayed, via the same optical path as a photographing 
field light, on one side of the photographing field F of the view finder, 
as display information I1 the letter "T", as shown in FIG. 17. This 
informs the photographer that the camera is in the shutter priority mode. 
Furthermore, among photography information values that are to be determined 
based on photographing conditions, an aperture value of the photo-taking 
lens 1, for example, is determined by an electric circuit which will be 
described later. This aperture value is displayed by means of the 
seven-segment pattern of an LED 226 with light emission, for example, as 
"5.6". Then, in the same manner as described above, the light of the LED 
226 enters the penta-Dach prism 214 from the bottom surface 214a. The 
light is then displayed as display information I2 which in this instance 
is "5.6" below the above display information I1 on the same side of the 
photography field F, as shown in FIG. 17. 
When the aperture priority mode is selected, an LED 222c lights up. The 
light of the LED 222c evenly illuminates a display mark 221c of the 
display film 221 which is "A" this time and the letter "A" is displayed 
within the view finder informing the photographer of the selection of the 
aperture priority mode. The brightness of an object to be photographed is 
measured by a light receiving photo-sensitive element 217. A shutter time 
value is computed by an electric circuit which will be described later. 
The computed shutter time value is displayed by means of the four place 
pattern of the LED 226. This computed shutter time value displayed under 
the aperture priority mode is generally one of the numerals shown in FIG. 
19, wherein the numerals in the left column represent shutter time values 
below 1 sec while those in the right column represent time values above 1 
sec. Therefore, the display pattern of the LED 226 has each of the highest 
place "1" and the lowest place "0" formed by one-segment. Furthermore, in 
forming the LED 226, it is possible to make the brightness of segments 
uniform by equalizing the current density of the segments. Furthermore, in 
order to provide uniformity the appearance of the places of "1" and "0" 
with that of other places, each may be divided into a plurality of 
segments instead of one, as shown in the pattern of FIG. 20. 
In the camera having an external and internal display arrangement mentioned 
in the foregoing, when the stopping-down button 209 is pushed, an 
automatic stop lever (not shown) operates stopping down the lens aperture. 
Then, concurrently, the camera is shifted to the stopped-down actual 
aperture priority mode. In this mode, it is only the part "SD" that lights 
up among others within the external display pattern shown in FIG. 14. 
Meanwhile, all the mode displays within the view finder are put out. 
Under this condition, when the shutter release button 203 is depressed a 
first stroke, the light measuring circuit operates. Then, a computed 
shutter time value for the actual aperture is displayed within the view 
finder by the LED 226 of the view finder display arrangement 218. At the 
same time, the computed shutter time value is displayed by using the 
four-place display part within the pattern of the external display 
arrangement of FIG. 14. In the stopped-down actual aperture priority mode, 
the eyepiece is closed by means of an eyepiece shutter 219 or the like to 
lessen light measurement error due to view finder reverse incident light 
coming via the eyepiece. In other words, although no view finder display 
is observable in this case, this display by the external display 
arrangement permits the photographer to observe the computed shutter time 
value through the display window 205. 
