HP seven-segment display patent


I just happened across this patent that I'd formerly overlooked:

US patent 3719849

HP patented putting the decimal point inside lower part of the seven-segment display, rather that to one side of the digit, as was more common. This was used on the Classic series (35/45/55/65/70/80), 67, 97, 19C, and Topcat series (91/92/95C/97).

I'd always wondered why they did that, and thought that perhaps they believed it improved legibility. The patent mentions that but also that it reduces manufacturing cost.

The Woodstock series went to the more common use of a decimal beside the digit, mainly to get more digits in less width by not "using up" a whole digit position for the decimal point.

The other thing I found interesting about this was the construction technique. I've never inspected HP's calculator displays closely enough to see how they were constructed, but have taken apart larger seven-segment displays, and those larger ones used multiple separate LED dice with light pipes to form the digits. It hadn't really occurred to me that the small ones might actually have a semiconductor substrate the size of the entire digit.

Possibly Related Threads...
Thread Author Replies Views Last Post
  New Blog Post: Length of a Polynomial Segment Eddie W. Shore 1 399 01-17-2013, 08:56 PM
Last Post: Namir
  Can the display for a HP32Sii be replaced with the display from another model? Bruce Larrabee 8 981 10-10-2012, 10:05 PM
Last Post: Luiz C. Vieira (Brazil)
  HP-35: once working, now only one dim segment on display elmwood 10 903 09-01-2011, 01:51 PM
Last Post: Thomas Radtke
  An Agilent patent on a calculator Eric Smith 9 845 07-07-2010, 12:11 PM
Last Post: Arnaud Amiel
  Classic display segment intermittent - cause? Mark Henderson 3 395 02-27-2010, 07:25 PM
Last Post: Mark Henderson
  16 segment Led display would mimic a HP-41 display? Giuseppe Marullo 3 561 11-12-2009, 08:08 PM
Last Post: db (martinez, ca.)
  Interesting FTC report concerning TI calculator patent enforcement Eric Smith 2 409 11-16-2006, 02:57 PM
Last Post: Hal Bitton
  HP-67 Interface & Display Segment Imran Farooq 8 741 05-12-2004, 06:26 PM
Last Post: Randy Sloyer
  HP-41 Patent Number Jason Doherty 0 246 09-19-2001, 04:20 AM
Last Post: Jason Doherty
  Can I use a HP 12C display as a replacement for a broken HP 15C display? Heather Hansson 2 392 05-01-2001, 10:44 PM
Last Post: Andrés C. Rodríguez (Argentina)

Forum Jump: