Digital information transmitting and displaying system for a photographic camera
This is a continuation of application Ser. No. 600,430 filed July 30, 1975, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to digital exposure information display systems for use with photographic cameras or exposure meters, and more particularly to a digital exposure information transmitting and displaying system for use with a digitally operated camera or exposure meter in which a digital exposure information once stored in a digital circuit of the camera or exposure meter is transmitted to a read-out device for digital display of the exposure information in the view finder of the camera. 
     2. Description of the Prior Art 
     With recent development of electronics, digital circuit devices have found their uses in the exposure control of photographic cameras. The employment of the digital circuit device in the exposure control apparatus provides various advantages such as of simplifying the circuit structure, reducing the apparatus size and improving the control accuracy. These advantages are very important factors in facilitating the compactness of the camera. With such digital exposure control apparatus, it is required that the display device for displaying exposure information such an exposure value be associated with the digital circuit device. For this reason, various types of digital display systems have been developed, most of which may be conveniently considered as comprising a number of memory means for memorizing the corresponding number of digits or symbols constituting a single exposure information or exposure value supplied from the exposure control apparatus of the camera, and read-out means connected to the memory means through respective signal-transmitting channels. As the number of digits increases, therefore, the necessary number of channels is increased, thereby giving a disadvantage of prejudicing the small, compact and rugged construction of the digital circuit device. Another disadvantage of the prior art display systems is that, in order to display the exposure information in the field of view of the camera, the read-out means with the channel means must be positioned in a limited space within the view finder optical system with the consequent sacrificing of the economical production of a complete camera. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an exposure information transmitting and displaying system adapted for association with a digitally operated exposure control apparatus of a photographic camera and which has overcome the above mentioned conventional drawbacks. 
     Another object is to provide an exposure information transmitting and displaying system comprising a number of memory means for storing the corresponding number of digits, or symbols, or combinations thereof which when sequentially arranged in a predetermined order constitute the numeral of an effective exposure value, a pulse counter, the corresponding number of AND gates having first inputs connected to the respective memory means and having second inputs connected to respective stages of the counter, and a single OR gate connected to the AND gates to permit sequential transmission of the corresponding number of signals each having a place-control components through a common channel to decoding means associated with read-out means, so that the digits are displayed as rearranged in accordance with the place-control components of the signals in the view finder of the camera. 
     Still another object is to provide an exposure information transmitting and displaying system of the character described in which when said digits are applied in sequence through the common channel to the read-out means, the sequence of application of said digits is controlled in conformance with the predetermined display arrangement thereof to permit the use of signals having no place-control components in transmitting the exposure information to the read-out means. 
     According to a preferred embodiment of the invention, the memory means, pulse counter, AND gates and OR gate are assembled in a common semiconductor device as a first LSI chip, while the display means including decording means is constructed in the form of a second LSI chip adapted for arrangement adjacent the optical system of the view finder of the camera, thereby it being made possible to connect these first and second LSI chips with each other through a minimized number of electrically insulated lead wires. 
     An advantage of the present invention deriving from the minimization in the necessary number of insulated wires interconnecting the first and second LSI circuits is that the design flexibility allowing camera structures of reduced size is not dependent upon the particular arrangement of the first and second LSI chips, permitting effective utilization of the spaces available in these structures within the camera housing for facilitating the compactness of the camera with a decreased weight and bulk thereof. The present invention is, therefore, preferably applicable to a high performance camera which is comparatively small, compact and rugged in construction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary schematic perspective view, partly broken away, of an arrangement of the essential components of an exposure information transmitting and displaying system according to a preferred embodiment of the present invention as applied to a single lens reflex camera. 
     FIG. 2 is an enlarged elevational view of a digital read-out device suitable for use in the system of FIG. 1. 
     FIG. 3 is a side sectional view of the basic components of a view finder optical system illustrated in connection with an arrangement of the read-out device of FIG. 2. 
     FIG. 4 is a plane view of the image of an exposure information representing character arrangement appearing to a photographer looking through the eye-piece of the view finder of FIG. 3. 
     FIG. 5 is a schematic diagram, partly in block form, of circuitry suitable for use in an example of an exposure information transmitting and displaying the system according to one embodiment of the present invention. 
     FIG. 6 is a pulse timing chart illustrating an example of the manner in which the system of FIG. 5 may be operated. 
     FIG. 7 is a schematic diagram, partly in block form, of circuitry suitable for use in another example of the embodiment of the invention. 
