Comment by themanmaran
17 days ago
One thing people always forget about traditional OCR providers (azure, tesseract, aws textract, etc.) is that they're ~85% accurate.
They are all probabilistic. You literally get back characters + confidence intervals. So when textract gives you back incorrect characters, is that a hallucination?
I'm the founder of https://doctly.ai, also pdf extraction.
The hallucination in LLM extraction is much more subtle as it will rewrite full sentences sometimes. It is much harder to spot when reading the document and sounds very plausible.
We're currently working on a version where we send the document to two different LLMs, and use a 3rd if they don't match to increase confidence. That way you have the option of trading compute and cost for accuracy.
>We're currently working on a version where we send the document to two different LLMs, and use a 3rd if they don't match to increase confidence.
I’m interested to hear more about the validation process here. In my limited experience, I’ve sent the same “document” to multiple LLMs and gotten differing results. But sometimes the “right” answer was in the minority of responses. But over a large sample (same general intent of document, but very different possible formats of the information within), there was no definitive winner. We’re still working on this.
What if you use a different prompt to check the result, did this work? I am thinking to use this approach, but now I think maybe it is better to use two different LLM like you do.
It’s a question of scale. When a traditional OCR system makes an error, it’s confined to a relatively small part of the overall text. (Think of “Plastics” becoming “PIastics”.) When a LLM hallucinates, there is no limit to how much text can be made up. Entire sentences can be rewritten because the model thinks they’re more plausible than the sentences that were actually printed. And because the bias is always toward plausibility, it’s an especially insidious problem.
It's a bit of a pick your poison situation. You're right that traditional OCR mistakes are usually easy to catch (except when you get $30.28 vs $80.23). Compared to LLM hallucinations that are always plausibly correct.
But on the flip side, layout is often times the biggest determinant of accuracy, and that's something LLMs do a way better job on. It doesn't matter if you have 100% accurate text from a table, but all that text is balled into one big paragraph.
Also the "pick the most plausible" approach is a blessing and a curse. A good example is the handwritten form here [1]. GPT 4o gets the all the email addresses correct because it can reasonably guess these people are all from the same company. Whereas AWS treats them all independently and returns three different emails.
[1] https://getomni.ai/ocr-demo
The difference is the kind of hallucinations you get.
Traditional OCR is more likely to skip characters, or replace them with similar -looking ones, so you often get AL or A1 instead of AI for example. In other words, traditional spelling mistakes. LLMs can do anything from hallucinating new paragraphs to slightly changing the meaning of a sentence. The text is still grammatically correct, it makes sense in the context, except that it's not what the document actually said.
I once gave it a hand-written list of words and their definitions and asked it to turn that into flashcards (a json array with "word" and "definition"). Traditional OCR struggled with this text, the results were extremely low-quality, badly formatted but still somewhat understandable. The few LLMs I've tried either straight up refused to do it, or gave me the correct list of words, but entirely hallucinated the definitions.
> You literally get back characters + confidence intervals.
Oh god, I wish speech to text engines would colour code the whole thing like a heat map to focus your attention to review where it may have over-enthusiastically guessed at what was said.
You no knot.
We did this for a speech to text solution in healthcare. Doctors would always review everything that was transcribed manually (you don’t want hallucinations in your prescription), and using a heatmap it was trivial to identify e.g. drugs that were pretty much always misunderstood by STT
I know nothing about OCR providers. It seems like OCR failure would result in gibberish or awkward wording that might be easy to spot. Doesn't the LLM failure mode assert made up truths eloquently that are more difficult to spot?
> is that they're ~85% accurate.
Speaking from experience, you need to double check "I" and "l" and "1" "0" and "O" all the time, accuracy seems to depend on the font and some other factors.
have a util script I use locally to copy some token values out of screenshots from a VMWare client (long story) and I have to manually adjust 9/times.
How relevant that is or isn't depends on the use case.