FIG. 21 shows, by way of example, an electric circuit required for 
operating the display arrangement 218 described. Referring to FIG. 21, a 
light measuring circuit 230 photo-electrically converts the object 
brightness coming through the lens, the prism 214, etc. by means of a 
light receiving photo-sensitive element 217 such as SPC (silicon 
photo-cell) or the like. An A/D converter 231 repeatedly converts a 
photo-metric output voltage of the light measuring circuit 230 into a 
digital pulse number in a predetermined cycle. A film sensitivity (ISO) 
setting circuit 232 produces a pulse code corresponding to a film 
sensitivity value set by operating the safety button 206 and the operation 
button 204'. With the safety button 206 depressed, a safety switch 232a is 
closed. Then, with the operation button 204' depressed, a film sensitivity 
setting switch 232b is closed, rendering the film sensitivity setting 
circuit 232 operative. More specifically, the setting circuit 232 consists 
of a one-shot circuit, a timer circuit, a counter, etc. With the safety 
switch 232a closed, the film sensitivity setting switch 232b is shifted 
from open state to closed. Then, the one-shot circuit produces one-shot 
pulses. The counter counts the one-shot pulses. The film sensitivity value 
is set based on the pulse count number. If the film sensitivity setting 
switch 232b is kept closed, the timer circuit produces pulses at 
predetermined time intervals and then the counter also counts the number 
of pulses produced from the timer circuit besides the above one-shot 
pulses. Therefore, a film sensitivity value can also be set by opening the 
film sensitivity setting switch 232b when the count value of the pulses 
from the timer circuit reaches the desired film sensitivity value. A lens 
maximum opening F-number information pulse code plate 233 produces a pulse 
code corresponding to the maximum F-number of the lens to be mounted on 
the camera. A shutter time information setting circuit 234 produces a 
pulse code corresponding to a shutter time value set based on a length of 
time during which an information setting switch 235 is kept closed by an 
operation performed on the shift knob 207 of FIG. 13. An aperture 
information setting circuit 236 produces a pulse code corresponding to an 
aperture value likewise set based on a length of time during which the 
information setting switch 235 remains closed. A safety switch 237a is 
interlocked with the above safety switch 232a and closes when the safety 
button 206 is depressed. A photography mode setting switch 237b closes 
when the operation button 204 of FIG. 13 is pushed. An APEX computation 
circuit 238 performs digital computation and produces information 
necessary for the photography mode selected by the photography mode 
setting switch 237b with the digital computation being performed on the 
basis of information on the object brightness obtained respectively from 
the A/D converter 231 and setting information values produced from the 
film sensitivity setting circuit 232, the maximum F-number information 
pulse code plate 233, the shutter time information setting circuit 234 and 
the aperture information setting circuit 236. A photography mode setting 
circuit 239 selects one of its output lines corresponding to one of the 
selectable photography modes including the shutter priority mode (Tv), the 
aperture priority mode (Av) and the manual mode (M) and make the level of 
the selected output line high. This photography mode setting circuit 239 
comprises a one-shot circuit, a timer circuit, a counter, a decoder, etc. 
When the photography mode setting switch 237b is shifted from open to 
closed with the above safety switch 237a closed, the one-shot circuit 
produces one-shot pulses. The one-shot pulses are counted by the counter. 
The count value is decoded by the decoder. Then, one of the output lines 
of the decoder is selected and the level of the selected output line 
becomes high. In other words, the desired photography mode can be selected 
by repeatedly opening and closing the photography mode setting switch 
237b. Furthermore, if the photography mode setting switch 237b is kept 
closed, the timer circuit produces pulses at predetermined time intervals 
and then the counter also counts the number of pulses thus produced from 
the timer circuit along with the number of one-shot pulses. Therefore, the 
photography mode can also be set by opening the setting switch 237b when 
the desired photography mode is set while the photography mode setting 
switch 237b is closed. A LED driving circuit 241 causes the display dot 
LED's 240a, 240b, 240c and 240d to light up by supplying an applicable 
current to each of them. When a low level input is impressed on the reset 
terminal R of the LED driving circuit 241, it stops operating and none of 
the display LED's 240a, 240b, 240c and 240d light up. These display LED's 
240a, 240b, 240c and 240d respectively correspond to the LED's 222a, 222b, 
222c and 222d. A digital memory circuit 242 temporarily stores the output 
of the APEX computation circuit 238 at predetermined intervals. A data 
selector 243 supplies the information (or computed value) produced from 
the APEX computation circuit 238 via the digital memory circuit 242 and 
the shutter time information set by the shutter time information setting 
circuit 234 or the aperture value information set by the aperture 
information setting circuit 236 to an Av register 244 and a Tv register 
245 based on the photography mode. For example, under the shutter priority 
photography mode, the shutter time information (Tv) from the shutter time 
information setting circuit 234 and the computed information (Ev) of the 
APEX computation circuit 238 are respectively supplied to the Av register 
244 and the Tv register 245. The Av register 244 and the Tv register 245 
then store pulses corresponding to the aperture value information and the 
shutter time information from the data selector 243. They produce overflow 
outputs when the aperture value and the shutter time value deviate from a 
control range when the object to be photographed has a low brightness. 
When either the Av register 244 or the Tv register 245 produces an 
overflow output, an OR gate 246 produces a high level signal and supplies 
it to the LED driving circuit 241. A coincidence circuit 247 gives a 
signal to an aperture control circuit 249 when the content of the Av 
register 244 coincides with the digital value of an aperture pulse code 
plate 248. The aperture pulse code plate 248 produces pulses corresponding 
to the lens aperture value. The aperture control circuit 249 controls an 
aperture control magnet 250 on the basis of a signal produced from the 
coincidence circuit 247 when the computed aperture value, i.e. the content 
of the Av register 244 coincides with the actual aperture value of the 
lens, i.e. the content of the aperture pulse code plate 248. In response 
to the above control, the aperture control magnet 250 stops the siding 
movement of the aperture pulse code plate 248 causing the aperture value 
of the lens to coincide with the computed aperture value. Furthermore, 
when the manual photographing mode is selected by means of the photography 
mode setting switch 237b, a signal is produced from the photography mode 
setting circuit 239, rendering the aperture control circuit 249 
inoperative permitting manual aperture adjustment. A release sequence 
circuit 251 instructs the aperture pulse code plate 248 to slide and the 
aperture control circuit 249 to operate when a release switch 252 is 
closed. In addition, the release sequence circuit 251 performs sequential 
control over various parts of the camera (not shown). The release switch 
252 operates in response to the second depression stroke on the shutter 
release button (not shown). A clock pulse oscillator 253 produces 
reference pulses. A frequency divider 254 frequency divides clock pulses 
produced from the clock pulse oscillator 253. A shutter time expansion 
circuit 255 expands the digital value of the Tv register 245 into a 
shutter time value on the basis of the frequency divider 254 output. A 
shutter control circuit 256 controls a shutter driving magnet 257 based on 
the output of the shutter time expansion circuit 255. The shutter driving 
magnet 257 controls a shutter (not shown). Decoders 258a and 258b convert 
the digital values (binary) of the Av register 244 and the Tv register 245 
into segment display codes for a LED 260 and a liquid crystal 261' 
provided for external display. A LED driving circuit 259 is arranged to 
supply a current to the LED 260 lighting up the LED 260 making a display 
on the basis of the outputs of the decoders 258a and 258b. The reset 
terminal R of the LED driving circuit 259 is connected to a switch 263. 
The LED driving circuit 259 stops operating and no display is made by the 
LED 260 when the switch 264 closes, impressing a low level input on the 
terminal R of the circuit 259. The LED 260 corresponds to the LED 226 
shown in FIG. 16 and displays an aperture value and a shutter time value. 
An external display arrangement 261 is composed of a liquid crystal or the 
like and arranged displays a photography mode, a shutter time value, and 
an aperture value as shown in FIG. 14. A portion 261' of the external 
display displays the shutter time value and the aperture value and is 
composed of the liquid crystal consisting of the same segments as in the 
LED 260. A stop-down switch 262 has one terminal thereof connected to the 
terminal R of the LED driving circuit 241, while the other terminal is 
grounded. The switch 262 closes in response to depressing the stop-down 
button 209 shown in FIG. 13. Another switch 263, which is mentioned in the 
foregoing, corresponds to the switch 220 of FIG. 15 and closes when the 
eyepiece shutter 219 is closed. AND gates 264, 265 and 266 have their 
output terminals respectively connected to the electrodes of the display 
parts "M", "AV" and "Tv" of the external display arrangement 261, their 
common input terminals to the switch 262 and their other input terminals 
respectively to the terminals M, Av and Tv of the photography mode setting 
circuit 239. An inverter 267 has its output terminal connected to the 
electrode of "SD" of the external display device 261. An OR gate 268 has 
its output terminal connected to the electrode of the liquid crystal 261'. 
Arranged are OR gates 269, 277 and 281; AND gates 270, 273, 274, 275, 276, 
279, 280 and 282; and inverters 271, 272 and 278. 