     FIG. 8 is a pulse timing chart illustrating an example of the manner in which the system of FIG. 7 may be operated. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 through 4, there is shown one embodiment of an exposure information transmitting and displaying apparatus according to the present invention as applied to a single lens reflex camera having a housing 12. The apparatus comprises an exposure information-to-signal converting circuit including a digital signal transmitting circuit incorporated in a first large scale integrated circuit (LSI) chip 1, a number of terminals 2 connected to the chip 1, and the corresponding number of insulated lead wires 3 connected at one ends thereof to the respective terminals 2, the opposite ends of which are connected to a display control circuit including decoders, drivers, shift registers incorporated in a second LSI chip 13 mounted on a read-out device such as of the seven segment type as shown in FIG. 2. The read-out device 11 is positioned adjacent a prism 8 attached to the bottom face of a penta prism 9 at the rear marginal portion thereof constituting part of a view finder optical system of the camera. As shown in FIG. 3, the view finder optical system further includes a tiltable mirror 5, a focusing screen 6, a condenser lens 7 and an eye-piece 10. A view field of the finder appearing to a photographer looking through the eye-piece 10 is shown in FIG. 4, as being comprised of an image area 14 to be photographed and an exposure value indicia-display area 15. 
     Referring now to FIG. 5, there is shown one embodiment of an exposure information transmitting and displaying system according to the present invention as including a clock pulse generator CP which may be common to that of a digitally operated exposure control system of the camera, a control counter PC such as a ripple type connected to the clock pulse generator CP, a scale-of-8 ring counter RC connected to the ripple counter PC, eight 7 bit-shift registers R 1  through R 8  with the registers R 1  through R 5  being responsive to binary coded signals constituting an effective shutter speed supplied from the exposure control system, and with the registers R 6  through R 8  being responsive to binary coded signals constituting an effective aperture value, eight AND gates A 1  through A 8  having gating control inputs connected to respective stages of the ring counter RC and having signal inputs connected to the respective outputs of the shift registers R 1  through R 8 , and a single OR gate OR connected to the outputs of the AND gates A 1  through A 8 . These components PC, RC, R, A and OR are assembled as a single first unit I. Each of the 7 bit-shift registers R 1  through R 8  is so constructed that the first three bits generally designated by character D serve to register a place control signal, and the other four bits generally designated by character SS or AV serve to register numeral or symbol control signal. For example, the first 7 bit-shift register R 1  has the first three bits D 1  adapted to register a binary coded signal (0, 0, 0) representative of the first place and the other four bits SS 1  adapted to register a binary coded signal (1, 0, 1, 1) indicative representative of a symbol &#34;1/&#34;  indicating whether or not the shutter speed is longer or shorter than one second. The combination of registers R 2   through R 5  is adapted to represent a shutter speed in 4 digit decimal number at large, while the combination of registers R 6  through R 8  is adapted to represent an aperture value in 2 digit decimal number. 
     The system of FIG. 5 further includes a 7 bit-shift register SP having an input connected to the output of the OR gate OR of the first unit I, seven AND gates AD 1  through AD 7  having signal inputs connected to the respective bits of the shift register SP and gating control inputs connected to the output of the ripple counter PC of the first unit I, a 7 bit register PP connected to the outputs of the AND gates AD 1  through AD 7 , a digit decoder DD 1  connected to the first three bits of the register PP and having a control input connected to the ripple counter PC, a segment decoder SD 1  connected to the other four bits of the register PP, a digit driver DD 2  responsive to the place control signal supplied from the digit decoder DD 1  for selecting one of eight read-out elements and for driving the selected read-out element, a segment driver SD 2  responsive to an indicium control signal supplied from the segment decoder SD 1  for selecting certain segments from the seven ones or a fixed number of segments in the above-identified read-out element and for driving the selected segments to display any one of the ten digits from 0 to 9 and two symbols &#34;1/&#34; and &#34;.&#34; (decimal point), and a read-out element assembly E with eight read-out elements arranged in laterally side-by-side relation. These components SP, AD, PP, DD 1 , DD 2 , SD 1 , SD 2  and E may be assembled in a single second unit II. 
     It will be appreciated that the binary coded signals supplied from the 7 bit shift registers R 1  through R 8  are transmitted in sequence throught a common channel to the read-out element assembly E, while the sequential signal transmission is controlled by the ripple or control counter PC of scale-of-7 type through a separate channel. One set of indicia including the ten digits and symbols &#34;1/&#34; and &#34;.&#34; of which the ten digits can be produced by the seven segments of the read-out element is exemplified in connection with binary coded signals for the place control and indicium control as shown in the following tables 1 and 2. 
     
                       Table 1                                                     
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Place    1      2      3    4    5    6    7    8                         
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Indicium 1/                                .                              