The decoders 258a and 258b are for displays by the LED 260 and the liquid 
crystal 261' and are, therefore, provided with the same number of output 
lines as the number of segments of the LED 260 and the liquid crystal 
261', although the block diagram of FIG. 21 gives a simplified 
illustration of this arrangement. Actually, therefore, the AND gates 273, 
274, 275 and 276 are connected to the decoders 258a and 258b, the OR gates 
277 and 281 are connected to the output terminals of the decoders 258a and 
258b and the AND gates 279 and 280 are also connected to the output 
terminals and in the same numbers as the number of segments of the LED 260 
and those of the liquid crystal 261'. 
The electric circuit arranged as described above operates as follows: The 
first depression stroke of on the release button 203 shown in FIG. 20 
closes a power supply switch (not shown). A current is supplied from the 
power source to each of the applicable parts. The light measuring circuit 
230 produces a voltage corresponding to the brightness of the object to be 
photographed. The voltage is repeatedly A/D converted in a predetermined 
cycle by the A/D converter 231. The voltage is thus converted into a pulse 
number. In other words, for an APEX value, a pulse number corresponding to 
Bv-Avo is produced. This pulse number is computed by the APEX computation 
circuit 238 with a signal Sv produced from the film sensitivity setting 
circuit 232 and a signal Avo produced from the maximum F-number 
information pulse code plate 233. Then, a value (Bv-Avo)+Sv+Avo is 
obtained as a value Ev. The value Ev thus obtained is further computed 
with a signal Tv produced from the shutter time information setting 
circuit 234 or a signal Av from the aperture pulse code plate 248 based on 
the photography mode. Under the shutter priority mode, for example, the 
value Ev is computed with the signal Tv of the shutter time information 
setting circuit 234 (Ev-Tv=Av) and a pulse number corresponding to a 
computed value Av thus obtained is produced from the APEX computation 
circuit 238. The computation content based on the photography mode is 
determined by the safety switch 237a and the photography mode setting 
switch 237b. The pulse number produced from the APEX computation circuit 
238 based on photography conditions and the photography mode is 
temporarily stored at the digital memory circuit 242. The stored value is 
transferred to the data selector 243. Under the shutter priority mode, for 
example, a pulse number corresponding to the signal Tv from the shutter 
time information setting circuit 234 is supplied via the data selector 243 
to the Tv register. In the meantime, a pulse number corresponding to a 
computed aperture value Av computed from the object brightness, film 
sensitivity and shutter time is transferred as follows: APEX computation 
circuit 238.fwdarw.digital memory circuit 242.fwdarw.data selector 
243.fwdarw.Av register 244. When these values received by the Av and Tv 
registers 244 and 245 are outside an aperture value and shutter time 
control range, either one of or both of the registers registers 244 and 
245 produce overflow outputs, producing a sign output level are at the OR 
gate 246. 
The display operation of the dot LED's 240a, 240b, 240c and 240d is as 
follows: With a photography mode set by means of the safety switch 237a, 
the photography mode setting switch 237b and the photographing mode 
setting circuit 239, one of the output lines Tv, Av and M of the 
photography mode setting circuit 239 is selected based on the set 
photography mode. A high level signal is at the selected output line. This 
signal causes the LED driving circuit 241 to operate lighting up the 
applicable dot LED 240a, 240b, 240c or 240d. If the shutter priority 
photography mode is selected, for example, the LED 240b lights up. The LED 
240c lights up when the aperture priority photography mode is selected. 
Furthermore, in the event of a shutter time value or an aperture value 
deviating from the control range as mentioned above, the high level signal 
from the OR gate 246 is impressed on the LED driving circuit 241, lighting 
up the LED 240d giving a warning in addition to the lighting up action of 
one of the other LED's 240a, 240b and 240c. The detailed circuit 
arrangement of the LED driving circuit 241 is similar to the circuits 
shown in FIGS. 11 and 12. 
An an aperture control operation is as follows: The release switch 203 
closes in response to the second depression stroke on the release button 
203. Then, the release sequence circuit 251 instructs the aperture control 
circuit 249 to operate. In accordance with this instruction, power is 
supplied to the aperture control magnet 250. The aperture of the lens then 
shifts from full open toward the smallest opening. The aperture pulse code 
plate 248 pulse number then varies corresponding to the the aperture 
shift. Since the aperture pulse code plate 248 corresponds to the aperture 
value of the lens, when the pulse number thereof coincides with the pulse 
number of the Av register 244, the coincidence circuit 247 detects it and 
sends a signal to the aperture control circuit 249, cutting off power to 
the magnet 250. With the power supply cut off, the aperture of the lens 
stops and the lens is fixed at that aperture position. 
Shutter time control is performed as follows: The shutter time expanding 
circuit 255 expands the pulse number of the Tv register 245 on the basis 
of the output of the frequency divider 254 obtained by frequency dividing 
the reference clock pulses produced from the clock pulse oscillator 253. 
An expanded signal thus obtained is used to drive the shutter driving 
magnet 257 via the shutter control circuit 256. The magnet 257 then 
controls the shutter (not shown). 
The display operation of the LED 260 and the liquid crystal 261' is as 
follows: First, if either the shutter priority photography mode or the 
manual photography mode is selected through the safety switch 237a, the 
photography mode setting switch 237b and the photography mode setting 
circuit 239 and if the aperture of the lens is not stopped down while the 
eyepiece 215 is left open. Under this condition, the level of either the 
output line Tv or the output line M becomes high among the output lines of 
the photography mode setting circuit 239. Then, the stop-down switch 262 
and the switch 263 are open. Therefore, the output level of the OR gate 
269 is low and that of the AND gate 270 is also low. This renders the LED 
driving circuit 241 operative, lighting up either of the LED's 240b and 
240c. Since the level of the common input to the AND gates 264, 265 and 
266 is high, the output level of either of the AND gates 264 or 266 
becomes high to, displaying "TV" or "M" at the external display 
arrangement 261. Meanwhile, the content of the Av register 244 is decoded 
by the decoder 258a and is impressed on the input terminals of the AND 
gates 275 and 276. The output level of the OR gate 269 is low and that of 
the inverters 271 high. Therefore, the AND gate 276 transmits the content 
of the decoder 258a to the OR gate 277. As a result, the computed aperture 
value is displayed by the LED 260. The content of the Tv register 245, on 
the other hand, is decoded by the decoder 258b and is impressed on the 
input terminals of the AND gates 273 and 274. The output level of the 
inverter 272 is as high as that of the AND gate 270 is low. Then, the 
content of the decoder 258b is transmitted from the AND gate 274 via the 
OR gate 281, the AND gate 280 and the OR gate 268 to the liquid crystal 
261'. The liquid crystal 261' then displays the set shutter value time. In 
other words, under the shutter priority photography mode or the manual 
photography mode, a shutter time setting value is displayed at the 
external display device 261. A computed aperture value computed and 
obtained from the object brightness, shutter time, film sensitivity, etc, 
is displayed by the LED 260, which is included in the view finder display 
arrangement 218. 
When the aperture priority photography mode is selected by means of the 
safety switch 237a, the photography mode setting switch 237b and the 
photography mode setting circuit 239 and if the aperture is not stopped 
down and the eyepiece 215 is left open, the output line Av level alone 
becomes high among the output lines of the photography mode setting 
circuit 239. Since the stop-down switch 262 and the switch 263 open, the 
output level of the OR gate 269 becomes high and that of the AND gate 270 
is also high. Then, since the levels of both inputs to the AND gate 265 
become high, the AND gate 265 produces a high level output displaying "Av" 
at the external display arrangement 261. This informs the photographer of 
the selection of the aperture priority photography mode. Furthermore, the 
content of the Av register 244 is decoded by the decoder 258a and is 
impressed on the input terminals of the AND gates 275 and 276. Since the 
output level of the AND gate 270 is high, the AND gate 275 transmits the 
content of the decoder 258a to the liquid crystal 261' via the OR gate 
281, the AND gate 280 and the OR gate 268. The liquid crystal 261' 
displays the set aperture value. Furthermore, the content of the Tv 
register 245 is decoded by the decoder 258b and is impressed on the input 
terminals of the AND gates 273 and 274. Since the output level of the OR 
gate 269 is high, the AND gate 273 transmits the content of the decoder 
258b via the OR gate 277 to the LED driving circuit 259. Then, since the 
switch 263 is open, the LED driving circuit 259 operates, causing the LED 
260 to display the content of the decoder 258b, which is a computed 
shutter time value. Under the aperture priority photography mode, 
therefore, the aperture setting value is displayed at the external display 
arrangement 261 while the computed shutter time value obtained based on 
the object brightness, the setting value of aperture and that of film 
sensitivity are displayed by the LED 260, which is included in the view 
finder display arrangement 218. 