Register with                                                             
first three                                                               
bits     D.sub.1                                                          
                D.sub.2                                                   
                       D.sub.3                                            
                            D.sub.4                                       
                                 D.sub.5                                  
                                      D.sub.6                             
                                           D.sub.7                        
                                                D.sub.8                   
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                                           Table 2                                 
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                     Indicium control signal                              
                     Indicium                                             
Place control signal                                                      
                Binary                                                    
                     Register                                             
Register                                                                  
     Binary code                                                          
                code of                                                   
                     SS.sub.2 -SS.sub.5                                   
                           Register                                       
                                 Register                                 
bit  of signal                                                            
            Place                                                         
                signal                                                    
                     AV.sub.1, AV.sub.3                                   
                           SS.sub.1                                       
                                 AV.sub.2                                 
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D.sub.1                                                                   
     0 0 0  1st 0000                                                      
D.sub.2                                                                   
     0 0 1  2nd 0001                                                      
D.sub.3                                                                   
     0 1 0  3rd 0010                                                      
D.sub.4                                                                   
     0 1 1  4th 0011                                                      
D.sub.5                                                                   
     1 0 0  5th 0100                                                      
D.sub.6                                                                   
     1 0 1  6th 0101                                                      
D.sub.7                                                                   
     1 1 0  7th 0110                                                      
D.sub.8                                                                   
     1 1 1  8th 0111                                                      
                1000                                                      
                1001                                                      
                1010             Decimal                                  
                                 point.                                   
                1011       Symbol                                         
                           1/                                             
                1100                                                      
                1101                                                      
                1110                                                      
                1111 blank blank blank                                    
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     The operation of the system of FIG. 5 will be understood with reference to FIG. 6, wherein a line (1) shows a clock pulse train from the clock pulse generator CP, a line (2) shows the conductivity conditions of the scale-of7 ripple counter PC, and lines (3) through (10) show the conductivity conditions of the respective stage St 1  through St 8  of the scale-of-8 ring counter RC. The shift registers R 1  through R 8  are now assumed to be in positions for registering an exposure information of a shutter speed of 1/2000 and an aperture value of 5.6 supplied from the exposure control system not shown of the camera. When a clock pulse train at line (1) is applied to the control or ripple counter PC, the ripple counter produces a pulse train at a pulse repetition rate 1/7 times that of the clock pulse train, as shown at line (2). Responsive to a first control pulse counting from the left as viewed in FIG. 6(2), the ring counter RC produces a strove pulse St 1  at line (3) in such a manner that the lagging edge of the first control pulse from the ripple counter PC coincides with the leading edge of the strove pulse St 1 . During the time the strove pulse St 1  of duration 7 times the time interval between the successive two clock pulses is applied to the gating control input of a first AND gate A 1 , the first AND gate A 1  is gated on to pass a combined signal of a place control binary coded signal (1, 1, 1) representative of the eighth place and an indicium control binary coded signal (0, 1, 1, 0) from the shift register R 8 , which is then applied through the OR gate and a channel designated by Senal In to the 7 bit-shift register SP of the second unit II. When all of the AND gates AD 1  through AD 7  of the second unit II are gated on in response to application of a second control pulse at line (2) of which the lagging edge coincides with the lagging edge of the strove pulse St 1 , the place control signal is applied to the digit decoder DD 1  through register PP, and the indicium control signal is applied to the segment decoder SD 1  through the register PP. Responsive to the binary code (1, 1, 1) of the place control signal, the digit decoder DD 1  causes the digit driver DD 2  to drive the eighth read-out element counting from the left in the read-out element assembly or device E. On the other hand, responsive to the binary code (0, 1, 1, 0) of the indicium control signal, the segment decoder SD 1  causes the segment driver SD 2  to drive six of the seven segments of the eighth read-out element, thereby a numeral &#34;6&#34; is displayed in the eighth place of the read-out device E. At a moment all of the AND gates AD 1  through AD 7  are set to the &#34;off&#34; condition, a second strove pulse St 2  is applied to the second AND gate A 2  of the first unit I, so that a combined signal representative of the decimal point from the shift register R 7  is transmitted to and displayed by the seventh read-out element in the read-out device E in a manner similar to that shown in connection with the display of the eighth place numeral &#34;6.&#34; The other binary coded signals from the shift registers R 6  through R 1  are likewise transmitted to the respective read-out elements, thereby the indicia 1/2000  and 5.6 are displayed by the read-out device E which can be viewed by the photographer looking through the view finder of the camera. 
     DESCRIPTION OF AN ALTERNATE EMBODIMENT 
     An alternate embodiment of this invention for transmitting a number of indicia constituting a single exposure information in the form of the corresponding number of binary coded signals having no place control components through a common channel to respective read-out elements, while the sequential transmission of the signals to the read-out elements respectively assigned thereto being controlled by use of an additional ring counter is illustrated in FIG. 7, and the conductivity conditions of the additional ring counter are illustrated in FIG. 8. The same reference characters are employed in that figure to denote parts of that embodiment of the invention which remain substantially unchanged from the embodiment illustrated in FIG. 5, and the same reference characters primed are employed to denote similar parts thereof with slight modification. 