If the lens aperture is stopped down regardless of the set positions of the 
photography mode setting switch 237b, etc. and the eyepiece 215 is left 
open, the stop-down switch 262 is closed and the switch 263 opens. 
Accordingly, the inverter 267 produces a high level output. The OR gate 
269 also produces a high level output. Furthermore, the output level of 
the AND gate 270 is low. Meanwhile, the terminal R output of the LED 
driving circuit 241 becomes low and operation of the LED driving circuit 
241 stops putting out all the LED's 240a-240d. Since the output level of 
the inverter 267 is high, the electrode level of the display part "SD" of 
the external display arrangement 261 becomes high, displaying "SD", 
informing the photographer that the camera is in the stopped down actual 
aperture priority photography mode. The content of the Av register 244 is 
decoded by the decoder 258a and is impressed on the input terminals of the 
AND gates 275 and 276. However, since the output level of the AND gate 270 
is low and that of the OR gate 269 high, the output level of the inverter 
271 becomes low, making one input level of each of the AND gates 275 and 
276 low. Therefore, the AND gates 275 and 276 do not transmit the content 
of the Av register 244 to the LED 260 and the liquid crystal 261'. As a 
result, the aperture value is not displayed at all. Furthermore, the 
content of the Tv register 245 is decoded by the decoder 258b and is 
impressed on the input terminals of the AND gates 273 and 274. However, 
since the output level of the OR gate 269 is high and that of the AND gate 
270 is low, the output level of the inverter 272 becomes high, causing the 
AND gate 273 to transmit the content of the decoder 258b to the LED 
driving circuit 259 via the OR gate 277. Then, since the switch 263 is 
open, the LED driving circuit 259 is operative and causes the LED 260 to 
display the computed shutter time value. Furthermore, the content of the 
decoder 258b is transmitted by the AND gate 274 via the OR gate 281 and 
the AND gate 280 to the liquid crystal 261', also displaying the computed 
shutter time value by the liquid crystal 261' in the same manner as with 
the LED 260. In other words, under the stopped-down actual aperture 
priority mode, no preset aperture value is displayed while the shutter 
time value computed from the object brightness, the setting value of 
aperture, the film sensitivity, etc. is alone displayed at both the LED 
260 and the external display arrangement 261. Then, when the eyepiece 
shutter 219 which is shown in FIG. 15 is closed, the switch 263 closes. 
This lowers the terminal R level of the LED driving circuit 259. The LED 
driving circuit 259 stops operating. The LED 260 displays nothing. The AND 
gate 282 output is at a low level and the terminal R level of the LED 
driving circuit 241 is also low. The dot LED's 240a-240d, thus, also 
display nothing. Therefore, the light measuring circuit 230 is not 
affected by any stray light from the dot LED's 240a-240d. With the 
eyepiece shutter 219 closed in this manner, i.e. when the switch 263 is 
closed, if the photography mode selected by the photography mode setting 
switch 237b is the shutter priority photography mode, the level of one 
input of the AND gate 280 becomes low by closing the switch 263. In that 
instance, the AND gate 281 produces a low level output regardless of the 
OR gate 281 output. Meanwhile, since the inverter 278 produces a high 
level output, the AND gate 279 transmits the output of the OR gate 277 of 
the OR gate 268. Accordingly, with the eyepiece shutter 219 closed, the 
information displayed at the LED 260 under various photography modes is 
displayed at the liquid crystal 261' of the external display arrangement 
261. In this case, the output of the decoder 258a, which is obtained by 
decoding the content of the Av register 244, is transmitted via the AND 
gate 276 and the OR gate 277 to the AND gate 279. Then, the output is 
further applied via the OR gate 268 to the liquid crystal 261', displaying 
the computed aperture value at the liquid crystal 261'. 