     Referring now to FIG. 7, an exposure information transmitting and displaying system is shown as comprising a scale-of-4 ripple counter PC&#39; having a clock pulse input terminal CP, a first scale-of-8 ring counter RC connected to the ripple counter PC&#39;, eight AND gates A 1  through A 8  having gating control inputs connected to respective stages of the ring counter RC, eight 4 bit-shift registers R 1  &#39; through R 8  &#39; connected to respective signal inputs of the AND gate assembly A, an OR gate OR connected to the outputs of the AND gate assembly A, all of the above mentioned parts being assembled as a first unit I, a 3 bit-shift register SP&#39; of a second unit II connected through a single channel to the output of the OR gate of the first unit I, the register SP&#39; having a function of processing the sequential signals supplied from the first unit I in synchronism with the clock pulses at line (1) in FIG. 8 to produce parallel outputs, a segment decoder SD 1  having four inputs one of which connected to the output of the OR gate OR and the other three of which are connected to the respective bits of the register SP&#39;, a seven-segment driver SD 2  responsive to the output of the segment decoder SD 1  for selecting certain segments from the seven segments, or a fixed number of segments in a selected read-out element of a read-out device E and for driving the selected segments to display any one of the ten digits from 0 to 9 and two symbols &#34;1/&#34; and &#34;.&#34; (decimal point), a second scale-of-8 ring counter RC&#39; connected to the scale-of-4 ripple counter PC&#39; for producing place-control signals at lines (10) through (18) in synchronism with the driving sequence of the AND gates A 1  through A 8  , and a digit driver DD 2  responsive to the place control signal supplied from the second ring counter RC&#39; for selecting one of the eight read-out elements in the read-out device E and for driving the selected read-out element. 
     The operation of the system of FIG. 7 is as follows. A camera control system not shown, applies digital coded signals such as binary coded signals to the shift registers R 1  &#39; through R 8  &#39;. Each of these signals is representative of any one of the ten digits 0 to 9, or a symbol &#34;1/&#34; or &#34;.&#34; (decimal point). Responsive to a clock pulse train applied to the input terminal CP, the ripple counter PC&#39; produces a pulse train at a pulse repitation rate 1/4 times that of the clock pulse train, as shown at line (2) in FIG. 8, which is then applied to the first ring counter RC to produce pulses St 1  through St 8  in sequence in synchronism at the leading edges thereof with the lagging edges of the pulses of the ripple counter PC&#39;, as shown at lines (3) through (10) respectively. Assuming that the register R 8  registers a binary code (0, 1, 1, 0) representative of a numeral &#34;6,&#34; a binary coded signal (0, 1, 1, 0) is derived from the register R 8  in a time interval during which four clock pulses are applied to the ripple counter PC&#39;, as the AND gate A 1  is set in the &#34;on&#34; condition by the strove pulse St 1 . Next, the strove pulse St 2  gates on the AND gate A 2  to derive a binary coded signal, for example, (1, 0, 1, 0) representative of the decimal point. Such a procedure is repeated each time a control pulse is produced from the ripple counter PC&#39; to derive binary coded signals from all of the registers R 1  through R 8 . These signals are transmitted in sequence through the OR gate and a common channel from the first unit I to the second unit II. In the second unit II, the binary coded signals are applied in sequence to the 3 bit-shift register SP&#39;, while the application of the four components of each binary coded signal, for example, (0, 1, 1, 0) of R 8  to the register SP&#39; are synchronized with occurrence of the clock pulses. Upon application of the fourth component, in this instance, &#34;0&#34; to the register SP&#39;, the second ring counter RC&#39; causes the digit driver DD 2  to drive the read-out element in the eighth place in the read-out device E, thereby a numeral &#34;6&#34; is displayed by the read-out element through the segment driver SD 2  after the output of the register SP&#39; is decoded by the segment decoder SD 1 . Such a procedure is repeated each time a pulse is produced from the second ring counter RC&#39; in sequence as shown at lines (11) through (18). As a result, a complete exposure information is displayed by the read-out device E in the form of an arrangement of digits, or symbols, or combinations thereof. 
     The present invention has been described in connection with the two embodiments in which the registers are employed as the memory means. Instead of using this type of memory means, it is possible to use magnetic type memory means. Further, instead of using these static memory mean, it is possible to use dynamic memory means. Moreover, the above-described embodiments of the invention is illustrated as applied to a single lens reflex camera. But the system of the invention is applicable to digitally operated exposure meters constructed in the separate form from the camera, or to external display apparatus adapted for attachment to the camera body from the outside thereof.