As described above, when the eyepiece shutter 219 is closed, the display 
arrangement within the view finder is completely put out and the computed 
information is alone displayed at the external display arrangement 261 
regardless of the photography mode selected. 
FIG. 22 is a circuit diagram showing, by way of example, the details of the 
LED driving circuit 241 of FIG. 21. The circuit arrangement of FIG. 22 is 
the same as that of FIG. 11 with the exception that, in this case, a block 
C is added to the circuit of FIG. 11. The block C includes a resistor 308 
and an inverter 309. The input terminal of the inverter 309 is connected 
to the terminal R of the LED driving circuit 241 while the output terminal 
thereof is connected to the base of an NPN transistor 310. The transistor 
310 has its emitter connected to the ground GND and its collector to one 
terminal of each of resistors 393, 394, 395 and 396. With the LED driving 
circuit arranged in this manner it operates as follows: When a power 
supply switch (not shown) is pushed, a DC voltage is impressed between the 
power source Vcc and the ground GND. A constant voltage is produced from a 
constant voltage circuit 390 and is impressed on the inversion input 
terminal of an operational amplifier 391. The operational amplifier 391 
has negative feedback coinciding the voltage of its non-inversion input 
terminal with that of the inversion input terminal. Then, the voltage of 
the terminal of a resistor 392, which is not connected to the power source 
Vcc, becomes equal to that of the output of the constant voltage circuit 
390. In other words, the resistor 392 has a constant voltage, which is the 
difference between the voltage of the power source Vcc and the output 
voltage of the constant voltage circuit 390 impressed on the two terminals 
thereof. As a result, a constant current flows to the resistor 392. Then, 
assuming that a transistor 301 is non-conductive with its base potential 
being zero and transistors 302, 303 and 304 are all conductive with their 
base potentials being high, the base potentials of transistors 398, 399 
and 300 are low and they become non-conductive since no base current is 
supplied to them from the resistors 394, 395 and 396. Thus, no current 
flows between the collector and emitter of each of the transistors 398, 
399 and 300. A transistor 397 alone becomes conductive and the constant 
current which flows to the resistor 392 flow between the collector and 
emitter of the transistor 397. Therefore, the constant current also flows 
to the LED 340a which is connected to the emitter of the transistor 397. 
The LED 340a lights up. In the same manner, if the base potential of the 
transistor 302 is alone at a low level while those of the other 
transistors 301, 303 and 304 are all high, a constant current flows to the 
LED 340b lightening it up. It is thus possible to have a constant current 
flow to only one of the plurality of LED's by means of a single 
operational amplifier. 
The LED lighting operation of the circuit is as follows: Among the outputs 
of a LED driving circuit 341-1, only one of them becomes a low level based 
on the photography mode selected. However, the time at which the output 
level becomes low is only when the output level of a pulse oscillator 307 
is high. In other words, one of the LED's 340a, 340b, 340c and 340d 
intermittently lights up at time intervals at which the output level of 
the pulse oscillator 307 becomes high. Furthermore, as mentioned in the 
description of the operation of the electric circuit of FIG. 21, in the 
event of a warning with the shutter time value or aperture value outside a 
control range, the output level of the OR gate 346 becomes high. However, 
the output level of the NAND gate 305 becomes low and a constant current 
flows to the LED 340d only when the output level of the pulse oscillator 
307 is low. When any one of the LED's 340a, 340b and 340c is lit, the LED 
340d does not light up, even under a warning condition. The LED 340d 
lights up at the warning time only when none of the other LED's 340a, 340b 
and 340c are lit. If the cycle of the pulse oscillator 307 is short, 
however, the LED 340d appears to light concurrently with one of the LED's 
340a, 340b and 340c due to the after image effect of the eye. 
When the terminal R level becomes low, the inverter 309 produces a high 
level output, rendering the transistor 310 conductive. The collector level 
of the transistor 310 becomes low. Therefore, the connection point levels 
between the resistor 308 and the resistors 393, 394, 395 and 396 become 
low. The base levels of all the transistors 397, 398, 399 and 300 become 
low and no emitter current flows for these transistors 397, 398, 399 and 
300. As a result, the LED's 340a, 340b, 340c and 304d become extinct. 
FIG. 23 shows the essential parts of the circuit arrangement required for 
the display operation of the LED 260. In this drawing, the parts in FIGS. 
21 and 22 are identified by the same reference numerals. The circuit 
arrangement includes a transistor 411. The base of the transistor 411 is 
connected to the switch 263 and also to the collector thereof via a 
resistor 412. The collector is connected to the power source Vcc. The 
emitter of the transistor 411 is connected to the decoders 258a and 258b. 
The decoder 258a is composed of a five-bit decoder 258a' (having a 
terminal E as power supply terminal) and a display matrix decoder 258a. 
The decoder 258a decodes the five-bit information of the Av register 244 
and selects an aperture value corresponding to the information. Then the 
output line level for the selected aperture value becomes high. The 
display matrix decoder 258a has output lines a, b, c, d, e, f, g, h, i, j, 
k, l, m, n, o, p, q and r which are respectively connected to the segments 
of the LED 260 including segments a, b, c, d, e, f, g, h, i, j, k, l, m, 
n, o, p, q and r through the AND gate 276, the OR gate 277 and the LED 
driving circuit 259 shown in FIG. 21. The display matrix decoder 258a also 
includes parts .circle. which are conductive parts between aperture 
values and the segments a-r. The other decoder 258b is also composed of a 
decoder 258b' having a terminal E as the power supply terminal and a 
display matrix decoder. The decoder 258b decodes the four-bit information 
of the Tv register 245. Then, a shutter time value corresponding to the 
information is selected and the output line level for this value becomes 
high. The output lines a-r of the display matrix decoder are connected 
respectively to the segments a-r of the LED 260 through the AND gate 273, 
the OR gate 277 and the LED driving circuit 259 of FIG. 21. With the 
circuit arranged in this manner, it operates as described below: 
In the shutter priority or manual photography mode with the eyepiece 
shutter 219 left open, i.e. with the switch 263 open, the base of the 
transistor 411 is biased through the resistor 412. Power is supplied from 
the emitter of the transistor 411 to the terminal E of the decoder 258a' 
to render the decoder 258a' operative. The content of the Av register 244 
is decoded by the decoder 258a'. The level of one aperture value output 
line corresponding to the information of the Av register 244 becomes high. 
When the computed aperture value is F 1.2, for example, the Av register 
244 information makes the output line level for F 1.2 high at the decoder 
258a'. Then, the levels of the output lines b, c, i, k, l, n, o and p, 
which have marks .circle. on the output line of F 1.2, become high, 
lighting up the segments b, c, i, k, l, n, o and p of the LED 260 making a 
display "1.2" and showing that the computed aperture value is F 1.2. 
When using the aperture priority photography mode with the eyepiece shutter 
219 open, power is supplied from the power source to the terminal E of the 
decoder 258b' to render the decoder 258b' operative. The content of the Tv 
register 245 is decoded by the decoder 258b'. The level of one of the 
output lines of the decoder 258b' which corresponds to the information or 
content of the Tv register 245, becomes high. If the computed shutter time 
is 1 sec in this case, for example, the information of the Tv register 245 
makes the output line level for the shutter time value "1" high at the 
decoder 258b'. Then, the levels of the display matrix decoder output lines 
b, c, j and n, which have marks .circle. on the line for "1", become 
high. As a result, the segments b, c, j and n of the LED 260 light up, 
displaying "1", showing that the computed shutter time in this case is 1 
second. For shutter time values other than 1 sec, the display matrix 
decoder of the decoder 258b is capable of displaying shutter time values 
ranging from 1/1000 to 2 sec in the same manner as described in the 
foregoing with reference to FIG. 19. 
Furthermore, in situations where the eyepiece shutter 219 is closed, i.e. 
the switch 263 is closed, the base of the transistor 411 is grounded 
regardless of the photography mode. In that event, therefore, the emitter 
of the transistor 411 produces no voltage. The levels of all the output 
lines a-r of the display matrix decoder become low and the LED 260 does 
not light up. 
The liquid crystal 261' of the external display arrangement 261 has the 
same segment arrangement as that of the LED 260. Accordingly, the liquid 
crystal 261' performs a display operation in the same manner as the LED 
260.